# ![](media/image1.png){width="0.6986111111111111in" height="0.9270833333333334in"}

June 16, 2008

# LARP Annual Report -- FY08

Editor: Eric Prebys, FNAL

# Table of Contents

Executive Summary 2\
1 Accelerator Systems 3\
1.1 Instrumentation 3

1.3 Collimation 11

1.4 Accelerator Physics 15\
2. Magnet Systems 23\
2.2 Model Quadrupoles (HQ) 25

2.3 Supporting R&D (LQ) 29

2.4 Materials 36\
3. Program Management 42\
3.1 Administration 42\
3.2 Commissioning 43\
3.3 Joint IR Studies 44

# EXECUTIVE SUMMARY

# 

# *(in progress)* 

# 1 ACCELERATOR SYSTEMS

## 1.1 Instrumentation

## 1.1.1 Phase 1

*A. Ratti, LBNL*

While the LHC is rapidly reaching operating temperatures, most LARP
systems are ready for LHC beam commissioning. The Schottky monitors are
installed and ready to operate; the AC dipole and tune feedback systems
were prepared by CERN in collaboration with the LARP collaborators. Only
the luminosity monitors, victim of the failure of commercial cables, are
only partially installed in the machine.

Beam experiments both at RHIC and the SPS greatly enhanced the
understanding of the luminosity monitors. A correlation better than 99%
with the RHIC ZDCs shows the device has the potential required to
maintain its promise of measuring relative changes in luminosity to
better than 1%.

Tune and Coupling feedback, a world first, is now routinely part of RHIC
operations, and programmed in the LHC's system ready for beam
commissioning.

This task has ended, and LARP has moved into te development or
chromaticity feedback, needed to overcome snapback during the ramps.

The schottky monitors, built by CERN on drawings provided by LARP (FNAL)
are installed in the LHC. FNAL also provided the signal processing
electronics, which as been fully tested and is ready for commissioning,
as well as the controls interfaces added this year.

The AC dipole grew from LARP and has led to parallel developments at all
three colliders (Tevatron, RHIC and LHC). Systems are now exercised for
measurements in both the tevatron and RHIC.

In general, experimental data from US colliders has been used to develop
and define the technical approach for the LHC.

As devices are completed, LARP instrumentation tasks are closed and the
responsibility and support of the instruments falls on LARP hardware and
beam commissioning activities.

## 1.1.1.1 Tune, Coupling and Chromaticity Feedback 

*P. Cameron, BNL*

With the first successes of simultaneous tune and chromaticity feedback
in 2006, this technique, developed by US-LARP (BNL and FNAL in close
collaboration with CERN) has proven to be an essential feature and is
now routinely used in RHIC operations.

This task was successfully terminated in FY07 and the focus in FY08 was
moved to studies intended to lead to the control of chromaticity during
the ramps.

Limited funding in FY08 has reduced the length of the RHIC run, limiting
the progress made in this direction to the results of a couple of short
shifts during machine studies.

The technical approach tested during the studies was to use the same
technique used in tracking tunes. This was tested and showed promising
results although limited by a couple of factors. On one side, mains
harmonics are quite strong and interfere with the measurements. This is
an issue specific to RHIC, since the power supplies about to operate in
the LHC are not expected to have similar problems.

In addition, the anomalous beam transfer functions measured below
transitions with the direct diode detection method are not fully
understood. As a result chromaticity tracking had mixed results and will
require further studies and development before we can attempt closing a
loop.

In addition to these studies, RHIC functioned as a test bed for CERN's
planned implementation of the LHC tune and coupling feedback system.
Personnel both from BNL (Cameron) and FNAL (Tan) will be traveling to
CERN to contribute to the upcoming commissioning of the LHC.

## 1.1.1.2 Luminosity Monitor 

*A. Ratti, LBNL*

The results of the RHIC beam test were very encouraging. We installed a
prototype detector in the former PHOBOS area (2010) near a RHIC ZDC.

These were ideal conditions to test the device using a known calibrated
source.

With such a setup we could complete vernier scans, and compare the two
devices. Fig. 1.1.1.2.1 shows the differences between two of the
channels of the luminosity monitor and the RHIC ZDC. Fig. 1.1.1.2.2
shows a corresponding scatter plot, with the

![](media/image2.png){width="3.0861111111111112in" height="2.3875in"}

**Fig 1.1.1.2.1 -- Vernier scan in RHIC. (grey, pink -- lumi;
black=ZDC)**

![](media/image3.png){width="3.915277777777778in" height="3.025in"}

**Fig. 1.1.1.2.2 -- scatter plot between RHIC ZDC and one channel of
lumi**

We also completed a test at CERN in the SPS fixed target area where we

Meanwhile production of all units was complete. However we encountered
an unexpected problem with the commercial cables that carry the high
voltage to the chamber. When biased to higher voltages, they would
suffer from leaks. Since we connect a very sensitive charge pre
amplifier to this detector, any even minimal leak in the cable appears
to be like events in the chamber.

After meeting and discussing with the vendor, we decided to redesign the
flanges and cabling that is integrated in the flange. This resulted in a
new configuration, using commercial feedthroughs rated to 5 kV. This
process has caused a significant delay and we may not have all detectors
installed in the LHC before the first circulating beams.

The first two completed units are at CERN. All parts for the remaining
two are also at CERN awaiting the next set of flanges and cables to
complete two more detectors.

We also are completing the front end pre-amplifier, integrated with the
high voltage distribution board. This is a redundant two board system
where one can switch from one board to the next is case of sudden
failure of the first.

The programming of the readout system is also underway. Taking advantage
of several AB/BI installations of the DAB-based systems, we have
imported the programming platform from CERN and implemented the
necessary environment to run our detector. One of the sets of firmware
that was essential, was taken from LARP's tune feedback systems, and is
now running in the current lumi readout system. Plans for readout in
2008 are limited to counting mode, while we plan to enhance the
capabilities of the system in 2009.

The gas panels are built and will be shipped to CERN by July. These are
equipped with an electronic monitoring system which is networked and
read remotely. The first version of the remote monitoring system is also
available.

## 1.1.1.4 Schottky Monitor 

*A. Jansson, FNAL*

While last year we installed the beamline hardware and some electronics,
this year we were asked by CERN to provide some of the controls
interfaces that will be necessary for remote operation of the device.
This included the control interfaces for all switches, amplifiers, and
step attenuators.

These have now been fully tested with Labview on a laptop PC that has
been brought to CERN in May of 2008.   Dave Peterson has written the
Labview VIs and for those who would like to view them, they are on the
LARP doc database at

<https://larpdocs.fnal.gov/LARP-private/DocDB/ShowDocument?docid=700>

![](media/image4.jpeg){width="3.328472222222222in"
height="2.4965277777777777in"}

**Fig. 1.1.4.1 -- LARP and CERN personnel during the hardware
installation in the tunnel**

![](media/image5.jpeg){width="3.497916666666667in"
height="2.263888888888889in"}

**Fig. 1.1.4.1 -- Schottky signal processing chasses**

With the delivery, installation, and commissioning of this hardware all
deliverables from Fermilab and the LARP collaboration have been
completed. Pete Seifrid and Ralph Pasquinelli traveled to CERN to
install and commission the mentioned hardware the week of May 19-23,
2008. The Labview software includes an intuitive graphic interface and
is intended solely for the initial commissioning of the hardware.
However it could also be used with first beam studies if application
software has not been written by then. CERN plans to replace the CAEN
serial VME interface card in the first slot with a PC at which time;
application software will be a necessity.

