# ***US/CERN LHC Accelerator Collaboration***

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# **DESIGN REPORT**

**for the**

# **1.2. Interaction Region Dipoles**

# **and the**

# **2.1. RF Region Dipoles**

####### Magnet Group

Brookhaven National Laboratory

September 3, 1999

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# 

# **Table of Contents**

# 

# **Introduction**

##### Objectives, Specifications and Requirements

1.  Overview

2.  Dipole Cold Mass

3.  Assembled Magnets

#### C. Technical Description

1.  Superconductor

2.  Dipole Beam Tube

3.  Dipole Coil

4.  Collars

5.  Dipole Yoke and Helium Containment of the 2-in-1 Magnet

6.  Analysis of the Collar-Yoke and the Yoke-Shell Interfaces

7.  Electrical Connections and Quench Protection

8.  Dipole Cryostats

9.  Interfaces to LHC Systems and Magnet Cooling

10. Transfer Function, Quench Field, Inductance, and Stored Energy

11. Magnetic Field Quality - Measurements

12. Magnetic Field Quality -- Measurement Errors

13. Magnetic Field Quality -- Expected Values

14. Current Imbalance in the Left/Right Apertures

15. Magnet Shipping

16. Installation at CERN

**D. R&D Program**

**E. Production Plan and Schedule**

**References**

# **A. Introduction**

The dipoles required in the Intersection Regions (IRs) of the LHC have
field and aperture requirements close to those of the RHIC \[1\] arc
dipole magnets. Thus the superconducting coils developed for those
magnets can be used in a cost-effective dipole design that satisfies
CERN's requirements. Under the auspices of the US/CERN LHC
Collaboration, the required magnets will be built at BNL. Tooling
constructed for the RHIC program will be used, so far as possible. RHIC
magnets were built commercially but the company that built those magnets
was not interested in this modest construction program. All magnets will
be tested in the existing BNL cryogenic test facility, then shipped to
CERN for installation in the LHC lattice. Close coordination is required
between the two laboratories to ensure that they meet all requirements
for operation in the LHC.

##### B. Objectives, Specifications and Requirements

**B.1 Overview**

The dipole magnets to be built will be a single aperture dipole labeled
D1 and double aperture dipoles labeled D2, D3a, D3b, D4a, and D4b. The
D1 magnet will be a single RHIC-type cold mass in a cryostat. The D3
magnets will be built with two single aperture RHIC-type cold masses in
a single cryostat. The D2 and D4 magnets will be built as 2-in-1 cold
masses in a single cryostat.

The D1 and D2 magnets bring the two beams of the LHC, separated by 194
mm in the arcs, into collision at four separate points, then separate
the beams again beyond the collision point. The D2 magnets are specified
for IRs 1, 2, 5 and 8. The D1 magnets will be used in IRs 2 and 8; for
IRs 1 and 5, warm magnets not supplied by the US collaboration are
planned. One side of one such region is shown in Figure 1.

![](media/image3.wmf){width="5.454166666666667in"
height="1.2479166666666666in"}

Figure 1 Geometry in Intersection Region 2 of the LHC. Dipole magnets D1
and D2 bring the beams into collision at IP2.

The D3 and D4 magnets increase the separation of the beams of the LHC
from the nominal spacing of 194 mm to 420 mm so that individual RF
cavities can be installed for each beam, and then return the beams to
the nominal 194 mm spacing. This is planned for IR 4 of the LHC. A
drawing of one side of this region is shown in Figure 2.

![](media/image4.wmf){width="5.740277777777778in"
height="1.3708333333333333in"}

Figure 2 Geometry in the RF Region of the LHC. The nominal 194 mm
separation of the beams in increased to 420 mm so that there is space
for independent RF acceleration cavities for the two beams.

The dipole magnets are designed with a common element: superconducting
coils that are mechanically the same as those built for the RHIC arc
dipole magnets \[1,2\]. The RHIC dipole is a well understood magnet with
good quench performance and field quality. The D1 magnets are designed
with one RHIC-style cold mass in a cryostat and the D3 magnets are
designed with two such cold masses side-by-side in a common cryostat.
The cold masses are built straight, without the 47 mm sagitta of the
RHIC magnets. The D2 and the D4 magnets are built with coils that are
prestressed with stainless steel collars. These collared coils are
assembled into yokes with common outside dimensions but with varying
internal features (iron saturation control holes, aperture spacing)
depending on location. The use of common outside dimensions reduces
tooling cost. The yoke size has been constrained to fit into cryostats
similar to those designed by CERN.

These 2-in-1 magnets have the field in each aperture in the same
direction. This is different from the more usual 2-in-1 designs, such as
used in the LHC arcs, where the fields are in opposite directions and
the flux in one aperture returns through the other. With these in the
same direction, the fields of the two apertures are decoupled and are
like those in independent magnets, provided there is sufficient iron
available to contain the flux. Judiciously placed cutouts in the yoke,
where the placement is altered for each particular separation of the
coil apertures, control the field asymmetries that would otherwise be
generated and minimize changes in the harmonics with excitation (field
quality is discussed in Sections C.11 through C.14). Again, this latter
goal is aided by having sufficient iron on the midplane to reduce
saturation effects.

The field quality expected in these magnets is suitable for the LHC for
nominal proton and heavy ion operation, both for injection and for
collision lattices. This has been confirmed by Accelerator Physics
tracking studies carried out as part of the US/CERN collaboration \[3\].
In these studies, both the dynamic aperture and the tune footprint were
used as quantities to evaluate the impact of magnet errors.

The dipole magnets to be built by BNL for the LHC are summarized in
Table 1.

**Table 1** Dipole magnets to be built by Brookhaven for the LHC. The
coil aperture is 80 mm. The overall length of the magnets is
approximately 10 meters.

+------+--------------+-----------+-----------------+----------------+
| ##   | ## Style     | Number    | Aperture        | Operating      |
| Name |              | (Spares)  | Separation      | Temperature, K |
|      |              |           | (cold), mm      |                |
+------+--------------+-----------+-----------------+----------------+
| D1   | Single       | 4(1)      | \-\--           | 1.9            |
|      | Aperture     |           |                 |                |
+------+--------------+-----------+-----------------+----------------+
| D2   | 2-in-1       | 8(1)      | 188             | 4.5            |
+------+--------------+-----------+-----------------+----------------+
| D3a  | Dual 1-in-1  | 2(1)      | 420             | 4.5            |
+------+--------------+-----------+-----------------+----------------+
| D3b  | Dual 1-in-1  | 2(1)      | 382             | 4.5            |
+------+--------------+-----------+-----------------+----------------+
| D4a  | 2-in-1       | 2(1)      | 232             | 1.9            |
+------+--------------+-----------+-----------------+----------------+
| D4b  | 2-in-1       | 2(1)      | 194             | 1.9            |
+------+--------------+-----------+-----------------+----------------+

Table 2 gives the magnetic field required in the various magnets for
three values of the LHC energy: injection, nominal and 8 % above
nominal.

