# Chapter 5. Stage 1 Components

## 5.1 Magnets

### 5.1.1 Introduction

The magnet system of the 20 TeV Stage-I VLHC is one of the main
components of the collider, and has a strong influence on the total cost
of machine. For these reasons, the general design goal is to reduce the
cost per Tesla-meter of the collider. The arcs of VLHC-1 are based on
warm-iron, combined function gradient dipole magnets\[1-3\], which are
excited by a single turn 100 kA superconducting transmission line. A
cross-section of the magnet, including the cryogenic service line and
return bus, is shown in Figure 5.1. The flux lines surrounding the
transmission line are shaped by an iron yoke, and two gaps in the yoke
provide the apertures for the two beams. The 20 TeV bending field is
1.966 T. The magnets have a field gradient of ±4.73%/cm, which provides
focusing and eliminates the need for separate quadrupoles. The 135.5 m
long half-cell is made of two 65.75 m long gradient magnets.

![](media/image1.png){width="5.830555555555556in"
height="4.324305555555555in"}

Figure 5.1 Cross-section of the gradient dipole magnet used in the arcs
and\
dispersion suppressor of the Stage-1 VLHC.

At the end of each half-cell, where the beta function is maximum in one
plane and minimum in the other, a 3.5 m long space is left open for
correction coils. The transmission line is diverted into the cryogenic
service pipe, near the return bus, allowing the use of conventional,
room temperature, air cooled iron magnets, as shown in Figure 5.2. Three
correctors are installed at each location: a vertically or horizontally
steering dipole, a quadrupole and a sextupole corrector.

*{remove this figure:}*

![](media/image2.png){width="6.4875in" height="2.729861111111111in"}

Figure 5.2 Correction coils placed at each half-cell.

The dispersion suppressor sections are made in a similar fashion. Here
the 101.6 m long half-cell is made of two 48.81 m long dipoles, with a
field at 20 TeV of 1.766 T and an increased gradient of ±9.449 %/cm.
Correctors are employed at each half cell as in the arcs.

In the long straight sections, the space not occupied by the interaction
regions or machine utilities are FODO channels made from conventional
water cooled quadrupoles. Two 6.1 m long, 70 T/m quadrupoles make one
half-cell. Special optics for the machine utilities -- injection, abort,
the RF system, and beam cleaning, are constructed using quadrupoles of
the same design but with special lengths. The matching section for the
low-beta insertions at the interaction regions are also constructed from
the same quadrupoles. The low-beta triplets themselves utilize 300 T/m
cos2θ superconducting quadrupoles made from Nb~3~Sn cable. Special
dipole magnets, similar in design to the gradient magnets in the arcs
and excited by the transmission line, are used to bring the beams into
collision at the interaction regions, to separate the beams to implement
independent RF systems for the two beams, and to cross the beams over at
two opposite points in the ring to ensure equal path lengths for the two
beams.

Table 5.1 summarizes the main parameters of the magnets used in the
VLHC-1 design.

The arc dipoles will clearly dominate the system cost. During the past
three years, most of the R&D effort has concentrated on the dipole
design, with considerable attention focused on the 100 kA
superconducting transmission line cable. The arc dipole design has been
refined through intense prototyping of the major magnet components, and
various types of transmission line cables were tested at a 17m length
superconducting test stand \[4\]. Several short magnet iron core
configurations were tested, using a room temperature test stand \[5\].
Two 6 m magnet prototypes have now been manufactured to confirm the main
technical decisions.

Section 5.1.2 describes the combined function arc and dispersion
suppressor magnets in detail, including magnetic design, design of the
100 kA transmission line, and the mechanical and thermal designs. The
correctors are described in section 5.1.3 and the interaction regions in
section 5.1.4. Section 5.1.5 presents the various special magnets,
including straight section quadrupoles; beam separation, recombination
and cross-over dipoles; and injection and abort system magnets.
Production of the 66 m long gradient dipoles and the testing and
measuring of them are described in sections 5.1.6 and 5.1.7
respectively. Transport, installation and alignment methods are
summarized in section 5.1.8.

Table 5.1 Main parameters of magnets in the Stage-1 VLHC.

+--------------+--------+--------+--------+--------+-------------------+
| *Magnet      | *      | *      | *      | *      | *Notes*           |
| Type*        | B~nom~ | G~nom~ | L~mag~ | Number |                   |
|              | (T)*   | (T/m)* | (m)*   | of     |                   |
|              |        |        |        | ele    |                   |
|              |        |        |        | ments* |                   |
+--------------+--------+--------+--------+--------+-------------------+
| Gradient     | 1.97   | 9.73   | 65.75  | 3136   |                   |
| dipole (arc) |        |        |        |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| Gradient     | 1.80   | 16.88  | 48.81  | 160    |                   |
| dipole (DS)  |        |        |        |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| Special      | 1.95   |        | 25 -   | 52     | Separation,       |
| dipoles      |        |        | 35     |        | recombination,    |
|              |        |        |        |        | and cross-over    |
+--------------+--------+--------+--------+--------+-------------------+
| Straight     |        | 70     | 4.8 -  | 464    |                   |
| sect quads   |        |        | 6.8    |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| Low β        |        | 300    | 9.2 -  | 8      |                   |
| quadrupoles  |        |        | 10.9   |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| Correctors   |        |        |        |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| > Dipole     | 1.0    |        | 0.50   | 1648   |                   |
| > (horiz.)   |        |        |        |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| > Dipole     | 1.0    |        | 0.50   | 1648   |                   |
| > (vert.)    |        |        |        |        |                   |
+--------------+--------+--------+--------+--------+-------------------+
| > Quadrupole |        | 25     | 0.50   | 3296   |                   |
+--------------+--------+--------+--------+--------+-------------------+
| > Sextupole  |        | 1750   | 0.80   | 3296   | Gradient in       |
|              |        |        |        |        | T/m^2^            |
+--------------+--------+--------+--------+--------+-------------------+

### 5.1.2 Combined function Arc Magnets

The magnet system of the 20 TeV Stage-I VLHC is based on superferric
(\~2 Tesla) superconducting transmission line magnets \[1-7\]. The low
parts cost and simple manufacturing process for these magnets are
expected to compensate for the cost of the long circumference of this
machine. All bending magnets share a common single turn excitation
transmission line winding. The superconducting transmission line is
described in section 5.1.2.2. There are several advantages of this type
of winding: simple construction, low cost, low field in the
superconductor area, absence of turn to turn insulation, low magnetic
forces and heat leak, high stability and simple quench protection.
Nevertheless there are some negative effects: a return bus with 100 kA
maximum current, fringing magnetic field, lower half-core iron
saturation, and uncompensated magnetic forces. It is possible to
optimize the magnet geometry and return bus position to reduce the
magnetic forces.

The main problem for correctors and other magnets placed in the regular
cells is the transmission line fringing field, which is \~ 0.3 T on the
beam orbit. An iron or a superconducting screen winding should carefully
screen the good field region of these magnets. Another option is to bend
the main transmission line to the return bus in the space between
magnets. It will reduce the fringing field of the two lines, and
air-cooled correctors may be placed there without screens.

#### 5.1.2.1 Magnetic design

One of the challenges in this design is obtaining a high quality
magnetic field in an iron-dominated magnet over a large range of field
variations (0.1 - 2.0 T). Two techniques were investigated:
"crenellated" poles, and poles with holes. Magnetic measurements of
various pole configurations confirmed the attractiveness of the poles
with holes technique.

Another challenge for such a magnet design is the mechanical stability
of both the conductor and the dual air gaps. Various technical solutions
for the air gap stability were tested on mechanical models. The special
superconductor test facility was commissioned at Fermilab to investigate
100-kA transmission line cables \[4\].

##### (a) Basic Design Choices

The magnet design is oriented towards lowering overall cost per
Tesla-meter of accelerator, achieving a good magnetic field quality, and
using existing technologies. This analysis led to the following choices:

-   A warm iron core and single turn coil to simplify the cryogenic,
    vacuum, power supply and quench protection systems.

-   An alternating-gradient design which eliminates arc quadrupoles and
    allows the magnet to be continuous in long lengths.

-   Magnetic fields formed by iron poles with sufficient accuracy that
    the strong correction coils needed for conventional design
    iron-dominated magnets would not be needed.

-   Superconducting transmission line conductor which can be made from
    well-known and relatively economical NbTi cable.

-   Open "C-magnet" air gaps to facilitate magnetic measurements and
    vacuum pipe installation.

Table 5.1: Main Parameters of Dipole Magnet

  ----------------- ----------- ---------------------- --------------------
                                *Main dipole*          *Dispersion
                                                       Suppressor*

  Beam gaps (height             18 mm x 28 mm          
  x width)                                             

  Magnet air gap in             20 mm                  22.26 mm
  the orbit center                                     

  Two beams                     150 mm                 
  separation                                           

  Magnet length                 65.74 m                48.81 m

  Half-cell length              135.5 m                101.6 m

  Gradient                      ± 4.73 %/cm            ± 9.449%/cm

  Magnetic field:   injection   0.1 T                  0.09 T

                    maximum     1.966 T                1.766 T

  Good field        injection   20 mm                  
  diameter (0.02%):                                    

                    maximum     10mm                   

  Maximum current               90 kA                  

  Magnetic field                790 kJ                 473 kJ
  energy                                               

  Superconducting               Braided NbTi           
  cable                                                

  Peak Operating                6.5-7 K                
  Temp.                                                

  Iron Core                     Low carbon Steel (AISI 
                                1008)                  
  ----------------- ----------- ---------------------- --------------------

The magnetic design incorporates several features which are different
from those of other superconducting accelerator magnets. The main
problem of a superferric magnet design is the formation (using only iron
poles) of a high quality magnetic field over a wide range (0.1T - 2.0T)
of field. Fig. 5.2 shows the magnet cross section. A superconducting
NbTi cable generates the magnetic field in two 20 mm height air gaps.

##### (b) Magnetic Field Quality

![](media/image3.wmf) investigated. The magnetic field in the magnet was
calculated by POISSON, OPERA 2D and ANSYS codes. The number of
correction holes had a linear correlation with the field quality.

Fig. 5.1 Superconducting transmission line magnet

![](media/image4.wmf)

+-----------------------------------------------------------------------+
| > *Editorial notes (VK):*                                             |
| >                                                                     |
| > *The results of pole profiles optimizations for positive and        |
| > negative gradients with harmonics and field quality in the range    |
| > 0.1- 1.96T will be later placed here.*                              |
| >                                                                     |
| > *Fig.5.3 Magnet geometry and flux lines for positive gradient*      |
| >                                                                     |
| > *Fig.5.4 Magnet geometry and flux lines for negative gradient*      |
| >                                                                     |
| > *Table 5.2 Field quality. Harmonics.*                               |
+-----------------------------------------------------------------------+

{what happened to figure?}

Fig. 5.5 Test Stand for the Room Temperature Field Measurements

#### References {note\-- for 5.1.2}

\[1\] R.R. Wilson, Proceedings of Snowmass 1982.

\[2\] "The Pipetron: a Low-Field Approach to a Very Large Hadron
Collider," Snowmass '96.

\[3\] G.W.Foster, "Transmission Line Magnet Status Report", VLHC
Information Packet for HEPAP Subpanel, Fermilab 1998.

\[4\] G.W.Foster, V.S.Kashikhin, E.Malamud, P.Mazur, H.Piekarz,
J.Fuerst, R.Rabehl, P.Schlabach, J.Volk, "The 100 kA VLHC Transmission
Line Magnet Superconducting Cable Test Facility," MT-16, IEEE Trans. of
Applied Superconductivity, Vol.10, No.1, March 2000, pp.318-321.

\[5\] J.DiMarco, G.W.Foster, V.Kashikhin, A.Makarov, P.Schlabach,
"Measurements of a Crenellated Iron Pole Tip for the VLHC Transmission
Line Magnet," PAC 99, pp. 3327 -- 3329.

\[6\] G.W.Foster, V.S.Kashikhin, I.Novitski, "Design of a 2 Tesla
Transmission Line Magnet for the VLHC," MT-16, IEEE Trans. of Applied
Superconductivity, Vol.10, No.1,March 2000, pp.202-205.

\[7\] G.W. Foster, V.S.Kashikhin, V.V.Kashikhin, "Pole Profile
Optimization of VLHC Transmission Line Magnet," EPAC 98.

#### 5.1.2.2 Superconducting Transmission Lines

##### 5.1.2.2.1 Superconducting Cables

Magnetic field in a superferric dipole magnet is generated by a current
carried in a drive conductor centrally positioned between the two stacks
of iron laminations as shown in Fig. 5.1. In order to suppress distant
magnetic fringe fields, a return conductor (current flow is in the
opposite direction) is placed outside the magnet laminations. At the mid
point of the accelerator, the drive conductor returns back through the
first half of the magnets (but outside the lamination stack). Then it is
used as a drive conductor for the second half of the magnets, and then
returns to the Power Supply (again outside the laminations). For the
VLHC Stage I accelerator, the continuous length of the superconducting
cable is about 464 km.

![](media/image5.jpeg){width="3.4in" height="2.2in"}

Fig. 1 The cross-section of the conductors with SSC outer and inner
strands

The currently selected cable is a braid made of 288 NbTi strands
arranged in a pattern of two sets (positive and negative angle) of 24
crossing bundles, each bundle with six strands (2 x 24 x 6 = 288). For
conductors at the corrector magnet space an assembly of 9 SSC inner
dipole Rutherford cables is proposed. The cross-sections of the
conductors with SSC outer and inner dipole strands are shown in Fig. 1.
The superconducting cable is a coax-style cable that consists of a core
of perforated invar pipe which serves both as a liquid helium channel
and as a support for the conductors. There is also a copper braid placed
underneath the conductors that provides an additional copper balance. A
thick wall outer invar pipe holds the conductor assembly together, and
it is a pressure pipe. The conductor braid is secured in a position by
swaging up the inner invar pipe against the outer one. In the swaging
procedure a series of carbide steel balls of incremental diameters are
pulled through the core invar pipe. The core pipe diameter increases in
average by about 1 mm (or less than 5%). The conductors made of the
Rutherford cables are secured in position by welding the outer invar
clam shell under pressure. The return conductor has the same number of
superconductor strands. Its helium flow is supplied from the preceding
flow of the drive conductor. In order to minimize the pressure drop in
the return conductor, the diameter of its helium channel has been
increased from \~ 2.6 cm (drive) to \~ 4.0 cm.

##### 5.1.2.2.2 Critical Temperature vs Current and Quench Behavior

![](media/image6.jpeg){width="4.6in" height="3.1319444444444446in"}The
critical temperature vs current for the braided conductor as well as for
the assembly of the 9 SSC inner dipole cables is shown in Fig. 2. At the
100 kA current the critical temperatures are 6.4 K and 6.9 K for the
braided conductor and for the 9 SSC cables assembly, respectively. The
measurement errors do not exceed 0.1 K. The supercritical helium of 4.5
K and 4 bar pressure is supplied to the conductor lines from 12
cryo-plants. It is assumed that at the furthest end of each flow the
helium temperature will not exceed 6 K, thus allowing for at least 0.5 K
operational safety margin.

Fig. 2 The critical temperature, Tc, vs current for drive and return
conductors

The quench propagation velocities were measured in a 17 m long conductor
loop. It was found that in a forced quench by a local heating of \~10 K,
quench propagation velocity rises linearly with current, and it reaches
about (10-12) m/s value at \~80 kA. Above this current, it rises
exponentially reaching about (30-40) m/s value at 100 kA. This indicates
that by applying a current dump circuit of a time constant of 1 s, the
stored magnetic energy released in a quench would be at most that of a
half length of a dipole magnet (33.88 m long), thus not exceeding 1 MJ
value. Assuming a quench initiated by a hot spot of 10 K, the initial
LHe temperature of 4.5 K and two relief valves (orifice \~0.65 cm^2^,
relief pressure of 6.8 bar), each at the end of a dipole magnet (67.75
m), we project the peak pressure after quench at about 24 bar, and the
peak temperature of conductor cable of \~170 K. In order to comply with
the safety requirements we designed the transmission line conductors to
operate up to 40 bar (MAWP) pressure.

##### 5.1.2.2.3 Cryostats, Cold Pipe Support and Heat Shield

![](media/image7.jpeg){width="5.4in" height="4.0in"}A three dimensional
view of a drive conductor transmission line is shown in Fig. 3. The
transmission line consists of (from inside out) the conductor cable as
described above, the cold pipe support, a cryoshield, the
superinsulation blanket, and the vacuum jacket. The cold pipe support
sets conductor cable centrally to the vacuum jacket which in turn is
placed centrally inside the magnet lamination. It also supports the
cryoshield pipe which in turn supports the superinsulation blanket.

Fig. 3 A 3D view of the drive conductor transmission line

A cross-section of the drive conductor cryostat is shown in Fig. 4. At
present it is proposed to use the injection molded ULTEM to fabricate
the cold pipe supports. In order to minimize the de-centering force, the
conductor cable must be placed precisely on the central line of the
magnet laminations. The offsets of the order of 0.5 mm (which can be
expected due to tolerances in fabrication of the components) may lead to
the de-centering forces of the order of 100 kG/m. In addition, these
supports must withstand 100,000 mechanical cycles of the accelerator
lifetime. As shown in Fig. 4, there are two pairs of pegs pointing up
and down, the direction of the magnetic force. The inner pair of pegs
support the cold pipe, while the outer pegs support the vacuum shell.
Although in the laboratory tests these supports have withstood 100,000
mechanical cycles under the 300 kG/m force, three times that of the
design requirement, a continued R&D may reveal better solutions to the
cold pipe support.

> ![](media/image8.jpeg){width="5.194444444444445in"
> height="2.9916666666666667in"}

Fig 4. The details of the drive conductor cryostat

The cryo-shield is made of extruded aluminum pipe segments of \~50 cm
long, and the two supports are placed by at least 0.5 mm apart to allow
for the thermal contractions. The 0.25" diameter invar pipe that is used
to provide the 50 K pressurized helium is "snapped in" to the cavities
at the top and the bottom of both the shield and the supports. The
shield pipe is wrapped with 40 layers of a dimpled superinsulation
blanket. The vacuum jacket is made of extruded aluminum, and it is of a
"squared" shape to firmly fix its position inside the iron laminations.
This also helps to prevent potential rotation (and/or twist) of the cold
pipe supports.

The return conductor is located inside a large magnet support pipe (12"
dia.). This tube houses also two cryo-service pipes (the 40 K shield
supply flow, and the 70 K flow return). We assume that all cryo-pipes
(just as conductor cold pipes) are made of invar. With a dipole magnet
length of 67.75 m the expected thermal contraction of an invar pipe is
about 2.5 cm. Such amount of contraction can be suppressed by anchoring
those pipes to the magnet support pipe. The most natural location for
all cryo-pipe anchors (including conductors) is the corrector magnet
space.

A schematic view of the conductors and the cryo-pipes arrangement
between two dipole magnets is shown in Fig 5. The bend and straight
section of the conductors are spliced to the conductor ends of two
dipole magnets. A set of clamps holds conductors in place in spite of a
repulsive magnetic force of the order of 3 Ton/m.

> ![](media/image9.jpeg){width="6.868055555555555in"
> height="4.033333333333333in"}

Fig. 5 A schematic view of conductors and cryo-pipe arrangement in
correctors space

All cold pipes are anchored to the magnet support pipe which in turn is
anchored to the ground creating in this way an anchor for the whole
magnet. Portions of the bend and straight sections of conductor are
dedicated to provide for the LHe inlets and outlets, quench pressure
relief outlets and instrumentation ports (more on all of that in the
next section). The space between dipole magnets is also a natural place
for the cryostat vacuum break. The ceramic seals withstanding pressure
up 40 psig are available in sizes of up to 2.8" internal diameter, which
is large enough for both drive and return conductor. A cross-sectional
view of the cold pipe arrangement is shown in Fig. 6. All cold pipes are
enclosed in a 70 K shield, which is formed out of aluminum sheets
clipped to the 70 K helium return flow pipe. The spacing between all
pipes has been arranged to allow for the orbital automatic welding of
these pipes. A possible extraction of the helium gas after quench into
the pressure relief pipe is also shown in Fig. 6. As this pipe would get
cold only temporarily there is no need for it to be inside the cryostat.
A moisture condensation can be prevented with a help of the external
insulation. Both the drive conductor cryostat and the return conductor
cryostat have bellows at their ends in order to allow to access
conductors for the splicing procedure. For the same reason the beam
pipes are equipped with bellows at each dipole magnet end.

![](media/image10.jpeg){width="5.9in" height="4.321527777777778in"}Fig.
6 The cross-sectional view of a possible arrangement of conductors\
and cryo-pipes in the corrector magnet space.

##### 5.1.2.2.4 Splicing Superconducting Cables, Flow Plugs and Instrumentation Ports

The unit of the arc magnet assembly is its half cell of 135.5 m length.
With \~3200 magnets in the accelerator ring this requires some 12,800
conductor splices including both the drive and the current return lines.
Consequently, the heat generated at the splice area is of major concern
as it generates a considerable heat load on the cryogenic system. A
longer splice area can reduce the resistive heating but within the space
available between the dipole magnets the splices can not be longer than
10-15 cm. In a test of a 15 cm long splice between braid and 9
Rutherford cables (SSC inner dipole strands) an upper limit on the
splice resistance was established at 0.02 nΩ. At 100 kA current this
would generate heat of \~ 0.2 W per splice, or about 2560 W for the
accelerator. The cryogenic system has been designed to accommodate this
heat source.

> ![](media/image11.png){width="5.0in" height="2.254861111111111in"}

Fig. 7 A conceptual arrangement of the LHe inlet/outlet and the
instrumentation ports

All helium inlets and outlets as well as the instrumentation ports must
be electrically isolated from the conductors. The expected voltage at
the occurrence of quench is about 2000 V. At the same time helium
pressure in the conductor lines may rise up to 40 bar. This situation
requires that the electrical isolators can withstand both high voltage
and high pressure at the ports with cross-sectional areas of up to 10
cm\^2. At present there is no technology that allows to construct such
ports using a single isolator segment. This is an area where the further
R&D effort may bring new solutions which will make all the above
applications much easier.

#### 5.1.2.3 Mechanical and thermal design

##### 5.1.2.3.1 Magnet structure

###### (a) Magnet support by cryogenic service pipe

The final assembly of the 67.5m length has two parts mounted as a one
unit, the magnet yoke with a conductor cryostat and the cryo-service
line. The 300x5 mm tube of cryo-service line is made from A36 type of
steel and is a housing of all cryogenic pipelines and current return.
The tube serves as a vacuum jacket and as a base for the iron core
assembly, and provides mechanical rigidity of the magnet. The magnet
core is periodically (D=0.5m) welded to the tube to increase assembly
vertical stiffness and to reduce system deflection. The combined
structure is rigid enough that supports every 6m (20') are sufficient to
align the structure. Total magnet weight is \~ 33 tonne (\~500kg/m).

###### (b) Magnet yoke

The laminated magnet yoke consists of upper and lower iron half cores.
Core laminations are stamped from 1.5-mm thick low carbon steel. The
stack of laminations is pressed and welded into a block. Two blocks,
upper and lower, separated by two steel spacer bars are welded to the
stainless steel strips from the inside of the central hole. The welds
provide a prestress no less than 5 tons/m to receive high stability of
the pole geometry near the beam gaps. The side gaps remain open for
magnetic measurements and vacuum chamber installation.

The conductor cryostat is positioned in the center of the core hole. All
gaps between core and cryostat are filled by epoxy. Mechanically, the
magnet core and the cryostat are a monolithic structure.

##### 5.1.2.3.2 Transmission line mechanical analysis

###### (a) Vertical deflection and stress between support points

The magnet is installed on the vertical supports. A distance of 6 m was
chosen between supports. Numerical simulations were done in order to
estimate structural stresses and deformations \[1\]. The maximal
deflection of the magnet under weight load is 1.2 -- 2.1 mm, depending
on the final magnet design. In any case, if the magnet core will be
connected with lower vacuum tube by welds, the vertical sag is close to
1.2 mm and maximal stresses will not exceed 50 -- 60 MPa. For bolted
connection without welds the sag is close to 2.1 mm and maximal stresses
reach 90 MPa.

###### (b) Force to introduce sagitta

Magnet horizontal sagitta is \~15 mm over 67 m length (Lring=232km,
Rring=36.9km). To estimate deformations of the straight magnet structure
introduced by this sag during alignment in the tunnel, the numerical 3D
simulations were performing using 12-m section model \[2\]. Over such a
distance the sag is \~0.5 mm. Both model ends had been restricted from
motion. The model with a distributed weight was loaded by horizontal
force applied to the central supports of the vacuum tube. The result
shows the magnet block moves about 0.9 mm for 1 mm movement of the
vacuum tube. The force needed for 1 mm motion is 150 kg, without
estimating friction. Taking into account the load of \~3 tons for each
support, the friction force may be estimated about 300 kg. [Total force
will be \~450 kg]{.mark} per 1 mm displacement. Difference in relative
movement of the iron halves of the magnet can reach 30 μm for a support
movement of 1 mm.