Accomplishments during the May trip include physical installation of the
hardware and its commissioning. In particular the group performed a
complete RF characterization of the installed systems, including delay
of cables, signal levels, calibrations, timing etc.

This task is now considered complete. Funding has been requested from
LARP hardware and beam commissioning to support the beam operations in
late 2008 and 2009.

## 1.1.1.5 AC Dipole

*S. Kopp, UT Austin*

The AC dipole collaboration is very active at all three labs involved
(BNL, FNAL, CERN). FNAL has successfully converted a kicker into an AC
dipole, using a commercial high power audio amplifier as the power
source. The LHC design is based upon this approach. CERN has selected a
Lab-Gruppen Class-H amp as the driving pinger (MKQs). The amplifier will
be required 1800 A in MKQ for 7σ @ 7 TeV, and with the use of a 4:1
matching transformers the group at FNAL could obtain 1500 A~pk~ using
two amplifiers.

The FNAL group used this setup to perform non linear optics measurements
by making known changes in the settings of some parameters, in
particular sextupoles and octupoles. Sextupole driving terms are
measured by observing the change in closed orbit and the 3^rd^ order
mode.

![](media/image6.wmf){width="4.4944444444444445in"
height="1.8736111111111111in"}

**Fig 1.1.1.5.1 -- Effects of changes in a skew sextupole**

After setting the sextupole and a family of octupoles to various values,
the FNAL group managed to apply a vertical AC dipole and observe turn by
turn data and its fourier transform. By observing changes in the closed
orbit and its third order mode it was possible to reconstruct the
modified optics.

![](media/image7.wmf){width="3.8375in" height="2.473611111111111in"}

**Fig 1.1.1.5.2 -- Turn-by-turn BPM data in the presence of detuning**

The BNL group is working on the electronics needed to support a high Q
AC dipole. This would require dynamic tuning. The approach is based upon
a single capacitor switched by a MOSFET switch, after simulations showed
that a tuning range of ∆ν \~ 0.01 should be achievable. The electronics
is being built and will be tested using a half meter RHIC AC dipole.

## 1.3 Collimation

## 1.3.2 Phase II

## 1.3.2.1 Rotatable Collimators 

*T. Markiewicz, SLAC*

**Personnel:**

During this period, T. Markiewicz .became head of LARP Accelerator
systems and Jeff Smith was hired as a postdoc. Partially in response to
SLAC's volunteer layoff program, engineer Eric Doyle went to half-time
and will leave early in Q4 of FY08 while physicist Lew Keller
volunteered but continues to work according to his interests and our
needs. Engineer Steve Lundgren and designer Gene Anzalone are supported
100%. The SLAC klystron brazing shop, mechanical fabrication shop and
external vendors produce the collimator prototypes.

**Technical accomplishments:**

-   The first short (20 cm length) copper mandrel, completed in Q1 of
    FY07 was vacuum tested in Q3 and then sectioned to examine the
    quality of the braze junctures. The results of the vacuum test
    depend critically on the vacuum of the empty measurement oven and
    location of the gauge (4.3E-7 Pa). While the test piece (6.0E-8 Pa)
    satisfied the LHC vacuum requirement of 1E-7 Pa, a 5x longer sample
    would not. This test was deemed a success. However, as a result, the
    inner corners of the jaws to be brazed to the next sample were
    trimmed so as to provide extra pumping channels. While sectioning
    the unit showed that the coil-jaw braze quality was good, it also
    revealed micro-fracturing along copper grain boundaries. The
    fractures were further examined by testing thin samples in an
    electron microscope. While not ideal it was felt that the
    micro-fracturing would not cause structural, thermal or vacuum
    problems. Nonetheless, a slower rate of heating and cool-down was
    advised for all future brazes.

-   The second short copper mandrel, whose cooling coil was wound in Q2
    of FY07, was brazed early in Q3. Eight half length quarter-round
    jaws were then brazed to the coil-wound mandrel. These steps took
    several iterations to understand the tolerances and amount of braze
    material required. This unit was then also vacuum tested and
    sectioned. While the longitudinal abutments brazed together nicely,
    extra braze cycles were required to adequately fill the joint
    between them.

-   A semi-round jaw of Glidcop® was fabricated and subjected to the
    same number of braze heat cycles as the second short copper
    collimator. Upon sectioning, no cracking was observed. The final
    Glidcop jaw segments will need to be copper plated before they can
    be brazed to the copper mandrel and cooling coil.

-   A mechanism to accurately rotate the collimator while providing
    support and allowing for thermal effects, gravity sag and tilt was
    developed and a version fabricated in Q3 of FY07.

-   At the end of Q2 of FY07, concerns over how best to braze Molybdenum
    and Copper led to an unfortunately protracted R&D effort. In
    conjunction with team and SLAC klystron shop develop methods to deal
    with problematic Cu-Mo braze joints and tolerances/techniques
    required for jaw-mandrel braze

-   Difficult acquisition (SLAC bureaucracy) of a CERN Phase I
    collimator and equipping collimator lab with stepper motors & LVTDs
    for motion testing

-   First full length jaw completed after several technical difficulties
    and thermal mechanical testing begun

-   First use of SLAC's 3-D printer to manufacture plastic example parts

-   Acquire expertise and test equipment to design and test several
    options for the collimator RF design; interface with SLAC ACD group
    and CERN experts

-   Clean room for thermal-mechanical tests gets sign off from all
    safety committees and is in regular use

-   Heater testing of jaw with thermocouple and capacitive sensor system
    begins

## 1.3.2.2 Crystal Collimation 

*N. Mokhov, FNAL*

**Participating laboratories:** FNAL, BNL

**FY08 Goals**: Perform needed improvements to the Crystal Collimator
(CC) hardware and install it to the tunnel, install enhanced beam
instrumentation, perform Monte-Carlo calculation required, perform
tuning and tests with the beam followed by full-scale measurements of
the CC performance.

**Status:**

1.  The strip crystal and goniometer were removed from the tunnel in
    December 2007 after several unsuccessful attempts during 2007 of EOS
    studies in the Tevatron. Crystal is too radioactive to perform its
    characterization. The original O-shaped crystal of successful
    studies of 2005-2006 was shipped to Europe in January 2008 for its
    analysis. Analysis with 2-MeV He+ ions performed by V. Guidi at
    Ferrara, INFN, has shown that quality of the surface of the O-shaped
    crystal is very good, and it needs no treatment. X-ray measurements
    of bending angle and miscut angle with 5% accuracy performed by Yu.
    Ivanov, PNPI. The crystal is back at Fermilab and in May 2008 was
    ready for installation to the tunnel.

2.  The goniometer inchworm motor has been eliminated, and replaced with
    a linear actuator. The stepping motor and LVDT are now external to
    the vacuum. The linear actuator provides .025" linear travel per
    revolution = 200 steps, with the control providing for 1600
    microsteps per revolution. A frictional problem with the swing arm
    dragging on the stationary arm has been repaired. A vibrational
    problem with the crystal target holder has been solved with locking
    screws. Motion of the swing arm can now be observed through a glass
    viewport on the top.