Table 2 Position parameters and fields required in the magnets at
injection energy, nominal energy, and 8% above nominal energy. The
numbers listed for the bend center-to-center distance and the deflection
are those specified in Version 6.0 of the LHC lattice. The magnetic
length of the magnets is 9.45 m.

+----------+--------+----------------+---------+--------------------+
| #        | ##     | Bend           | Defl    | Field (T) for E    |
| # Magnet |  IR Lo | Ce             | ection, | (TeV)              |
|          | cation | nter-to-Center | m       |                    |
|          |        | Distance, m    |         | 0.45 7.0 7.56      |
+----------+--------+----------------+---------+--------------------+
| D2       | 1 & 5  | 87.432         | 0.097   | 0.1761 2.7393      |
|          |        |                |         | 2.9585             |
+----------+--------+----------------+---------+--------------------+
| D1 or D2 | 2 left | 62.697         | 0.097   | 0.2456 3.8201      |
|          |        |                |         | 4.1257             |
+----------+--------+----------------+---------+--------------------+
| D1 or D2 | 2      | 66.062         | 0.097   | 0.2331 3.6255      |
|          | right  |                |         | 3.9155             |
+----------+--------+----------------+---------+--------------------+
| D1 or D2 | 8 left | 65.582         | 0.097   | 0.2348 3.6520      |
|          |        |                |         | 3.9442             |
+----------+--------+----------------+---------+--------------------+
| D1 or D2 | 8      | 62.522         | 0.097   | 0.2463 3.8308      |
|          | right  |                |         | 4.1372             |
+----------+--------+----------------+---------+--------------------+
| D3 or D4 | 4      | 39.100         | 0.113   | 0.2294 3.5679      |
|          |        |                |         | 3.8534             |
+----------+--------+----------------+---------+--------------------+

##### 

##### B.2 Dipole Cold Mass

The D3 magnets will be built as two side-by-side cold masses in a common
cryostat. D3a cold masses will have center line separations of 420 mm
and D3b cold masses will be separated by 382 mm. The cold masses will be
similar to those in the main arc dipoles of RHIC, and the reader is
referred to the RHIC Design Manual \[1\] for details on the design of
this magnet. Some changes are necessary, however. The cold masses will
be straight, not curved with a 47 mm sagitta as in RHIC. Quench
protection heaters will be required so that the magnets can be protected
from absorbing excessive energy in case they quench. This protection was
provided by diodes in RHIC but these diodes are not suitable in the high
radiation environment of the LHC. The two magnets for each beam will be
cooled in series and each series loop will have independent connections
to the cryogenic header. A substantial support cradle to hold two
side-by-side cold masses on a common post is part of the design.

The D2 and D4 magnets will be built as 2-in-1 cold masses in which the
two beam apertures are in a common yoke. This design allows the close
spacing of the apertures required in the machine at those locations. The
aperture spacings will be 188 mm for D2, 232 mm for D4a, and 194 mm for
D4b. The necessary prestress cannot be applied to the coils with the
yoke, however, as is done in the RHIC magnets. Therefore, stainless
steel collars are used to apply the necessary prestress, and then the
collared coils are installed side-by-side into the yoke, which is split
on the horizontal mid-plane. The stainless steel collars are intended to
constrain the full Lorentz forces when the magnet is powered. The
laminated, cold steel yoke, encased in a stainless steel
helium-containing cylinder, mechanically supports the coils. The helium
vessel is also a structural part of the yoke assembly.

The cold masses will be installed into an LHC-diameter (0.914 m) vacuum
containment. CERN will supply the support posts and the heat shield
support extrusion. Brookhaven will build a heat shield that fits around
the cold masses and will include the necessary cryogenic piping and its
supports.

In the LHC, some of these magnets will be on an incline and cooled with
a static bath of liquid helium operating at 1.3 bar, 4.5 K, as compared
to RHIC where the magnets are level and are cooled with single phase 5
bar, 4.5 K helium flowing at 100 g/s. To accommodate this cooling, the
magnets must be fitted with vent pipes at their up-hill ends (which
varies with position in the lattice) and with liquid level sensors in a
suitably-sized volume. Piping in the cryostat is arranged to deliver
helium to the down-hill end for initial cooling and at the uphill end
for steady state operation, and to remove vapor at the up-hill end. The
magnets can be operated at temperatures higher than 4.5 K to provide the
required field; there is about a 3.5 % reduction in quench field with
each 0.1 K temperature rise in this range.

In the lattice, these magnets are to be powered in series from a common
power supply. This scheme is suitable for magnets that are all alike,
because the magnet transfer functions could then be expected to be,
within acceptable errors, close together in value. In the present
design, however, this will not be the case. Even though the coils in the
D3 and the D4 magnets will be the same, the different style of yoke
surrounding the magnets will cause the required currents to differ by up
to 400 A (\~10 %) for a given field (see Section C.10). Several options
exist for dealing with this difference; CERN will develop a strategy for
accommodating it in powering the magnets.

Figure 3 shows cold mass cross sections for the four designs of magnets.

![](media/image5.wmf){width="4.752777777777778in"
height="3.9784722222222224in"}

Figure 3 Cross sections of the various cold masses. The drawings are to
the same scale.

Figure 4 shows a more detailed cross section of one of the 2-in-1
magnets, D4a.

![](media/image6.wmf){width="3.3868055555555556in"
height="2.7194444444444446in"}

Figure 4 Cross section of the cold mass D4a.

#### B.3 Assembled Magnets

The cold masses are assembled into cryostats to make completed magnets
(see Section C.8). The cryostat consists of a cylindrical vacuum vessel,
aluminum heat shield, blankets of multi-layer thermal insulation,
cryogenic pipes, and the magnet support system. A variety of
measurements, both mechanical and electrical, will be made on the
magnets during the construction process. All subassemblies must satisfy
the test requirements before incorporation into a magnet. Completed
magnets are tested at cryogenic temperature, then packaged and shipped
to CERN for installation into the LHC.

#### C. Technical Description

**C.1 Superconductor**

A 30-strand (wire) superconducting cable will be used in the fabrication
of all the dipole magnets. A similar cable was used for the RHIC arc
dipole and quadrupole magnets \[1\]. Consequently, the cable fabrication
methods are well developed. The superconductor wire to be used in the
cable was purchased for the SSC program and has been kept in storage
since the end of that project. Its properties are similar to those of
the wire used for RHIC, but with a copper to superconductor ratio of 1.8
rather than 2.25. With active quench protection in the magnets, and a
sizable margin between required operating current and predicted quench
current, it is anticipated that this material will give satisfactory
results.

The mechanical and electrical properties of the superconducting wire to
be used are summarized in Table 3. Each wire consists of 4165 NbTi alloy
superconducting filaments with a nominal diameter of 6 μm and a spacing
of \>1 μm. The exact number of filaments was chosen by the
superconductor vendor based on the details of the billet design. Copper
is used as the matrix between filaments, it occupies the central core of
the wire, and it provides an outer covering for the wire. Copper
represents about 64% of the wire cross section and is important for the
cable and magnet operational stability as well as for protection against
burn-out through overheating during a quench. The wire diameter of 0.648
mm was tightly controlled during final stages of manufacturing and was
checked with a laser micrometer.