###### (c) Magnetic forces on transmission line

In the ideal case, the magnetic forces equal zero because of the design
symmetry of the two iron poles surrounding the transmission line.
Nevertheless, the iron saturation effect and incorrect position of
superconducting cable will cause uncompensated magnetic forces \[3\].
The magnet air gaps introduce force gradients of 228 kg/mm in vertical
direction and --100 kg/mm in horizontal direction for 1 m length of
drive conductor at 100 kA current. The return conductor has gradients an
order of magnitude less in both directions. The magnetic forces between
transmission lines with 0.29 m vertical separation in the space between
magnets are 700 kg/m and increase to \~4000 kg/m at 10 mm separation.

###### (d) Thermal stress and thermal forces 

The conductor tubes in the transmission line magnet are made of invar
and consist of continuously welded lines. The cool down shrinkage in
this case will be minimized, but is 65 mm over 135 m distance with 67
MPa of thermal stress. Therefore, two invar conductor pipes (A=200mm^2^)
give \~1400 kg tension force applied on the end of the pipe support at 5
K. The radial force on the invar pipe support for ring shrinkage
compensation is small, \~0.12 kg/m.

All other cryo-lines are made from steel or aluminum and can not be
continuously welded because of high thermal stress level. Table 1
describes the situation for different pipe materials after cool down to
5 K.

Table 1. Pipe at 5 K after cool down from 300 K

+-------------+-------+-------+--------+----------+-------+---------+
| ###         | *∫    | *E    | *σ=E\  | *σyield* | *σyie | *       |
| ## Material | αdt,* | (5K)* | *∫αdt* |          | ld/σ* | ∆L(mm)* |
|             |       |       |        | *MPa*    |       |         |
|             | *     | *GPa* | *MPa*  |          |       | *       |
|             | mm/m* |       |        |          |       | L=135m* |
+-------------+-------+-------+--------+----------+-------+---------+
| > 304 SS    | 3     | 220   | 660    | 600-1200 | 0.    | 405.0   |
|             |       |       |        |          | 9-1.8 |         |
+-------------+-------+-------+--------+----------+-------+---------+
| > 6061 Alum | 4.1   | 80    | 328    | 380      | 1.15  | 553.5   |
+-------------+-------+-------+--------+----------+-------+---------+
| > Invar     | 0.48  | 140   | 67     | 700-1000 | 10.4  | 64.8    |
|             |       |       |        |          | -14.9 |         |
+-------------+-------+-------+--------+----------+-------+---------+

The steel pipes have to be equipped with compensation bellows every
\~33m (135m/(405mm/100mm)) to reduce shrinkage to the level of \~100mm
and to avoid stress build up in the end supports.

###### (e) Yoke deflection under magnetic forces

The dipole magnet at maximum field of 2 T has 25 t/m magnetic force
applied to the poles. The force is zero at injection field and rises
during acceleration cycle. This force is taken across support spacers in
the relatively small \~1 cm distance between the transmission line
vacuum jacket and beam pipe. The yoke assembly has to be rigid enough to
keep the air gap stable. Two welds inside the central bore of the magnet
connect both half-cores together and provide pre-stress \~5 tons/m. The
prestress removes all clearances between spacer bars and half-cores. The
1 m model with outer spacer bars was successfully tested at the room
temperature test stand and no field gradient shift was measured up to
1.7 T \[4\].

The test of a short mechanical model with air gaps open on both sides
showed that the left gap shrinks by 12 μm and the right gap by 6 μm
vertically. The horizontal change was less than 4 μm. These changes were
reproducible. They can only influence the dipole field component and can
be compensated by magnet calibration.

###### (f) Mechanical analysis of support spider 

Loads from transmission line magnetic forces are transmitted from the
drive conductor to the pipe, through the supports (spiders) to the
vacuum jacket, and to the magnet core. A cross-section of the drive
conductor transmission line is shown in [Fig. {5.1.2.2-3}.]{.mark}

In the horizontal direction, the conducting cable is a self-centering
system and does not need strong supports. However, the part of the
conductor inside the magnet is at a point of unstable equilibrium in the
vertical direction. The field gradient gives rise to an instability in
which the current-carrying pipe bends into a sinuous curve with a period
of twice the support distance. Therefore, the support interval 0.5 m has
been optimized for lowest conductor displacement (0.5 mm) chosen for
production accuracy and pipe tolerances \[5\].

The conductor is centrally positioned by spiders made from ULTEM, which
has a low value for the thermal conductivity integral. The spider pegs
have a rectangular cross section 2.5x3.5 mm. A flexible ring unites the
four pegs together and serves as a base for thermal shield assembly.
Perfectly positioned pegs are under compression inside the cryostat. The
compression depends on the leg over-sizing and on the variation in pipe
diameter. A 0.5 mm tolerance is required on the roundness of both pipes.
The pressure range is 20-40 kg. These numbers increase up to 70-100 kg
at cold conditions and under action of magnetic force. For verification,
the prototyped injection-molded supports were exposed to 100,000
mechanical cycles with a load force of 300 kg/m (three times the
expected one). Although a discoloration of the ULTEM was observed, the
supports did not break.

The spider acts as a flexible membrane if the relative axial motion of
the inner-cold conductor line and the outer-warm vacuum jacket tube
occurs without sliding. If motion is \~2 mm, the maximum stress in the
spider material due to bending is \~300 MPa. However, the ultimate
strength for ULTEM is169 MPa, and the fatigue limit for 10^7^ cycles is
100 MPa \[6\]. We therefore have a strong requirement for a longitudinal
anchoring system, since the relative pipe motion can be \~20 mm during
magnet transportation or by temperature variation in the tunnel. This
motion is caused by the difference in thermal contraction between steel
and invar under a 10 K temperature change from 330 K. The sliding range
of the peg needs to be carefully verified. If it is insufficient,
another sliding support system can be used \[7,8,9\].

##### 5.1.2.3.3 Transmission line thermal analysis

Transmission line heat load estimates are divided into two components:
the primary heat load on the 4.5 K system and the heat load to the 50 K
shield system. The calculated heat loads are presented in Tables 2 and 3
\[10\].

Table 2. Estimated Heat Loads into 50 K Shield System\
(all values in W/m)

  ---------------------------- --------- -------------------------- -------
  Transmission Line Shield     0.578     Shield Return Header       0.471

  Conductive Heat Load         0.432     Conductive Heat Load       0.199

  Longitudinal Anchor          0.011     Longitudinal Anchor        0.011

  MLI Heat Load /meter         0.110     MLI Heat Load /meter       0.236

  Instrumentation Leads        0.020     Instrumentation Leads      0.020

  Valve boxes                  0.005     Valve boxes                0.005
  ---------------------------- --------- -------------------------- -------

Table 3. Estimated Heat Loads in 5K at Transmission Line and Return Bus\
(all values in W/m)

  ---------------------------- --------- -------------------------- --------
  Transmission Line 5K Flow    0.048     Return Bus 5K Flow         0.014

  Conductive Heat Load         0.040     Conductive Heat Load       0.006

  Longitudinal Anchor          0.0003    Longitudinal Anchor        0.0003

  Radiation Heat Load          2E-04     Radiation Heat Load        5E-04

  Instrumentation Leads        0.002     Instrumentation Leads      0.002

  Valve boxes                  0.001     Valve boxes                0.001

  Splice heat load             0.004     Splice heat load           0.004
  ---------------------------- --------- -------------------------- --------

##### 5.1.2.3.4 Interconnects, pipes, and bellows 

###### (a) Axial anchoring for transmission line and return line

The magnet anchor system consists of the vacuum barriers, the
force-anchors, the transportation locks and the vacuum jacket anchors.
The vacuum barrier or breaks are used to insulate subsystems in order to
facilitate installation, troubleshooting, and repair. It provides a good
vacuum in the transmission line ring section \[11,12\]. The vacuum
barriers are designed to withstand a differential pressure of 0.15 MPa
(\~1000 kg longitudinal force) and to minimize the heat in-leak. It is
made of an all-welded construction of thin-wall stainless steel tubes.
The barrier is electrically insulated from the invar conductor pipes by
ceramic insulators.

![](media/image12.wmf){width="6.2868055555555555in"
height="2.147222222222222in"}Figure 1. [Anchor system for the]{.mark}
[magnets]{.mark}

All magnet pipes will be physically constrained by the vacuum breaks at
same location. Logically, frequency of break location depends on vacuum
pump distribution and is divisible to the magnet length ([67.75]{.mark}
[m]{.mark}). Distance between breaks is not clear yet. 400-500 m comes
from LHC analogy \[13\]. With a [67.75 m]{.mark} interval, only one
magnet will be damaged if insulation vacuum is accidentally lost. We
assume [a period of *n* magnet lengths, where *n*≤4]{.mark}, is
acceptable.

The pipe force anchor restrains thermal forces from invar pipe shrinkage
(5000 kg) during cool-down and warm-up. This anchor consists of tie rods
and G-10 spider, and connects the invar pipes to the vacuum jacket. The
vacuum break and pipeline anchor can be combined into a single unit.

The vacuum jacket is connected to the ground by the jacket anchors at
the end of the magnets. These points define an immovable magnet
cross-section in case of accidental vacuum loss and jacket thermal
contraction resulting from a cool down to about 250 K \[14\]. The jacket
bellows at the interconnect region compensates for a length change.

The transportation lock is located on the opposite end of the magnet
from the vacuum break. It is mounted in place during production and
removed after magnet installation in the tunnel.

###### (b) Cryostat Interconnection

After magnet alignment, interconnection activities will take place. The
magnet and the cryo-service line need to be connected every \~67.5 m.
There are two interconnection regions between magnets, 3.5 m and 1 m
long.

Both conductors will be spliced at these areas. To compensate magnetic,
thermal and hydraulic forces in the 3.5 m region, where transmission
line conductors make a loop and are located close to each other, an
additional set of special spacers, clamps and tension rods will be used.
The weld on the conductor line can apparently take place directly over
the copper/superconductor structure without damaging it \[15\].

Three carbon steel pipes having stainless bellows will be automatically
orbital welded at both areas. Aluminum thermo-shield made from two
pieces will cover all pipeline connections \[16\]. Multi-layer
insulation blankets are mounted around shield to reduce radiation heat
load. The vacuum jacket is connected by a bellows at 3.5 m region and by
a thin steel skin at 1 m region.

##### 5.1.2.3.5 Beam tube mechanical design

![](media/image13.wmf){width="3.9652777777777777in"
height="2.6909722222222223in"}The vacuum system of the transmission line
magnet is an extruded-aluminum system shown in [FigX]{.mark}.
Non-Evaporable Getter (NEG) strips located in a high-conductance
antechamber (see Fig 2) provide primary pumping \[15\]. Lumped
sputter-ion pumps are required every \~100 m to pump methane and noble
gases, which are not pumped by the NEG strip. To start the NEG, a
temperature of XX°C is required.

Figure 2. Magnet beam pipe

High luminosity operations will require a bakeout of the pipe for
surface outgassing and good pumping efficiency. For an aluminum beampipe
this means that entire lengths of a 67 m pipe must be heated in-situ for
24 hours to either 150°C (for aluminum segments), 300°C (for stainless
steel segments), or 350°C (for stainless steel segments with NEG pumps)
\[17\]. Bellows will be required to compensate for the thermal expansion
of beampipe segments every [67.75 m]{.mark}. The BPMs occur every half
cell ([135.5 m]{.mark}). However, the ELETTRA storage ring has an
experience with no in-situ baked out aluminum vacuum chamber \[18\].

Yielding of the aluminum is an issue because of the elevated bakeout
temperature, the use of high-purity aluminum, and the desire for as thin
an extrusion wall as possible in the region immediately above the beam.
Another issue is the beampipe insertion into the yoke gap from the side.
The elliptical beam chamber has to be vertically squeezed in size by 2
mm along its entire length to pass through the pole shim area on the
magnet core. The wall thickness has to be small enough to allow that,
but big enough for buckling stability under atmospheric pressure.
Buckling stability is achieved by a 2 mm pipe vertical extension after
installation. All of these situations were analyzed by ANSYS program.
Results show reasonable stress level in the wall \[19\].

#### References *{ed. note -- for sec. 5.1.2.3}* {#references-ed.-note-for-sec.-5.1.2.3 .Reference-heading}

\[1\] V.Tsvetkov, "Transmission Line Magnet Mechanics", TD TN XXXX 2001.

\[2\] V.Tsvetkov, "Alignment of the Transmission Line Magnet in the
tunnel", TD TN XXXX 2001

\[3\] V.S.Kashikhin, "Transmission Line Magnet for VLHC. Magnetic Forces
and Magnet Deflection," TD TN XXXX. February 2001.

\[4\] V.S.Kashikhin, "Mechanical model 2 test results", TD TN XXXX.
February 2001.

\[5\] M.McAshan, "Cryogenic System for the 3 TeV Injector Study",
Fermilab TN-XXXX,1997

\[6\] I.Novitski, "Analysis of the spider support", TD TN XXXX 2001

\[7\] E.C.Quimby et al., "VJR/VJRR Design, Construction, Installation,
and Performance," ACE, vol 43, New York, 1998.

\[8\] G.Grygiel et al., "Status of the TTF Cryogenic System," ACE
vol.41, New York, 1996

\[9\] K.Hosoyama et al., "Development of a High Performance Transfer
Line System", ACE vol. 45, 2000

\[10\] G.W.Foster, "Transmission Line Magnet R&D", Second Annual VLHC
Meeting, Danfords, Port Jefferson Long Island, NY, Oct. 16-18, 2000

\[11\] V.Parma et al., "The Insulation Vacuum Barrier for the Large
Hadron Collider Magnet Cryostats", ICEC 18

\[12\] B.Jenny et al., "A Composite vacuum Barrier for the LHC Short
Straight Section", ACE vol.41, New York 1996

\[13\] "Technical Specification for a Compound Cryogenic Helium
Distribution Line for the Large Hadron Collider (LHC)", IT-2399/lhc/lhc,
Geneva, Switzerland, December 1997.

\[14\] M. Chorowski, "Risk analysis of the LHC cryogenic system", ACE
2000

\[15\] G.W.Foster, "Status Report on the Transmission Line Magnet",
Fermilab report, September 1997

\[16\] R.C.Niemann, "Model SSC Dipole Magnet Cryostat assembly at
Fermilab", Supercollider 1, New York 1989.

\[17\] "5.6 Beampipe," URL
http://felix.web.cern.ch/FELIX/Loi/HTML/C5/node7.html

\[18\] A. Gambitta et al., "Experience with Aluminum Vacuum Chambers at
ELETTRA", EPAC 2000, Vienna, Austria.

\[19\] I.Novitski "Beam pipe mechanical design" TD TN XXXX 2001.

### 5.1.3 Correctors

The sources of closed orbit distortions which the corrector system must
address are dipole, gradient and sextupole field strength errors.
Various factors and effects (main magnet manufacturing and installation,
iron core saturation, fringing fields, residual fields, and magnet
displacements over time) contribute to these errors. The accelerator
lattice design defines spaces of 3.5 m between combined function magnets
at each half-cell end and 1 m in the middle of the half-cell for
placement of dipole, quadrupole and sextupole correctors (see Fig.1). A
promising approach to optimize corrector strengths is to optimize pole
profiles and correction hole positions of the main arc dipoles for the
minimum and maximum fields. In this case, during only a short period of
time in the acceleration cycle will the correctors need to work at full
power. At maximum field they will compensate residual effects after
magnets calibration.

The main issue for correction system is the high fringing field
generated by the main supply and return 100 kA conductors in the space
between dipole magnets. This field is \~0.3 T at the vacuum chamber
areas and causes large magnetic forces 1000 kg/m applied to the
superconducting cable. The distance between outer shell of
superconducting transmission line and vacuum chamber center is only 30
mm, and it is a nontrivial task to form needed correction field in this
area. There are several options to solve this problem:

1.  Cold ferromagnetic screen with superconducting windings \[1\]

2.  Room temperature horizontal and vertical dipole correctors with iron
    core as a ferromagnetic screen

3.  Room temperature air-cooled correctors with a nearly coaxial
    configuration of transmission line and return bus in the space
    between magnets (described below)

4.  Main dipole pole windings

5.  Iron-dominated correctors

6.  Permanent magnet correctors

All these options were investigated. From the point of view of cost and
operation, the best choice is conventional room temperature air-cooled
magnets (option 3). All other options may be used only if their total
cost will be less than for conventional magnets.

One of the options to minimize the transmission line fringing field is
to bend the main transmission line and place it as close as possible to
return bus (see Fig.1). The bent sections of transmission line at the
arc magnets ends will be forced to the closest iron corrector cores.
Longitudinal anchors should accommodate uncompensated forces. Electrical
insulation should be applied in the space between the two lines which
can withstand \~5 kV voltage during quench. The collar around both lines
should accommodate large magnetic forces. conventional dipole and
multipole correctors can be installed in the magnetic field-free space
between main dipole magnets. For easy installation and replacement, all
correctors can be separated in the median plane, as shown in Fig. 1.
Magnets will have separate power supplies placed nearby to reduce the
cost of cables and operational cost. One consequence to be considered is
that correctors will dissipate power in the tunnel and will give an
extra heat load for the ventilation system.

![](media/image14.wmf)Fig. 1 Correctors installed in the space between
Arc magnets\
{refer instead to previous identical figure}

Table 1. Corrector Parameters

  --------------------------------- ------------- ----------- -------------- -------------
  *Corrector type*                  *Horizontal   *Vertical   *Quadru­pole*   *Sextupole*
                                    dipole*       dipole*                    

  Maximum magnet strength           1.0 T         1.0 T       25 T/m         1750 T/m²

  Field quality, 18mm diameter      1.0           1.0         1.0            1.0
  area, %                                                                    

  Effective magnet field length, m  0.5           0.5         0.5            0.8

  Integrated field at r=1cm, T\*m   0.5           0.5         0.125          0.14

  Half-cell integrated field at     260           260         260            260
  1cm, T\*m                                                                  

  Half-cell field correction at     19            19          4.8            5.4
  1cm,units                                                                  

  Magnet core length, m             0.48          0.48        0.5            0.5

  Current, A                        25            25          1.0            1.0

  Voltage, V                        15            15          140            175

  Power, W                          400           400         150            200

  Number of coils per magnet        2             2           4              6

  Number of turns per coil          328           328         1240           633

  Copper conductor, mm              5 x 5         5 x 5       ǿ 1            ǿ 1

  Copper weight, kg                 242           ?           40             50

  Core weight, kg                   300           ?           30             50
  --------------------------------- ------------- ----------- -------------- -------------

#### 5.1.3.1 Dipole correctors

![](media/image15.wmf)

Fig. 2. Horizontal Corrector

#### ![](media/image16.wmf)5.1.3.2 Quadrupole correctors

Fig. 5. Quadrupole correctors

Fig. 6. Flux lines in quadrupole corrector Fig. 7. Magnetic field in
corrector air gap

#### 5.1.3.3 Sextupole correctors

*{figs 3,4, 6-10 have been removed}*

#### References: *{ed. note -- for sec. 5.1.3}* {#references-ed.-note-for-sec.-5.1.3 .Reference-heading}

\[1\] TD Note N xxxxx

*{HDG -- Should we have some text giving a brief description of each
type of corrector? Or are the pictures themselves enough? Are the field
distribution pictures really essential?}*

### 5.1.4 Interaction Regions

VLHC has provisions for two large colliding experiments located on the
present Fermilab site. The beam interaction points will be located
symmetrically from the two non-interaction beam crossing points. The
closest crossing point is 13 half cells or 1700 meters from the
interaction points.

A system of magnets on each side of the interaction regions is required
to bring the beams into collision. With these magnets comes additional
requirements for the accelerator including power supplies, beam
absorbers to protect the magnets and prevent activation of the tunnel,
and an alignment system for the magnetic elements. For the
superconducting magnets there is quench protection system, cryogenics,
and interconnects for room temperature to cold transitions of
instrumentation and powering.

Figure 1 shows a schematic of the interaction regions magnetic elements.
Each interaction region spans a space of 6 half cells, from 20 meter to
approximately 810 meters from the interaction points. The interaction
regions consist of four high gradient "inner triplet" quadrupoles, two
separation dipole elements, and an outer system of lower gradient
quadrupoles. There will also be orbit and local field corrector magnets.
The separation dipoles, "outer" quadrupoles and correctors are used in
other parts of the accelerator and are thus described in section 5.1.5.
The high gradient inner triplet quadrupole is described below.

![](media/image17.wmf){width="4.897222222222222in"
height="2.5444444444444443in"}

Figure 1. Principal magnetic elements for the VLHC-1 interaction region.

#### 5.1.4.1 Low-beta IR quadrupoles

These magnets form the final focus at the two collision points. The
required gradient is 300 T/m with a length of 10 meters and a single
aperture of \~80 mm. The field quality must be very good because the
beams could be separated by as much as 12.5 mm due to the crossing
angle.

A design developed by INFN-LASA for a possible upgrade of the LHC low-β
quadrupoles, with an aperture of 85 mm \[1\], can be used as a starting
point to meet these requirements. The basic design as shown in figure 1
has two Nb~3~Sn layers in a cos (2Θ) geometry, wound using the cable
described in Table I. The cable has a target critical current density of
3000 A/mm^2^ @ 4.2 K, 12 T \[2\]. Internal splices can be avoided using
the double pancake technique. The main characteristics of the magnetic
design are reported in Table II. The field quality of the basic design
(aperture = 85 mm) gives acceptably low values for the allowed
harmonics. The value of the b6, b10 and b14 multipoles, normalized to
the gradient and using a 10 mm reference radius are respectively 1.5
e-6, 1.6 e-8 and \< 1.0 e-9. The relative field error is lower than 1.1
e-5, at 12.5 mm from the center on the midplane. Iron saturation effect
has to be studied.

Table I: Conductor characteristics

  ------------------------------------------ ----------------------------
  Superconductor                             Nb~3~Sn

  Critical current non Cu (@ 4.2K 12T)       3000 A/mm^2^

  Strand diameter                            0.825 mm

  α = Cu/nonCu                               1.3

  Number of strands                          36

  Cable dimension                            1.34 ÷ 1.60 x 15.0 mm^2^

  Effective filament diameter                \< 40 μm
  ------------------------------------------ ----------------------------

![](media/image18.wmf){width="3.298611111111111in"
height="2.040277777777778in"}

Figure 2 Basic design cross section with field quality at maximum
gradient

> Table II: Magnetic design characteristics at short sample limit

  -------------------------------------- --------------------------------
  Aperture                               85 mm

  Gradient                               300 T/m

  Current                                20218 A

  Self inductance                        4 mH/m

  Stored energy                          820 KJ/m

  Horizontal Magnetic force (per octant) 2.78 MN/m

  Vertical Magnetic force (per octant)   3.43 MN/m

  Number of turns                        10 + 4 + 19

  Collars thickness                      20 mm

  Iron inner radius                      93.5 mm
  -------------------------------------- --------------------------------

The quench protection has been studied at an operating current
corresponding to 93% of the short sample limit. Simulations were
performed using a version of the QLASA code \[3\] modified at Fermilab
\[4\] for the study of FNAL Nb~3~Sn high field magnets. These studies
show that full coil coverage by heaters on both layers is required, and
the delay time between the spontaneous quench start and the beginning of
the heater-induced quench must be very short. This solution has an
impact on magnet technology, because if the insulation of the heaters
between the inner and outer layers cannot withstand the conductor heat
treatment, the double pancake technique must be abandoned. Furthermore,
protection redundancy will not be possible (or at least very
complicated) and fault scenarios have to be addressed. The short time
delay necessary to avoid excessive hot spot temperature and the lack of
protection redundancy should be the object of an appropriate R&D.

A possible solution for the mechanical design is the one proposed for
the upgraded version of the LHC IR low-beta quadrupoles presented in
\[5\]. It uses 20 mm thick stainless steel collars, which can provide
part of the required prestress and magnetic force containment. The rest
of prestress and support are provided by a thick skin. The yoke is only
in contact with the collars close to the midplanes, in order to transfer
the stress from the skin to the coils where it is most necessary. The
effectiveness of this design for the higher forces developed in the VLHC
IR quadrupoles is still under investigation. A finite element analysis
of coils and collars, simulating the rest of the mechanical structure by
use of an external load, showed that the maximum stress in the coil can
be kept below 160 MPa. The design of yoke, skin and contact regions must
still be optimized to provide the required support on the coils.

In summary, it can be concluded that a two layer design using Nb~3~Sn at
4.2 K is a good candidate to meet the requirements for these magnets, if
the critical current target is reached. Some design optimization will be
required for the quench protection and mechanical design.

#### 5.1.4.2 Interaction Region Subsystems

Most of the 800 meters of the interaction region will be in the standard
VLHC tunnel. Since these magnets elements need to be "tunable" they
require a special gallery to handle the power supply and electronics of
these magnets. There will likely be a global alignment system that
connects the experiments to the final focussing elements. Finally, the
tunnel will need to be wider near the IP to accommodate the extra
shielding and vacuum connections and instrumentation associated with the
collision detection and IP interconnect.