3.  The goniometer new linear slide has a threaded lead-screw drive, as
    opposed to the previous ball-screw drive. This was changed to
    prevent motion due to vacuum loading, and the motor shaft brake is
    now unnecessary and has been eliminated. Total available motion is 2
    inches over 40,000 steps. The fully inserted position (moving out
    from the Tevatron center) puts the face of the crystal approximately
    in the center of the 4" beam tube. Fully extracted (moving towards
    the Tevatron center) puts the face of the crystal at the edge of the
    4" beam tube. The hardware went through the vacuum certification and
    was ready for installation to the tunnel at the beginning of June
    2008.

4.  New scintillation telescope counters were installed in the tunnel at
    E1. Corresponding timing module programming was performed with the
    working modules ready in May. The hardware and software are ready
    for measurement as of beginning of June.

5.  The flying wire setup hardware and software were modified for
    measurements of the halo and deflected beam at E11.

6.  Multi-turn tracking simulations with the CATCH and STRUCT codes were
    performed to provide channeled, volume-reflected and scattered beam
    profiles at 9 critical locations in the Tevatron.

7.  June 2008: waiting for a mini-shutdown for installation in the
    tunnel and starting beam tests.

## 1.4 ACCELERATOR PHYSICS

## 1.4.1 Studies

*Wolfram Fischer, BNL*

**Overview, budget, and spending**

Funding for accelerator physics activities is primarily for labor and
related costs, with the exception of the construction of a Gaussian
profile electron gun (\$15k). FY2008 Accelerator Physics funding is 40%
higher than FY2007 funding, primarily due to the new electron lens task
and substantially increased funds in the new initiatives task. Through
the end of April, funds were used less than proportionally to the time
elapsed during this fiscal year. This is primarily due to other
commitments that LARP collaborators have, which are tightly linked to
operating machines, and due to the fact that most of the funding in the
new initiatives task has been provided only recently from contingency.
It is expected that all funds will be used by the end of the fiscal
year.

  ----------------- -------------- ---------- ---------- ---------- ----------- ------------ ---------- ---------- ---------- -----------
                    **FY08 Funding                                              **FY08                                        
                    allocation**                                                expenses to                                   
                                                                                04/30/08**                                    

                    **BNL**        **FNAL**   **LBNL**   **SLAC**   **Total**   **BNL**      **FNAL**   **LBNL**   **SLAC**   **Total**

  **Accelerator     **215**        **330**    **200**    **175**    **920**     **38**       **151**    **116**    **17**     **322**
  Physics**                                                                                                                   

  Electron cloud    75             0          160        0          235         2.6          0          89         0          92

  Beam-beam         0              120        40         40         200         0.0          79         27         9          115
  simulations                                                                                                                 

  Beam-beam wires   50             0          0          0          50          21           0          0          0          21

  Electron lenses   45             80         0          40         165         14           71         0          9          94

  Crab cavities     25             0          0          0          25          0            0          0          0          25

  New initiatives   20             130        0          95         245         0            0          0          0          0
  ----------------- -------------- ---------- ---------- ---------- ----------- ------------ ---------- ---------- ---------- -----------

There are currently 6 tasks in accelerator physics (see table above).
The electron cloud task concentrates on electron cloud simulations. In
the next fiscal year, the focus of this task will shift to the electron
cloud induced instability in the SPS. The SPS performance with nominal
LHC beam parameters is marginal due to this instability.

The three beam-beam tasks provide experimental data to benchmark
beam-beam simulations for long-range beam-beam problems, and investigate
long-range and head-on beam-beam compensation for the LHC. We plan to
consolidate all beam-beam activities in one task.

The crab cavity task is new in this fiscal year and small in scope. Its
main purpose is to prepare for a full task in FY2009.

The new initiative task is to prepare for new task in the following
fiscal year. It is planned to move this task to program management in
the following year, and increase its funding to a level that would allow
the start of a task in mid-year.

## 1.4.1.1 Electron Cloud 

*M. Furman, LBNL*

The goal of this task is to simulate electron cloud effects in the LHC
and the LHC injectors in order to optimize the operation and design of
these machines when limited by electron clouds.

Personnel: M. Furman, J.-L. Vay (LBNL), Arduini, J.M. Jimenez, G.
Rumolo, F. Zimmermann (CERN)

The main simulation effort is to investigate incoherent (i.e. below the
instability threshold) emittance growth from electron clouds. Such
emittance growth could be relevant in the LHC and is likely to have
affected proton emittances in RHIC. The figure below shows the emittance
growth as a function of time for different electron cloud densities and
without and with longitudinal motion. These calculations were also
compared with HEADTAIL showing good agreement.

With nominal LHC beam parameters the SPS performance is marginal,
limited by electron cloud induced beam instabilities. The instability
was studied in simulations in terms of frequency and power content. From
this a model can be derived to design an instability feedback, which can
also be tested in simulations. Construction of the feedback would be
part of the LAUC.

A number of other items are also pursued in collaboration, at a lower
level. These include SPS electron cloud build-up, electron cloud
detection with microwaves, electron cyclotron resonances, and the PS2
upgrade.

It is planned to consolidate this existing task in FY2009 with the
planned SPS electron cloud instability feedback study and the chamber
studies.

![](media/image8.jpeg){width="5.581944444444445in"
height="3.6847222222222222in"}

**Figure 1.4.1.1.1: Warp LHC simulation of incoherent emittance growth
for different electron cloud densities and without and with longitudinal
motion. (Courtesy M. Furman)**

## 1.4.1.2 Beam-Beam Simulation 

*T. Sen, FNAL*

The goal of this task is to benchmark beam-beam simulations codes with
experimental data, currently primarily from RHIC, and evaluate the LHC
beam-beam performance with long-range and head-on beam-beam compensation
as well as for crab cavities.

Personnel: H.-J. Kim, T. Sen (FNAL), J. Qiang (LBNL), A. Kabel (SLAC)

At FNAL the code BBSIM is used. This code has now reproduced the onset
of increased beam loss rates as a function of the distance between the
wire and the beam for a number of the RHIC experiments. One example is
shown below for the latest measurement with deuteron beam. In a second
and more ambitious effort, the beam size is evolved with diffusion
coefficients sampled in phase space. For deuteron beams in RHIC the
emittance evolution in vertical plane could be reproduced, but not for
the horizontal plane. Further improvements that were added to the code
include resistive wall wake fields and the bunch length effect of the
beam-beam interaction. It is planned to add a coherent beam-beam module
and exercise it for RHIC and the LHC.

At SLAC the weak-strong code PLIBB is used, primarily to calculate the
beam lifetime. In the reporting period the emphasis was on code
development. New features include the use of the MAD-X input language to
read in full LHC lattices, intrabeam scattering, electron lenses, and
transverse beam transfer functions.

At LBNL the strong-strong code BeamBeam3D is used. In the reporting
period comparisons with beam transfer functions in RHIC were made.

It is planned to consolidate this task in a single beam-beam task in
FY2009.

![](media/image9.jpeg){width="4.420138888888889in"
height="3.720833333333333in"}

**Figure 1.4.1.2.1: Simulated and measured beam loss rate as a function
of the beam-wire separation distance for RHIC deuteron beam measurements
in FY2008 (see below).**

***1.4.1.3 Wire Beam-Beam Compensation\
**W. Fischer, BNL*

The goal of this task is to provide experimental data for long-range
beam-beam effects as strong as in the LHC that can be used to benchmark
beam-beam simulation codes.