The wire minimum critical current is defined at a temperature of 4.22 K,
an applied magnetic field of 5 T perpendicular to the wire axis and a
resistivity of 1×10^--14^ Ω⋅m based on the total wire cross section.
This current corresponds to a minimum current density in the NbTi
superconductor of 2750 A/mm^2^ at 5 T. The SSC wire meets or exceeds
this minimum specification. The wire critical current at 3 T will be
sampled in order to monitor the effects of superconductor magnetization
at low field.

**Table 3** Superconducting wire parameters.

+-----------------------------------+---------+-----------------------+
| Item                              | Units   | Value                 |
+-----------------------------------+---------+-----------------------+
| Mechanical                        |         |                       |
+-----------------------------------+---------+-----------------------+
| ###  Nominal filament diameter    | µm      | 6                     |
+-----------------------------------+---------+-----------------------+
| Nominal filament spacing          | µm      | \> 1                  |
+-----------------------------------+---------+-----------------------+
| ###  Nomin                        |         | (1.8 ± 0.1):1         |
| al copper to superconductor ratio |         |                       |
+-----------------------------------+---------+-----------------------+
| Number of filaments               |         | 4165 ± 20             |
+-----------------------------------+---------+-----------------------+
| Wire diameter                     | mm      | 0.648 ± 0.003         |
+-----------------------------------+---------+-----------------------+
| Wire twist direction              |         | Right                 |
+-----------------------------------+---------+-----------------------+
| Wire twist pitch                  | mm      | 13 ± 1.5              |
+-----------------------------------+---------+-----------------------+
| Electrical                        |         |                       |
+-----------------------------------+---------+-----------------------+
| Wire min. critical current at 5   | A       | 325                   |
| T, 4.2 K                          |         |                       |
+-----------------------------------+---------+-----------------------+
| Wire maximum critical current at  | A       | 1.6  measured I~c~ @ |
| 3 T                               |         | 5 T                   |
+-----------------------------------+---------+-----------------------+
| Wire maximum R(295 K)             | Ω/m     | 0.082                 |
+-----------------------------------+---------+-----------------------+
| Wire minimum RRR                  |         | 38                    |
+-----------------------------------+---------+-----------------------+

![](media/image7.wmf) Thirty wires are fabricated into a Rutherford-type
cable by first twisting them around a mandrel, then rolling them into a
flat, keystoned shape with dimensions given in Table 4 and Figure 5. The
variations of the cable dimensions, especially the cable mid-thickness,
will be tightly controlled because the magnetic field quality of the
magnets and the coil prestress are dependent on them. The cable lay is
chosen to be opposite to the wire twist and requires a cabling machine
operating in a planetary mode for fabrication. The cable minimum
critical current (see Table 4) is defined in a similar way to that for
the wire, but with the magnetic field perpendicular to the wide surface
of the cable and with compensation for self-field. The cable minimum
critical current can be obtained from the wire minimum critical current
at 5 T times 30 (number of wires in cable) and multiplying by 0.95
(allowance for 5 % degradation in cabling). Wire piece lengths are large
enough to allow all cable lengths to be produced without cold welds.

**Table 4** Superconducting cable parameters.

  -------------------------------------------- ------------ -------------
  Item                                         Units        Value

  Mechanical                                                

  Number of wires in cable                                  30

  Cable mid-thickness                          mm           1.166 ± 0.006

  Cable width                                  mm           9.73 ± 0.03

  Cable keystone angle                         deg          1.2 ± 0.1

  Cable lay direction                                       Left

  Cable lay pitch                              mm           74 ± 5

  Electrical                                                

  Cable minimum critical current at 5 T, 4.2 K A            9260

  Cable maximum R (295 K)                      Ω/m          0.00287

  Cable minimum RRR                                         38
  -------------------------------------------- ------------ -------------

Several differences with respect to RHIC magnets are noted. The cable
interstrand resistance may differ from that in the Oxford-produced cable
used in the RHIC production magnets. This will change the field
distortions due to eddy currents while the magnets are ramped. In
addition, the SSC wire to be used has at least some annealing vs. no
annealing of the wire used in RHIC (indicated by cable RRR higher than
\~ 40). Coils made with this wire are expected to have less post-cure
shrinkage than experienced with the RHIC coils, so the coil lengths will
be somewhat longer than in RHIC. These differences are not expected to
compromise magnet performance in any significant way.

As mentioned, the wire to be used for these magnets was purchased in the
SSC program and is now available for the LHC program. Wire from four
vendors is available and may be used. In order to study its properties,
cable was made from each type of wire, and the properties of the cable
were measured \[4\]. Some results are listed in Table 5.

Table 5 Selected properties of the prototype cable made from wire
available to the LHC program. The properties of the available wire are
known to vary, however.

+---------+-----+---------+--------+--------+-------+----+----------+
| Vendor  | Cu  | Inte    | I~c~,  | J~c~,  | R,    | R  | Shri     |
|         | /SC | rstrand | kA     | A      | Ω/m   | RR | nkage,%, |
|         | Ra  | Resi    |        | /mm^2^ |       |    | 1 hr@225 |
|         | tio | stance, | (5T,   |        | (     |    | C        |
|         |     | μΩ      | 4.2K)  | (5T,   | 295K) |    |          |
|         |     |         |        | 4.2K)  |       |    |          |
+---------+-----+---------+--------+--------+-------+----+----------+
| Alsthom | 1   | 127     | 9.651  | 2770   | 0.    | 44 | 0.41     |
|         | .87 |         |        |        | 00276 |    |          |
+---------+-----+---------+--------+--------+-------+----+----------+
| F       | 1   | 12      | 9.949  | 2762   | 0.    | 39 | 0.40     |
| urukawa | .76 |         |        |        | 00283 |    |          |
+---------+-----+---------+--------+--------+-------+----+----------+
| Ou      | 1   | 14.2    | 10.448 | 2983   | 0.    | 53 | 0.30     |
| tokumpu | .82 |         |        |        | 00280 |    |          |
+---------+-----+---------+--------+--------+-------+----+----------+
| Oxford  | 1   | 542     | 10.349 | 2887   | 0.    | 45 | 0.36     |
|         | .79 |         |        |        | 00280 |    |          |
+---------+-----+---------+--------+--------+-------+----+----------+

##### 

##### C.2 Dipole Beam Tube

The magnets include cold beam tubes with dimensions given in Table 6.
Two sizes are required. Magnets that operate at 4.5 K need a larger gap
between the beam tube and the coil for effective cooling by the liquid
helium \[5\]. For magnets that require a maximum aperture, a smaller gap
can be allowed if the magnets are cooled by superfluid helium (1.9 K).