Four independent power systems are required for each side of an
interaction region: one for the inner triplet, one for each separation
dipole and one for the outer quadrupoles. Additional quadruples in the
IR region will likely be powered in series with other straight section
quadrupoles in the accelerator and are not include here. The high
gradient quadruples require a 25 kA, 10 Volt supply, the conventional
separation dipoles require 1 kA, 100 Volt supplies while the
conventional outer quadrupoles need a 7kA, 10 volt supply. Correctors
will be powered independently with supplies comparable to the outer
quadrupole conventional magnets.

Superconducting circuits will rely on quench heaters for protection.
With the relatively small amount of stored energy (50 MJ) and small
number of magnets/circuit (4 or less) it is not clear whether the
complications of an extraction circuit and bypass diodes are worth the
effort. Thus, in the event of a detected spontaneous quench, the circuit
power converter will be phased off, all quench protection heaters on all
the magnets in a circuit will be energized.

As stated, inner triplet quadruples will likely need protection levels
comparable to or greater than a similarly sized LHC IR quadrupole
magnet. Thus 4-8 quench heater circuits plus the requisite electronics
are required for each magnet. The total space for power supplies and
electronics required for each quench heater circuit is approximately 2
6U VME crates. Thus a space of approximately 70 6U crates are required
for each side/IR.

LCW and electrical power will be required for the power supplies and
conventional magnet. The LCW system will be required to deliver several
hundred liters/minute per IR.

Superconducting magnets rely on 4.5 K helium. The estimated dynamic heat
load/side/IP will be approximately 600 Watts or 2.4 kW for both
interaction regions \[6\]. Local heating in the quadrupoles could be
quite large due to the strong focusing elements (G.dl \~ 3000 T/m \*m).
This could be a non-negligible load on the Phase I cryogenic
requirements.

This heat load, if taken directly by the 4.5 K helium will require
approximately ½ of a VLHC-1 power plant. Thus the cryogenic plant
located on site would have to be upsized. Since the IR temperature and
pressures profiles and requirements will differ from the transmission
lines, there will likely be a need to be a separate transfer line from
the cryogenic system. The helium requirements might be reduced by
carrying away some of the heat load by actively cooled absorbers in the
80 mm beam tubes.

A distribution box will be required in order to make a connection
between the room temperature and cryogenic electrical elements, as well
as supply the cryogens to the magnetic elements. Elements include
voltage taps, strip heater leads, thermometry and other cryogenic
instrumentation. 25-30 kA HTc leads would be used to supply the
excitation currents.

A particle absorber system will be required to protect the IR magnets
from the excessive radiation from particles produced from the
interaction region. Using the LHC as a guide, the system will require a
hadron and neutral particle absorber. The primary hadron absorber will
be located on the IP side of the inner triplets. The size of the
absorber will be comparable to the LHC absorber but will have
significantly larger heat loads, estimated to be 2 kW per IR \[7\]. Thus
an actively cooled absorber will likely be necessary. The neutral
absorber, located between the separation dipoles would be necessary to
protect the outer quadrupoles, possibly the transmission line magnets
and the walls of the tunnel from activation. It, too, will likely need
to be actively cooled. If water cooled the requirements would be modest
and would be parasitic to the magnet and power supply LCW system.

Alignment tolerances are likely to be comparable to those of the LHC
Interaction region. Transverse alignment tolerances will thus need to be
on the order of 100-300 microns over both sides of the IP. Thus an
alignment system will be required to tie together the two sides of the
IR and the detector.

#### References *{note -- for sec. 5.1.4}* {#references-note-for-sec.-5.1.4 .Reference-heading}

\[1\] G. Ambrosio et al. *"Preliminary Proposal of a Nb3Sn Quadruple
Model for the Low-beta Insertions of the LHC"* INFN Report,
INFN/TC-95/25, Sept. 13, 1995.

\[2\] R. Scanlan, *"Conductor Development Program"* Low Temperature
Superconducting Workshop, Santa Rosa (CA), Nov. 8-10, 2000.

\[3\] M. Canali, L. Rossi, *"DYNQUE: a computer code for quench
simulation in adiabatic multicoil superconducting solenoids"*, INFN
Report, INFN/TC-93/06, 1993

\[4\] L. Imbasciati, G. Ambrosio, P. Bauer, V. Kashikhin, A. Zlobin,
*"Quench Protection of the Common Coil Racetrack (CCRT-1)-Results of
Adiabatic Model Calculations",* TD-00-056, FNAL (Sept. 2000)

\[5\] G. Ambrosio, G. Bellomo and L. Rossi, *"A 300 T/m Nb3Sn Quadrupole
for the Low-beta Insertions of the LHC"*, Proc. of EPAC96, Sitges
(Barcelona), p. 2290.

\[6\] Nikolai Mokhov, private communication

\[7\] Bill Turner, private communication

### 5.1.5 Special Collider Ring Magnets

This section covers mostly different magnets installed in the straight
sections of the ring. Totally there are 10 straight sections, 5 in each
half of the ring. On the Fermilab side there are two Interaction Region
straight sections, two Utility straight sections and one Beam Crossing
straight section. Straight sections on the opposite side of the collider
basically are the mirror reflection of what is on the Fermilab site
except that there are no IRs and utility equipment installed in this
area. As a transition from an arc to a straight section, a matching
dispersion suppression section cell is used, described in section 3.2.

Beam focusing in the straight sections is provided using a classical
quadrupole triplet cell made of four quadrupoles of equal integrated
strength of 427 T. The basic cell half-length is about 135.5 m that
gives a scale of space that can be used to install required equipment.
Quadrupoles of the triplets are installed back-to-back in both rings
providing focusing in different directions for different rings. The
basic beam-beam spacing of 150 mm and required beam pipe size of 20 mm
implies certain restrictions on the achievable quadrupole field
gradient. The chosen reference gradient of 70 T/m results in the basic
quadrupole length of 6.1 m. Taking into the account this length and
space between the quadrupoles in the focusing cell, only a 100-m gap is
available for the utility equipment. When this space is not enough, or
when some special features are to be introduced into beam optics,
modifications of focusing lattice are to be done.

#### 5.1.5.1 Straight section quadrupole

Focusing quadrupole has been designed so that pair of them can be
installed back-to-back in both rings. This gives certain flexibility
when increased beam separation is used in the Utility section. The lens
uses water-cooled windings. Preliminary magnetic design indicates that
field quality is not going to be a problem for this lens: there is
plenty of space to make needed pole shaping. Magnetic field in steel is
quite acceptable, reaching 1.9 T at the pole base, but there are regions
in the minimal pole separation area where field exceeds 2.0 T at 70 T/m,
so good quality low carbon steel must be used for lens fabrication.
Table 1 summarizes the quadrupole parameters.

Table 1. Parameter list of a conventional straight section quadrupole

  --------------------------------------------------------- -------------
  Gradient, T/m                                             70

  Pole spacing, mm                                          22

  Length, m                                                 6

  Width (mm)                                                148

  Height (mm)                                               168

  Number of coils per winding                               4

  Number of turns per coil                                  12

  Conductor cross section area, mm^2^                       61.5

  Resistance of the winding                                 0.177

  Rated current, A                                          283.3

  Voltage drop, V                                           53

  Power consumption, kW                                     15

  Conductor hole diameter, mm                               5

  Water temperature rise at 1 MPa (deg. C)                  15
  --------------------------------------------------------- -------------

For this study, we tried to use conventional quadrupoles because this
provides more flexibility and freedom to install the devices in areas
where absorbed radiation power can question performance of
superconducting devices. Nevertheless, superconducting quadrupole has an
advantage of higher gradient and can be used when appropriate or when
space requirements become a critical issue \[1\].

#### 5.1.5.2 Beam Cross-Over Section

The two beam cross-over regions in the collider are introduced to make
perimeters of the rings in the collider equal. To accommodate the
magnets in the cross-over region a short straight section is used that
consists from the only focusing cell that differs nevertheless from the
basic focusing cell. At the input into the cross-over region, the ring
beams are in the horizontal plane separated by 150 mm. To make a
cross-over, it is necessary to bring the beams together horizontally,
separate them vertically before the crossing, and make the opposite
transformation after the crossing. Vertical shift of each beam, which is
required to eliminate beam-beam interaction effects, is 4.5 mm that
results in the beam-beam separation of 9 mm, more that 18σ. To reduce
number of magnets required for beam manipulation, tilted dipoles are
used to bend beams both horizontally and vertically. The cell layout is
shown schematically in the Fig. 1.

![](media/image19.wmf){width="4.251388888888889in"
height="2.354861111111111in"}

Fig. 1 Cross-over straight section layout

Magnet length L~m~ and tilt angle θ can be found based on defined
magnetic field level and length of gaps between the magnets in the
string. As it is in the arc dipoles, transmission line is used for
magnet excitation. More over, because of the large required pole width
of the magnet, return line is also used as active part of the magnet
excitation wiring. To minimize iron core saturation effects, magnetic
field was chosen of the same level as it was for the arc dipoles:
B~m~=1.95 T. This results in magnet length of 34.95 m and tilt angle of
θ = 6.84° if 2-m gap is assumed between the magnets. The total length of
the beam cross-over magnetic system is then about 150 m as it can be
seen on the picture in the Fig. 1. The dipole gap is 44 mm to
accommodate the two beams with their vacuum pipes while tilted. Pole
width provides good field region for beams separated by 150 mm. Because
of big difference in the gap thickness for the pole and flux return
regions, force applied to the cable is significant, up to 2000 kg/m for
this magnet. Special arrangements must be made to strengthen the cable
\"spider\" to the needed level at this location. Magnet cross-section is
shown in Fig. 2.

![](media/image20.wmf){width="4.225in" height="2.7069444444444444in"}

Fig. 2. Beam crossing dipole

To allow 150-m gap for the tilted magnet installation, basic focusing
cell was modified, that resulted in increased length of the cell
quadrupoles: 19 m for each of the two inner quadrupoles and 17 m for
each of the two outer quadrupoles. Significantly increasing the basic
quadrupole length above 6 m would result in the increased cooling water
temperature rise, so the total required focusing strength can be
obtained only by increasing the number of quadrupoles. The length of one
of the quadrupoles in the quadrupole strings can be adjusted to 6.8 m
for inner quadrupole sets or to 4.8 m for outer quadrupoles. So, totally
for the each of the two cross-over sections we need:

6.1-meter quadrupoles - 8,

4.8-meter quadrupoles - 2,

6.8-meter quadrupoles - 2.

#### 5.1.5.3 Conventional Magnets for Interaction Region

As described in section 5.1.4, the IR straight section requires certain
beam manipulation to allow using of low-beta high gradient quadrupoles.
For this purpose, so called \"separation/recombination\" dipoles are
used that bring the two beams together within the low-beta lens string
region and place the beams onto the nominal orbits before they go into
the regular part of the straight section (see Fig. [??]{.mark} in sect.
5.1.4).

Existing transmission line cable is used for excitation of these
magnets, as in the case for the cross-over section. A 1.95 T maximal
magnetic field in the dipoles has been chosen as in the arc dipoles. The
magnet length needed to make a 75 mm beam shift within the available 120
m gap in the lattice is 28 m. Beam displacement inside the dipole of the
specified length is about 12 mm. This displacement must be taken into
account when good field region of the dipoles is specified.

To bring the beams together, the \"recombination\" dipole bends
simultaneously the two beams separated by 150 mm. This requires one
direction of bending field for both beams. \"Separation\" dipole
separates beams moving in the opposite directions. Final beam separation
at the outer edge of the magnet is 24 mm. To reduce force applied to the
transmission line and to avoid field asymmetry, a symmetrical iron core
configuration was chosen. The magnet cross-section is shown in Fig. 3.
Good field region area for this dipole is 35 x 20 mm, which is enough to
accommodate the two shifted beams.

![](media/image21.wmf){width="3.098611111111111in"
height="2.204861111111111in"}

Fig. 3. Separation dipole.

The double-channel separation dipole makes use of both excitation and
return transmission lines for excitation. As it was for the single
aperture dipole, gap height is 26 mm. Maximal force applied to the
superconducting cable is about 65 kg/m at maximal field strength. Magnet
cross-section is similar to Fig. 2 above, except the pole gap and pole
width are smaller resulting in a more compact magnet with 650 x 350
mm^2^ cross-section. Good field area of the dipole is 185 x 20 mm^2^,
which is slightly larger than is necessary for this dipole location.
This allows using the dipole in the utility straight section where
larger beam separation is required.

Besides the separation/recombination dipoles, each of the two IR
sections requires a set of focusing quadrupoles similar to described in
section 5.1.5.1. Quadrupoles with lengths longer than 6.1 m are made by
combining two quadrupoles, one of them of a complimentary length. For
each IR, the table below provides the needed number of lenses:

6.1-meter quadrupoles - 34,

4.4-meter quadrupoles - 4.

#### 5.1.5.4 Utility Section Conventional Magnets

Utility straight section is introduced into the ring lattice to provide
needed space for various accelerator systems like RF accelerating
station, injection, extraction, and abort system. In the utility
sections, where RF sections are installed, required beam separation is
450 mm. To manipulate the beams, separation dipoles are used similar to
that used in the IR sections. At the input and the output to the
section, these dipoles have gap width that accommodates both beams. In
the middle of the section, individual separation dipoles installed in
parallel, back-to-back are used for each ring. Cross-section of the
dipoles can be found above (Fig. 2 and 3). Length of the dipoles in the
utility section is 25 m, which allows shifting of each beam by 150 mm
within the available space of 235 m, as shown in Fig. 5 below.

For beam focusing a total of 48 quadrupoles are used in the utility
section. 40 of them have gradient of 70 T/m and they do not differ from
the straight section quadrupoles described earlier. Quantity and lengths
of the 70 T/m quadrupoles are summarized below:

6.1-meter quadrupoles - 28,

4.3-meter quadrupoles - 12.

The remaining 8 quadrupoles are installed in the abort section and are
described below.

Because it provides needed interface with Tevatron, used as an injector,
and with beam dump facility, it is relevant at this point to refresh
injection/extraction scheme of the machine. As it was described in
section 2, the Tevatron run bipolar is used to inject protons into the
collider rings. Beams for both collider rings are extracted using two
sets of equipment installed at B0 area. Two identical injection transfer
lines end at the corresponding collider downstream utility section where
injection lambertsons and kickers are installed (see Fig. 4).

![](media/image22.wmf){width="3.8506944444444446in"
height="1.7013888888888888in"}

Fig. 4. Injection and beam abort system scheme

Transfer lines use permanent dipole and quadrupole magnets, which looks
logical taking into the account fixed injection energy. At the end of
the transfer channel, Lambertson and dipole magnets bring proton beam
into position close to an appropriate ring where it moves almost
parallel to the equilibrium orbit crossing it in the horizontal plane.
At the location of the crossing, a kicker magnet adjusts injected beam
propagation direction, so that it follows as close to the equilibrium
orbit as reasonably possible. All these magnets belong to the injection
system described below. The layout of the utility section that includes
injection line elements is shown in Fig. 5.

![](media/image23.wmf){width="3.926388888888889in"
height="2.439583333333333in"}

Fig. 5. Utility straight section

##### 5.1.5.4.1 Injection System

30 meters of pulsed kicker magnets with magnetic field 0.05 T provide
the horizontal angular kick of 0.5 mrad to the injected beam. Horizontal
beam displacement in the beginning of the kicker magnet string is 7.5
mm. The nearest Lambertson with the 25 mm horizontal separation of the
injected beam from the orbit is installed 35 meters before the kicker.
With the magnetic field level of 0.5 T in the lambertsons, 30 m of
magnets is required to achieve vertical beam separation of 75 mm.
Vertical angular kick provided by the lambertsons is 5 mrad. Beam
displacement inside the lambertsons in the horizontal plane is about 15
mm; this sets requirement for the field free region depth of about
40 mm. A set of dipole magnets with magnetic field of 0.8 T and total
effective length of 37.5 m brings beam angular kick to 15 mrad with
vertical separation of 450 mm and horizontal separation of 59 mm. An
additional set of dipoles with gap field of 0.8 T and total length of
about 56 m is installed to bring angular kick to the required 30 mrad
value \[3\]. The total longitudinal space required to place injection
magnets is about 135 m, which fits comfortably into the available space
in the utility section.

The duration of the kick provided to the injected beam is about 20 μsec
and is defined by the length of the extracted beam from the Tevatron.
Kicker magnetic field rise time is about 150 nsec; this defines time
separation between the next two (of 72) injected batches. To allow a
reasonable amount of time for the abort kicker current rise, a
3 microsecond gap is arranged between the first and the last injected
batches. This gap also sets requirement for the current decay time in
the injection kicker. Because the kicker magnet must be rather fast,
working in the MHz frequency range, it is difficult to use high magnetic
field in this device. As a reliable reference field value, 0.05 T field
strength is used for this study, close to that used for SSC injection
system with similar pulse shape requirements \[2\]. The system is
composed of 30 separate modules, each 1 m long. Each module is fed by an
individual pulse forming network (PFN). A C-shaped magnet is made from
ferrite blocks and with additional capacitors forms a twelve-cell lumped
delay line with a characteristic impedance of 16.6 Ohm. The ceramic beam
pipe has thin resistive coating on the inside surface, and conductive
strips for image current on the outside. Table 2 lists the injection
kicker system parameters. Equivalent PFN/kicker circuit does not differ
much from the SSC \[2\].

Table 2. Injection kicker system parameters

  ---------------------------------------------- ------------------------
  Impedance (Ohm)                                16.6

  Maximum field (T)                              0.05

  Maximum current (kA)                           2.1

  Maximum voltage (kV)                           70

  Total length (m)                               30

  Number of modules                              30

  Rise time (0 to 100%) (nsec)                   150

  Fall time (μsec)                               3
  ---------------------------------------------- ------------------------

**Injection system Lambertson** makes use of permanent magnets for field
generation. Cross-section of the injection Lambertson is shown in Fig.
6. The magnet pole is made of a solid piece of annealed, low carbon
steel to reduce magnetic field in the field free region. To simplify
vacuum problems, both pole pieces are enclosed within a thin-wall
stainless steel shell. The pole gap is fixed with the use of stainless
steel spacers. For magnet excitation, high strength Nd-Fe ferrite blocks
are used that can provide needed gap field.

![](media/image24.wmf){width="4.8in" height="2.6395833333333334in"}

Fig. 6. Injection Lambertson magnet

Transfer channel dipole magnets, that do not have field free region,
have been designed using the same permanent magnet approach, and allow
higher gap field. Vacuum pipe is used for beam transportation in the
magnets, so no vacuum skin is needed. Because separation between the two
rings changes to 450 mm in the utility section to accommodate RF
section, installation of the transfer line quadrupoles and bending
dipoles is straightforward. The transfer line magnets are described in
\[3\].

##### 5.1.5.4.2 Beam Abort System

The abort magnet system consists of a kicker magnet, Lambertson, and a
beam sweeper. Beam normally goes through the field free area of the
Lambertson magnet. Whenever it is necessary to dump the beam, kicker
magnet provides needed radial kick to beam, and the beam is bent by the
Lambertson in vertical direction into a beam dump channel equipped with
a beam sweeper. So at each moment, magnetic field of the kicker,
lambertson and sweep-magnet must be related to the beam energy. On its
way from the kicker to the Lambertson, the beam that must pass through
the set of quadrupoles as shown in Fig. 5, acquires a radial
displacement of 17 mm, making it impossible to use a regular focusing
quadrupole described earlier in section 5.1.5.1. Special quadrupole with
enlarged horizontal aperture has been designed for this area. For this
quadrupole, lower field gradient (of about 45 T/m) can be achieved, and
longer quadrupole lengths are required for beam focusing. Table 3
summarizes the major abort quadrupole parameters.

Table 3. Main Parameters of the special quadrupole

  --------------------------------------------------- -------------------
  Gradient, T/m                                       45

  Aperture radius, mm                                 20

  Quadrupole width, mm                                260

  Quadrupole height, mm                               260

  Length, m                                           10

  Number of coils per winding                         4

  Number of turns per coil                            12

  Conductor size, mm                                  11.7x11.7

  Conductor cross section area, mm^2^                 104

  Resistance of the winding, ohms                     0.174

  Rated current, A                                    625

  Voltage drop, V                                     120

  Power consumption, kW                               73.6

  Hole diameter, mm                                   6.35

  Water pressure drop, MPa                            2

  Cooling circuits per winding                        8

  Water temperature rise (deg. C)                     30
  --------------------------------------------------- -------------------

A longer quadrupole results in higher power consumption and cooling
water temperature rise. Using two 5-meter quadrupoles instead of one
10-meter, it is possible to have a lower water temperature rise at the
expense of higher total water flux. A total of eight 5-meter quadrupoles
are then to be installed.

**Kicker magnet** switches the beam between the ring orbit and the abort
channel; its strength is chosen to provide needed beam separation of 17
mm at the entrance to the abort Lambertson located 300 m downstream.
Assuming kicker field strength of 0.2 T, required length of a kicker is
30 m. Cross-section of the kicker is shown in Fig. 7.

![](media/image25.wmf){width="3.7125in" height="2.0208333333333335in"}

Fig. 7. Abort System Kicker Magnet

Current rise time of injection kicker is about 3 μsec, so a beam abort
gap in the ring beam of about 3 μsec is needed. This requirement results
in using a high frequency magnetic material for magnet core fabrication.
Mn-Zn MN8CX (Ceramic Magnetics) ferrite was chosen for this study. The
core is made of ferrite blocks and assembled using epoxy bonding after
windings and ceramic vacuum pipe are installed inside. At nominal field
of 0.2 T, windings current is 2410 A. Maximal field in the core is about
0.45 T, which is below the material saturation level. Pole width was
optimized using pole profiling by attaching 1-mm ferrite stripes near
the pole wedges. With this shaping, field uniformity in the entire
vacuum pipe region is within 0.1 %, which is good enough for this
device. In the configuration shown, magnet inductance is 2.5 μH/m. Ten
3-m sections are used, installed one following another, with each
section having 7.5 μH inductance and 2.5 ohm resistance. Each section is
fed independently by its own pulser.

The abort kicker pulser uses a two-stage scheme. The first stage
delivers high voltage for a fast current rise time. Capacitor discharge
is used at this stage. Then, in the second stage, a long SCR regulated
pulse with much lower voltage is used to support needed flat top level.
For the three-meter section, discharge capacitor with C = 0.5 μF insures
needed current rise rate. This results in the maximal voltage at the
first stage of 9600 V. Energy stored in the capacitor bank or in the
magnetic field is about 25 J, a modest energy scale.

Flat top length for the abort kicker magnet is defined by the ring
circumference and is about 800 μsec. To have this long pulse shape, a
separate power source must be switched on when current in the primary
circuit starts to decay. Because this is a typical long-pulse pulser
implementation (see, for example, \[2\]), we will not go into further
details.

**Lambertson magnet** uses superconducting transmission line as an
excitation winding. This ensures that at each moment magnetic field is
proportional to the beam energy. The magnet cross-section is shown in
Fig. 8.

![](media/image26.wmf){width="4.3in" height="3.0097222222222224in"}

Fig. 8. Lambertson magnet

The magnet part that includes field free beam channels is placed inside
a stainless steel vacuum box. Only one field free channel is used in
this device; another channel has been added to obtain needed symmetry.
Magnetic field in the field free area limits the maximum field in
Lambertson magnet. The deflecting gap field value of 0.8 T was chosen to
have field in the field free region on the level of 20 Gauss. The 67 m
total length of the Lambertson gives the beam a kick of 0.8 mrad that
results in at least 200 mm of beam separation at the location of the RF
cavities. Force applied to the transmission line is about 25 kg/m for
this magnet. Main parameters of the Lambertson are summarized in Table 4
below.

Table 4. Main Parameters of abort system Lambertson Magnet

  ------------------------------------------- ---------------------------
  Maximum field, T                            0.8

  Total length, m                             67

  Air gap, mm                                 20

  Field homogeneity, %                        0.1

  Maximum field in the hole, Gauss            20

  Maximum current, kA                         100

  Weight, kg/m                                330
  ------------------------------------------- ---------------------------

**Sweeping system** is introduced to reduce heating of the dump block by
distribution of beam energy through a larger dump surface area. Although
reliability of this sweeping system must be high, the field quality
requirements for sweeping magnets can be quite modest, allowing about
10% of field uniformity in the sweeping magnets. Sweeping magnets
deflect beam in X and Y direction with amplitude that corresponds to
beam striking the dump block at a location close to its radial
dimension. If phase difference between X and Y oscillations is 90°, beam
projection on the dump surface will move along a circular path. The
velocity of this movement must be high enough to allow beam circling
around the block at least twice during the extraction time, \~800 μsec.
This requires about 2 kHz of beam oscillation frequency. Required
magnetic strength of the sweeping magnets must be about 12 T⋅m in each
direction. 0.3 T of field strength was chosen for this device, resulting
in 40 m magnet. Taking into account possible steering mistakes due to
kicker malfunction and larger beam size in cases of emergency
extraction, required aperure must be about 50 mm. To make the system
simple and reliable, the two steering systems are combined in a single
unit, as shown in Fig. 9.

![](media/image27.wmf){width="4.697222222222222in"
height="3.4194444444444443in"}

Fig. 9. Sweeping magnet cross-section.