Personnel : N. Abreu, R. Calaga, G. Robert-Demolaize, W. Fischer (BNL),
T. Sen,\
H.J. Kim (FNAL), A. Kabel (SLAC), J.P. Koutchouk, F. Zimmermann (CERN)

Since no machine exists with long-range beam-beam effects as strong as
in the LHC 2 wires, one for each ring, were built, and installed in RHIC
for the 2007 Au-Au run. In FY2007, experiments were made with Au beams.
In these experiments the position and current of the wires were varied
and their effect on the beam lifetime recorded. For this year it was
planned to repeat these scans with proton beams and including head-on
beam-beam collisions. Protons have a beam-beam parameter about 3 times
larger than heavy ions. In addition, the compensation of a single
long-range interaction was planned.

Due to the shortened RHIC run, only 3 ½ weeks were available for
polarized proton physics operation. Physics operation is necessary to
make time available for beam experiments. Emphasis in the available
experimental time was the RHIC polarized proton performance, and no
long-range beam-beam data could be obtained. One scan with deuteron beam
had been taken almost parasitically to set up the experimental equipment
earlier (below).

It is planned to make the proton scans during next year's polarized
proton run after which the work of this task is finished. It is also
planned to consolidate this task in a single beam-beam task in FY2009.

![](media/image10.jpeg){width="4.501388888888889in"
height="3.3944444444444444in"}

**Figure 1.4.1.2.1: Top: deuteron total and bunched intensity (left
scale) and beam loss rate (right scale). Bottom: wire current set point
and measured current (left scale) and wire position above the beam axis
(right scale). Measurement on 28 January 2008 (fill number 9664).**

## 1.4.1.5 Electrons Lens 

*V. Shitsev, FNAL*

The goal of this task is to evaluate the LHC luminosity improvement with
electron lenses for head-on beam-beam compensation, and other possible
applications of electron lenses.

Personnel: N. Abreu, W. Fischer, Y. Luo (BNL). V. Kamerdzhiev, V.
Shiltsev,\
A. Valishev (FNAL), A. Kabel (SLAC), J.-P. Koutchouk, F. Zimmermann
(CERN)

In FY2008 a Gaussian profile gun was constructed to be used in a
Tevatron electron lens. A Gaussian profile is needed for head-on
beam-beam compensation. The gun is awaiting installation and experiments
are planned to demonstrate its effect on the tune footprint, and to
determine acceptable current and position noise with the gun.

In addition, simulations were done for the LHC, using the code
LIFETRACK. In these simulations the beam-beam parameter and the phase
advance were varied and the lifetime without and with head-on beam-beam
compensation calculated. An example is shown below where the simulated
extends over 15 min of real time. For a beam-beam parameter of ξ = 0.01
an improvement in the beam lifetime is clearly visible.

This effort is in close collaboration with an effort at RHIC to
investigate the use electron lenses for head-on beam-beam compensation
in that machine.

An electron lens with a hollow profile is also studied as a primary
collimator for ions. Collimation of heavy ions is fundamentally
different from protons since many ions are not scattered in the primary
collimator but break up.

It is planned to consolidate this task in a single beam-beam task in
FY2009.

![](media/image11.png){width="4.893055555555556in"
height="3.6645833333333333in"}

> **Figure 1.4.1.5.1: LHC beam lifetime simulation with LIFETRACK for
> cases without and with head-on compensation and for two beam-beam
> parameters. (Courtesy A. Valishev)**

## 1.4.1.6 Crab Cavities 

*R. Calaga, BNL*

The goal of this task is the design, construction and installation of a
crab cavity in the LHC, and the evaluation of its potential for
luminosity upgrades.

Personnel: I. Ben-Zvi, R. Calaga (BNL), (FNAL), (LBNL), (SLAC)

The crab cavity task has gained significant momentum in FY2008 starting
from a small collaboration of 3-4 scientists from CERN/BNL-LARP to more
than 50 scientists from the four LARP laboratories, international
institutions including CERN, Daresbury, KEK and others. The main goals
set for FY2008 were:

-   Initiate a detailed study of a small angle crab scheme and address
    the different beam dynamics and rf issues associated with the scheme

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-   Organize an international collaboration and identify synergy with
    ILC and light source crab cavity developments

A BNL/LARP/CARE-HHH mini-workshop (LHC-CC08) was held at BNL in February
2008 (http://indico.cern.ch/conferenceDisplay.py?confId=24200). The main
goal of this workshop was to bring together the various interested
collaborators to define a road map for a crab system for the LHC and
discuss the associated R&D and beam dynamics issues. The workshop was
extremely successful in accomplishing the goals set forth.

1.  It was determined that a prototype crab cavity at 800 MHz will be
    the most effective way to validate both rf and first demonstration
    of crab operation in hadron colliders.

2.  Global crab scheme where the cavities are placed in IR4 to comply
    with both RF and LHC space requirements. Associated impedance and
    aperture issues require careful investigation and related tolerances
    should be detailed.

3.  Noise effects in the presence of beam-beam and rf curvature should
    be carefully evaluated and the required tolerances need to be
    demonstrated with the available rf controls technology

Following LHC-CC08, points of contacts (POCs) at the four LARP
laboratories and other participating institutes were established to
distribute the different aspects of the cryomodule R&D and beam dynamics
studies based on respective interests and expertise. A central
repository was established to coordinate the ongoing R&D and share the
state-of-art developments among the participating institutes. Regular
WebEx meetings are held to discuss the technical progress and evaluate
priorities. At the LARP-CM10 meeting, exact sub-tasks to be undertaken
by the 4-LARP labs were detailed along approximate time line and budget
requests to significantly ramp up the task in FY2009/10. It is expected
that the participating labs will be able to continue this effort in
cryomodule design in FY08 until the FY09 budget will be able to support
the task financially both for design studies, prototyping, and testing.
It is also foreseen that engineering design and fabrication of some of
the cryomodule will be requested via SBIRs in FY2009.

## 1.4.1.4 New Initiative Studies 

*T. Markiewicz, SLAC*

The goal of this task is to prepare for new task in the following fiscal
year.

Personnel: W. Fischer, S. Peggs (BNL), E. Prebys (FNAL), A. Ratti
(LBNL),\
T. Markiewicz (SLAC), O. Brüning (CERN) -- The Accelerator System
Advisory Committee (ASAC)

The new initiatives reviewed were:

-   LLRF Studies at LHC

-   Control of e-cloud instability in the SPS with transverse rf damping

-   SPS e-cloud remediation via grooved and coated vacuum chambers

-   The CRYSTAL collimation experiment at SPS

-   An optical diffraction monitor for LHC

-   Coherent electron cooling for LHC

-   Collimation studies at LBNL's HCX facility

-   Studies of intensity dependent performance limits to the LHC
    injector chain

-   PS2 studies (space charge)

-   Instrumentation commissioning

-   PEP-II "Model Independent Analysis" at LHC

-   PEP-II "Phase Advance Analysis" at LHC

The outcome of the discussion is summarized in the document "Evaluation
of LARP FY2009 New Initiatives".

It is planned to move this task to program management in FY2009, and
increase its funding to a level that would allow the start of a task in
mid-year.

# 2 MAGNET SYSTEMS

*P. Wanderer, BNL*

During the last year, we have made considerable progress toward both our
near-term goal (200 T/m in a long quad by the end of CY2009) and our
long-term goal (Nb~3~Sn quads for the Phase 2 LHC upgrade).