The tubes are centered inside the coils: horizontally with G-10 bumpers
spaced axially at regular intervals, vertically by the collars or by the
phenolic spacers in the case of the 1-in-1 magnets. The gap between tube
and coil defines a helium buffer space. The tube is seamless, 316 LN
stainless steel and is wrapped with 25 μm Kapton with 66% overlay. This
provides 75 μm of insulation, which is tested for integrity to ground at
5 kV.

Beam tube liners will be installed into these magnets at CERN.
Therefore, except for D1, the tubes do not require copper-plating on the
inside surface. Experimental requirements at the LHC require the maximum
aperture in two of the D1 magnets, leaving no space for a full length
liner. In those magnets, copper-plating will be required to reduce the
beam impedance.

Table 6 Dipole beam tube parameters.

+--------------------------------+------+--------------+--------------+
| Item                           | ## U | ## E         | ## S         |
|                                | nits | nlarged Tube | tandard Tube |
+--------------------------------+------+--------------+--------------+
| Magnet                         |      | D1           | D2, D3, D4   |
+--------------------------------+------+--------------+--------------+
| Outer diameter                 | mm   | 78.00 ± 0.38 | 73.00 ± 0.38 |
+--------------------------------+------+--------------+--------------+
| Outer diameter inc. Kapton     | mm   | 78.1         | 73.1         |
| wrap                           |      |              |              |
+--------------------------------+------+--------------+--------------+
| Wall thickness                 | mm   | 1.96 ± 0.18  | 1.96 ± 0.18  |
+--------------------------------+------+--------------+--------------+
| Inner diameter, nominal        | mm   | 74           | 69           |
+--------------------------------+------+--------------+--------------+
| Weight, nominal                | kg   | 38           | 34           |
+--------------------------------+------+--------------+--------------+
| Beam tube-coil radial gap,     | mm   | 1.0          | 3.5          |
| nominal                        |      |              |              |
+--------------------------------+------+--------------+--------------+

**C.3 Dipole Coil**

The superconducting coil is assembled from two half-coils that are wound
on automated machinery and then formed into a specified size in a
precision molding operation. It consists of a single layer of 32 turns
per half-coil arranged in four blocks with intervening, symmetric copper
wedges; the sizes and positions of the wedges and pole spacers give
field harmonics that are small (Section C.13). The four current blocks
per half-coil design is identified as 9B84A. The cable is insulated with
2 double layers of the polyimide film Kapton CI. The first double layer
has polyimide adhesive on the outer side of the film; the second has it
on both sides. This all-polyimide insulating system requires a brief
exposure to a temperature of 217 °C to set; an appropriate curing cycle
was developed and extensively used in the RHIC program with excellent
results. The coil ends have been designed to simplify construction and
to reduce harmonic content. The number of spacer parts, machined from
Ultem, in the two ends of each half-coil totals 27: 17 turn spacers, 2
end saddles, and 8 wedge tips. The coil design parameters are given in
Tables 7 and 8.

The coil length given is that of RHIC production coils. As mentioned
earlier, the superconductor wire in those coils was "full-hard", whereas
the SSC surplus wire to be used in these coils is "half hard". This
means that it was annealed after wire draw-down. Coils have a tendency
to shrink and develop considerable tension during the curing process, so
that they become shorter upon removal from the curing mandrel. This is
due to tension in the superconducting filaments within the wire, which
is developed during wire manufacturing in the draw-down steps, and which
is released as the copper anneals during curing. Those that have been
made with annealed wire demonstrate less shortening, so the length of
these coils for the LHC magnets in expected to be somewhat longer
(several millimeters) than given in Table 7.

Table 7 Dipole coil design parameters.

+-------------------------------------------------------+-----+-------+
| Item                                                  | ##  | ##    |
|                                                       |  Un | Value |
|                                                       | its |       |
+-------------------------------------------------------+-----+-------+
| Inner diameter                                        | mm  | 80    |
+-------------------------------------------------------+-----+-------+
| Outer diameter                                        | mm  | 100   |
+-------------------------------------------------------+-----+-------+
| Length, overall                                       | m   | 9.646 |
+-------------------------------------------------------+-----+-------+
| Length, coil straight section                         | m   | 9.266 |
+-------------------------------------------------------+-----+-------+
| Cable length per half-coil                            | m   | 610   |
+-------------------------------------------------------+-----+-------+
| Cable mass per half-coil, bare                        | kg  | 50    |
+-------------------------------------------------------+-----+-------+
| Cable mid-thickness with insulation, under            | mm  | 1.352 |
| compression                                           |     |       |
+-------------------------------------------------------+-----+-------+
| Dielectric strength: current to ground @ 5 kV         | μA  | \<    |
|                                                       |     | 200   |
+-------------------------------------------------------+-----+-------+
| Coil-collar insulating Kapton thickness, inc. quench  | mm  | 0.64  |
| resistor                                              |     |       |
+-------------------------------------------------------+-----+-------+
| Midplane Kapton thickness                             | mm  | 0.10  |
+-------------------------------------------------------+-----+-------+
| Cable wrap material thickness, Kapton CI              | μm  | 25    |
+-------------------------------------------------------+-----+-------+
| Pole angle                                            | deg | 73.18 |
+-------------------------------------------------------+-----+-------+
| Number of turns per half-coil                         |     |       |
+-------------------------------------------------------+-----+-------+
| 1^st^ block (pole)                                    |     | 4     |
+-------------------------------------------------------+-----+-------+
| 2^nd^ block                                           |     | 8     |
+-------------------------------------------------------+-----+-------+
| 3^rd^ block                                           |     | 11    |
+-------------------------------------------------------+-----+-------+
| 4^th^ block (midplane)                                |     | 9     |
+-------------------------------------------------------+-----+-------+

Table 8 Coil wedge parameters.

+-------------+-----------+------------------------+-----------------+
| Wedge       | ## A      | ## In                  | ## R            |
|             | ngle, deg | ner edge thickness, mm | adial width, mm |
+-------------+-----------+------------------------+-----------------+
| 1 (pole)    | 16.68     | 7.12                   | 9.70            |
+-------------+-----------+------------------------+-----------------+
| 2           | 9.83      | 3.09                   | 9.70            |
+-------------+-----------+------------------------+-----------------+
| 3           | 8.10      | 0.39                   | 9.65            |
| (midplane)  |           |                        |                 |
+-------------+-----------+------------------------+-----------------+

**C.4 Collars**

In the 2-in-1 magnets, collars apply mechanical prestress to the coil
and separate the coil from the steel yoke. This separation is 10 mm
larger than in the 1-in-1 magnets, resulting in reduced saturation
effects at high field. In addition, they key the coil to the yoke
laminations so that precise alignment of the magnetic field can be set
and maintained. The collars are punched from high-manganese stainless
steel. This material was used with good results in the SSC program and
features high strength, low permeability, and a low thermal coefficient
of expansion. The collars are placed around the coil in packs that are
\~150 mm long. Sheets of insulating Kapton and quench protection heaters
are first placed around the coil, and mid-plane caps of Kapton between
coil halves. A press (existing) compresses the collars around the coil.
They are held together with phosphor-bronze keys inserted in keyways in
the outer surface. The nominal design preload in the coil is 69 MPa at
room temperature. This reduces to no less than 33 MPa at cryogenic
temperature.