Field uniformity in this magnet is at an acceptable level of about 5% at
reference radius of 15 mm. Positive sextupole component in the whole
aperture results in additional beam defocusing on the target. Magnet
yoke is made of standard toroidal iron powder cores T520-40D by
Micrometals. Core effective permeability is 60 to 150 in the frequency
range up to 100 kHz and in the flux density range up to 1 T. Main
parameters of the magnet are sumarized in the Table 4.

Table 4. Sweeping Magnet Parameters

  ------------------------------------------ ------------- ---------------
  *Parameter*                                *Unit*        *Value*

  Magnetic field                             T             0.3

  Magnet length                              m             40

  Maximum field in the core                  T             0.45

  Stored energy / meter                      J/m           160

  Number of turns                                          2 x 8

  Wire diameter                              mm            5

  Maximum current                            A             2000

  Inductance                                 μH            2 x 80
  ------------------------------------------ ------------- ---------------

For safety reason, sweeping magnet is made of 10 separate 4-m sections
powered by independent pulsers. Simultaneous failure of two sections,
which is a very low probability event, does not compromize safety of the
unit. For each section, current in the magnet windings is supplied by a
simple pulser that utilizes capacitor bank discharge onto the windings.
For each 4-meter section, capacitance required to have oscillation
frequency of 2000 Hz is about 20 μF. With circuit impedance of 4 Ohm and
resistance of windings at 2000 Hz of about 0.1 Ohm, one can expect
periodic discharge with a rather low rate of current decay. Adding some
resistance to the circuit, it is possible to adjust decay rate to a
desirable value to ensure a better beam current distribution through the
dump block surface. Maximal voltage is about 8000 V, requiring about
12000 V of windings and capacitor bank insulation rating because high
reliability of the system is required. This voltage and current level,
and also relatively low frequency, allow using very reliable
semiconducting switching devices like SCRs, and besides can allow a
reserve.

Summary.

-   Lattice arrangements in straight sections allow placement of sets of
    magnets for beam injection, abort, IR, and cross-over systems

-   Feasible design solutions have been found for major systems

-   Magnets located in straight sections can be made using conventional
    technology

#### References *{note -- for sec. 5.1.5}* {#references-note-for-sec.-5.1.5 .Reference-heading}

\[1\] V.V. Kashikhin, I. Terechkine. \"Superconducting straight section
quadrupole magnet for low-field VLHC\", FNAL, TD-01-008, Feb. 2001.

\[2\] Conceptual design of the Superconducting Super Collider.
SSC-SR-2020, DE93 007234.

\[3\] J. Volk, Injection transfer line magnets. TD note \# [????]{.mark}

### 5.1.6 Magnet Production

Construction of the VLHC Stage 1 accelerator will require the
fabrication of several thousand magnets. The largest and most numerous
of these are the combined function arc magnets. They, along with the
dispersion suppressor dipoles, represent the majority of magnet costs.
They are also the most technically challenging as they are a significant
departure from existing magnet technology and, because of their extreme
length, require unique assembly procedures and facilities. All of the
other required magnets are variations of magnets previously produced for
other accelerators. They do not pose any significant technical challenge
as fabrication methods are well understood and a board experience base
exists at various facilities within the labs and in private industry. A
breakdown of magnet type and quantities is shown in Table 1.

Table 1. Magnets required for the VLHC Stage 1.

  ---------------------------------- ------------------- -----------------
  **Magnet Type**                    **Magnetic Length** **Quantity
                                                         Required**

  Combined Function Dipole/Quad      65.75M              3136

  Dispersion Suppressor Dipole       48.8M               160

  Quadrapole                         6.0M                160

  Quadrapole, Large Aperture         10.0M               10

  Dipole Corrector                   0.5M                3460

  Quadrapole Corrector               0.5M                3136

  Sextapole Corrector                0.8M                3136
  ---------------------------------- ------------------- -----------------

It is important that the magnet fabrication schedule be well coordinated
with the construction of the tunnel to permit installation as soon as
the magnets are built. This is especially important in order to minimize
magnet storage requirements of the combined function arc magnets. The
fabrication schedule is assumed to occur over a six-year period with
magnets being installed in the tunnel almost immediately after being
produced and tested.

The extreme length of the combined function and dispersion suppressor
dipole magnets makes the fabrication process unique. The obvious
problems associated with the transport of these long devices make it
necessary to assemble the magnets on site at assembly facilities
strategically located to facilitate delivery of the completed and tested
magnets directly to the accelerator tunnel. Two production facilities
are envisioned. One facility will be located adjacent to the injection
transfer line with the other remotely located on the opposite side of
the ring.

The facilities are considered assembly centers rather than manufacturing
sites. The magnet components will be fabricated off site at
subcontractor facilities to the highest level of completeness (value
added) possible, considering that the components will need to be
transported to the final assembly site. Constraints have been applied to
the maximum length of component parts and subassemblies so as not to
prohibit fabrication at remote locations around the country or overseas.
Twelve meters was chosen, as it is the standard for shipboard containers
and can easily be trucked over roadways without the need for special
permits and vehicles. The on site assembly facilities will do only that
work that cannot be done off site given the above constraints. Magnet
fabrication is projected to take place over a six-year period.

In any large scale production program, a thorough quality assurance
program must be carried out during all stages of manufacture. Inspection
of parts upon receipt, testing of components where needed, and
statistical sampling techniques will be employed to ensure that
specifications are met. Warm magnetic measurements will be performed on
all magnets as part of the QA program. Cold tests will be performed on
all of the initial, low rate arc dipole production magnets and will
continue during full production at rates determined by the test
capacity.

In this section we will concentrate on fabrication of the arc dipoles:
they are a cost driver and present some unique requirements, including
the superconducting transmission line. The facilities design, dominated
by the 65m length of the final magnet assemblies, is discussed first.
Factory throughput, labor required, and fabrication details associated
with the transmission line magnet are then proposed. Key components of
the arc dipoles are the iron yokes, the transmission line, and the
vacuum chambers; these items are discussed in some detail as well. Costs
and schedules are tabulated elsewhere, in sections 5.x.x and 5.x.x.

#### 5.1.6.1 Production Facilities

The fabrication of the transmission line magnets (combined function and
suppressor dipole) takes place in two separate custom facilities each
with an approximate size of 120 meters by 150 meters. A floor plan of
the building is shown in Figure 1. Each facility has three distinct
areas; 1) component storage, 2) assembly and test, 3) storage and
staging into tunnel.

Component storage: The facility will be used as the terminus for
components fabricated off site. These components range from 12-meter
long iron core subassemblies to individual small parts. The space is
sufficient to house stock for at least three months of production. In
addition to bulk storage, space is allocated for staging (kitting)
components at the various assembly area stations.

Assembly and test area: The bulk of the facility is dedicated to magnet
assembly. There are fourteen "areas", each devoted to a specific step in
the fabrication process. Each fabrication area includes one or more
stations needed to achieve the required throughput for specific
operation. Each area will work autonomously and have the capability of
locally storing one week's production. The facility will be manned 24
hours per day (three shifts) five days per week. Two shifts (shifts 2
and 3) will do production at the assembly stations. One shift (shift 1)
will be used exclusively to move product between the various stations,
stage components at the stations and provide routine maintenance. The
output of the each facility is one magnet per day. Table 2 lists each
area, its function, number of stations required, and a list of the
tooling necessary to accomplish the stated function. A more detailed
description of the tooling necessary is included in reference \[1\].

The factory will have special handling requirements. Since the magnets
and their subassemblies are 65 meters long, and will need to be
transported laterally between areas, no columns can be located within
the primary assembly area. A custom hoist system is required to lift and
transport the long subassemblies between the various assembly area
stations. Storage areas, associated with each assembly area, will be
needed, to house finished subassemblies before moving to the next
higher-level assembly area. Most stations will require a staging area
where the various component parts for the day's production are
marshaled. Figure 2 shows, schematically, an elevation of a section of
the plant, showing the workstations in five areas, including the
component moving system.

Storage and staging into tunnel: The completed and tested magnet will be
stored until it is needed for transport into the tunnel for
installation. The custom hoist system (described previously under
assembly and test area) will move the magnet from the test stand to a
storage area. Space is allocated for storing two month's production
using special support stands to allow for vertical storage. An area is
provided to allow transfer from the storage area to a specially built
transporter rig (*see section 5.x.x*).

![](media/image28.wmf){width="4.519444444444445in"
height="5.654861111111111in"}

Figure 1. Transmission Line Magnet Assembly Factory Floor Plan

Table 2. Assembly area and tooling Summary

![](media/image29.wmf){width="5.997916666666667in"
height="6.229166666666667in"}

![](media/image30.wmf){width="6.498611111111111in"
height="1.448611111111111in"}

Figure 2. Transmission Line Magnet Assembly Factory Elevation

#### 5.1.6.2 Factory Throughput

Each magnet construction factory is designed to produce one magnet per
day, accomplished in approximately 2 shifts. As with any normal
production scenario, initial throughput would be much lower than one
magnet per day, with the schedule eventually ramping up to the peak
production levels.

Table 3 lists, for each area, the times required for each operation, the
number of man-hours required per day in each area to manufacture one
magnet, and the number of stations needed in each area to complete the
required tasks. All activities shown in Table 3 are accomplished in two,
8 hour shifts per day.

Reference \[2\] shows detailed schedules for each sub-assembly
manufactured for the transmission line magnet, with breakdown of times
elapsed for each individual operation described in section 5.1.6.3.
"Throughput" schedules for each work area are also shown.

*Table 3. Transmission Line Daily Factory Plan (one factory)*

![](media/image31.wmf){width="5.990972222222222in"
height="3.533333333333333in"}

At the end of each day, enough components or subassemblies are completed
in each area to produce one magnet. The subassemblies are stored on a
rack near each station after they are completed. A third shift is used
to move the components to the appropriate area of operation for the next
day's work. Maintenance of tooling is also done on the third shift or
weekends.

#### 5.1.6.3 Magnet Assembly

Assembly of the transmission line magnet for the VLHC Stage 1
accelerator is summarized in this section. It is described in more
detail in reference \[1\].

###### A. Assembly of Drive Transmission Line for Stage 1. VLHC

Mount 6, 12-meter long invar pipes together into one continuous section
at Area #1. Weld using automatic rotary welding heads, and inspect
mechanically. Tooling pulls the copper and superconducting braids over
the invar tube at Area #2. The outer tube is fed, in 12-meter sections,
over the assembly, then returned to Area #1 to be welded, then leak
checked at Area #5. The welded transmission line is moved to Area #3 for
ball swaging. 3 carbide balls, each of increasing diameter, are pulled
through the inner tube, swaging out the diameter and compressing the
braid between the two tubes. The line is moved to Area #4 for the
cryostat assembly. Support rings and aluminum thermal shield sections
are automatically fed onto the transmission line from the end. Trace
tubes for 60K helium are installed on the sides. 30 layers of
superinsulation are individually spiral wrapped onto the shield, while
the cryostat rotates on the assembly table. Tooling punches holes in the
insulation as it is being wrapped, to accept the penetrations from the
support rings. The extruded aluminum vacuum jacket is then fed over the
insulated assembly in 12-meter sections, returned to Area #1 and welded,
then leak checked at Area #5. The end of the drive conductor is bent
into a dogleg shape at Area #6. It is then moved to storage to wait for
installation into the iron at Area #11. Total time to fabricate a drive
transmission line is approximately *27* hours.

Assembly of the transmission line will require somewhat complex tooling,
which must perform seven types of automatic processes; automatic rotary
welding, feeding parts longitudinally onto pipes, pulling copper and
superconducting braid onto pipes, installing trace tubes, pulling
carbide balls through the assembly to swage the inside diameter, and
bending the line into the dogleg shape. Pictorial representations of
each of these processes are shown in reference \[1\].

###### B. Assembly of the Return Transmission Line 

The return transmission line design is similar to the drive transmission
line, except a slightly larger size. The return transmission line is not
surrounded by an individual cryostat, as was the drive line. Instead, it
is included in the cryopipe assembly. Fabrication scenario is identical
to that given for the drive assembly, excluding the cryostat.
Approximate time required is *15* hours.

###### C. Fabrication of Cryopipe Assembly

Weld the 6.5K flow return pipes, the 40K shield supply header, and the
70K shield return header pipes together longitudinally in Area #1, and
leak check in Area #5. Transport the three pipes, together with the
Return Transmission line, to the assembly station Area #7 \[1\]. Mount
and align the four pipes. Feed 34 spiders over the pipes, spaced every
two meters. Attach shield sections. They are each two meters long, and
will clip on between each spider. Attach (*xxx*) braids to intercept
from 4.5K with connection to 6.5K Apply superinsulation. Inspect, and
transport to storage area. Time required to fabricate a cryopipe
assembly is approximately *11 hours.*

###### D. Installation of iron and structural support over the cryopipe assembly and transmission lines.

At Area #11 the Transport Drive Transmission Line, Cryopipe Assembly are
positioned in space using special tooling. The 12 meter long Iron and
Structural supports subassemblies slide over the prepositioned drive
line and cryopipe assemblies, are positioned and attached. Welds are
made at each junction between the magnet support tubes (vacuum vessel).
The vacuum vessel is leak checked, and the entire assembly is inspected.
This operation takes approximately *14 hours*.

E. End Assembly

Still at Area #11, connect drive transmission line shield cooling line
to 70K header. Assemble end components. Fit up and weld end vacuum
vessel. Leak check completed vacuum vessel.

F. Assembly of the beam tube and vacuum pumping chamber

Start at Area #8. Beam Tube sections are received in 12-meter long
extrusions. Two pieces must be seam welded together to make the final
assembly \[1\]. Inner and outer pieces are butt welded together into
68-meter long sections. Interior welds are inspected, while the assembly
is still in two pieces. Getter pumps are installed into outer piece.
Then connect beam tube halves and make longitudinal seam weld at Area
#9. Leak check and bake out beam tube at Area #10. Transport to beam
tube storage area. Time required to fabricate two beam tube assemblies
is approximately *16 hours*.

###### G. Measurement of the magnetic field of the assembly.

As a quality control measure and to characterize the magnetic field, all
magnets are measured magnetically. This must be done before the beam
tube and vacuum pumping chamber is installed, because the test probe
must be placed in the area occupied by the beam tube. 90% of the magnets
will be measured with the transmission line at room temperature. 10%
will be measured with the transmission line cooled to cryogenic
temperatures. During the initial stages of production, a larger fraction
of magnets could be cold tested, or the duration of a cold test
lengthened. The test stands are capable of testing 1 per day at room
temperature, and 1 per week cold. Separate stations are used for warm
and cold testing. A schematic representation of the test cycle,
excluding setup, cooldown and warm-up is given in Table 4. The testing
operation takes approximately 30 hours for a warm test and 70 hours for
a cold test.

Table 4 Test Cycle

  ------------------- ----------------- ----------------- -------------------
  task                description       duration          

  precycle            <0-100kA-0@100>   2x1000 s          33 min
                      A/s                                 

  up ramp meas cycle, Iinj on-the-fly,  1000              17 min+60 min+5 min
  pos A               Imax              s+tinj+tflattop   

  down ramp           on-the-fly        1000 s            17 min
  measurement cycle,                                      
  pos\'n A                                                

  precycle            <0-100kA-0@100>   2x1000 s          33 min
                      A/s                                 

  up ramp meas cycle, Iinj on-the-fly,  1000              82 min
  pos B               Imax              s+tinj+tflattop   

  down ramp meas      on-the-fly        1000 s            17 min
  cycle, pos B                                            

  total (excluding                                        2.5 hr
  setup)                                                  
  ------------------- ----------------- ----------------- -------------------

Details of the individual probe configuration and magnet measurement
process are explained in Section 5.1.7.

###### H. Installation of the beam tube and vacuum pumping chamber

Beam Tube Assemblies are mounted onto Structural Support and installed
from the sides at Area #14. On half the assemblies, the beam tube must
be "sprung" into position, but then will stay in position after being
installed. On the other half, they will slide into position easily, but
will need to be secured afterward. This operation requires approximately
*5 hours.*

#### 5.1.6.4 Critical Components

In general, the technology to fabricate all of the individual components
required for the magnet is well understood. There are no technologies
that are marginal with regard to performance and/or tolerance
requirements. The biggest challenge involves the logistics and methods
for coping with the length of 65 meters. Nevertheless, there are some
areas of the magnet design which are critical to performance and deserve
some discussion.

A. Transmission Line Fabrication.

The transmission line, in the present manufacturing system, will consist
of four components made by outside vendors; an inner tube, a
superconducting braid, a copper braid, and an outer tube. The tubes are
to be welded at the assembly plant, with the braids installed over the
inner tube, then the outer tube welded\...\...\...\.....

B. Iron and structural support fabrication. These parts would be made
off site, and delivered to the Assembly factory in 12-meter sections. It
consists of\...\...\...\.....

C. Transmission Line Insertion into Iron.

The transmission line, complete with cryostat, needs to be inserted
longitudinally into the iron, with an accuracy of +/- ½ mm with respect
to the iron laminations. This will be accomplished by sliding the tube
long a track of steel balls\...\...\...\...\...

#### References *{note -- for sec. 5.1.6}*  {#references-note-for-sec.-5.1.6 .Reference-heading}

\[1\] J. Carson, R. Bossert, \"A Proposed Production Procedure for Stage
1 Transmission Line Magnets\", TD-01-xxx, 2001.

\[2\] J. Carson, R. Bossert, \"Throughput for Stage 1 Transmission Line
Factory\", TD-01-yyy, 2001.

### 5.1.7 Magnetic Measurements and Testing

In this section, we focus discussion on testing of the combined function
magnets during production since these magnets are the dominant element
of the Stage 1 machine. No doubt measurement and testing of other
magnetic elements in the ring are necessary, but most of these are of
more conventional design which can be accommodated by existing equipment
and approaches. Also because of their length and small bore, the
combined function magnets are the most difficult to measure.

Unlike 'conventional' superconducting magnets, the conductor of the
combined function magnets (transmission line) is not in a high field
region and quench 'training' is not a significant issue for magnet
performance. Thus magnetic field measurements dominate the magnet
testing process, both as a quality control measure and as
characterization necessary for machine operation.

Field measurements will be performed on all magnets. This must be done
before the beam tube and vacuum pumping chamber is installed, because
the test probe must be placed in the area occupied by the beam tube.
Roughly 10% of magnets will be measured with the transmission line
cooled to cryogenic temperatures allowing characterization of the field
to full current. The remainder will be measured with the transmission
line at room temperature. During initial stages of production when the
fabrication rate is lower, we will cold test all magnets. As rates
approach one magnet per day, the fraction of total magnets cold tested
will be determined by test facility capacity and test needs as indicated
by initial results.

We first discuss a conceptual design for a measurement system to be used
for the combined function magnets. We then follow with a brief overview
of the approach to cold testing and conclude with a few remarks on other
test and measurement considerations.

#### 5.1.7.1 Measurement System

As described above, magnetic measurements are the primary concern of the
test program. While one would also expect to perform an extensive series
of measurements, possibly using several measurement techniques, during
the R&D phase of magnet development, here we have chosen to present one
concept for measurements of production magnets. This concept utilizes a
rotating coil. We try to define the most important issues related to
this concept and examine the consequences. A brief discussion of other
approaches follows.

The main parameters of the arc dipole magnets are \~2 T field, ≤12%
horizontal gradient, 65 m length, and 20 mm gap. Measurement of the
integrated dipole field is needed with an accuracy of a few parts in
10^4^. Desired measurement accuracy for the higher order harmonics is
0.1 units.[^1] We begin by examining the implications of requirements
for field strength measurements. Based on this discussion we present a
concept for a measurement system. Given this system we then address the
issue of measurement of field harmonics.

With respect to measurement of the integrated field strength, there are
two issues. The fractional accuracy of the measured field goes as ∆*R/R*
where *R* is the radius of the rotating coil \[1\]. This requires that
the radius of the probe be known with high accuracy. Typical
manufacturing and measurement uncertainty for magnetic measurement
apparatus is \~0.001 inch (25 μm) which translates into a field error of
3e-3 for a probe of 10 mm maximum radius. At least an order of magnitude
greater precision (3e-4 strength error) is required. This level of
precision can only be achieved using a calibration magnet in which the
strength is known at least as well as one need know it in the subject
magnets.[^2] The second issue is unique to measurement of combined
function magnets. Due to the horizontal field gradient, an error in the
horizontal position of the probe translates into an error in measured
field strength. In a magnet with 10% gradient, measurement of the
strength to 1 part in 10^4^ requires positioning the probe with 0.1 mm
accuracy. Although difficult, this can be achieved using mechanical
fixtures referencing to the magnet laminations. Vertical placement of
the probe is not as critical.

The main conclusions from the preceding discussion are that (1) a
rotating coil of the size we are considering can be calibrated with
sufficient precision, and (2) that the horizontal position of the probe
can be set with mechanical fixtures. For reasons we list below, we
choose to insert the rotating probe into the aperture from the side
rather than from the end. The probe is supported on a frame attached to
the magnet as shown in Fig. 1. Principle elements of the design are the
following:

-   The probe body is clamped to a precisely machined fixture
    ('strong-back') on an edge which describes the magnet sagitta.

-   The strong-back slides horizontally in a series of guide brackets
    ('jaws ') attached to the vertical member of the frame. The
    strong-back is spring loaded so that it and the probe are forced
    against the magnet laminations at the edge of the magnet gap,
    referencing the horizontal probe position with respect to the
    laminations.

-   The vertical position of the probe is defined by the precision with
    which the frame is attached to the magnet and the precision of the
    jaws relative to the vertical member of the frame and the horizontal
    surfaces of the strong-back. A tilt sensor is mounted on the
    strong-back to monitor its alignment.

-   The motor for rotation and encoder for probe angle readout are
    mounted on the frame and connected to the probe by a mechanism such
    as a toothed belt or right angle drive. Other drive components could
    also be mounted outside the magnet bore (e.g. gearboxes).

-   Development of slip rings small enough to fit the probe bore is
    assumed although one might choose to digitize and transmit the
    signals from inside the bore. A pre-amplifier circuit sized to fit
    the bore is also assumed allowing a boost in signal size.

![](media/image32.jpeg){width="3.201388888888889in"
height="2.2319444444444443in"}

Figure 1: Measurement Fixture. Note that the magnet sagitta is highly
exaggerated.

A consequence of insertion from the side is that one loses a few extra
mm of probe radius due to the reduction in gap at the magnet edge of the
focusing magnet. One also needs to allow space for the clamps holding
the probe to the strong-back and for clearance during insertion.

Given a probe radius, we need to examine the accuracy of the measurement
of field harmonics. From \[1\] we see that probe calibration matters
little in measuring harmonics. Accuracy of 10% or so is adequate. This
requires knowing the probe radius to 10e-3. What is of greater interest
is the evaluation of the interplay of signal size with harmonic
measurement. This has implications for the required level of excitation
current during test. For a reasonable set of probe parameters,
pre-amplifier gain of 100, measurement accuracy of 0.1 unit through n=9
requires at least 200 A excitation current \[1\]. This should be
possible for room temperature measurements. We would no doubt increase
the gain and run at the highest tolerable current for increased
accuracy.

A probe length of 6.5 m was assumed above. Ten measurements are then
required to construct the integral field. The time required for
measurement is estimated as 2.5 hours with 2 crews of 3 technicians
using 4 sets of measurement apparatus \[1\]. This certainly allows for
the required production throughput. Automation and optimization of
procedures will reduce the time required. We also note that the
apparatus described could be used for either warm or cold measurements.
The only special consideration for cold measurements would be to
construct the strong-back of a nonmetallic material to prevent the
formation of eddy currents during ramping.

We have chosen a probe inserted in the magnet bore from the side and
supported by an external frame. An alternative approach would be a
\"mole\", such as have been developed for measurements of SSC \[2\] and
LHC magnets \[3\] which are probes with drive and angular alignment
systems built in. The obvious advantage of this approach is that the
probe can be larger by as much as 25% as insertion is from the magnet
end rather than the side. A larger probe produces larger signals.
However, development of drive apparatus operating in a strong magnetic
field is neither trivial nor cheap. We have no doubt that this could be
done; however, we have chosen a simpler approach that removes elements
of the measurement system other than slip rings and pre-amplifiers from
the bore accepting as a consequence somewhat smaller signals.

#### 5.1.7.2 Cold Testing

As a quality control measure and to characterize the magnetic field of a
sample of the magnets to full current, we plan to cold test at least 10%
of produced magnets. The peak rate of 2 magnets built per day requires 1
magnet cold test per week. As discussed in the introduction, quench
training is not a significant issue for the superferric design employed.
However, it is important to have a full set of field measurements of
magnets produced early in the program to check the overall design, iron
saturation, yoke fabrication, and related effects on the field quality
and transfer function. This increased testing also produces a
statistically significant warm-cold correlation for the field harmonics.
As the production rate rises, measurements check mechanical properties
of the magnets as well as properties of the materials used to build
them; and the set of measurements can be reduced to those necessary for
quality assurance.