Highlights of work toward our 2009 goal include:

-   Work on coils and support structures, both collar and shell, for the
    long quadrupole (LQ) is well underway. Our plans testing the
    performance of these structures were reviewed and approved by an
    outside committee last fall. Our most recent 3.6 m practice coil is
    flat after reaction. The next one may be suitable for impregnation.
    Tests of the shell fixture with dummy coils will be made this
    summer. We are on schedule to test two or three LQ magnets during
    CY2009.

-   Model quads made and tested in the technology quad (TQ) series have
    reached the same fraction, \~ 90%, of the estimated conductor limit
    for both the collar and shell structures. The ten magnets made as
    part of this series have allowed us to establish procedures for
    making and assembling coils. Progress in this area has recently been
    speeded up through collaboration with CERN, established initially by
    LBNL, in assembling and testing TQs.

-   A 3.6 m racetrack coil has demonstrated excellent performance (91%
    of the conductor limit, 11 T on the coil) when supported by a shell
    support structure. A modification of the shell structure, designed
    to reduce the differential axial thermal contraction between yoke
    and shell, was used during the second test of these coils and worked
    well.

-   The Materials group has supplied the current standard Nb~3~Sn
    (Oxford RRP 54/61) as needed to the coil production effort while
    continuing to expand the database of superconductor properties.
    Studies currently underway include measurement of the effect of
    strain on critical current and temperature (4.2 K and 1.9 K) on
    magnet stability. The need for these latter measurements was
    demonstrated during the testing of the TQ quads. The group is also
    developing a strand with an increased number of filaments (108/127).
    This development is needed for larger-aperture magnets.

Highlights of work toward our long-term goal include:

-   Design studies of quads, called HQ, which will have a larger
    aperture or higher gradient than the 90 mm quads in the TQ and LQ
    series. Initial tests of HQ components (e.g., cable winding) have
    been made. The HQ designs include apertures in that the range that
    the CERN committee planning for the Phase 1 LHC IR upgrade (LIUWG)
    is considering. We expect the LIUWG CDR this month.

-   Materials development will be needed to more firmly establish the
    strain limits of Nb~3~Sn, reduce eddy current effects, and tackle
    other possible problems. The support structures developed for the
    model magnets will continue in support of the materials R&D program.

-   Looking ahead, we see the HQ design evolving into QA, a longer quad
    which will be designed to have the same nominal performance as the
    NbTi quads that CERN will design, but with the added gradient or
    temperature margin that Nb~3~Sn is, in principal, capable of.
    Comparison of QA with the NbTi Phase 1 quad should make the
    advantages of Nb~3~Sn more apparent, and speed its acceptance for
    use in the Phase 2 upgrade.

-   Looking still further ahead, a quad, QB, will be designed according
    to the optics of the Phase 2 upgrade.

A more complete statement of our goals and plans is appended to this
report.

Budget:

-   In FY08, the contingency of 20%, distributed starting at mid-year,
    was about right. We will use the same fractional contingency in
    FY09.

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-   Funding of planning work for the LAUC construction project will
    impact progress, except for the most optimistic case of a \$13 M
    LARP budget, with the planning funded separately.

-   We are assuming a continuing resolution in FY09. This will restrict
    our ability to make large purchases (e.g., superconductor).

-   The program has benefited from the good consistency of year-to-year
    funding from DOE. This has allowed us to explore the most critical
    aspects of conductor and magnet performance. However, there are a
    number of R&D topics which will need to be addressed before Nb~3~Sn
    magnets are fully accelerator-qualified and which have not been
    funded to date due to a lack of funds.

## 2.2 Model Quadrupoles

## 2.2.1 TQ Models

*G. Sabbi, LBNL*

The 90 mm aperture Technology Quadrupoles are used as a basis toward the
development of Long Quadrupole models. In total, 10 TQ have been
completed so far. Of these, four magnets used a collar-based (TQC)
structure and six used a shell based (TQS) structure. The coils for both
TQC and TQS models are wound/cured at FNAL and reacted/impregnated at
LBNL. It should be noted that for the same conductor properties, the
short sample gradient is lower in TQC than in TQS, due to higher peak
field in the end regions and a slightly shallower load line. Therefore,
the same fraction of the short sample limit corresponds to a \~10% lower
gradient in TQC with respect to TQS.

During the last year, two collar-based (TQC) models were completed. The
first magnet, TQC02-E, was tested at FNAL in October 2007. It used four
"Exchanged" coils made of OST-RRP 54/61 conductor that had been
previously trained in the shell-based structure (TQS02a model). The
maximum gradient achieved by these coils in the TQC structure was 200
T/m at 4.5 K and 197 T/m at 1.9 K. The last part of the test was
dominated by repeated quenches in the current leads. The second model,
TQC02a, was tested at FNAL in January 2008. It used four un-trained
coils made with the same RRP strand and fabrication process as the
previous ones. In this case, the magnet performance was limited to about
155 T/m at 4.5 K and fluctuated in the range 137-163 T/m at 1.9 K. The
cause of this behavior is still under investigation but appears to be
related to the magnet assembly phase.

LARP funding for the shell-based (TQS) models was discontinued after the
TQS02a test (June 2007) which achieved a gradient of 220 T/m at 4.4K and
fluctuated in the 204-224 T/m range at 1.9K. However, two additional
quadrupoles were fabricated and tested with support from the LBNL core
program and CERN. These magnets allowed further improving the
performance by replacing selected coils where specific weaknesses had
been identified. The new tests also allowed a better understanding of
the factors limiting the magnet performance. In particular, it appears
that above 200-220 T/m, the performance issues are mainly related to
imperfections in the coils. Therefore, better tooling and control of the
coil fabrication process are critical for further improving the gradient
in TQS.

The TQS02b model was assembled at LBNL in January 2008. Two of the coils
which were used in TQS02a were replaced with new ones. Both coils had
participated in the TQS02a training and one of them (#21) had ultimately
limited the magnet performance with repeated quenches in the outer
layer. TQS02b was tested at CERN in March 2008. The outer layer quenches
did not reappear. However, the magnet was now limited to about 201 T/m
at 4.5 K and 206 T/m at 1.9 K by quenches occurring at a single location
in one of the new coils (#29). This weakness was traced back to the coil
winding phase, when 5 turns had been un-wound and re-wound in the
opposite direction after a cable setup error was discovered. It was
therefore decided to replace coil #29 with coil #20 and re-test the
magnet as TQS02c. The disassembly, reassembly and test were carried out
at CERN in May-June 2008 by a joint LBNL-CERN team. TQS02c started its
training at 215 T/m and achieved a maximum gradient of 221 T/m at 4.4 K
(209 T/m at 1.9K). For the first time in a TQ model, there were no
quenches below the 200 T/m benchmark. The ultimate limitation again came
from a single location of a single coil, in this case the inter-layer
ramp of coil 23.

A summary of the training quenches in the TQ02 models tested during the
last year is shown below. One common feature of these tests is a lack of
improvement at 1.9K with respect to 4.5K. This result correlates with
tests carried out on RRP strands showing that the stability limits at
1.9 K may be lower with respect to 4.5 K. However, the TQS magnet
performance degradation appears in the same coils and locations at the
two temperatures, pointing at a common root cause for both cases. In the
case of TQS02b, this root cause could be traced back to the coil
fabrication. The ramp area limiting TQS02c is also known to be
problematic and originated tin leaks during reaction in some of the
early TQ coils.