Finite element calculations \[6\] using ANSYS have established the
collar width (the width of the material on the midplane) of 20 mm in the
straight section of the magnet. The collars will be spot-welded in pairs
as was done in the SSC program. Some refinements in the design of the
collars have been incorporated with respect to the designs used in the
SSC program \[7\]. In particular, the radial gap between the coil and
every other collar has been eliminated, a gap that needed brass shims to
bridge in order to eliminate damage to the Kapton ground plane
insulation. Also eliminated was the interlocking tang/recess feature on
the arms of the collars in favor of a simpler shoulder/recess
arrangement, made possible by the spot-welded feature.

With a coil compression of 57.9 MPa, the vertical elongation of the
collared coil radius is expected to be 75 μm. The Lorentz force at full
field results in collar deflections outward in the horizontal direction.
After 50-100 μm of radial movement (depending on the actual clearance,
nominally line-to-line, between collared coil and yoke inner diameter),
the yoke restrains the collared coil and further motion is not possible.
Small elastic motions such as these are acceptable and do not compromise
quench performance.

In the lead end of the magnet, it is necessary to bring the lead from
the pole turn of the coil to the outside over the top of the coil. This
is done with a spacer incorporating a path for the cable to follow.
Enlarged collars are designed to fit over this spacer. To avoid
potentially inadequate support of the coil at the pole in the critical
end turn-around, the collars' width is increased from 20 mm to 25 mm.
This design results in an enlarged cutout in the yoke, which also has
the desired effect of reducing the peak field in the ends. The same yoke
cutout is implemented at the return end to maintain symmetry between the
ends of the magnet and to reduce the peak field there as well.

With a width of 25 mm, the radial vertical distortion of the end collar
is 150 μm under a collaring load of 84 MPa \[8\]. For most of the end,
the modulus of the coil is insufficient to maintain so high a
compressive load, so the 150 μm distortion occurs over only a short
section of the coil near the pole turn-around.

Figure 6 shows a drawing of the radial construction of the magnet along
its length including its two ends. A view of a half-coil including the
design for the exit of the lead from the coil pole turn to the outside
is shown in Figure 7. The turn is first deflected to the center of the
pole, then is ramped up to clear the end turns as it exits the magnets.
Parts that fit the geometry and that can be compressed by the collars
are used to ensure that the large Lorentz forces exerted on this lead
are well constrained. The geometry is difficult because the locations of
all parts move as the collars are squeezed onto the coil, yet the parts
must fit with good precision in the assembled magnet if the conductor is
to be free of Lorentz motion.

![](media/image8.wmf){width="4.2in" height="2.8in"}

![](media/image9.wmf){width="4.2in" height="2.6527777777777777in"}

**C.5 Dipole Yoke and Helium Containment of the 2-in-1 Magnet**

The 2-in-1 yoke is optimized to minimize the current dependence of
multipoles at high fields. To reduce saturation-induced harmonics (such
as a normal quadrupole term in the dipole), the yoke is made wide enough
to contain the flux lines at the maximum design field. Since more iron
is required at the midplane, the oblate shape is adopted. This is done
by vertically offsetting the center-of-curvature of the half-yoke from
the magnet center.

The vertical size is made equal to the LHC dipole yoke outer diameter so
that some of its cryostat's hardware can be used. In the present design
the yoke outer diameter is 630 mm and, after offsetting the
center-of-curvature, the two half-yoke centers, above and below the
midplane, are separated by 80 mm. This matches the vertical size of LHC
dipoles, which have an outer diameter of 550 mm.

The high field current dependence due to iron saturation is minimized by
optimizing the size and location of the saturation control holes or
cutouts. In the optimized solution, the computed change in the
saturation-induced harmonics (allowed and non-allowed) is within one
unit (@ 17 mm radius) in all the dipoles. The saturation is controlled
by the various holes placed symmetrically in the yoke, in particular the
holes between the two apertures.

Figure 8 shows the flux lines in a 2-in-1 yoke at high field (4 T). As
can be seen in the figure, there is ample room in the yoke to contain
the flux and little crowding of the flux lines is evident. This explains
the low value of the normal quadrupole harmonic at high field, where the
left-right asymmetry of the yoke around each aperture might otherwise
allow a quadrupole field component to develop.

![](media/image10.jpeg){width="3.4in" height="2.94375in"}

The yoke laminations are punched from 1.5 mm thick, low-carbon steel
sheet. The desired rms variation for the magnetic field integrated over
the length of the dipoles requires that the weight of steel in the yoke
be controlled to within 0.07%; to achieve this, the laminations that
make up the yoke are weighed and adjusted to this tolerance.

For assembly, the bottom yoke laminations are set up on rails to provide
alignment, the two collared coils are placed into the laminations, and
the top yoke laminations are placed over the assembly. Stainless steel
shells, 9.5 mm thick (designed to meet pressure vessel code
requirements), are positioned around the yoke while the yoke is
supported through holes in the bottom shell. This support fixture
maintains alignment in the subsequent welding operations. The shells are
welded together along the horizontal midplane with high
manganese-content filler rod \[9\]. Stainless steel strips fabricated to
the required shape back-up the weld (written assembly procedures give
the actual sequence of steps required). This welding operation closes
the structure and forms a high-pressure (2.1 MPa) helium containment
vessel. The shrinkage of the weld compresses the steel yoke and ensures
that any residual gap on the yoke midplane is closed. Further
compression is provided at operating temperature due to the differential
contraction of the stainless steel shell relative to the steel yoke.

The weld back-up strips are shaped to fill the aperture available
between the yoke and the shells. A simple bent piece of flat material
was originally planned for this strip, but an ANSYS analysis indicated
that the shell would develop unacceptable local stresses from a moment
around the corner of this cutout when the slot was not filled and the
vessel was pressurized at its maximum rating \[7\].

Following the longitudinal welding of the shell, oval end plates are
welded to the shell at each end of the magnet. Set screws that press
shaped, stainless steel bars against the ends of the coil are installed
in the end plates. They serve to restrain the axial Lorentz forces. The
magnitude of these forces determines the thickness of the end plates;
the goal, as specified for the RHIC magnets, is typically to prevent
deflections in the plate of more than 0.25 mm. According to an ANSYS
analysis in which the total Lorentz end force is transmitted to the end
plate, the specified end plate thickness of 69.8 mm limits the
deflection to 0.125 mm \[7\].

Additional operations on the cold mass include the welding of closure
plates over the alignment holes in the shell and the attachment of
cradles to support the cold mass on posts in the cryostat. After
completion of electrical interconnect work at the ends of the magnets,
cylindrical end bells with domed ends are mounted on machined shoulders
and welded to the oval end plates to close the helium volume and to make
the transition to the neighboring magnet or cryo-module.

Some yoke design parameters are listed in Table 9. For comparison, the
RHIC dipole parameters (original design operating field was 3.4 T) are
also listed.

Table 9 Dipole yoke and yoke containment design parameters.