The cold parts of the magnet are the transmission line and return bus
and their relatively small cryostat. Refrigeration requirements are
modest; cool down and warm up times, short. The associated test
equipment -- cryogenic end boxes, transfer lines, pumps, and
refrigerators -- is simple and inexpensive when compared to facilities
developed for testing 'conventional' superconducting magnets. Cold
testing can be done in a small area in the production facility in
conjunction with warm measurements rather than in a large, separate cold
test laboratory. The actual time spent in hooking up, cooling down,
testing, warming up, and disconnecting the magnet is small when compared
with conventional superconducting magnets. A peak production cold test
cycle occupying the test stand for one five day week would allocate a
two shift day to each of these tasks: installation and connection of the
magnet on the stand, cool down, testing, warm up, removal.

#### 5.1.7.3 Other Testing Considerations

One of the difficult issues in design and construction of a magnet
system of the scale proposed is the understanding of its overall
reliability. Failure rates for the magnets must be very small if
collider availability is to be kept at the level necessary to carry out
the physics program. Determining failure rate is itself a difficult task
as it is unrealistic to plan for the number of tests necessary to
'prove' that the magnets as constructed will meet the lifetime
reliability requirements for the collider (even assuming that we could
agree on a 'proof'.) However, since the iron yoke design and peak fields
are similar to conventional magnet designs in use for decades, we do not
envision reliability problems here. Key components will be subjected to
'lifetime' testing -- equivalent magnetic and thermal cycles (if
appropriate) --to verify that they meet requirements. While it is
impossible to argue the statistical validity of a small sample of test
magnets, accelerated life testing of a few early magnets will be used to
validate design and provide feedback early in production should any
degradation in performance be detected.

####  {#section .Reference-heading}

#### References *{note -- for sec. 5.1.7}* {#references-note-for-sec.-5.1.7 .Reference-heading}

\[1\] P. Schlabach, \"Magnetic Measurements during Production of VLHC
Low Field Combined Function Magnets\" TD-01-007, 2001.

\[2\] G. Ganetis, et al., \"Field Measuring Probe for SSC Magnets\",
Particle Accelerator Conference, 1987.

\[3\] L. Walkiers, \"Measurements for the Acceptance Tests of the LHC
Superconducting Magnets\', Eleventh International Magnet Measurement
Workshop, 1999.

### 5.1.8 Magnet Installation, Survey, and Alignment

#### 5.1.8.1 Magnets transportation, installation and alignment at the tunnel

Stage I magnets (LFM) transportation, installation at the tunnel are
discussed below. The LFMs have:

\- length 65 m

\- weight 32.5 tons

\- low cross sectional bending stiffness and torsion stiffness.

Besides, the LFMs transportation, installation and supporting should be
done at the confined VLHC tunnel.

The high field magnets (HFM) have sizes and weights close to, for
example, RHIC magnets. Therefore, it is reasonable to apply the same
methods for HFM transportation, installation and supporting which were
used at RHIC.

The LFMs have complicated design, therefore were accepted reasonable to
minimize number transport operations with the magnets (lifting, shifting
and moving) and decrease any magnet deformations during transportation.

An inexpensive vehicle are described below for the LFMs transportation.

##### 5.1.8.1.1 VLHC tunnel.

The cross sectional view of the 3 meter in diameter VLHC tunnel are
shown on fig.1. The tunnel has flat concrete flow with track way --
simple floor profile for vehicle steering. The 1st stage magnets are
overhead. The HFM are beneath. Also LFM supports with jacks are shown.

![](media/image33.png) Distances between supports at the tunnel are
chosen 6 meters in accordance with calculations.(see below)

Fig.1. Cross sectional view of the VLHC tunnel.

*{ refer to other (better) figure }*

##### 5.1.8.1.2 LFM vehicle.

Longitudinal view of the LFM vehicle are shown in fig. 2.

The vehicle consists of 11 identical transporters with payload up to 3
tons. Distances between transporters are 6 meters. Each transporter has:

-   four inflated tires(to reduce dynamical loads and increase
    transportation speed);

-   two axles: rear -- driving axle; front -- negligible veering axle;

-   DC reversible motor about 10 kW;

-   Lead-acid battery block;

-   A special mechanism to shift LFM during installation procedure. The
    special mechanism and driving axle use single DC motor.

So, the LFM vehicle uses distributed power between the transporters.
Total driving power is about 110kW. It is enough for LFM transportation
at speed up to 5mph and grade up to 4%. Also, it is enough for LFM
shifting during installation procedure.

Cross sectional view of the LFM vehicle are shown in fig.3. The LFM
transportation level is about 6 feet over the floor and 4 inches over
the supports level.

![](media/image34.png)Fig.2. Longitudinal view of the LFM vehicle at the
tunnel.

![](media/image35.png)Fig.3. Cross sectional view of the LFM
transporter.

*{ this figure is incorrect! LFM is on floor }*

##### 5.1.8.1.3 LFM installation.

The transporters fix its position with special legs before LFM
installation (see fig.4). Then the LFM safely is shifted to the supports
with the transporter's mechanism. The support's jacks accept weight of
the LFM. The telescopic parts of the transporters are removed and the
vehicle rolls out.

![](media/image36.png)Fig.4.LFM Installation on the supports.

##### 5.1.8.1.4 LFM supporting at the tunnel.

LFM will install on the vertical supports. A distance between supports
was chosen 6 meters. A numerical simulations were done in order to
estimate stresses and deformations. The maximal deflection of the LFM
under weight load are between 1.2 -- 2.1 mm. It depends from final
design of the LFM. In case if properly magnet will connect with vacuum
tube with welds, the sag is close to 1.2 mm and maximal stresses are not
exceed 50 -- 60 MPa. Without welding connection between magnet block and
vacuum tube the sag is close to 2.1 mm and maximal stresses reach up to
90 MPa.

*{ Fig 5 has been removed. Replace with text: talk about strain }*

##### 5.1.8.1.5 LFM alignment. 

To estimate deformations of the LFM during alignment at the tunnel
numerical 3D simulations were done of the model of 12 meters LFM fixed
on the both ends and are loaded with horizontal force applied to the
central supports of the vacuum tube and distributed weight load. The
properly magnet block moves on about 0.9mm at vacuum tube movement 1mm.
The horizontal force needed to move LFM on 1mm depends from the position
of the alignment point concerning to the ends of the LFM and changes
from 40kgs to 150kgs without taking into account friction force. Taking
into account that each support supports 3 tons of the LFM weight the
friction force may be estimated as about 300kgs.

Difference relative movement iron halves of the properly magnet can
reach 30μm at magnet movement 1mm.

More accurate calculations and studying are needed using a fine mesh
taking into account importance alignment problem.

##### 5.1.8.1.6 Movement of the LFM along an arc way

The LFM has the straight axis. When it is transported along the arc way
the LFM is deformed and axis accepts the arc shape.(We can except it at
a first approaching)

There is simple analytical decision for arc deformed beam:

*+++++++++++++++++++++++++++++++++++++++++++ Reduce to simple
paragraph:*

1/R = M/(EJ);

For example, for an estimation we can define allowable radius R of an
arc for cryoline vacuum jacket

R = unknown -- arc radius;

E = 200 Gpa -- steel elastic modulus;

J = πD^3^t/8 -- jackets moment of inertia.

M -- bending moment;

Stresses are equal:

σ = M/W;

W -- section modulus;

So,

M = σW.

\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*

If we accept allowable static stresses for LFM:

\[σ\] = 50 MPa;

And

W = πD^2^t/4 - cryoline vacuum jacket section modulus;

> D = 0.3m -- jacket external diameter;

t = 0.006m -- jacket thickness.

We will have:

1/R = \[σ\]W/(EJ) = 2\[σ\]/DE

R = 1/2DE/\[σ\] = ½\*0.3\*200000/50 = 600 meters

Unfortunately, LFM has a complicated composed design. And giving correct
decision totally the analytical estimation can not to take into account
local stresses which can dominate. Therefore, we need to use numerical
simulation to get information about local stresses.

As an example, such simulations were done for a case when first
transporter of the LFM transportation vehicle are on the arc with R =
1000meters, the rest are on the straight way. At this case, a difference
between straight line of the LFM and arc with the distance 6 meters is
0.018m(see Fig.6.). Another words, it means one support of the magnet is
vertically moved on 1.8cm.

![](media/image37.png)

Fig.6.

Numerical 3D simulation with Ansys code show that equivalent stresses
exceeds 200 MPa at this case. It should be noted it is result static
calculations. So as dynamic factor is about 2 we can get unallowable
stresses if arc way will have radius about 1000m. The maximal stresses
are at the closest to the supports plates and welds which connect the
properly magnet block and vacuum jacket. Also large stresses more then
100 MPa are at the vacuum jacket at the area closest to the supports.
Take into account that the welds are concentrators of stresses may
conclude we need to decrease stresses at least at 4 times. It means that
arc transportation way should have minimal radius about 4000m. Larger is
better because most of LFMs will have transportation deformations only
one time.

Stresses concentrators(bolts, welds) at the LFM design are required more
accurate studying and more calculations.

*{Sec 5.1.8.2 has been removed}*

#### 5.1.8.3 Magnet alignment for the VLHC

##### 5.1.8.3.1 Introduction

The low field transmission line dipoles for the VLHC are envisioned to
be 65 meters long. Conventional optical techniques (Theodolites and
laser trackers) for alignment will have angular errors in the range of
10 microns per meter, corresponding to ± 300 microns at the magnet ends
from a setup at the center of the magnet. This would be marginally
adequate to meet the magnet alignment specification of 250 microns RMS
over the length of the magnet. However this accuracy can be exceeded
using the hydrostatic leveling and stretched wire techniques described
below.

For each magnet there will be a support every 6 meters with horizontal,
vertical and roll adjustment capability. The magnets will be built
"laser straight" in the factory. The magnets will be installed in the
tunnel with a 15mm sagitta over the 65-meter length. The stiffness of
the magnet will allow an independent range of motion of approximately
± 2mm horizontally or vertically at each adjuster. Motions outside this
range will require coordinated movements of nearby adjusters. The range
of adjustment in roll angle is TBD. The magnet will be roughed in using
optical techniques along the beam line relative to the internal tunnel
network. At each of the support stands there will be a hydrostatic
leveling pot for vertical alignment, capacitive stretched wire pick up
for horizontal alignment, and a electronic gravity sensor for roll. As
the adjustment screws are turned there will be real time readout of both
systems to allow for the positioning of each segment of the magnet. A ±
3cm range of the adjusting screws will be sufficient to put in the
sagitta and to compensate for installation errors in the magnet stands
as well as drift and settling of the tunnel (± 1cm maximum) over a
20-year lifetime.

##### 5.1.8.3.2 Leveling

Hydrostatic leveling is a sophisticated form of the carpenter's water
filled garden hose. A hydrostatic system has been in use at ESRF in
Grenoble France since the early '90s and reported on in 3^rd^
International Workshop on Accelerator alignment, 1993. A similar system
has been used to measure ground motion in the North Aurora mine near
Fermilab \[ref. Shiltsev\]. The system consists of several chambers
filled with a fluid, water or glycol, all connected by tubing. The fluid
in the chambers will seek it's own level. Each of the chambers will be
attached to the stands near the magnet. Inside each chamber is a
capacitive pickup attached to the magnet and free to move up and down
relative to the fluid level. As the pickup moves the capacitance will
change giving a relative vertical position. Alignment of ± 60 microns
for several chambers is possible. This exceeds the 250 micron RMS
"quad-to-quad" vertical alignment requirement for acceptable
closed-orbit distortion *\[sect 2.\*\*\*\].*

![](media/image38.wmf)

Over longer distance scales, absolute horizontal alignments of ± 1 mm
per kilometer have been achieved at Grenoble. The gravity field of the
earth can be expressed as a series of equipotential surfaces. While
these surfaces are smooth and piece-wise continuous, due to variations
in the earth density these surfaces are somewhat irregular. For short
distances, 65-meters, the plumb line (that is the line perpendicular to
the equipotential surface) can be used to establish vertical. For the
larger machine, 70-kilometer diameter, corrections to the plumb line
must be made. This will require careful study of the Geoid and the
change in the density of the earth in the region of the machine.
Corrections to the vertical can then be imposed on each magnet.

##### 5.1.8.3.2 Magnet Roll

In a manner similar to the leveling of the magnets a fluid filled
container with capacitive readout can be used to establish a real time
display of the roll of the magnet at each adjustment station. Given a
base support as shown in section 5.1.2 of 500 mm and a resolution of 2
microns for the hydrostatic levels an roll angle of ±4 micro-radians is
achievable. This exceeds the 1 mrad requirement \[sect 2\*\*\] for
acceptable vertical closed-orbit distortion.

##### 5.1.8.3.3 Horizontal Alignment

For horizontal alignment stretched wired can be used. A small diameter
(less than 1 mm) copper beryllium wire attached to both ends of the
magnet is the reference. Two wires separated vertically can be used to
reduce the signal to noise. A sinusoidal voltage of a few kilohertz will
be imposed on the wire. At each support stand there will be capacitive
pickups around the wire. As horizontal displacement of the magnet is
made the readout will change allowing the entire 65 meters to be placed
on the desired horizontal axis. Data from KEK indicate that a resolution
of 5 nm is possible for short segments. Alignment of the entire 65-meter
magnet to within ±100 microns should be possible.

![](media/image39.wmf)

To set the sagitta of 60 mm for the magnet all the adjustments must be
made at the same time. Starting with optical tooling the rough sagitta
can be set to an accuracy of ±300 microns. Once this is done the
stretched wire system can be installed. Each capacitive pick up will
have a different offset from the magnet to account for the saggita. The
final adjustment will involve moving all adjusters at the same time.

A varying degree of automation is possible. The simplest approach is for
the person at the central display of magnet alignment data to give
directions to one or more workers with wrenches. A more sophisticated
alternative is to manually place motorized wrenches at each of the
adjusters, then run automated software procedures to bring the entire
magnet into alignment. If these systems were permanently installed and
coupled with motorized adjustment stands they could be used as an active
alignment that continually aligns the magnets as the machine runs. Beam
position monitor information could also be used.

## 5.2 Accelerator Systems *(export this intro to section 2?)*

Accelerator systems are divided between the standard "once per turn"
systems (located primarily in the Utility straight sections and IR's on
the Fermilab site) and the repetitive instrumentation in the long arcs
of bend magnets.

A completely conventional approach is taken to the standard utilities in
the straight sections. Warm iron/copper magnets use LCW cooling and
standard power supplies. Electronics and power supplies are located in
underground shielded instrumentation rooms that are accessible with beam
on. A larger tunnel, conventional power systems, and generous cable
trays provide the infrastructure for RF systems, injection and
extraction kickers and Lambertsons, beam crossovers, beam halo scraping,
beam current and beam profile monitoring, etc. Concentration of these
major subsystems at the Fermilab site makes maintenance and
accessibility requirements similar to other Fermilab accelerators. A
warm beam pipe is used everywhere except the IR triplet (and optionally
the superconducting RF) thus providing simple instrumentation
connections to the vacuum system. Quadrupole spacing in the straights is
typically 150m which leaves ample room for expansion.

All the standard components of the once-per-turn systems are technically
equivalent to those of recently completed projects: (Fermilab Main
Injector warm magnets, utilities and installation, B-factory/LHC RF, IR
quads from the USLHC collaboration, etc.). Thus adequately accurate cost
estimates can be obtained by scaling from these projects on a unit-cost
basis. The choice of 53MHz bunch crossing frequency supports
standardization of the instrumentation and controls with other machines
in the FNAL injector and minimizes EDIA and software costs associated
with new designs.

In the long arcs of bending magnets the situation is different. The
once-per-turn subsystems and their cabling, power and cooling
requirements are absent. No LCW system is required. Only the repetitive
instrumentation and corrector power supplies at each of the 1760 "quad
locations" (every 135m around the ring at the location of beta-max in
each half-cell) is required. These electronics are located in a
radiation-shielded modules buried in "holes-in-the-wall" at each quad
location. Average power dissipation is approximately 15 W per meter of
tunnel. All cables for instrumentation and corrector magnets are
pre-assembled on the magnet and factory tested before installation.
Every other quad location (270m) cryogenic thermometry and a valve
controller are used to regulate the 50K shield flow. Every 10km there is
a walk-in alcove that contains conventional electronics racks and
provides network connection, tunnel safety systems, bulk DC power for
the instrumentation modules, and cryogenic instrumentation for the
cooldown valve box and located at the 10km points. The 10km alcoves are
associated with a tunnel egress point and may be accessible with beam
on.

Reliability is at a premium for the arc instrumentation due to the large
size of the machine. Repair technicians at a centrally located facility
require a 20mi drive to reach the surface facility and begin the access
into the tunnel. Minimum repair time will likely double the minimum 1.5
hour time needed to refill the machine and reaccelerate the beams. For
this reason fully redundant capability is provided for all
mission-critical subsystems in the arcs. Power distribution is provided
to each module by two independent loop feeders with auto-resetting
circuit breakers and remote disconnects. Two independent power supplies
are provided for each corrector magnet and control function. Redundant
network connections to each module are provided. The critical function
of beam loss monitoring is provided by redundant sensors read out from
alternate quadrupoles modules, so that even the death of a handful of
control modules will not require immediate maintenance.

### 5.2.1 Power Supplies

Stage 1 power supplies are summarized in the table below. The
Interaction Region power supplies, current leads and quench protection
are discussed in sect 5.1.4. Total Stage 1 power supply requirements
(both ramping and steady state) are less than a quarter of the Fermilab
Main Injector.

Table 5.2.1: Power Supply, Current Leads and Quench Protection Summary
for Stage 1 Machine

+----------------+------------+-------------+------------+------------+
|                | Tr         | IR          | Straight   | Corrector  |
|                | ansmission | Quadrupole  | section    | Magnets    |
|                | Line Power | Power       | Warm       | (warm      |
|                | Supply     | Supplies    | Magnet     | copper)    |
|                |            | (sect       | Power      |            |
|                |            | 5.1.4)      | Supplies   |            |
+----------------+------------+-------------+------------+------------+
| Number         | 1          | 2           | 16 approx. | 12,000     |
+----------------+------------+-------------+------------+------------+
| Location       | FNAL       | at          | Straights  | Quad       |
|                |            | Experiments |            | locations  |
+----------------+------------+-------------+------------+------------+
| Voltage per    | 62         | 10V typ.    | 1000V typ. | 100 Typ    |
| supply         |            |             |            |            |
+----------------+------------+-------------+------------+------------+
| Current per    | 100kA      | 25kA        | 200A typ   | 2A typ     |
| supply         |            |             |            |            |
+----------------+------------+-------------+------------+------------+
| Ramping MVA    | 6.2 MVA    | 1 MVA       | \-         | \-         |
| (tot)          |            |             |            |            |
+----------------+------------+-------------+------------+------------+
| DC Power       | 0.4 MW     | 0.6 MW      | 3.2 MW     | 2.1 MW     |
| (total)        |            |             |            |            |
+----------------+------------+-------------+------------+------------+
| LCW            | \-         | \-          | 100        | *(air      |
| Consumption    |            |             | liters/sec | cooled)*   |
+----------------+------------+-------------+------------+------------+
| Quench         | 1 Circuit  | 2           | \-         | \-         |
| Detection      | at PS      | ci          |            |            |
|                |            | rcuits/quad |            |            |
+----------------+------------+-------------+------------+------------+
| Quench         | Dumps @    | 4           | \-         | \-         |
| Protection     | 20km       | h           |            |            |
|                |            | eaters/quad |            |            |
+----------------+------------+-------------+------------+------------+
| SC Current     | 100kA-pair | 60kA-pair   | \-         | \-         |
| leads          |            |             |            |            |
+----------------+------------+-------------+------------+------------+
| **Peak Ramping | **12.3     |             |            |            |
| Supply Power** | MW**       |             |            |            |
+----------------+------------+-------------+------------+------------+
| **Total Power  | **6.3 MW** |             |            |            |
| Supply**       |            |             |            |            |
|                |            |             |            |            |
| **Power in     |            |             |            |            |
| Collision**    |            |             |            |            |
+----------------+------------+-------------+------------+------------+

#### 5.2.1.1 Straight Section (Warm Magnet) Power Supplies

In each straight section all F and D quadrupoles are powered in series
by a single supply. The IR straight sections have a larger number of
independently programmable "tuning quads" but the total power and LCW
usage is approximately the same as a normal straight section. The power
supplies are located in shielded rooms (one per straight section) which
contain \~400kW of power supplies and are accessible with beam on. These
are single quadrant supplies. Given the limited scope of these supplies
it is desirable to make them fully redundant, especially those at the
far side of the ring from FNAL.

Correctors dipoles and quads identical to the arcs are provided at each
quad location. Dipole magnets used to separate and cross over the beams
are powered by the 100 kA transmission line and require no separate
supplies.

#### 5.2.1.2 Main Transmission Line Power Supply

The low inductance (3uH/m, 0.6H ring total) and low stored energy
(10kJ/m, 3GJ total) of the single-turn transmission line magnet allow
the entire ring to be powered from a single supply \[ref Steve Hays
detailed write-up\]. See figure 5.2.1.1 A voltage of 62V allows ramping
the machine up or down in 1000 seconds. The design current of 100kA at
flattop exceeds the 90kA required for the transmission line magnet to
reach its design field. The supply will be located on site at Fermilab
in a shielded underground room approximately 25' x 50' in size. The
ramping power and footprint of the power supply is comparable to one of
the six Main Injector power supply buildings. Superconducting current
leads will be located immediately adjacent to the supply to minimize
power loss in warm busswork. Superconducting busswork will carry the
current through a short connecting conduit to the transmission line
magnets in a manner identical to the MS6 test string \[ref Henryk\].

The power supply is actually two supplies in series. The main ramping
supply generates the positive or negative voltage to transfers the
inductive energy into and out of the magnets. It is not used when the
magnet is at constant current. The second "holding" supply maintains the
current during long periods at flat top and injection, and provides only
the voltage necessary to overcome resistive losses in the current leads,
warm busswork, superconducting splices, and the shorting SCR switch
across the ramping supply. This approach minimizes the cost of the
ramping supply, simplifies the power distribution system, and moves the
tightest regulation and ripple requirements to the precision holding
supply.

![](media/image40.png){width="5.54375in" height="3.7958333333333334in"}

Figure 5.2.1.1: 100kA Power Supply and Quench Protection For
Transmission Line Magnets

The Main Ramping Supply design (fig 5.2.1.2) is based on paralleling
8500A modules of design similar to Main Injector supplies. This approach
permits spare modules to be taken off line for repair, and permits the
use of commercially available 10kA DCCTs for current regulation. A
2-quadrant 12-phase SCR bridge permits returning inductive power to FNAL
as the magnets ramp down. Ramping systems are designed to have RMS power
sized to be halfway between the peak (6.2MVA) and the RMS (3.1 MVA).
This has proven to be a reliable design methodology for similar supplies
at Fermilab. The RMS feeder load of 4,800KVA is less than one feeder
cable for the source.

![](media/image41.wmf){width="6.5in" height="1.9520833333333334in"}

Figure 5.2.1.2: 100kA Ramping Supply Schematic (one 2 x 8.5kA module
shown)

The 2.5V 100kA holding supply is essentially a copy of the 100kA
switching converter \[ref.\] constructed for the R&D magnet test. The
device consists of a 450VDC 500kW bulk supply followed by ten 10kA DC-DC
converter modules in parallel. This two-stage regulation scheme provides
immunity to variations in input line voltage. The modules use tape-wound
cores and Schottky power diodes. The switching frequency is \~2 kHz. To
minimize output ripple the 10 modules will be phased to switch
sequentially. This pushes the fundamental ripple frequency up to 10x the
switching frequency or \~20kHz. The switching will be phase locked to
the revolution frequency so that beam emittance growth due to power
supply ripple will be negligible. The control system for this switcher
will be integrated into that of the main ramping supply to simplify
regulation and load hand-off.

![](media/image42.wmf){width="4.270833333333333in"
height="1.554861111111111in"}

![](media/image43.png){width="4.008333333333334in"
height="1.082638888888889in"}

Figure 5.2.1.3: 2.5V Switching supply module for MS6 String test

***[\*\*\*DO WE NEED DISCUSSION OF EMITTANCE GROWTH AND SUPPLY
RIPPLE?]{.underline}***

### 5.2.2 Current Leads

Superconducting current leads are required for both the main
Transmission Line and IR quadrupoles. Current leads IR quadrupoles are
assumed to be identical to the commercially available HTS leads \[ref\]
used by the LHC IR's. The total current leads requirement for the Stage
1 machine is about 150kA-pair, or about 1/10 of the leads required by
the LHC \[3.5MA from Lynn Evans' stump speech\].

A single pair of 100kA current leads is required for powering the
transmission line. These could either be conventional copper leads
identical to the leads developed for the MS6 transmission line test
facility\[Yuenian\], or could be a High-Temperature Superconductor (HTS)
version using the 50K transmission line shield flow as the inter-stage
temperature. The cryogenic wall power associated with the conventional
100kA leads is approximately 300kW. This could be reduced by a factor of
4-5 with HTS leads \[Cryo Engr. Handbook\]. Payback time for the
electrical cost savings from HTS leads is approximately 3 years.