![](media/image12.wmf){width="4.629166666666666in"
height="3.392361111111111in"}

> **Figure 2.2.2.1.1 Quench Training for TQ models tested in the last
> year**

The next step for the TQ program is the fabrication of 4 new coils using
RRP 108/127 strand, to qualify this conductor for use in future models.
It is planned to test these coils first in the TQS structure, and then
in the TQC structure. In addition, a new TQC model (TQC02b) is being
fabricated with support from the FNAL core program, using two of the
older MJR coils and two of RRP coils from TQC02.

## 2.2.2 HQ Models

*G. Sabbi, LBNL*

The HQ (High gradient/aperture Quad) series of short models will be used
to develop the design of the 4-m long QA quadrupoles. These magnets will
use the parameters and accelerator quality specifications of the Phase 1
NbTi quads (except for length) to facilitate their evaluation for use in
the LHC. Goal of both HQ and QA is to demonstrate large performance
margins with respect to the NbTi quads, on the timescale of the Phase-1
upgrade. In addition, the full set of features needed for an accelerator
magnet will be gradually incorporated into successive HQ magnets and
used in QA.

![](media/image13.jpeg){width="3.8131944444444446in"
height="2.946527777777778in"}

**Fig. 2.2.2.1: HQ Quadrupole Design**

The HQ model development started with a design study carried out in
2006-2007. This study allowed to investigate the main technical issues
(magnetic, mechanical, quench etc) and to explore the aperture design
space in the range of 90-140 mm. In FY08, considerable progress was made
toward the start of magnet fabrication. Several cables were fabricated
and evaluated from both the mechanical and electrical standpoint. Two
cross-sections (114 mm and 134 mm aperture) were optimized, and detailed
analyses of the coil stresses were carried out for different variants of
the supporting structure geometry. Prototype end parts were fabricated
and used for winding experiments. A final determination of the magnet
aperture is expected in a few weeks, following the publication of the
Phase 1 conceptual design report. It should be noted that during the
last several months the aperture range under consideration for Phase 1
has been narrowed from 90-140 mm to 110-120 mm. In parallel with CERN,
we have focused our work toward the detailed coil, tooling and structure
design of the 114 mm aperture case. After a final iteration of the coil
and tooling design we will start procuring the various components,
followed by winding of the first practice coil. Test of the first HQ
model is expected in September 2009.

## 2.3 Supporting R&D (Long Quadrupoles)

*G. Ambrosio, FNAL*

## 2.3.2.3 LRS02 Assembly and test

Work at LBNL:

-   Modification of LRS01 shell structure by dividing it into 4 segments

-   Assembly of LRS02 shell-yoke sub-assembly (4 for segments)

-   Instrumentation with strain gauges of the segmented shell structure
    for LRS02.

-   Analysis of test results

Work at BNL:

-   Assembly of LRS02 by insertion of the LRS01 coils into the segmented
    shell-yoke sub-assembly

-   LRS02 preparation for test

-   LRS02 test at 4.4K (training, ramp-rate and heater studies).

-   Analysis of test results

Note: the better performance of LRS02 (higher SSL, and more uniform and
constant strain gauge readings) has shown that structures with a long
aluminum shell need the shell to be segmented.

![](media/image14.jpeg){width="4.166666666666667in"
height="2.7527777777777778in"}

> **Figure 2.3.2.3.1: Quench history of LRS02 (filled markers) and of
> LRS01 (empty markers). LRS02 reached 96% of the SSL.**

## WBS 2.3.4.1 Coil & Collar Fabrication at FNAL

*F. Nobrega, FNAL*

Status:

-   Designed, procured, assembled and inspected tooling for LQ coil
    fabrication (winding, curing, reaction and impregnation).

-   Completed modifications of infrastructures for LQ coil fabrication.

-   Added stiffener plate to reaction fixture.

-   Wound and cured a copper practice coil, ready for shipment to BNL.

-   Fabricated, inspected, and measured two LQ practice coils.

-   Introduced changes to tooling and procedures based on inspection and
    measurement of practice coils (in progress)

-   Implemented modifications to parts for stabilizer leads, coil
    lifting holes, and procedure changes after practice coils.

-   Wound and cured first coil for LQ01.

-   Procurement of long-lead items for collar-based structure (shell and
    die for collars) is in progress.

-   Set-up discrepancy reporting for LQ coil fabrication

Plans for remaining of FY08:

-   Finalize procedures for LQ coil heat treatment.

-   Fabricated three coils for LQ01.

-   Ship to BNL a practice coil.

-   Wind, cure, and ship a coil to be reacted and impregnated at BNL,

-   Design and procured two splice boxes usable on both structures.

-   Complete procurement of long-lead items for collar structure.

![](media/image15.jpeg){width="4.111805555555556in"
height="3.290277777777778in"}

**Figure 2.3.4.1.1: LQ practice coil after heat treatment**

## 2.3.4.2 Coil Fabrication at BNL

*J. Schmalzle*

Status as of June 9, 2008:

-   Design modifications needed in order to use the FNAL LQ reaction and
    impregnation tooling at BNL have been completed. Fabrication of the
    tools is underway.

-   Tooling for lifting and handling the reaction and impregnation
    fixture has been designed and fabricated.

-   Tooling for hanging the impregnation fixture vertically has been
    designed and fabricated.

-   Tooling for lifting the LQ coils has been designed. Fabrication of
    the parts is underway.

-   Design work has been completed to adapt an existing shock mounted
    shipping strongback for use in shipping LQ coils. Fabrication of
    parts for two shipping fixtures is underway.

Plans for remaining of FY08:

-   Complete fabrication of all coil tooling.

-   Assemble the coil shipping fixture and send to FNAL for shipping the
    cured practice coil to BNL.

-   Assemble the 2^nd^ coil shipping fixture and send to FNAL for
    shipping complete coils to LBNL.

-   React, impregnate and inspect the copper practice coil.

-   React, impregnate and inspect one LQ coil.

-   Ship coil to LBNL for use in LQS01.

-   Design and fabricate LQS shipping fixture utilizing LBNL assembly
    rafts.

![](media/image16.jpeg){width="4.750694444444444in"
height="2.4993055555555554in"}

**Figure 2.3.4.2.1: LQ reaction fixture**

## 2.3.4.3 LQ Shell Fabrication

*P. Ferracin*

The goals of the task are:

-   Design, fabricate, and analyze a shell-based support structure for
    the 3.3 m long LQ coils (the structure is a direct extension of the
    TQS design, with some modifications implemented to facilitate
    handling and improve coil stress distribution);

-   Assemble and pre-load a 1 m long segment of the structure with dummy
    coils and perform a cool-down to 77 K;

-   Assemble and pre-load a full length structure with dummy coils and
    simulate final assembly and loading procedure.

A full 2D and 3D mechanical analysis has been performed with finite
element models to compute the stresses in coil and structure and target
conditions to be reached at the end of the assembly. Through 2D and 3D
magnetic finite element models, the main magnet parameters (maximum
gradient, peak field in the straight section and peak field in the ends)
have been calculated. The procedure to assemble the components and
pre-load the structure has been defined.

The engineering design and the procurement of all structure components
(shell, yoke laminations, pad laminations, masters, and dummy coils)
have been completed; all the components have been inspected once arrived
at LBNL. Shell and dummy aluminum coils have been instrumented with 32
strain gauges to monitor strain in the azimuthal and axial direction.