+------------------------------------+----------+----------+----------+
| Item                               | ## Units | ## Value |          |
|                                    |          |          |          |
|                                    |          | 1-in-1   |          |
|                                    |          | 2-in-1   |          |
|                                    |          |          |          |
|                                    |          | (RHIC)   |          |
|                                    |          | (LHC)    |          |
+------------------------------------+----------+----------+----------+
| Aperture for collared coil         | mm       | 119.4    | 141.6    |
+------------------------------------+----------+----------+----------+
| Yoke horizontal size               | mm       | 266.7    | 625      |
+------------------------------------+----------+----------+----------+
| Yoke vertical size                 | mm       | 266.7    | 550      |
+------------------------------------+----------+----------+----------+
| Lamination length                  | m        | 9.64     | 9.64     |
+------------------------------------+----------+----------+----------+
| Length inc. end plates             | m        | 9.72     | 9.79     |
+------------------------------------+----------+----------+----------+
| Overall length                     | m        | 10.23    | 10.35    |
+------------------------------------+----------+----------+----------+
| Weight of steel                    | kg       | 2,757    | 16,700   |
+------------------------------------+----------+----------+----------+
| Shell, wall thickness              | mm       | 4.8      | 9.5      |
+------------------------------------+----------+----------+----------+
| Shell, weight                      | kg       | 306      | 1340     |
+------------------------------------+----------+----------+----------+
| End plate, thickness               | mm       | 31.8     | 69.8     |
+------------------------------------+----------+----------+----------+
| End plate, weight                  | kg       | 18       | 110      |
+------------------------------------+----------+----------+----------+
| Cold mass weight                   | kg       | 3,607    | 19,200   |
+------------------------------------+----------+----------+----------+

**C.6 Analysis of the Collar-Yoke and the Yoke-Shell Interfaces**

In the assembly of the yoke around the collared coil, it is important
that the dimensions and tolerances be well controlled so that yoke
closure is assured. Gaps of more that \~50 μm on the yoke midplane could
lead to undesirable harmonics. A number of design features have been
incorporated to address this concern. First, the keyway position on the
collar laminations has been offset to yield a round collar after keying
at the minimum expected coil stress of 57.9 MPa. An ANSYS analysis has
determined that this radial deflection after collaring will be 75 μm. As
an additional precaution, an assortment of collaring keys will be
available for the prototype magnets. Measurements will be taken to
determine the actual collar diameters after keying and the key size will
be adjusted to minimize the ovality. Independent adjustments will be
made to the lead end, straight section and non-lead end collars. Changes
in the size of the pole and midplane shims can be made in the prototype,
if necessary, in order to maintain the proper pre-stress.

A tolerance analysis was performed to determine the maximum possible
yoke midplane gap on subsequent production magnets, once the preceding
optimization on the prototype is complete \[10\]. Tolerances on the
collar outside diameter, keyway position, key thickness, yoke inside
diameter, and yoke ID position were considered. Variations in collar
outer diameter due to variations in coil size/stress were also included.
The maximum possible yoke midpane gap prior to shell welding was found
to be 0.3 mm. It is expected that such a gap would be eliminated as a
result of stresses developed in the shells during welding. Measurements
will be made on the production magnets to verify this expectation.

**C.7 Electrical Connections and Quench Protection**

The electrical connections to the magnets will be made with the usual
convention in which current into the positive or "A" lead produces a
normal dipole field with the South pole at the top. Definitions and
conventions used at Brookhaven in the building and measuring of magnets
are given in \[11\].

The bus conductor for each magnet and its immediate neighbors is placed
inside an insulating conduit that is then installed as a completed
package into the bus slots of the yoke, typically at the bottom. The
electrical connections between bus conductors and magnet leads are at
the ends of the magnets, within the end volume contained between the
stainless steel magnet end plate and the end of the magnet cold mass.
This end volume also contains the thermal expansion joints for the bus
conductors. These will follow BNL designs as developed for RHIC. No
magnet warm-up heaters to accelerate the occasional warm-up of the cold
mass are planned; warm gas only is used for warm-up in the LHC

Quench protection heaters are used to protect the coils from excessive
local energy deposition during a quench. The basic heater design was
developed and extensively tested by BNL in the SSC program. The heaters
run the full length of the magnet, one per quadrant, and are installed
between the collars and coils at the time of coil assembly for
collaring. Two independent circuits per magnet are included. In
operation, these magnets will be connected in series and the quench
protection system will, when triggered, fire one of these independent
heater circuits in all the magnets (up to 4 apertures).

Until measurements are made on a prototype magnet, it is not possible to
predict exactly the temperature that will be reached in a coil during a
quench. The active quench protection system being planned for these
dipoles will result in much lower peak quench temperatures than is the
case in the similar RHIC dipoles, which are protected with diodes only,
even though the conductor in these magnets will contain less copper. In
the RHIC program, measurements were made of ∫*I*^2^d*t* (10^6^ A^2^ sec
or MIITS) versus temperature for a preliminary version of a RHIC dipole.
This enabled calibration of a model used for predicting the quench
margins in the final version of the RHIC dipole. Final estimates of
worst case ∫*I*^2^d*t* values in RHIC magnets for conductor with a
copper-to-superconductor ratio (Cu:SC) of 2.25:1 and a single quench
protection diode for each magnet gave a value of about 12.4 MIITS,
compared with an estimated cable damage level of 13.8 MIITS. This
converts to a temperature margin of about 250 K before the damage
temperature of 835 K is reached. This damage temperature was measured in
earlier experiments on full sized magnets at Brookhaven.

**C.8 Dipole Cryostats**

The cryostats for D2, D3 and D4 will be the same as those for the main
LHC dipoles \[12\] wherever possible (D1 is housed in a RHIC-design
cryostat). The lengths will be different (shorter), the support points
for the cold mass will be adjusted, and the support cradles will be
designed to accommodate the dual 1-in-1 or the 2-in-1 cold masses, but
the diameter of the vacuum tank, the support posts \[13\], and the heat
shield support extrusions will be the same. A substantial amount of bus
work that services the magnets in the adjacent LHC arc passes through
the D4 magnets. It is planned that this bus work will be placed in a
separate tube in the cryostat. Drawings of the various cryostatted
magnets are shown in the following Figures 9 to 12.

![](media/image11.wmf){width="5.7555555555555555in" height="7.4in"}

![](media/image12.wmf){width="5.1618055555555555in" height="6.5in"}

##### 

##### 

![](media/image13.wmf){width="5.020833333333333in" height="6.3in"}

![](media/image14.wmf){width="4.909027777777778in"
height="6.438888888888889in"}

##### C.9 Interfaces to LHC Systems and Magnet Cooling

Each magnet that is delivered by BNL to CERN must fit correctly into a
predetermined slot and must be so configured that connection to the LHC
cryogenic and electrical system is facilitated. This requires a great
deal of careful design work and back-and-forth communication with the
staff at CERN. The present plans for these interfaces are given in
reports by S. Plate \[14\] and K. C. Wu \[15\].