![](media/image44.png){width="3.979861111111111in"
height="2.4305555555555554in"}

Figure 5.2.2: 100kA Superconducting Current Leads and switching
converters developed for the MS6 test string. The leads and power
converter are compact enough to be used for partial-ring comisssioning.

### 5.2.3 Quench Protection

The only superconducting magnets of the Phase I collider are the IR
Quadrupoles and the transmission line magnets. Protection of the IR is
described in section 5.1.4.

The low inductance and low stored energy of the transmission line magnet
allows a simple and inexpensive quench protection system (fig. 1). The
magnets themselves require no internal quench detection or protection
circuitry. Ring-wide quench detection is performed by a single circuit
located at the power supply terminals. Quenches are detected by a
voltage imbalance at the power supply. When a quench is detected,
magnetic energy is extracted with a 1-second L/R time constant by
cryogenic "dump resistors" spaced at 20km intervals around the ring.
This keeps the peak temperature in the quenched section of the conductor
below 250k TBD as described in section 5.1.3.2.1. The dump resistors are
specialized 60m sections of transmission line which are deliberately
quenched to absorb the magnetic stored energy. Quench protection system
parameters are given in table 5.2.5.2. A detailed write-up is given in
\[Piekarz/GWF\].

The protection circuit for the 100kA current leads and power supply is
integrated into the quench protection system. When an overtemperature or
overvoltage is detected in the current leads, nearby copper busswork, or
power supply components, power supplies are shut off and a ring wide
dump is forced.

Table 5.2.3 - Stage 1 Quench Detection and Protection Parameters

  ----------------------------------- -----------------------------------
  Transmission Line Current           100 kA

  Magnetic Stored Energy \@100kA      10 kJ/meter, 2100 MJ/ring

  Magnet Inductance at low field      3uH/m 600mH/ring

  Energy Dump Time Constant           1 second

  Peak Voltage To Ground during Dump  ± 3 kV

  I^2^t during dump                   5 x 109 Amp^2^Seconds

  Peak Temperature of Conductor       250K TBD
  During Quench                       

  Peak Pressure of Helium During      30 Bar TBD
  Quench                              

  Pressure relief during quench       At cool-down valves every 10km (no
                                      local relief)

  Effective Copper Cross Section of   3cm2
  Conductor                           

  Quench Detection Threshold          1 Volt

  Quench Detection Method (primary)   Deviation from V=LdI/dt at power
                                      supply terminals

  Quench Detection Method (backup)    Analog bucking with midpoint of
                                      current return bus

  Energy Dump Resistance              60 mΩ per location,

  Dump Switch Locations               at cryoplants and midpoint of arc
                                      (20km spacing)

  Dump Switches                       Quenched superconducting cables 65m
                                      long

  Superconducting Dump Switch         1:1 CuNi:NbTi "Switch Wire"
  Conductor                           soldered to SS bars

  Stainless Steel Bar Cryogenic Dump  65m long x 20cm2 SS 304 bars or
  Resistors                           pipe

  Final Dump Temperature after Dump   325K
  from 100kA                          

  LHe Required for recovery after     1600 liters (less if shield flow
  Dump from 100kA                     used for pre-cooling)
  ----------------------------------- -----------------------------------

Each string is divided into quench cells 20km long. When a quench is
detected, all dump switches open to divert the current into "dump
resistors" which absorb the magnetic stored energy with a 1 second L/R
time constant. Here the "dump switches" are deliberately quenched
sections of transmission line conductor built with Cu-Ni stabilized NbTi
"switch wire" which is designed to have a very high normal state
resistance. These dumps are efficiently recooled using helium from the
cryogenic shield flows and transmission line flows, with the warm gas
vented into the return header.

![](media/image45.wmf){width="5.75in" height="1.8743055555555554in"}

Fig. 5.2.3 - Quench Protection Cell of the Transmission Line Magnet

It is instructive to compare this quench protection system to those of
other accelerators. The LHC for example \[Refs PAC '99 papers\] requires
a crate of quench detection electronics in the tunnel underneath each
dipole in the tunnel. Each LHC magnet has more than 10 voltage taps and
instrumentation feed-throughs. The LHC also requires a much larger array
of energy dump resistors, dump switches, and current leads around the
circumference of the ring. Despite the larger machine circumference, the
quench protection system of the Stage 1 magnet is simpler and should be
more reliable.

### 5.2.4 Arc Instrumentation

The primary challenges of the repetitive instrumentation of the arcs are
cabling, power distribution, and reliability.

#### 5.2.4.1 Cabling in the Arcs

In the Fermilab Main Injector, the cable tray to each service building
contains 316 cables with a total cable cross sectional area of 28 square
inches \[table 3.9.1 in FMI Design Report\]. Over 95% of these cables
service Beam Position Monitors (BPMs), Beam Loss Monitors (BLMs), ion
pumps, corrector magnets, and temperature and vacuum monitoring. The
superconducting Tevatron also has a large cable plant associated with
quench protection and cryogenic monitoring and controls. The
installation, termination, and testing of these cables are a significant
cost and schedule item.

The Stage 1 design eliminates most cabling costs by multiplexing the
signals to a local electronics module (fig 5.2.6.1) at each halfcell
boundary or "quad location". Signals are digitized locally and sent to
the control room via network fiberoptics. Instrumentation and corrector
magnets are clustered at the quad location and cable runs are typically
5 meters. Cable harnesses are prefabricated by outside vendors and
mounted on the magnets and tested in the factory.

![](media/image46.wmf){width="5.541666666666667in"
height="3.6284722222222223in"}

Fig. 5.2.4.1 --Cabling Layout on the Transmission Line Magnet. Cables
and instrumentation are preinstalled and factory-tested on the 65m
magnets. Each magnet has a 5m "extension cord" which jumpers to an
electronics module located in a hole in the wall at each quad location
(135m spacing).

![](media/image47.wmf){width="3.047222222222222in" height="2.275in"}
![](media/image48.png){width="3.1840277777777777in"
height="2.283333333333333in"}

Figure 5.2.4.2: DC-DC Power Converters for corrector supplies and
instrumentation are in an electronics module at each quad location
(every 135m). Modules are in a radiation-shielded "hole in the wall" and
dissipate their power in the ambient tunnel air via a heat
pipe/thermosiphon and heat sink.

#### 5.2.4.2 Corrector Power Supplies

The warm (air-cooled copper) correction magnets \[sect 5.1.3.3\]
dominate the power consumption in the arcs. The electronics module at
each quad location has 6-8 corrector magnet loads with a maximum
installed power of approximately 1400W. Average corrector power is
\< 1000W in a realistic operating scenario. At maximum current
approximately 90% of the power is dissipated in the magnets themselves
with the remaining 10% (\~150W) in the power supply converters.
Instrumentation and control power at each quad location is estimated to
be \~100W for a total of 250W dissipated in the module. Power at this
level can be passively carried away from the electronics via a heat pipe
and removed by the tunnel airflow of \~1m/sec (see
<http://www.thermacore.com/papers.htm>).

#### 5.2.4.3 Power Distribution in the Arcs

Completely redundant DC-DC power converters are provided both for module
control power and for each trim magnet. Power can be drawn from either
of two redundant 1kV feeders that loop the ring. Power supplies are
connected in parallel at each load. Under normal circumstances the load
is shared and each power supply operates at \< 50% of rated load,
encouraging long lifetimes. Under failure conditions the load is taken
over by a single supply which operates near its design rating (or less,
if the corrector magnet setting is below 100%).

![](media/image49.wmf)

*Figure 5.2.4.3: DC Power Distribution Scheme in Arcs. Redundant Bulk DC
supplies in walk-in alcoves every 10km supply a redundant Loop Feeder.
Each local electronics module contains two DC-DC converters for each
load. Under normal conditions all supplies share loads and run at less
than 50% of rated capacity. By means of auto-resetting circuit breakers
(not shown), the system can tolerate short or open circuits on the loop
feeders, a failure of one or both bulk supplies at any alcove, a failure
of the AC surface feed to any single alcove, and individual failures on
many corrector supplies.*

Medium-voltage 1kV DC is chosen for power distribution to the
electronics modules at each quad location. The DC is provided by 100A
bulk supplies every 10km located in racks of electronics in walk-in
alcoves. Two redundant bulk supplies are provided at each location, and
two independent distribution loops are provided to route the power to
the modules. Under normal conditions 25A is sourced in either direction
onto each of the 500 MCM loop feeders, and less than 3% of the power is
lost in the distribution cabling. Under fault conditions one or both of
the bulk supplies at one of the 10km locations can fail, with the slack
being taken up by adjacent supplies in the loop feeders. A short-circuit
fault in one segment of the loop feeders can be tolerated by letting its
circuit breaker trip and relying on the remaining loop feeder. Each
module is protected with fault current limiting via automatically
resetting "solid-state fuses"\[ \] .

The advantages of DC power in this application are as follows. The main
power consumption is due to corrector power supplies that naturally
operate as DC-DC converters. These are more compact than
line-transformer based supplies, an important consideration for the quad
electronics modules. Modern DC-DC converters \[e.g.
[www.Vicr.com](../www.Vicr.com)\] have the following parameters: power
density 200W/in^3^, efficiency \~90%, cost \~\$0.35/watt. In fact,
essentially all modern AC devices (fluorescent light ballasts,
computers, high current welders, motor controllers...) rectify the AC
line power then chop the signal using DC-DC techniques. Rectification
requires bulky capacitors and produces current spikes with power factor
and noise problems that complicate AC distribution. DC power
distribution makes the most efficient use of the copper in distribution
cables, which is a major cost component in power distribution. DC power
also simplifies the design of loop feeders, which may be powered from
separate segments of the power grid without regard to the relative phase
of the incoming AC power. Finally, by phase-locking the switching
frequencies of the DC-DC converters to a frequency near the revolution
frequency of the machine, noise effects on emittance growth can be
essentially eliminated as discussed in section 5.2.xxx.

#### 5.2.4.4 Beam Position Monitors (BPMs)

Both X and Y BPMs (fig 5.2.4.4) will be provided at each "quad location"
at half-cell boundaries between corrector magnets. This is twice the
number used in the Main Injector where it was determined that
measurement of the second coordinate only improved the closed-orbit
distortion by 10% \[MI note 75\] and only a single coordinate readout
per quad location was provided. However the added redundancy obtained by
an independent readout of both coordinates every half-cell will be
beneficial given the small aperture and the long travel distance
required to repair failed BPMs.

Button style beam pickups similar to those used on electron machines and
the LHC are adequate. These devices are nonlinear outside the central
30% of their aperture. Given anticipated closed orbit distortions \<1mm
this is not a problem. In a few special locations near beam transfers
where multiple off-axis orbits must be measured, split-plate BPMs with
better linearity will be used.

BPM readouts using either AM/PM or Log Amp electronics are acceptable.
In the case of Log-Amp readout both log(A/B) and log(A)+log(B) would be
digitized to provide both position and intensity readout. In the case of
AM/PM conversion a separate channel (possibly a log amp) is required to
provide intensity information. In either case an in-situ calibration is
desirable. The calibration circuit injects equal signals of adjustable
amplitude into both channels to accurately determine the zero-offset
response at different input strengths. A recent example of log-amp
readout made for the SLAC B-factory fit on a 2.7" x 4.7" board which
also included calibration circuitry \[Medvenko & Smith, Beam
Instrumentation Workshop 2000, p.503\].

Digitization bandwidth is determined by the first turn and transient
response desired. A digitization rate \>25MHz can be supported by the
DMA channels of today's DSPs, with no external components other than the
flash ADC. A 10-bit digitization of log(A/B) would provide 20μm least
count resolution. Power dissipation for 4 channels of 10-bit 40 MHz
digitization would be 300mW total
(<http://products.analog.com/products/info.asp?product=AD9203>).

The cable run from the BPM to the quad electronics module is about 5m.
This is long enough that the signal must be terminated but short enough
that normal RG-58 can be used. The cable runs are short enough that no
cable trimming for phase matching is required if AM/PM electronics are
selected.

![](media/image50.wmf)
![](media/image51.png){width="2.7958333333333334in"
height="3.203472222222222in"}

Fig. 5.2.4.4 -- Beam Position Monitor (BPM) and Beam Loss Monitor(BLM)
for Stage 1 magnets. The BPM is a capacitive "button" style typically
found on small aperture beam pipes. The X&Y pickups are rotated by
45-degrees to avoid the synchrotron radiation (this is common for light
sources). The BLM is a permanently sealed Argon filled cable-style
ionization chamber. Two redundant BLMs run the full length of the
magnet. It features all metal and ceramic construction similar to the
Tevatron BLMs to allow the device to operate unattended for years (no
gas bottle to change).

#### 5.2.4.5 Beam Loss Monitors (BLMs)

The BLM function in the arcs is mission-critical in that no blind spots
may exist which might allow chronic beam loss to go undetected. (A rapid
intense beam loss at a single point will also cause large downstream
losses and quench the magnet, and would therefore not go undetected even
if the BLM coverage was incomplete). We therefore choose a cable style
BLM \[ref APS BIW\] which is essentially a long ionization chamber that
can provide complete coverage along the length of the magnet. The cable
will be all metal/ceramic construction (fig 5.2.4.4) so that no
gas-bottle changing will be required. For added redundancy, two
independent cable BLMs are provided. Each runs the full length of the
magnet but they are read out at alternate quad locations. These provide
complete coverage even when the electronics module at a single location
goes *incommunicado*. Separate BLMs on each side of the magnet provide
some differential sensitivity to beam losses in each bore. Electronics
required include a 2kV/100μA Cockroft-Walton DC-DC converter module, an
op‑amp integrator, and a medium bandwidth \~100kHz 14-bit ADC. Power
dissipation should be \<2W.

#### 5.2.4.6 Ion Pump Power Supplies & Vacuum Gauges

The electronics module for each 135m half-cell requires 12 ion pumps
(22.5m pump spacing in each bore). These are powered from the
electronics module. Each pump requires a 5kV supply with a starting
current of up to 30mA but an operating current less than 0.1mA. The
power for all 12 pumps is provided by single transformerless bulk supply
(a 5-stage Cockroft-Walton converter operating from the 1kVDC feeder).
High voltage DC relays (Cotto 5501) isolate each pump and give the
capability of providing the full starting current sequentially to each
supply. Individual current readback on each pump is provided via an
array of line-powered V/F converters operating at HV with an optically
isolated data link to the DSP.

Failure of the bulk supply shuts down all ion pumps in a 135m half-cell.
Pumping from the NEG strip remains intact. This results in a 50x rise in
the pressure of a single gas species (CH4) over the length of one half
cell, equivalent to a 3% rise in the average pressure of CH4 in the
ring. Redundancy in the ion pump power supplies is therefore
unnecessary.

#### 5.2.4.7 Network & Clock Connections

The electronics module at each quad location contains a Digital Signal
Processor (DSP) computer with an optical fiber connection running a
network protocol stack. This CPU can store, average, spectrum analyze,
and data-compress all digitized information before transmitting over a
conventional fiber network. A separate dedicated fiber handles the
FNAL-specific real time signals such as clock, event triggers, and beam
abort heartbeat signals. This will be handled in hardware logic by a PLD
in the electronics module.

A minimal set of fiber connection to each module consists of one network
connection plus one dedicated fiber for delivering Fermilab-specific
clock, event, and safety system signals. For cost estimation purpose we
have assumed four direct point-to-point fiber connections between each
quad location and redundant network hubs at located in the 10km alcoves.
The fiber cable will be a pre-assembled harness 5km long with 4-fiber
breakouts at quad locations every 135m. Installation will consist of
laying the fiber harness in the cable tray immediately below the
electronics modules (fig 5.2.6.2) and plugging the breakout into each
electronics module.

![](media/image52.wmf)

Figure 5.2.6.3: Fiberoptic Clock and Network Connections in the tunnel
including redundant hubs & clock fanouts at 10km alcoves.

The long-haul fiber backbone interconnecting the 10km alcoves around the
ring will be buried with the power duct in the invert. This provides
additional radiation shielding to compensate for the longer distance of
the backbone fiber runs.

#### 5.2.4.8 Miscellaneous Functions (creeping features) of the Quad Electronics Module

The networked DSP at each quad location provides the infrastructure for
additional features to be added at relatively low cost.

-   Tunnel temperature, humidity, and airflow transducers.

-   Integrated radiation dose monitor for the electronics module (FET +
    resistor).

-   RF modules to communicate with the cell phones and PDAs of tunnel
    crews.

-   Microphones for detecting quenches, tunnel dripping, and goofing-off
    crews.

-   Speakers to reprimand the above.

-   Cryogenic sensors and valve controls (presently estimated as a
    separate system)

-   Vacuum valve controls.

### 5.2.5 Once-per-Turn Instrumentation

A number of standard systems occur only once per ring. In general these
can be copied from existing systems in the Tevatron and/or Main
Injector. The 53 MHz bunch structure and modest beam currents (\~1/3 of
Tevatron fixed target) provide no special challenges. These are
discussed more fully in
<http://www-linac.fnal.gov/~mccrory/papers/VLHC_Controls>.

Table 5.2.5.2 -- Once-per-Turn Instrumentation Parameters

  ------------------------ ------------- --------------- --------------------------
  **FUNCTIONOccurances**   **Readout     **Comments**    
                           Frequency**                   

  Tune Measurement         a few/ring    10 Hz           Use Arc Module DSP's for
                                                         FFT?

  Beam Current Toroids     1/ring                        Also on injection lines

  Sampled Bunch Display    1/ring        1 Hz             

  Fast Bunch Integrator    1/ring        1 Hz             

  Synchrotron Light        1/ring        1 Hz             
  Monitor                                                

  Ion Profile Monitor      2/ring        .1 Hz            Small beam size may be
                                                         challenging

  Flying Wires             1/ring         \~few per       
                                         store           
  ------------------------ ------------- --------------- --------------------------

### 5.2.6 Beam Dampers (Lambertson/Marriner)

In the last 30 years high intensity storage rings have become absolutely
dependent on beam damper circuits. The Tevatron in fixed-target mode,
the Booster, and the LHC will not operate anywhere near design intensity
without them. At synchrotron light sources and B-factories the beams are
lost within milliseconds without dampers. It is thus not surprising that
the VLHC requires damper circuits to reach design luminosity for both
Stage 1 and Stage 2 operation. Fortunately this technology is well
developed and the application to the VLHC provides no special
challenges. One new element which does occur in the Stage 1 VLHC is the
necessity to distribute the dampers for one type of instability (the
coupled-bunch resistive-wall instability) around the large circumference
of the ring. While this provides some level of redundancy (since the
beam is stable even if one of the distributed circuits fails) it is a
new element which will be described below. All other dampers are
conventional.

#### 5.2.6.1 Distributed Transverse Dampers for Resistive-Wall Stability (Lambertson)

Growth of transverse motions of bunches in the LF ring will be
suppressed with active feedback systems. The strongest beam impedance
arises from resistive-wall. At the frequency of the first lower-sideband
coupled-bunch mode, which is (1-0.235)*f~0~* = 0.99 kHz, the transverse
beam impedance is (7.84+1.27j)10^10^ ohm/meter. This causes an
exponential growth rate of 2.53 x 10^3^ per second for a fully filled
machine. Prompt cancellation of this growth is provided by six localized
feedback stations spaced around the ring circumference. At each station,
radial and axial damping are the same and for each there are two
feedback systems displaced azimuthally by 270 degrees in betatron phase
to address both 'sine' and 'cosine' phases of the oscillation; this
makes the damping tolerant of changes of tune that might be desired.

![](media/image53.wmf)*Fig. 2 -- Layout of Pickup and Kicker positions
for the horizontal cooordinate at one station. Incoming beams with
sine-like or cosine-like oscillations have their positions sensed by
pickups at cell boundaries (F- locations) and are kicked back towards
the design orbit after one-quarter betatron oscillation. An identical
set of vertical pickups and kickers operates at D-locations. Six
identical stations are distributed around the ring, one at each stage 1
cryoplant location.*

In localized feedback, a kicker is located downstream from the pickup by
90 degrees in betatron phase (one lattice cell) and the signal is
transmitted promptly from pickup to kicker through foam-insulated coax
to minimize delay. Delay in the 271 meters of cable is 180 nanosec. to
which one adds about 50 ns. for electronic processing and amplification.
Although with this delay the signal from one bunch is delivered to the
12^th^ following bunch, the phase delay at 1 kHz is a negligible 1.5
milliradian. For higher-frequency sidebands the phase delay increases,
becoming a significant 1/8-oscillation at 550 kHz. The localized
feedback systems will be used up to 500 kHz; at that frequency the
impedance has become small enough to be controlled by a conventional
one-turn bunch-by-bunch system that extends up to the needed 26.5 MHz
bandwidth of coupled-bunch modes.

![](media/image54.wmf)

Fig. 1 -- Electronic Elements of the Coupled-Bunch Feedback System.

The hardware in a local feedback system consists of (1) a pair of
capacitive pickup plates, (2) electronics and cable to the kicker, and
(3) a 4-meter long stripline-pair kicker. The pickup strips are 25 cm
long and connect to high-impedance amplifiers. The signals are then
differenced and the unipolar pulses are stretched to half the interval
between bunches to give a baseband signal for the kicker. At the lowest,
strongest mode, the required feedback loop-gain is *G* = 0.287 and to
damp injection errors of 0.1 mm calls for a transverse kick of 83.3 kV.
The kicker delivers this with a power input of 1.10 kW. Injection in
bunch trains separated by 2 seconds produces unwanted transients,
especially if there is closed-orbit offset. Bunch signals will be
recorded and analyzed to generate a correction for the local
closed--orbit corrector; this will zero the closed-orbit well before the
second train of bunches is injected. After the ring is filled,
additional rejection of very low frequency excursions will be made by
the low-frequency cutoff of the feedback electronics; this is possible
with baseband operation as we have here. For damping both radial and
axial motions at 6 stations, 24 systems are required for each
circulating beam.

Pickup and kicker are located at points of maximum betatron amplitude in
slightly modified standard arc cells. The modifications \[ref J.
Johnstone presentation in Lake Geneva\] involve removing 5m of magnet
iron at the boundaries of 8 successive half-cells. An additional
quadrupole corrector is used at each location to repair damage to the
β-functions caused by the missing focusing. The \~10% dispersion wave
generated by the missing bend automatically cancels outside the
insertion by virtue of the 360° phase advance across the 8 half-cells.
The damper system uses at most 6 of the 8 available free spaces.

At the coupled-bunch mode frequency of 500 kHz, the growth rate has
reduced to 57 per second or 0.044 per turn. This and all higher
coupled-bunch modes are suppressed by the one-turn bunch-by-bunch
feedback system that operates over the range 53.1±26.5 MHz. The kicker
is a quarter-wavelength long at this frequency, 1.41 meter. The required
kick for 0.1 mm excursion is 26.4 kV and power is 513 watt. Power
amplifiers for this application are commercially available. The pickup
is the same length as the kicker and feedback gain is 0.108. Radial and
axial systems are similar.

\[words on dispersion...?\]

One can ask if electronic noise in these dampers will add emittance
during a long collision time. Fortunately, although the loop gains are
high, the small aperture and peak bunch current of 8.4 ampere make the
pickup signal strong and large electronic gain is not needed. The peak
current gives a pickup sensitivity
$\text{IZ}_{L}\frac{g}{b}\sqrt{2} = 2\text{.}6´\text{10}^{4}$
volt/meter. Input thermal power with an amplifier noise figure of 1 dB
is 1.2*kTB* =5.2x10^-21^*B* where *B* is the bandwidth. Equating this to
the pickup signal power with equivalent rms noise amplitude *X~N~* gives
$X_{N^{2}}\text{>=}3\text{.}7´\text{10}^{- \text{28}}B$. The higher
energy at collision reduces the gain to G =0.013. The 12 feedback
systems would then cause an emittance growth rate, without allowing for
damping, of

$\frac{de}{\text{dt}} = \text{12}\frac{f_{0}g}{2\beta} < G^{2}X_{N^{2}}\text{>=}2\text{.}1´\text{10}^{- \text{17}}$
m/sec

Nominal emittance is 1.7x10^-6^, thus this dilution rate is of no
concern and would actually be smaller because of damping by the
feedback. The broadband system produces a similarly negligible emittance
growth.

#### 5.2.6.2 TMCI Damper (option)

*\[The SLAC ministudy is here\--lets see what they say\]*

### 5.2.7 Injection

### 5.2.8 Extraction and Beam Stop

### 5.2.9 Beam Cleaning (Drozdhin)

### 5.2.10 Radiofrequency Systems (Sergey Belomestnykh)

### 5.2.11 Cryogenic System

#### 5.2.11.1 Cryogenic System Description

The magnet's superconducting transmission line is cooled by pressurized
supercritical helium at 4.5-6.0 K. The heat load of the magnet system is
removed by the sensible heat of the supercritical helium stream. The
fluid operates just outside the critical region expanding the helium
stream as it passes through the transmission line producing a large
effective heat capacity. Cryogens are fed from six (6) refrigerator
plants spaced at 38 km intervals around the ring.

![](media/image55.png)

Figure 1.