During the period June-September 2008, a 0.8 m long segment of the
structure will be assembled around aluminum dummy coils, pre-loaded, and
cool-down to 77 K. During all the operations, the strain on shell and
dummy coils will be recorded by strain gauges and compare with expected
values. The engineering design and the procurement of the assembly
tooling for the full length structure (rafts, cradles, lifting beams and
collars), as well as the coil lifting tooling and the coil axial support
(end plate and axial rods) will be completed. Assembly and loading of
the full structure with aluminum dummy coils will be carried out, and
results from strain gauges analyzed and compared with expectations.

![](media/image17.jpeg){width="4.571527777777778in"
height="3.435416666666667in"}

> **Figure 2.3.4.3.1: Solid model of LQS assembly: insertion of coil-pad
> sub-assembly into the yoke-shell sub-assembly**

## WBS 2.3.4.4 LQ Quench protection and Instrumentation

*H. Felice, BNL*

**[Task description:]{.underline}**

-   Design of the traces: the instrumentation of each coil will be
    implemented on flexible circuits called traces, which will be potted
    with the coils. These traces are made of a 0.0254 mm 304L austenitic
    stainless steel circuit, insulated from the coil by a 0.0254 mm
    kapton sheet. Each layer will have two 1.7 m traces going from the
    centre to one end, (i.e. four traces per coil). The coil traces need
    to accommodate the protection heaters, the voltage taps and the
    strain gauges when possible.

-   The design will be based on the TQ trace design.

-   The protection heater design will have to ensure 100% coverage

-   The voltage taps location has to be fine tuned based on TQ
    experience

-   Fabrication of 10 sets of traces and shipment to BNL/FNAL

-   The first set of traces will have to be validated before fabricating
    the others

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-   Assessment of readiness for LQ magnet test at FNAL, and plans for
    possible upgrades.

-   2 LQ coils instrumentation

### Done in FY08:

[- The coil instrumentation has been defined and the design of the coil
traces has been completed.]{.underline}

Each coil will be instrumented with:

-   The *protection heaters* designed based on the requirements of the
    quench computation (100% coverage) and of the coil handling (lifting
    holes).

-   20 *voltage taps*: 13 in the inner layer and 7 in the outer layer.
    All of them are part of the traces.

-   5 *stations of strain gauges* mounted on the Titanium pole. Each
    station is made of two full bridges, one measuring the azimuthal
    strain and the other the axial strain. Four stations will be mounted
    on the inner layer. All the strain gauges of the inner layer will be
    wired externally because of the lack of room on the traces. One
    station will be mounted on the outer layer and will be part of the
    trace.

[- 3 artworks and 2 sets of traces have been fabricated]{.underline}

The fabrication of the traces requires the fabrication of a negative
called artwork. One artwork per layer is needed. Three artworks have
been fabricated (1 for the inner layer (one iteration has been required)
and 1 for the outer layer). Two sets of traces have been fabricated and
validated in terms of resistance and voltage taps location.

[- The pockets in the end parts of the outer layer have been
designed]{.underline}

On the outer layer, some pockets have been designed in the end shoes to
provide room for the connection of the traces routes (strain gauges,
voltage taps, protection heaters) with the DAQ system and/or the
powering system.

[- The shell segments have been instrumented]{.underline}

The shell is segmented longitudinally in 4 segments called #1, #2, #3
and #4 from the lead end to the return end. Segments #1, #3 and #4 are
instrumented with 2 strain gauges stations and segment #2 is
instrumented with 4 stations. All the shell segments have been
instrumented.

[- One 1-meter dummy coil has been instrumented]{.underline}

Dummy coils are required to assemble the LQS magnet. 3 dummy coils are
going to be used: two 1-meter dummy coils and one 2-meter dummy coil.
Each dummy coil is made of 4 sectors in aluminum. One 1-meter dummy coil
has been instrumented with one strain gauge per sector.

**[To be done by the end of FY08]{.underline}**

-   Fabrication of a new artwork for layer 2 accommodating the pocket
    design

-   Fabrication of 8 sets of traces

-   Instrumentation with strain gauges of the remaining 1-meter dummy
    coil and of the 2-meter dummy coil with only one sector instrumented
    per dummy coil

-   Instrumentation of the rods

-   Instrumentation of the coils #4 and #5

![](media/image18.jpeg){width="5.983333333333333in"
height="2.6173611111111112in"}

> **Figure2.3.4.4.1: LQ traces with quench protection heaters, and
> wiring for voltage taps and strain gauges.**

***2.4 Materials***

*A. Ghosh, BNL*

During the last nine months the materials group has provided cables for
several magnet coils that are (or will be) fabricated. It has also
provided testing of strands both round and extracted as "witness"
samples for coil reactions.

OST has recently produced 180 kg of RRP 108/127 high Jc strand under a
fixed price contract. This is the first time that the high Jc strand has
been successfully manufactured. In the future more of this conductor
will be procured for the HQ magnet program.

There has been more testing of wires in superfluid helium where
instability has been observed in mid-field region rather than at low
fields. This study is still on-going.

At FNAL there were several incidence of copper-burst observed in RRP
strands. Similar bursts were found in a BNL sample (reacted at FNAL) and
a LARP strand reacted by CERN. This is under investigation by OST who
are examining these flaws in the samples from BNL and CERN.

An outstanding issue that is being addressed is that of strand testing
procedures of extracted strands at the three laboratories. During this
fiscal year, the three labs have been testing a NbTi Reference wire
provided by CERN lab. This has been extended to include the testing labs
at NIST, OST, CERN and NHMFL. We are in the process of documenting the
inter-lab comparison, which will be presented at the Applied
Superconductivity Conference at Chicago, IL.

## 2.4.1.1 Strand R&D 

*A.Ghosh, BNL*

**Summary**

During this year BNL and FNAL have been testing virgin strands and
extracted strands in support of the magnet programs primarily TQ and LQ
magnets. TQC02 and TQS02 are fabricated from 27-strand keystone cable
using the RRP 54/61 strand. Based on prior year work, strands and cables
are being reacted at a lower temperature of 640^o^C to improve the
observed stability current at low fields.

In addition strands from the CDP inventory, mostly the RRP strands of
different stacking designs which are of interest for LARP were also
tested as also were rolled wires of 54/61 design. Rolled wire studies
were made to better understand the effect of roll deformation on strand
critical current and stability at low fields and thereby provide input
for cable fabrication and dimensions.

The three labs have also tested a NbTi reference wire to ensure that all
labs obtain comparable data using their standard test procedures. NbTi
was chosen because it is easier to tests and less variable than Nb~3~Sn
which is strongly affected by the strain in the sample. The round-robin
testing has been expanded to include CERN, NIST, OST and NHMFL test
labs.

**I. BNL Activity:**

During FY 2008, 48 Nb3Sn strand samples were measured for LARP at BNL.
These included samples to qualify the cables fabricated as well as
witness samples for coil reactions which included round as well as
extracted strands from the cables that were used to wind the coils.
Rolled strands of 108/137 strand design were also measured, to determine
the effect of deformation on strand electrical properties. In addition,
10 measurements were made to determine the RRR of the strands. A summary
of the strands tested and the test results are available on the LARP
web-site. An additional 20 samples are expected to be tested during the
last quarter of FY08.