![](media/image15.wmf){width="6.45in" height="3.7840277777777778in"} The
dipoles will operate either in a static bath of liquid helium at 4.5 K
or in a static bath of superfluid helium at 1.9 K (see Table 1). The
operating temperature is determined by the logistics of position in the
lattice of the LHC. Depending on position in the LHC and the operating
temperature, provision must be made in the magnets constructed at BNL
for the correct interfaces, pipes and controls in each magnet. Typical
schematics are shown in Fig. 13 for D4 operating at 1.9 K and in Fig. 14
for D3 operating at 4.5 K.

![](media/image16.wmf){width="6.15in" height="3.8979166666666667in"}

There are a number of design features that are observed in the systems
operating with a static bath of helium at 4.5 K so that they will
function properly in the LHC, including the following:

-   Transfer liquid helium to the high elevation end for the make-up
    fill.

-   Transfer liquid helium to the low elevation end for the initial
    fill.

-   Allow helium vapor to return to the high elevation end through the
    helium containment of the magnet, mostly through the two upper
    helium passages.

-   Use the lower bus openings in the magnet for the superconducting
    bus.

-   Install a level gauge in the end volume to control helium flow and
    keep magnet coil and bus in the liquid region.

**C.10 Transfer Function, Quench Field, Inductance, and Stored Energy**

A plot of the expected field vs. current in the 2-in-1 dipole magnet D4b
is shown in Figure 15. The field is 3.8 T at 6030 A (0.630 T/kA). The
quench field (T = 4.5 K)is expected to be 4.8 T at a current of 7740 A,
assuming conductor with a short sample limit of 2750 A/mm^2^ at 5 T, 4.2
K. The current density in the copper at the quench point is 1218
A/mm^2^. The inductance of each aperture is 25.8 mH and the stored
energy in each aperture at 3.8 T is 470 kJ.

![](media/image17.wmf){width="4.8in" height="4.285416666666666in"}

Because of their differing yoke designs, each of the magnets will have a
slightly different field vs. current transfer function. Fig. 16 shows
the dipole field as a function of current in the various magnet types.
Figure 17 shows the currents relative to D3a for the same field in the
different magnets.

![](media/image18.wmf){width="3.0in" height="2.85in"}

**C.11 Magnetic Field Quality - Measurements**

Warm magnetic measurements to determine field multipoles will be made
when magnet construction has been completed, including all welding and
installation into the cryostat. This will allow detection of errors in
magnet construction that may not have been detected in the earlier
construction testing. Except for small systematic offsets in the lower
allowed multipoles, warm field measurements have been shown to be
closely related to the field multipoles measured when the magnet is
cold. The data will be examined for conformance to expected field
quality. This includes the dipole field angle orientation, the integral
of the magnet\'s dipole field, the multipole content of the field, and
the variations of the field parameters along the length of the magnet.
Just as for the RHIC dipoles, it is anticipated that all magnets
properly built to print will easily pass the field quality test, and
that only a magnet with construction deficiencies will fail to pass the
test. Following the warm tests, cold testing will be done on each magnet
in Brookhaven's Horizontal Test Facility to check quench performance and
to verify field quality. Magnets operating in static liquid helium in
the LHC will be tested with the planned slope under the same conditions
at BNL. Since the BNL facility does not operate at 1.9 K, those that
operate at 1.9 K in the LHC will be tested with supercritical forced
flow (5 bar, 4.5 K) at BNL.

The MOLE measuring system \[16\] developed at BNL and used for RHIC
field measurements will be used for the LHC magnets. Integral fields
will be measured with the stationary integral coil system \[17\] used
for RHIC magnets.

**C.12 Magnetic Field Quality -- Measurement Errors**

The extensive measuring program carried out for RHIC magnets has given
data that can be analyzed for systematic and random measurement errors.
Such an analysis has been carried out, including also an analysis of
errors in the calibration of the measuring coils. The analysis has been
summarized in a series of tables and plots \[18\]. Table 10 is excerpted
from the report. For clarity, the reference radius is 25 mm as in the
report. These errors apply to the measurement system used for the RHIC
arc dipole measurements, which will be used for these magnets, and will
be different for other measuring systems. They are, however, a good
benchmark for the accuracy that can be achieved in a carefully built and
calibrated system.

**C.13 Magnetic Field Quality -- Expected Values**

The magnets are designed to have harmonics that are small. Thus, the
geometric multipoles (harmonics) are expected to be near zero. At low
fields, persistent currents in the superconductor will generate normal
sextupole (b~3~) and decapole (b~5~) components. These as well as the
normal 14-pole (b~7~) are shown in Figure 18. The harmonics were
measured in the RHIC dipole DRG107. At high fields, some harmonics will
be induced by the saturation of the iron yoke, as shown in Figure 19.

![](media/image20.wmf){width="3.797222222222222in"
height="3.066666666666667in"}

![](media/image21.wmf){width="3.9in" height="3.6458333333333335in"}

Field integral and field angle errors in the 2-in-1 dipoles, based on
RHIC magnets \[1,2\], are given in Table 11.

Table 11 Estimated errors on integral field and field angle.

+-----------------------------------------------------------+----------+
| Item                                                      | ## Value |
+-----------------------------------------------------------+----------+
| Integral field, magnet-to-magnet variation, rms           | 5       |
|                                                           | 10^--4^  |
+-----------------------------------------------------------+----------+
| Single magnet, mean dipole angle, α                       | ± 3 mrad |
+-----------------------------------------------------------+----------+
| Single magnet, variation (twist) of dipole angle ∆α from  | 2 mrad   |
| mean, rms                                                 |          |
+-----------------------------------------------------------+----------+
| Mean angle between apertures, rms                         | 2 mrad   |
+-----------------------------------------------------------+----------+

The measured harmonics in the magnets may be non-zero due to design and
construction errors. The estimated integral values of field harmonics
and their errors in D4a are given in Table 12 \[19\]. The
saturation-induced harmonics are so small that they are included in the
uncertainty in the mean; this is true in the other dipole designs as
well. The estimated value of the persistent current-induced sextupole
harmonic around injection (\~0.3 kA or \~0.2 T) is -- 6 units.

The field errors in the magnets (which are based on the already
excellent RHIC field quality) may be somewhat smaller than given here
because the replacement of RX630 phenolic spacers with punched stainless
steel collars will result in smaller dimensional variations.
Nevertheless, techniques for adjusting the field harmonics by small
amounts have been developed in recent years \[20\]. These include coil
size adjustment during cure, adjustment of coil midplane and pole shims,
and coil wedge thickness adjustment. Changes can be made if field
measurements on the first one or several magnets indicate, through
tracking studies, that such adjustment would be appropriate. These
techniques will be available for use on the magnets as needed.