For efficiency reasons, refrigeration is provided at two (2) temperature
levels. Refrigeration at a higher temperature (40 K) provides cooling
for a heat shield that is used to intercept much of the heat that would
otherwise be absorbed by the lower temperature superconductor. Each
plant provides refrigeration for upstream and downstream magnet streams.
Each string is sub-divided into two (2) loops, referred to as "near" and
"far" loops.

![](media/image56.png){width="5.995833333333334in"
height="2.1694444444444443in"}

Figure 2.

##### 5.2.11.1.1 Helium Distribution System

The helium distribution system is designed to distribute refrigeration
to the magnet system with a minimal temperature variation. The
distribution system consists of cryogenic valve boxes, transfer lines,
and warm helium header.

###### (a) Cryogenic Valve Boxes

Cryogenic valve boxes are used to redistribute the helium between the
conductor loops for steady-state operation and perform various transient
state operations. These boxes are located every 9.5 km and house the
control valves and instrumentation required for each circuit. Boxes vary
in configuration dependent upon location in the magnet string. It is
believed these boxes are relatively simple devices mainly providing a
transition for flow redistribution.

###### (b) Transfer Lines

Transfer lines are a part of the magnet assembly. A line contains five
(5) circuits: 4.5 K superconductor supply line (near loop only), 6.0 K
superconductor return line, 40 K shield supply line, 70 K shield return
line, and a vacuum circuit. Each section of transfer line is equal in
length to a magnet (67.5 meters) and is attached to the magnet assembly
via a structural anchor at the midpoint of the magnet.

-   The 70 K return line is a 3 IPS stainless steel pipe connected to an
    extruded aluminum shield that surrounds all the inner lines. The
    shield is wrapped with a double-sided aluminized mylar (dimpled and
    perforated). The longitudinal contraction of the line is compensated
    with guided formed bellows in the inner connect. During this
    shrinkage, the G10 support structure is allowed to move within the
    vacuum space.

-   The 40 K shield supply line is a 2 1/2 IPS stainless steel pipe
    supported on the G10 spiders from the aluminum shield. Bellows are
    used at the end of each 67.5 m module to compensate for thermal
    contraction and expansion.

-   The 4.5 K supply -- near loop only -- and 6.5 K superconductor
    return line are Invar tubes which are also anchored at the midpoint
    of the module. These lines are a concentric design. The 6.5 K helium
    flows between two (2) concentric Invar tubes.

-   The 4.5 K supply line is suspended via G10 spiders from a 6.5 K
    inner line.

##### 5.2.11.1.2 Helium Pressure Relief and Venting System

Relief valves for each of the five (5) circuits are located every 540
meters. These valves will vent into the warm helium header that is
itself protected every 1 km at 3 MPa (30.4 bar) from over pressurizing.
Each relief is conventional in nature and set to the correct pressure
setting of its given circuit. The primary need for these reliefs are for
trapped volume and loss of insulating vacuum scenarios. The warm header
is further protected at the refrigerator (above ground) at a set
pressure of 0.2 MPa (2 bar), venting to atmosphere.

![](media/image57.png){width="5.991666666666666in"
height="2.5208333333333335in"}

Figure 3.

Quench protection of the transmission line is discussed in \[1,2\]. The
100 kA transmission line conductor contains enough copper that it can be
safely shut down with a 1 second time constant following a quench. A
number of detailed quench simulations have been performed \[3\]. The
peak temperature is \~250 K. The worst-case peak pressure comes from a
situation in which a mis-steered beam (kicker misfire) causes the beam
to oscillate side-to-side in the beam pipe and scrape heavily in a
series of locations separated by a half-betatron wavelength. In this
case the peak temperature is unaffected, but a worst-case pressure
occurs when the hydrodynamic shock waves from two adjacent quenches
collide at the midpoint between quenches. The peak pressure is below the
4.1 MPa (40 Bar) pressure rating of the transmission line. Thus no
helium needs be vented anywhere, even for a long period following the
quench. The pressure burst from the hydrodynamic shock wave, as
registered on pressure sensors along the transmission line, could
provide a convenient method of identifying where the quench occurred.

##### 5.2.11.1.3 Heat Shield Cooling System

Pressurized 40 K helium is used to intercept the radiation and
conduction heat leak to the transmission line. Helium is supplied from
the refrigerator at 1.72 MPa (17 bar) and returns at \< 70 K and 1.62
MPa (16 bar). Flow is supplied via a 3.5" O.D. tube and distributed via
a pair of 0.25-inch lines every 270 meters carrying 2.0 g/sec. This
scheme provides shield cooling for every two magnets. Control valves and
temperature sensors are included every 270 meters for heat shield flow
control based on temperature requirements.

##### 5.2.11.1.4 Transmission Line Heat Load Estimates

Transmission line heat load estimates are divided into two (2)
components: the primary heat load on the 4.5 K system and the heat load
to the 40 K shield system. The calculated heat loads are presented in
Table 1.

![](media/image58.wmf)

##### 5.2.11.1.5 Power Lead Cooling

Due to its low inductance (3 μH/m) and low stored energy (15 kJ/m), the
transmission line magnets require only a single 50 V power supply and a
single set of 100 kA current leads for the entire machine. If these are
conventional (gas-cooled metal) leads, the helium consumption will be 5
g/s for each lead. If desired, this power requirement can be reduced by
a factor of 4\~5 with the use of High Temperature Superconductor (HTS)
current leads.

#### 5.2.11.2 Refrigeration System 

The refrigeration system is composed of six (6), 4.5 kW @ 4.5 K capacity
facilities equally spaced around the ring. Each facility will also
provide 80 kW of 40 K refrigeration used in the shielding of the magnet
system. This provides approximately a 50% margin above expected steady
state requirements. This margin is required to ensure continued
operation when the heat load increases either due to events such as a
magnet quench or vacuum leak, or because refrigeration capacity falls
below its intended design value (i.e. decreasing machine efficiency or
inefficient heat transfer due to contamination). With this scheme, all
six refrigerators must be operational for the accelerator to function.
No plant redundancy is built into this design.

![](media/image59.png){width="2.8847222222222224in"
height="3.251388888888889in"}

Figure 4.

The process helium is compressed from suction pressure of 0.111 MPa
(1.01 bar) up to an intermediate pressure of 0.41 MPa (4.0 bar) by means
of first stage compressor discharging into a second stage, which
compress the helium to 1.88 MPa (18.5 bar). Turbo machinery is used for
the refrigeration plants while reciprocating machines comprise the
compressor system. There are two cold boxes: the upper and lower cold
boxes. A cold box contains five (5) plate-and-fin type heat exchangers
and three expanders. To avoid return helium gas instabilities due to the
elevation change from the tunnel to the surface, the lower cold box will
be located at the tunnel level. This requires a dedicated space of
16,000 cubic feet (20\' along the beam by 20\' transverse by 40\' high)
located near the accelerator tunnel.

These plants are well within the existing commercial vendor
capabilities. These plants contain no nitrogen pre-cooling. The cold
configuration is a horizontal carbon steel shell enclosure housing all
heat exchangers, piping, valves, cold end of turbo expanders and vessels
operating at cryogenic temperatures. The equipment within the cold box
and the inner face of the vacuum jacket are covered by multilayer
aluminized Mylar. The cold boxes are designed to withstand the outside
atmospheric pressure while they are evacuated and are also protected
against overpressure by safety valves. All internal valves, filters,
turbo expanders, bayonets and major pipe connections are fixed at the
top plate and are accessible from a structural steel platform along the
length of the cold box. The turbo expanders are self activated gas
bearing, superior in their performance to oil bearing turbines. Each
turbo expander is a small single-stage centrifugal turbine braked by a
direct-coupled, single stage centrifugal compressor. The turbine housing
is vertically mounted to a plate at the cold box top, projecting into
its vacuum space. Within the cold box are brazed aluminum heat
exchangers, pressure vessels containing and adsorbent to remove
impurities and the cold end of gas bearing turbo expanders. Part of the
outer shell cover is flanged and has an O ring seal, and can be moved
away on wheels, for complete access to all cold box internal components
and piping. Two cold box panels will be mounted on the structural steel
platform next to the cold box. One containing all instrument
terminations and transmitters, and the other an assembly of purge and
defrost valves. Provisions for purification of the process helium will
be provided at each plant as will oil removal systems. A commercial
control system package will permit the unattended operation of these
plants.

##### 5.2.11.2.1 Helium Compressor System

The compression package will consist of three oil flooded rotating screw
compressors. One compressor will compress from 0.111 MPa (1.1 bar) to
0.4 MPa (4.0 bar), and the two other will compress in parallel from 0.4
MPa (4.0 bar) to 1.88 MPa (18.5 bar). The first stage compressor is
smaller than the two (2) second stage machines. Each compressor skid
contains the compressor, main drive motor, oil reservoir/separator
vessel, and lubrication system mounted on a common rigid skid base. The
base plate provided is suitable for installation on a flat pad without
grouting. The helium enters the compressor and is compressed through the
rotating screw compressor, also flooded with oil. The oil seals the
rotor and absorbs some heat of compression. The compressed warm helium
passes through a water-cooled heat exchanger and then into a bulk oil
separator. The oil is also passed through a separate water-cooled heat
exchanger. Each compressor is direct driven by an electric induction
electric motor. The compressor assemblies are equipped with automatic
inlet and outlet block valves and automatic recycle valves.

The high-pressure helium from the compressors passes through a skid
mounted oil removal system. The oil removal system consists of three
stages of coalescing filter housings followed by a vessel containing
activated carbon. All entrained oil is filtered out of the gas stream by
the three stages of filters. The small amount of oil in the vapor phase
is removed by the activated carbon. The total amount of oil contained in
the helium leaving the oil removal assembly is less than 10 ppb (w/w).

##### 5.2.11.2.2 Helium Liquid and Gas Storage and Inventory Management

##### 5.2.11.2.3 Cryogenic Control System

#### 5.2.11.3 Design Operating Conditions

##### 5.2.11.3.1 Steady State

Helium is supplied from a refrigerator at 4.5 K, 0.4 MPa (4 bar) and
returned at 5.8 K, 0.19 MPa (1.9 bar). Supercritical supply helium is
fed from the helium plant to four parallel loops. Each loop is comprised
of 9.5 km of magnet and transmission line. There are cryogenic
connecting boxes at the beginning and end of each 9.5 km section. At the
exit of the refrigerator the helium process is split into four (4)
paths. There are upstream and downstream magnet strings that are mirror
images of each other. The typical flow schematic of a magnet string is
shown in Figure [?]{.mark}. As helium enters the upstream or downstream
magnet strings the flow is split into two parts: half enters the 4.5 K
transmission line circuit (for the near loop) and half enters the 4.5 K
current return circuit contained in the magnet (for the far loop). There
is expected to be an approximately 1 K gradient across each loop. These
loop flows are then re-distributed at valve boxes and become the return
6.0 K shield flow.

The cooling scheme relies on a balance between heat leak and pressure
drop. Any scenario causing an upset in the heat load (i.e. vacuum
degradation) can be compensated by increasing the helium flow rate and
supply pressure for the proper loop. The refrigerator has been oversized
by 50% to compensate for these types of upset conditions.

![](media/image60.wmf){width="2.917361111111111in"
height="2.0694444444444446in"}![](media/image61.wmf){width="2.792361111111111in"
height="2.0104166666666665in"}

Figure 5. Figure 6.

##### 5.2.11.3.2 System-Wide Purification

Purification of this machine will be done in two (2) steps. First each
sector will be pumped and backfilled five (5) times to 25 inches of
mercury via pump outs on every helium circuit at each valve box located
every 10 km. This method has been proven to work in the Tevatron. Levels
of contamination less than 100 ppmv are achieved with this first step by
using roughing pumps. The second step is dilution purification. A
purifier with a nitrogen cooled charcoal bed will be located at each
refrigeration plant. The discharge gas of the compressor system will be
circulated through this purifier and then will be distributed to the
magnet/transmission line system. Contamination instrumentation, such as
arc cells used on the Tevatron, will be used to monitor the ppmv levels
in each sector. The system will be ready for cool down when
contamination levels are \< 5 ppm. It is estimated that the purification
for a sector in the VLHC will be 72 hours.

##### 5.2.11.3.3 System-Wide Cool down

Cool down of the VLHC will be done in three (3) stages. The first stage
involves the cool down of the helium plants. The second stage is the
cool down of the transmission line to 40 K. Finally the transmission
line will be cooled done to operating temperatures.

In the first stage, cooling is provided by turbines and should not take
more than 24 hours per plant. In the second stage, the plant is setup in
the liquefaction mode and 40 K gas at 0.4 MPa (4 bar) is sent via cool
down valves located at each valve box back to the compressor suction
warm gas header located in the tunnel. Gas flows from the refrigerator
into the warm header through the near loop transmission line, the 6.5 K
return, and the current return circuits. When the temperature at the end
of the "near" loop (measured at the valve box) is 70 K the flow is then
re-directed to the "far" loop and into the return header. As the "far"
loop temperature reaches 70 K the second cooldown stage can be started.

During the second cool down stage the plant is re-tuned for an outlet
temperature of 4.5 K. The flow pattern for the second stage is the same
as the first stage. As the temperature for each loop is at 7 K the cool
down valves can be closed and the flow will be looped back in
refrigerator mode.

Total cool down time is expected to be on the order of 10 days.

#### References *{note -- for sec. 5.2.11}* {#references-note-for-sec.-5.2.11 .Reference-heading}

\[1\] Koepke et al.

\[2\] DR doc

\[3\] N. Shatil final report

### 5.2.12 Vacuum system

{ed. note\--*this clearly needs some editorial mods, which haven't been
done yet}*

#### 5.2.12.1 Introduction

In the present report the required pumping speed, a possible beam
current conditioning scenario, and the beam-gas scattering lifetime are
discussed for Stage 1 VLHC. A self-consistent calculation is performed
assuming that the beam lifetime depends on the beam tube vacuum gas
pressure and on the pp collision rate at two interaction points (IPs).
The vacuum tube pressure, and therefore the beam-gas scattering
lifetime, is a function of the beam intensity. The parameters necessary
for evaluating the beam tube vacuum in the Stage 1 VLHC are shown in
Tables 1 and 2. In Table 1, τ~pp~ represents the proton lifetime
determined by pp collisions at two IPs at the design luminosity 10^34^
cm^-2^s^-1^, with the pp cross section assumed to be σ~pp~=137 mb at 40
TeV cm.

![](media/image62.wmf){width="0.39166666666666666in"
height="0.24305555555555555in"}![](media/image63.wmf){width="0.3416666666666667in"
height="0.24305555555555555in"}![](media/image63.wmf){width="0.3416666666666667in"
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##### 

##### 

#### 5.2.12.2 Vacuum system for the Stage 1 VLHC

Photodesorbed gas is the dominant gas source in the beam tube, and the
photon intensity, 0.8x10^16^ ph/m-sec, at design current, is the most
important parameter for beam tube vacuum. The synchrotron radiation
power in the Stage 1 VLHC, 0.033 W/m, can be absorbed by the room
temperature beam tube and is low enough that active cooling is not
needed.

In Stage 1 the beam-gas scattering lifetime is affected by two
processes: (1) single proton-nuclear collisions leading to a lost proton
and (2) multiple small angle proton-nuclear Coulomb collisions leading
to an increase in emittance.

The luminosity loss rate τ~g~ due to beam-gas scattering is related to
the proton loss rate due to collisions with gas nuclei τ~c~ and the
emittance growth rate due to Coulomb scattering τ~ε~ \[1\], and is given
by:

$\frac{1}{\tau_{g}} = 7\text{.}2 \times \text{10}^{- 6}\sum_{j}^{}{\sigma_{\text{pj}}(\text{mb}){\overline{P}}_{j}(\text{nTorr}) + \frac{1\text{.}\text{33} \times \text{10}^{- 6}\text{γβ}(m)}{\text{cp}(\text{TeV})^{2}\varepsilon_{n}(\pi\text{mm} - \text{mrad})}\sum_{j}^{}\frac{A_{j}(\text{gm}){\overline{P}}_{j}(\text{nTorr})}{X_{0j}(\frac{\text{gm}}{\text{cm}^{2}})}}$
(1)

where *A~j~* is the gram molecular weight, *β *the average beta function
*233 m*, and *ε~n~* the normalized emittance *1.67 π mm-mrad* \[5\], the
proton collision cross section σ~pj~, the radiation length X~oj~ and the
initial photodesorption coefficient η~0j~ are listed in Table 2. For
H~2~O σ~pj~=644*mb*, X~oj~=36 *gm/cm^2^*. The first term in eq. (1) is
twice the proton loss rate and the second term is the emittance growth
rate. Beam-gas collisions will be negligible if τ~g~ is much larger than
the luminosity lifetime τ~L~=τ~pp~/2. We will define the beam-gas
scattering lifetime negligible when τ~g~\>\>5τ~L~ , with
τ~L~=τ~pp~/2=46.5 hrs.

Once τ~g~=5τ~L~ = 232 hrs. is fixed, we estimate the average beam tube
gas pressure for each gas species taken separately, with the results
given in Table 3. From Table 3, we can see that the CO scattering
equivalent tube pressure should be less than 0.33 nTorr to reach
τ~g~\>5τ~L~.

In addition to the degradation of luminosity lifetime, we have to
consider the consequences of the beam-gas scattered beam power which can
lead to undesirable heat loads and activation of storage ring
components. We estimate the beam tube pressure that would result in a
scattered beam power of 0.1 W/m, corresponding to a typical limit for
the global capacity of a cryogenic refrigeration plant. Results for each
gas species are given in Table 3, where we can see that the pressure
limiting factor is given by beam-gas scattering particle loss rather
than the power loss.

In the low field Stage 1 VLHC, we will consider a distributed NEG strip
plus lumped ion or cryo pump system in a pumping antechamber connected
to the beam tube with long slots.

The non-evaporable getter concept, similar to LEP, is a relatively
simple solution, a single NEG strip running inside the pumping
antechamber, but needs activation, reconditioning and significant lumped
pumping for methane. Since the critical energy for the Stage 1 VLHC is
so ![](media/image64.wmf){width="0.7082677165354331in"
height="0.2637795275590551in"}low, 86 eV, high Z shielding (e.g. a layer
of Pb) around the beam tube vacuum chamber is not needed.

We assume lumped ion pumps, with pumping speed S=100 l/s, are connected
to the pumping antechamber at an axial interval of L=22.5 meters. Their
pumping speed will be conductance limited by the beam tube and the
antechamber, and the effective pumping speed for CH~4~ is then
*S~eff~\~2.2 l/s-m*. In our calculations a NEG St101 strip, supplemented
by ion pumps for pumping methane, has been considered.

The dependence of the photodesorption yield, number of molecules
desorbed per incident photon, for each species "j", with the photon dose
D is given by:

$\eta_{j} = \eta_{0j}\text{ D}^{- \nu_{j}}$ (2)

where for practical use of the formula we have assumed a constant value
of the photodesorption yield ~0j~, up to an integrated photon dose of
\~10^19^ ph/m \[6\]. The photodesorption coefficents are key parameters
for the beam tube vacuum in a storage ring. For the calculations in this
paper the data given in Ref \[2\], obtained for in situ baked Al at a
critical photon energy of 86 *eV,* have been fit with Eqn. 1. The
inverse power dependence of the photodesorption yield on the photon dose
implies the so called conditioning effect, or the decreasing
photodesorption yield due to the removal of gas molecules from the near
surface oxide layer with continued exposure to photons. As a result, the
required pumping speed decreases in time as a function of the integrated
current intensity. This can have implications for the frequency of NEG
regeneration.

We will estimate the CO equivalent pumping speed necessary to achieve
the vacuum pressure indicated in Table 3, within a reasonably short
conditioning time. We may define as "reasonably short" equivalent to a
few tenths of a year of operation, e.g. 0.3, when the machine is running
at design beam intensity. An operational year is typically taken to be
\~ 10^7^ sec. Therefore, we estimate the CO equivalent pumping speed
needed to reach τ~g~=5τ~L~ by I\*t=158 *A-hrs*. In Fig. 1 the CO
equivalent pumping speed S~CO~ required to achieve a beam-gas scattering
lifetime τ~g~ is plotted as a function of the integrated current for
τ~g~/τ~L~ = 0.01, 0.03, 0.1, 0.3, 1, 3 and 10. From Fig.1 we may
conclude that a pumping speed S=32 l/s-m is required to reach a beam-gas
scattering lifetime of τ~g~=5τ~L~ after an integrated beam current
I\*t=158 *A-hrs* for the Stage 1 VLHC. For more detailed calculation and
formulae, see Ref. 1 and the future reports given in the abstract of
this paper.

![](media/image65.png){width="5.55in" height="3.4263779527559057in"}

## Conditioning Scenario

The conditioning effect will improve the beam lifetime which is itself
then function of the integrated current intensity. We present here a
possible conditioning scenario, for Stage 1 VLHC, where we increase the
initially injected beam current from 50 mA up to 190 mA (nominal), in
four steps. Our procedure is to inject beam with increased current
whenever the luminosity lifetime reaches τ~L~=46.5 hrs, corresponding to
the design parameter value. The possible beam current program for our
conditioning scenario is plotted in Fig. 2.

The beam lifetime τ~b~ is related to the vacuum pressure and to the pp
collision rate at the interaction point, and is defined as
1/τ~b~=1/τ~pp~+1/τ~g~. In Fig. 3 the beam lifetime is shown as a
function of time, for our conditioning scenario. The luminosity lifetime
is then given by τ~L~=τ~b~/2.

The total beam tube vacuum gas pressure decreases as the surface is
progressively cleaned, and is shown in Fig. 4 as the CO scattering
equivalent pressure. The equivalent CO scattering pressure of gas
species \"j\" is defined as:

$P_{s,j} = P_{j}\frac{\sigma_{j}}{\sigma_{\text{CO}}}$ (4)

and is also shown for each gas in Fig. 4. The CO scattering equivalent
gas pressure of species \"j\" is equal to the partial CO gas pressure
which would result in the same beam-gas scattering as the actual
pressure of species \"j\". In this way the partial pressures in Fig. 4
can be compared on an equal footing as they effect the beam-gas
scattering lifetime. We can see from Fig. 4 that CH~4~ is the gas having
the largest equivalent CO scattering pressure. The pumping speed of the
NEG material decreases in time as the pumped gas molecules accumulate on
the surface. For this reason we have taken into account, in our
calculations, the pumping speed variation of the NEG St101 strip (30 mm
wide, LEP type) as a function of the quantity of gas that has been
pumped as given in Ref. \[4\]. Once the NEG surface saturates, a surface
regeneration will be necessary to re-establish the maximum initial
pumping speed. The surface pumping capacity for CO is 10^-4^ Torr
l/cm^2^ \[3\]. We therefore have to consider reconditioning the NEG
after a total desorbed gas load of Q\~3 10^-2^ Torr l/m \[4\]. As an
example, after 100 hrs at the end of this conditioning scenario, the
total CO and CO~2~ gas amount pumped by the NEG is Q\~1.5 10^-2^ Torr
l/m, still a factor of two below the gas load needed for reconditioning.

![](media/image66.png){width="4.366535433070866in"
height="2.930708661417323in"}

## Beam scattered power at the interaction point

In addition to previous considerations on the beam tube vacuum issues
for the VLHC, we have estimated the beam scattered power at the IP, as a
result of the pp collisions, which is given by

*P~IP~=σ~pp~**L**E* (5)

where L is the luminosity. The beam scattered power per beam is shown in
Table 4, and compared to the LHC case.

![](media/image67.png){width="4.35in"
height="2.9192913385826773in"}![](media/image68.png){width="5.984251968503937e-2in"
height="6.73228346456693e-2in"}

Fig.3. Beam lifetime, beam-gas scattering lifetime, proton-proton
lifetime in this possible conditioning scenario.

#### ![](media/image69.png){width="4.441666666666666in" height="2.9868055555555557in"} {#section-3 .Reference-heading}

Fig. 4. Scattering pressure equivalent to CO, and total pressure in this
possible conditioning scenario.

####  {#section-4 .Reference-heading}

#### References *{note -- for sec. 5.2.11}*  {#references-note-for-sec.-5.2.11-1 .Reference-heading}

\[1\] W. Turner "*Beam Tube Vacuum in Low Field and High Field Very
Large Hadron Collider*", LBNL-39482, UC414, presented at the Snowmass
Conference, CO, October 1996.

\[2\] J. Gomez-Goni, O. Gröbner and A.G. Mathewson *"Exposure of a baked
Al lined stainless steel chamber to photons",* CERN, Vacuum Technical
Note 94-10 pg. 9, AT-VA/JGG.

\[3\] A. Chao and Tigner*, "Handbook of Accelerator Physics and
Engineering",* pg.329

\[4\] C. Benvenuti, *"Molecular Surface pumping: the getter pumps",* CAS
Cern Accelerator School - Vacuum Technology, CERN Yellow book, pg. 48.

\[5\] W. Foster and al. "*Staged VLHC Parameters List, version
2/23/01*", private comunication, Fermilab, Chicago, IL, February 2001.

\[6\] O. Gröbner, *"Dynamic outgassing",* CAS Cern Accelerator School -
Vacuum Technology, CERN Yellow book, pg. 130.