The non-zero skew quadrupole term a~2~ results from a warm-cold shift
upon cool down and is not explained. The non-zero values of the skew
terms a~3~, a~5~, etc. are primarily from the harmonics in the lead end,
as measured in the RHIC arc dipoles. In a single layer coil design such
as used in these dipoles, there are leads carrying the current into and
out of the coil that cannot be paired at every point. These leads,
particularly the lead at the pole, produce a low level of skew harmonics
in the lead end field. In addition, some normal allowed harmonics are
generated in the ends of a single layer coil because it is not possible
to completely balance the opposite multipoles generated by current turns
near the midplane vs. current turns near the pole in the end region of
the magnet.

#### C.14 Current Imbalance in the Left/Right Apertures

For various reasons, the 2-in-1 magnet D2 may be operated with a small
current imbalance in one aperture with respect to its neighboring
aperture. The following Figure 20 shows the effect of such an imbalance
on the fields in the magnet. In these calculations, 15 % additional
current is assumed in the left aperture and the field changes in both
the left and the right apertures are then plotted as a function of field
in the right aperture. The effects for both D4b, which has an aperture
separation of 194 mm, and D2, with an aperture separation of 188 mm, are
shown and are small. At 4 T, the maximum difference in left/right
harmonics is \~ 3 units for the sextupole term. The transfer function
difference is less than 0.1 %.

![](media/image22.wmf){width="5.4in" height="4.602083333333334in"}

#### C.15 Magnet Shipping

Once construction and testing of the magnets is complete, they will be
shipped to CERN for installation into the LHC. To prepare them for
transit, steel support posts and end restraining frames will be
installed to protect the cold mass support posts from damage. The
magnets will be sealed and filled with dry nitrogen so that moisture
cannot penetrate the cryostat or cold mass. Each magnet will be mounted
on a shock-absorbing frame and then placed into a standard 40-foot-long
shipping container. This container will be transported by truck to a
shipping terminal, then by ocean freight to a terminal in Europe, then
by truck to CERN. The frames will be returned to BNL for reuse. The
production rate is low enough that only two such frames are necessary
for this program.

##### C.16 Installation at CERN

CERN personnel will install the magnets into the LHC lattice. They must
be placed on stands supplied by CERN, and surveyed into place. The beam
tube liner must be installed, internal wiring and pipe connections to a
QQS module must be made, the several volumes welded shut, and various
leak checks and pressure checks carried out. CERN test apparatus will be
required to verify that the magnets have survived the trip and are
behaving up to specification. At this stage, the magnets become the
responsibility of CERN as that laboratory brings the LHC into operation.

##### D. R&D Program

Because the superconducting coils planned for these magnets are the same
as those used in the RHIC dipole magnets, the required R&D program is
reduced in scope from that normally required to develop a new design of
superconducting magnet. Two short 2-in-1 models, each \~ 3 m long, will
be built and tested in vertical dewars, with the following goals:

1.  Qualify tooling and construction techniques.

2.  Confirm the proper fit of all mechanical components.

3.  Monitor the coil prestress at room temperature and at cryogenic
    temperature using strain gauges.

4.  Check quench performance and field margin.

5.  Measure magnetic field for possible iteration of coil design to
    achieve the desired field uniformity.

6.  Check performance of quench protection heaters.

7.  Measure temperature rise in coil for quenches at various current
    levels using a system of voltage taps and spot heaters.

##### E. Production Plan and Schedule

Magnet production will take place at BNL in the buildings and facilities
that were used for RHIC magnet production, which ended in 1998. These
facilities will be reconfigured to build spare RHIC magnets as required,
and the LHC magnet production will share the space and manpower assigned
to that work. The LHC production has been planned earlier than required
to meet CERN schedules. This was done to match the available spending
profile in the US accelerator program. The schedule for dipole magnet
production is shown in Figure 21.

###### ![](media/image24.wmf){width="5.8in" height="4.0875in"}

**References**

\[1\] RHIC Design Manual, Brookhaven National Laboratory.

\[2\] E. Willen, Superconducting Magnets, BNL 64183.

\[3\] V. Ptitsin, S. Tepikian, J. Wei, BNL-Built LHC Magnet Error Impact
Analysis, RHIC/AP/174.

\[4\] A. Ghosh, Report on SSC-Purchased Superconducting Wire Proposed
for the LHC Magnets, BNL Magnet Note 581, April 22, 1999. Shrinkage
measurements courtesy of CERN.

\[5\] M. Rehak, R. Shutt, Pressure Drops and Temperature Increases in
RHIC Magnets, BNL Magnet Division Note 423, March 4, 1992.

\[6\] R. Alforque, LHC Magnet Central Collar,
<http://dekooning.cad.bnl.gov/design_safety/notes>, Number 9.

\[7\] M. Anerella, Presentation to the Dipole Magnet Conceptual Design
Review, BNL, July 16, 1998.

\[8\] R. Alforque, LHC Magnet End Collar, Rev.1,
<http://dekooning.cad.bnl.gov/design_safety/notes>, Number 12.

\[9\] Weld wire type ER385L, with nitrogen and manganese enhancement.

\[10\] J. Schmalzle, LHC 2-in-1 Dipole-Yoke Midplane Gap, BNL Magnet
Note 577, September 17, 1998.

\[11\] A. Jain, F. Dell, S. Peggs, D. Trbojevic, P. Wanderer, J. Wei,
RHIC Magnetic Measurements: Definitions and Conventions, BNL Magnet Note
562, January 29, 1997.

\[12\] J.C. Brunet, V. Parma, G. Pen, A. Poncet, P. Rohmig, B. Skoczen,
L.R. Williams, Design of the Second Series 15 m LHC Prototype Dipole
Magnet Cryostats, LHC Project Report 133.

\[13\] M. Mathieu, T. Renaglia, C. Disdier, Supporting System for the
LHC Cold Mass, LHC Project Report 139.

\[14\] S. Plate, Configurations of BNL-Built LHC Dipole Magnets, in
process.

\[15\] K. C. Wu, S. R. Plate, E. H. Willen, Cooling Scheme for BNL-Built
LHC Magnets, in process.

\[16\] G. Ganetis, J. Herrera, R. Hogue, J. Skaritka, P. Wanderer, E.
Willen, Field Measuring Probe for SSC Magnets, Proc. 1987 PAC,
Washington, DC, March, 1987.

\[17\] A. Jain, Field Quality Measurements in RHIC Dipoles, Proc. 9^th^
Int. Mag. Meas. Workshop, Vol. 1, Saclay, June 19-22, 1995.

\[18\] A. Jain, Estimation of Errors in the Measurement of Harmonics in
RHIC Arc Dipoles, Magnet Group Note 570, Brookhaven, November 18, 1997,
http://magnets.rhic.bnl.gov/publications.htm.

\[19\] A. Jain, R. Gupta, P. Wanderer, E. Willen, Magnetic Design of
Dipoles for LHC Insertion Region, EPAC98, June 1998,
http://www.cern.ch/accelconf/e98/PAPERS/TUP03F.PDF.

\[20\] R. Gupta, Estimating and Adjusting Field Quality in
Superconducting Accelerator Magnets, Proceedings of the LHC Collective
Effects Workshop, Montreux, 1995, published in Particle Accelerators,
**55**, \[375-385\]/129-139, 1996, and BNL Report 62952.