### 

### 5.2.13 Beam abort and absorbers

*Ed. note: see current version of 5.2.13 as postscript file in*
[\\\\tdserver1\\project\\VLHC\\TDDoc\\DesignStudyReport\\05_Stage1_components\\Draft3\\ed-design.ps](../../../../../../../../project/VLHC/TDDoc/DesignStudyReport/05_Stage1_components/Draft3/ed-design.ps)

## 5.3 Environmental issues during operation

*{ed. note: this section will be derived from the following material
provided by Cossairt}*

# IV. Potential Environmental, Safety, and Health Issues

**Environment, Safety, and Health Considerations for a New Accelerator
Facility**

**I. Introduction**

All of the possible future accelerators under study present a number of
considerations in the general area of environment, safety, and health.
It is the intent of this chapter to identify the character of these
challenges in a general way. The environment, safety, and health issues
peculiar to a particular possible accelerator are discussed in the
chapters related to that technology. Some of the considerations which
much be taken into account are very similar to those that have been
encountered and solved during the construction and operation of other
facilities at Fermilab and at similar laboratories elsewhere in the
United States and worldwide. Other considerations have not been
encountered on the same scale previously in connection with the
construction and operation of accelerator laboratories. These novel
issues will require particular attention as such a project proceeds to
assure their timely resolution in a manner that is cost-effective and
that meets the approval of the public. In this chapter, both the
conventional and the novel issues are discussed, with perhaps more
emphasis devoted to the latter. It is concluded here that with adequate
planning in the conceptual design stages, these problems can be
adequately addressed in a manner that merits the support of the
Laboratory, the Department of Energy, and the public.

**II. Procedural/Regulatory Matters**

The actual design, construction, and operation of any future accelerator
will have to meet a number of procedural/regulatory milestones in the
area of environment, safety, and health to assure timely and continued
support of this project by the public and by the Department of Energy.
The devotion of early attention to these issues is likely the best way
to enhance public support of any chosen accelerator technology.
Requirements in environment, safety and health are currently set forth
as a part of Fermilab\'s Work Smart Standards in Environment, Safety,
and Health that are incorporated in the current version of the contract
between Universities Research Association and DOE. Currently, the Work
Smart Standards are reviewed annually to assure that they adequately
address the hazards of the laboratory, including those of any new
facility. If changes are necessary they are negotiated with the DOE-FRMI
Group and the URA-DOE contract is revised accordingly. These standards
include listings of applicable Federal and State Regulations as well as
internally developed policies and national standards (WSS 99). Of
course, the contract under which Fermilab or a future accelerator might
operate in the future is likely to change in ways that could modify the
applicable requirements.

**A. [Environmental Protection Procedural/Regulatory
Matters]{.underline}**

All DOE activities are subject to the requirements of DOE\'s regulations
for implementing the National Environmental Policy Act (NEPA) (CFR 97).
First, any new project of the magnitude of those under consideration in
this report will be the subject of an Environmental Assessment (EA). A
review will be done of all possible impacts of this project on the
environment and the public. The required analysis is broad in scope and
includes societal impacts along with those topics that are more
generally associated with environmental protection such as the
discharges of pollutants, effects upon wetlands and floodplains, and
exposures of people to chemicals and radioactive materials. It will
include a review of the alternatives of carrying out the project
elsewhere or not at all. This process is centered on the production of a
comprehensive document but also includes the participation of the public
by methods that will be chosen by DOE. As a result of the environmental
assessment process DOE will either issue a Finding of No Significant
Impact (FONSI) or conclude that that the preparation of an Environmental
Impact Statement (EIS) is necessary. An EIS may well be required due to
the size, scope, cost, or impact on the human environment of the
project. For example, it is likely that an EIS will be required for any
new facility that extends beyond the present boundary of the Fermilab
site. The completion of the EIS process results in the issue of a formal
public notice called a Record of Decision (ROD). The EIS process is
generally considered to be an arduous one, but one that can be followed
to a successful conclusion stated in the ROD. The preparation of an EIS
is certain to be a large task having significant cost, customarily
accomplished using external resources. Regardless of the eventual path
of the NEPA process, project funds cannot be issued to support such a
Congressional \"line item\" project beyond the early conceptual stage
prior to the successful completion of the NEPA process. It is thus
crucial that this process be conducted in a manner that is honest and
which comprehensively addresses the potential concerns of members of the
public. A good working relationship with the Department of Energy is
also a necessity to a successful result.

Other procedural requirements apply in the area of environmental
protection. These will be more certainly identified as a part of the
NEPA process but early planning may well serve to avert problems later.
DOE facilities are generally subject to Federal and State environmental
protection regulations promulgated chiefly by the U. S. Environmental
Protection Agency (USEPA) and the Illinois Environmental Protection
Agency (IEPA), respectively. There are environmental permits to obtain
from both state and federal authorities that are likely to be found to
apply to any of the possible facilities. Some of these apply during the
construction stages, others apply during operations, and some apply
during both stages. Permits are likely to be required to cover such
topics as storm water discharges, discharges of cooling water, wetlands
mitigation, releases of air pollutants for both non-radioactive
pollutants and for radionuclides, and construction in any floodplains.
Archaeological sites are also located in the region that might need
further investigation and study prior to the commencement of
construction. The preparation of the applications for these permits and
approvals is generally straightforward, but must be accomplished with
the long lead times, typically 180 days, required by the issuing
agencies. Early coordination with the project design team should greatly
facilitate completion of the associated milestones. Any chose
accelerator is likely to be initially viewed by the public and by
Federal and State regulators as a poorly understood, esoteric
technology. In recognition this and also of the fact that any of the
chosen accelerators will involve some sort of impact beyond the
geographical boundaries of the present Fermilab site, early coordination
with the Federal and State regulatory agencies is recommended as a
vehicle to promote enhanced understanding of the nature and impact of
the chosen facility.

**B. [Safety and Health Procedural/Regulatory Matters]{.underline}**

In accordance with the Fermilab\'s Work Smart Standards, the Laboratory
will be required to prepare an assessment of the environment, safety,
and health issues associated with this project in the form of a Safety
Assessment Document (SAD). Given the size, scope, cost, and novelty of
any of the candidate facilities, the preparation of a first stage
document called a Preliminary Safety Assessment Document (PSAD) is
needed. The purpose of the PSAD is to identify the relevant
environmental, safety, and health issues at an early stage and propose
how they might be mitigated. A final Safety Assessment Document (SAD),
then, documents the resolution of all the pertinent issues raised by the
PSAD. Environmental issues are customarily integrated into the PSAD/SAD
process to promote program cohesiveness. Given the scope of any of the
candidate projects discussed elsewhere in this report, it is nearly
certain that DOE will choose to review these safety documents by
utilizing an external review team composed of both DOE staff and
representatives from other DOE facilities. Just prior to facility
operation, a readiness review will be conducted in similar fashion using
an external review team. DOE has specified a somewhat more rigorous
procedure for the conduct of this safety review process in its Orders.
The details of the procedures to be followed in the safety review
process will be determined by the terms of the contract under which the
Laboratory is operated at the time the project might proceed. Unlike
NEPA assessment activities, PSAD/SAD activities generally begin after
funds are issued. Nevertheless, careful consideration of PSAD/SAD in the
design can only result in beneficial results. Efforts should be taken at
early stages to promote consistency between the conclusions of the NEPA
assessment and the safety and health documentation.

DOE is presently \"self-regulating\" in the areas of industrial safety
and occupational radiation protection. There is a possibility that
during the development of the next accelerator facility, DOE activities
might become subject to \"external\" regulation in these areas, as well
as in occupational radiation protection. It is difficult at this time to
anticipate the form such external regulation might take or which
agencies might be involved. Fermilab staff and DOE continue to monitor
the status of DOE self-regulation in order to identify new requirements
or procedures that might apply to Laboratory activities.

**III. Occupational Safety During Construction**

Any of the accelerators under consideration will involve a great deal of
construction. In regions where the standard \"cut and fill\" method used
elsewhere successfully at Fermilab for many years, the standard
practices embodied in the Occupational Safety and Health
Administration\'s (OSHA\'s) regulations on the safety of construction
activities will be followed (see WSS 99). Particular requirements that
address excavations, the provision of applicable personnel protective
equipment, coordination of emergency response measures, fire safety,
chemical safety, and electrical safety would apply as they have for many
years to other civil construction projects on the Fermilab site.
Adequate means of egress of construction workers would need to be
provided. Given the nature of the candidate facilities, somewhat unlike
present facilities, significant slopes may be involved in some
locations. Well-thought means of prevent of accidents due to heavy
objects moving downhill should be included in the design.

The candidate facilities all involve a considerable amount of tunneling
in bedrock units, some of it horizontal and others with slopes. In
addition to the safety requirements pertaining to construction
activities, Federal regulations pertaining to underground operations
(e.g., \"mining\" activities) come into play. Solutions to these issues
are being developed to address challenges of this type encountered in
the excavation for the NuMI project. These include the standard concerns
about tunneling safety and material movement as the tunneling proceeds.
The choice of construction methods between the use of Tunnel Boring
Machines (TBMs) or the employment of drilling and blasting methods will
most likely be one of economics or availability. However, either
alternative has associated occupational safety considerations.
Provisions for emergency response including underground rescues will be
needed. Again, egress issues relevant to protection of the construction
workers will be of paramount importance.

Given the location within several major aquifers, and the existence for
some facilities of downward slopes at certain locations, it is clear
that stringent measures must be taken to prevent flooding both during
the construction period and thereafter. This problem must be addressed
in harmony with the related environmental protection concerns (see
Section IV). Likewise, any downward slopes in the bedrock units will
require the same attention to the prevention of uncontrolled movements
of heavy objects downhill as in the \"cut and fill\" zone. While such
control measures are well within those encountered in mining operations
elsewhere, they are novel at accelerator laboratories. The existence of
any steep slopes also needs to be carefully considered in planning for
emergency rescue operations that conceivably could be needed during
construction.

During project construction, industrial radiography, a tool commonly
used in general industry, is likely to be employed to assure the quality
if pipe welds, etc. Such radiographic operations, which typically use
radioactive sources of high activity and relatively hazardous compared
with the sources commonly used in particle physics experiments, would
need to be conducted in compliance with the pertinent requirements of
the State of Illinois in order to control the hazard to personnel of
these intense radioactive sources. In the course of construction, other
radiation-generating devices such as soil density gauges and media
water-content probes might also need to be used. Standard procedures
pertaining to such activities should be applied.

**IV. Environmental Protection During the Construction**

All of the candidate facilities will be placed in whole or in part
underground. Some portions will be located near the surface, in the
glacial till, while others will be located underground in the various
rock strata. For the portions near the surface, construction may proceed
by cut and fill techniques similar to those employed to build most of
the present facilities at Fermilab. Erosion control measures similar to
those in practice for a number of years will be employed in accordance
with good engineering practice and Federal and State regulations. Dust
from any spoil piles must be kept under control. Likewise, a storm water
management plan will need to be developed. If 5 acres (2.0 hectares) or
more of land surface are impacted by the construction, a National
Pollutant Discharge Elimination System (NPDES) Stormwater Permit for
construction will be needed which will include specific actions which
must be followed during the construction period. The usual precautions
to prevent pollution from spills of regulated chemicals from the
construction equipment will need to be taken. Noise from construction
activities is not expected to be significantly larger than that
associated with normal civil construction activities in the vicinity of
Fermilab.

The NEPA process described in Section II.A should result in a
determination of the impact of the project on wetlands and or
floodplains. A general description of how any identified effects will be
mitigated will have been developed. For example, if more than 3 acres of
wetlands are identified, it may be necessary for compensatory man-made
wetlands to be created. Rearrangement/enlargement of the Fermilab pond
system might prove to be necessary to compensate for possible
interference with floodplains. It may be especially important to
demonstrate adequate care for floodplains due to significant local
public concerns about flood prevention.

Tunneling in the bedrock units will result in the removal of a
considerable volume of rock, dependent upon project details. The
management of the spoil is a major issue that must be addressed and
provisions for its proper stockpiling provided. In particular, concerns
about dust may be more severe for this material, largely pulverized
rock. The duration of this storage may be temporary for the spoil that
is of marketable quality and longer for that requires reuse at Fermilab
or disposal. This should be carefully planned in accordance with
Fermilab\'s longstanding tradition of placing high importance on
aesthetic issues. The management of spoil materials will need especially
vigorous attention if its removal at any off site locations is needed.
The placement of such a project in any aquifers results in the need to
protect drinking water resources from contamination during construction.
Also, the \"dewatering\" of tunnels as the construction proceeds will
require measure to be developed to prevent the depletion of wells and
also to manage effectively any additional water discharges from this
source.

The storm water management plan will need to take into account any
releases of groundwater generated in the course of \"dewatering\" the
tunnel. Careful hydrogeologic studies need to be performed to understand
the interplay of the construction of the project with the various
aquifers. This must be done to establish with certainty that the
construction activities will not cause significant perturbations of the
local individual and municipal water supplies, either in quality or in
quantity. It should be mentioned that the exact depth of the various
aquifers are not known in detail at all locations involved in the
proposals discussed in this report. Accurate measurements will be
needed, through geological investigations over the entirety of the
affected region. The results can be used to plan a strategy for
preventing the tunnel from serving as a possible path of
cross-contamination from one aquifer to another. During construction
activities, precautions are needed to guarantee that spills of
chemicals, including lubricants and fuels from the construction
equipment, are captured before they enter the groundwater. The presence
of any downward slopes presents special considerations in this regard
that should be addressed.

Tunneling activities can generate considerable noise and vibration.
Should blasting techniques be used, quantitative standards apply to the
amplitude of the vibrations that are allowable at the surface. Noise
exposure, both occupational and to the public at the site boundary and
at off site locations will be an issue that needs to be addressed.

**V. Occupational Safety During the Operations**

**A. [\"Ordinary\" Occupational Safety Hazards]{.underline}**

The occupational safety hazards encountered at all other large particle
accelerator facilities will be found in all of the candidate facilities.
In this section, the focus is on the issues that have been successfully
addressed before, at Fermilab and elsewhere. These have been
successfully addressed by well-known techniques and are simply listed
here, along with the corresponding safety and health needs, for
completeness:

-   The facility will use high current electrical circuits on a large
    scale. Present techniques in managing power distribution and
    providing means to effectively lock out supplies should be adequate
    to address the electrical hazard.

-   Radiofrequency (RF) generation and distribution equipment will be
    used extensively. Present techniques for controlling possible
    exposures to non-ionizing radiation should be sufficient.

-   Large amounts of cables in cable trays will be installed. Current
    methods for addressing fire protection concerns should be adequate.

-   Long tunnels will be present. There is a need to adequately address
    Life Safety Code/fire protection issues to assure adequate
    provisions for egress and adequate means of prevention of and
    response to fires.

-   There will be movements and alignment of large, heavy components.
    There is a need to include considerations in the design related to
    ease of movement of equipment to facilitate the prevention of
    injuries.

All of these issues can be readily addressed by applying the present
collective experience to the design at an early stage.

**B. [Novel Occupational Safety Hazards]{.underline}**

This section is directed to those occupational safety hazards that are
not generally encountered at accelerator facilities. These will all
require consideration in the early planning stages in order to be
addressed in an efficient manner.

*i. Large Scale Use of Cryogens*

This facility requires the extensive use of superconducting materials
and cryogenics in both magnets and RF structures. While these
technologies are relatively new, a number of accelerators world-wide
have developed techniques adequate for addressing them. Provisions will
need to be made for the safe release of cryogens to the surface both
during normal operations and in the event of quenches. Current
accelerator facilities have developed mechanisms for using skilled
engineers to independently review such systems for safety during the
design and commissioning stages. The result has been the development of
a number of standard engineering practices to mitigate both direct
cryogenic hazards and the accompanying oxygen deficiency hazards (ODH).
This general approach, if taken, should adequately address these.

*ii. Ionization Cooling Technology*

Some concepts involve the use ionization cooling, a choice that presents
some novel hazards. The use of liquid hydrogen (LH~2~) is being
considered as a possibility preferable to hazardous or toxic materials.
While this choice may be preferred from environmental protection and
industrial hygiene standpoints due to the lack of the potential for
spills or exposures to hazardous or toxic materials, the fire/explosion
hazard represents an important consideration. In an ionization cooling
system, the LH~2~ cells will be interleaved with RF structures and
magnets that apply a great deal of electrical energy. The impact of the
absorption of energy from the particle beams is also a consideration. In
view of these considerations, a recommended approach would be to convene
a review committee of qualified individuals at the earliest reasonable
state in the design of any facility chosen which incorporates this
technology to assure adequate, cost-effective solutions.

*iii. Life Safety-Egress Considerations*

As during construction, the strong desire to minimize the number of exit
points will render adequate design and engineering with respect to the
Life Safety Code imperative. It is likely that special means of
communication underground will need to be provided, \"refuge\" locations
incorporated into the design, and adequate means of transport of
personnel, both healthy and injured, to the surface established. These
provisions will need to incorporate recommendations of a qualified fire
protection professional at the time of the development of the conceptual
design in order to assure adequate allowances for their costs. Later
involvement of fire protection engineering will also be needed as the
detailed design proceeds.

**VI. Ionizing Radiation Safety During Operations**

**A. [Prompt Radiation Shielding]{.underline}**

All of the possible choices of the future accelerator will likely
require significant amounts of passive shielding to attenuate prompt
radiation to levels acceptable to the members of the public. Indeed,
this fact is implicitly recognized by the proposed siting of these
facilities deep underground. The shielding demands of proton
accelerators are generally recognized to greatly exceed those of
electron machines especially with regard to attenuating the neutrons
produced at large angles. At the forward angles, given the copious
production of muons, and the increased importance of range-energy
straggling at high energies (Va87), the shielding requirements of any of
the new machines increase rapidly with energy and must be
well-understand at the earliest possible stage in the design and in the
NEPA process.

Some detailed understanding of the pertinent requirements must preface
further discussion. Current Department of Energy requirements are not
well-matched to discussions of radiation fields that exist beyond the
boundaries of DOE sites. DOE has specified the annual limits on the
radiation dose equivalent that can be received by occupational workers
and members of the public (see Regulation 10 CFR 835 in WSS 99 and DOE
93). These limits, in all situations expressed to date, pertain to the
dose equivalent delivered to people or to locations where people could
reasonably be. For individual members of the public, the primary limit
is 100 mrem (1 mSv) in a year, not including man-made, medical, or
enhanced natural radioactivity. This limit is intended to apply to all
sources of radiation exposure that a person might receive, even from
non-DOE manmade sources. Special reporting requirements apply when the
annual dose equivalent received by an individual exceeds 10 mrem (0.1
mSv) in a year. DOE has expressed the view that nonoccupational annual
doses to real members of the public are not expected to exceed a few
mrem in a year. In light of public concerns about radiation exposures,
any new facility should be designed to keep the dose that could be
reasonably received by actual members of the public to as small a value
as possible. Higher annual dose equivalents at underground locations
inaccessible to people but beyond the control of host laboratory might
well be allowable. These criteria should be selected early in the NEPA
process with the support of DOE secured. As a convenient reference
point, the average annual radiation dose equivalent received by
individuals living in the United States is about 360 mrem (3600
microSv). Of this exposure, about 300 mrem (3000 microSv) is due to
natural sources, including exposure to radon indoors (NCRP 87).

While the proper shielding against hadrons (mostly neutrons) and
electrons at high energy accelerators is quite well understood, several
new problems must be successfully solved for most of the facilities
under consideration. The likely large dimensions of the facility coupled
with the long ionization ranges and the increased importance of the
range-straggling phenomenon of muons in any new regime of higher energy
will require that the curvature and profile of the earth\'s surface be
taken into account to assure valid shielding calculations. Also, for
some facilities prompt radiation dose due to neutrinos may arise as a
significant consideration for the first time (Mo 99). Both of these
problems have considerable impact upon the selection of the
\"footprint\" of controlled, and uncontrolled property that is needed
for or impacted by the facility.

**B. [Residual Radioactivity of Components]{.underline}**

Several of the accelerators under study will have portions that must
handle beam powers of unprecedented magnitude. As is well known, in the
high energy region, most, but not all, of the radiation effects scale
roughly with the beam power for either accelerated electrons or protons.
In particular the effects of high residual activity levels should be
carefully taken into count at early stages of design of collimation
systems, targets, ionization cooling apparatus and other locations of
possible high losses of beam. The usage of materials in the target
stations of high atomic number and which might not be solids at their
operational temperature merit significant, early attention as plans
proceed and choices are made. Doses that might be received by workers
are an important subject that must be assessed as a part of the NEPA
process. The need to minimize the generation of radioactive wastes and
to eliminate the creation of wastes that contain materials that are both
toxic or hazardous and which contain radioactive is an important concern
at all points during the design effort.

**C. [Airborne Radioactivity]{.underline}**

The production of airborne radioactivity at a future accelerator needs
careful consideration. Federal Regulations promulgated by the U. S.
Environmental Protection Agency (EPA) have established an annual limit
on dose equivalent of 10 mrem (100 microSv) to any member of the public
that can be received as a result of operations of DOE facilities such as
accelerators (CFR 89). Further, the same regulations impose stringent
continuous monitoring requirements if the annual dose equivalent to any
member of the public is to exceed 0.1 mrem (1 microSv) in one year. In
addition, if the level of 0.1 mrem in one year is to be exceeded, then
an application for approval to construct and a notification of startup
must both, in proper sequence, be submitted to the U. S. Environmental
Protection Agency. Given the nature of the proposed facilities and their
extent beyond the present boundaries of the Fermilab site, careful
attention must be paid to the production of airborne radioactivity. The
high beam power of any of the possible machines can lead to the
production of airborne radionuclides that, while generally of short
half-life, have the potential to deliver annual doses above allowable
levels in areas accessible to the public. Care in design should be able
to mitigate these releases.

**D. [Radioactivity in Soil and Groundwater]{.underline}**

The placement of any of the future facilities in both the glacial till
and the underlying bedrock requires that the production of radioactivity
in these hydrogeologic units be given careful attention. Again the
anticipated beam powers require careful consideration of such
radioactivity. Before the exact footprint of any chosen facility is
irrevocably determined, detailed hydrogeologic studies should be
conducted to determine the relevant parameters precisely, as they are
known to vary significant in the vicinity of the Fermilab site. It is
clear that protection of groundwater against contamination with
radioactivity merits early, detailed attention in project design to
assure satisfaction of likely public concerns. It may well be that the
most prudent choice of design objectives might be far below present
regulatory standards for drinking water.

**VII. Non-Radiological Environmental Protection Issues During
Operations**

Operations of the facility should be planned in a way that incorporates
proper measures to control the generation of non-radioactive wastes.
Further, there is a need to address potential spills of hazardous or
toxic materials in a way that fully protects members of the public and
of environmental resources. The detailed attention to these issues will
be required as part of the NEPA process and the designs should provide
information of the quality needed to support all required permit
applications to State and Federal environmental regulatory agencies. For
the operational facility, in any enclosures located deep underground the
cross-contamination of the various aquifers must be prevented and any
dewatering operations must assure that local community or individual
drinking water supplies are not perturbed.

**VIII. Summary**

All of the candidate facilities result in a number of challenges in the
area of environment, safety, and health. Many of these have been
encountered, and effectively addressed, at other accelerator facilities.
Some of the problems are common to other recent projects undertaken at
Fermilab and elsewhere that have resulted in the need to develop new
methods to address them. Given the new scale of any of the candidates,
and their nature, some of these issues may have a greater importance
than found in the present experience. It is concluded here that with
adequate planning in the design stages, these problems can be adequately
addressed in a manner that merits the support of the Laboratory, the
Department of Energy, and the public.

**References**

CFR 89 United States Code of Federal Regulations, Title 40, Part 61,
Subpart H, \"National Emissions Standard for Hazardous Air Pollutants
(NESHAP) for the Emission of Radionuclides other than Radon from
Department of Energy Facilities\", 1989.

CFR 97 United States Code of Federal Regulations, Title 10, Part 1021,
\"\[Department of Energy} National Environmental Policy Act
Implementation Procedures\", 1997.

DOE 93 U. S. Department of Energy, \"Radiation Protection of the Public
and the Environment\", DOE Order 5400.5, January 7, 1993.

Mo 99 N. V. Mokhov and A. Van Ginneken, \"Neutrino Induced Radiation at
Muon Colliders\", presented at the 1999 Particle Accelerator Conference,
New York, New York, Marcy 19-April 2, 1999, FERMILAB-Conf-99/067.

NCRP 87 National Council on Radiation Protection and Measurements,
*Ionizing radiation Exposure of the Population of the United State and
Canada from Natural Background Radiation,* NCRP Report No. 94, December
1987.

Va 87 A. Van Ginneken, P. Yurista, and C. Yamaguchi, \"Shielding
calculations for multi-TeV hadron colliders\", Fermilab Report FN-447
(1987).

WSS 99 \"Fermilab Work Smart Standards Set\", Fermi National Accelerator
Laboratory, http://www-lib.fnal.gov/library/protect/worksmart.html,
November 15, 1999.

[^1]: One unit is 10^4^ • the harmonic normalized to the main field.

[^2]: Calibration in both a dipole and quadrupole magnet are required
    due to the large gradient which we want to measure with high
    accuracy.