Further tests of the reference wire were made to determine the effect of
barrel material on the measured Ic.

During this year, BNL conducted many tests in superfluid helium to
determine the cause of strand instability in the mid-field regime. These
tests are much longer in duration compared to tests at 4.2 K. These
tests are relevant in determining if this instability is limiting magnet
performance in superfluid helium at 1.9 K.

**II. FNAL Activity:**

The reference wire was also measured at FNAL; however, a final report of
the tests is in preparation and has not been released.

**III. LBNL Activity**

LBNL has improved the strand test station, and tested the reference
wire, a report of which has been published as an LBNL technical note.

The RRR of several witness samples from TQC coil reactions and the Ic of
a couple of wire samples were measured. Additional witness samples (\~ 9
more) are expected to be tested in the next few months.

## 2.4.1.2 Cable R&D 

*A. Ghosh*

## 2.4.1.2.1 Cable fabrication

Cabling at LBNL has been proceeding on a schedule commensurate with when
the cable is required for coil winding. During the last nine months,
LBNL has been using the RRP strand to fabricate rectangular and keystone
cables. These cables are being insulated using fiberglass sleeve treated
with palmitic acid as a sizing agent.

**I. LBNL Activity.**

During this period, LBNL has made several cabling runs. Six LQ cables
were fabricated and insulated at LBNL in FY08 and the cable numbers are:
B0973, B0975, B0978, B0979, B0983, and B984. A backup cable (B0953) made
for the TQ magnets was insulated and shipped to FNAL to be used in an LQ
coil.

![](media/image1.wmf)Four R&D cables have been made for HQ. The first
(B0974) provide preliminary information on the appropriate cable
parameters. Another two cables (B0976 and B0977) were fabricated with
parameters from the cable section of (B0974) that seemed to be the most
mechanically stable for coil winding. Cable B0977 was very mechanically
stable for coil winding. The initial HQ cable parameters (KC1) are
listed in Table I. The magnet designers requested a higher keystone
angle than the 0.7 deg. achieved in cable 977. Cable B0980 was an
attempt to make a cable with a keystone angle of 1.0 deg. Critical
current measurements by BNL on strands extracted from cable 977 have
shown a 7-9% loss in current. Another HQ R&D cable run is planned for
July or August of 2008. The HQ cable parameters need to be modified to
reduce the strand damage produced at the edge of the cable during
fabrication.

**II. Cable Acceptance**

The following cables were accepted for coil winding after strand and
cable tests:

L7O-B0973R

L7O-B0975R

L7O-B0953R

Cable acceptance documents are available on the LARP website.

**III.** **FNAL Activity**

During past year, the program has relied on FNAL transformer test to
establish the low-field stability of the cable. This is in addition to
the low field stability set by tests of extracted strands. Below is a
table of the cables that were tested.

Cable Tests

  ---------------------------------- ------------------ ------------------
  **HEAT TREATMENT**                 **Cable ID**       **Impregnation**

  **FNAL**                           **B0973R**         **N**

  **FNAL**                           **B0955R**         **N**
  ---------------------------------- ------------------ ------------------

**Test results show that minimum quench currents are \> than 20 kA.**

## 2.4.1.3 Strand Procurement 

*A. Ghosh*

In Dec 2007, an updated specification for magnet strand was released for
procurement, Spec. No.: LARP-MAG-M-8001-RevF. The strand specification
is shown below. The main change was in the defining the strand design to
be 108/127 with filament diameter of 50 mm at 0.7 mm. In addition the
spacing between the sub-elements was increased by 50%, to improve the
tolerance of the sub-elements under mechanical deformation. This also
meant that the copper fraction in the wire increased fro 48% to 52%.

![](media/image2.wmf){width="5.061805555555556in"
height="2.54375in"}**[Main parameters of the strand]{.underline}**

The Table below shows the present status of the LARP and CDP orders. The
quantity of wire is in kilograms and all wires are of the RRP-54/61
design except the strand delivered in Feb-08 which is of the 108/127
strand design. This inventory is currently at LBNL. Note that there are
several billets delivered 11/15/06 that have poor piece lengths, and are
not being used for fabricating production cable. These billets had
mono-filament rods that led to excessive wire breakage. This problem
which affected many multi-billets was analyzed at OST and corrective
action has been taken to prevent future such occurrences. Billets
processed since then have had good piece lengths.

During this fiscal year, LBNL placed an order for 85kg of 54/61 wire
under a new specification that targets the HQ program; namely
LARP-MAG-M-8002 Rev-A. The specification targets a higher Jc and relaxes
the requirement on RRR of the Cu-stabilizer. A requirement for Jc at 15T
is also introduced as HQ magnets will see peak fields \~ 15T. This is
due to be delivered in Dec'08. Another order for 75 kg will be placed in
Aug'08 for delivery in Apr'09.

## 

![](media/image3.wmf){width="5.995138888888889in"
height="5.558333333333334in"}**Table of LARP and CDP orders to OST**

## 2.4.1.4 Cable Characterization 

*A. Ghosh, BNL*

There is much uncertainly about the strain and stress sensitivity of the
new RRP stand. Data from FNAL for a single RRP strand in a Rutherford
cable of Cu strand has shown that there is a sharp drop in Ic for
stresses above 150 MPa. Prior measurements on full size cables with
older generations of stand have shown that stress up to 200 MPa are
reversible. To resolve this discrepancy LARP has decided to once again
to test cable at the cable test facility at the National High Magnetic
Field Laboratory (NHMFL) in Tallahassee, FL.

# Samples Preparation

LBNL has assembled 3 samples, one of cable 947R and two of 953R, of
cables used in TQ and LQ magnet. The samples were reacted with the same
heat treatment profile as that used for the TQ coils. In the last
quarter of FY08 the 3 samples will be instrumented, placed in test
tooling, and epoxy vacuum impregnated to provide a robust package for
shipment and testing. The samples design also mimics a section of the
coil as it would be loaded in a coil.

# Test Facility at NHMFL

There are two aspects of testing at NHMFL less than ideal. One is that
the sample current supply is used to power Cu Bitter coils in the user
facility. The second is the reliability of the pressurization system for
applying stress to the samples.

1\. Powers Supply Issues

This requires that the power supply time be scheduled in advance but
also the time slot is only 8 hours per day. This does not permit enough
to perform system checks and test samples. Therefore, LBNL has designed
and is fabricating a superconducting current transformer. The
transformer would make the cable test facility at NHMFL independent of
the power supply schedule. A transformer will also increase the current
range for testing. One power supply at NHMFL can provide 20,000A. The
transformer is designed for 50,000A. A transformer a CERN with a similar
design achieved 35,000A.

There is another important cost benefit of using a transformer; LHe
costs will also be reduced significantly. A typical LHe cost for 1 week
of testing is about \$20,000. The cost estimate for fabricating the
transformer is about \$50,000. Therefore, three testing campaigns would
recoup the cost of the transformer. The transformer should also
significantly reduce the electrical noise permitting better voltage
sensitivity during a test.

2\. Applying Load to the Samples

The pressurization system used to apply a load to the cables uses
bellows made with 5 pleats welded together forming an assembly that
looks like an accordion. The welded joints at the inner and outer pleats
have failed several times during testing, when this occurs the testing
campaign is over since the magnet system has to be warmed to room
temperature for the bellows to be removed and repaired. In the last few
months of FY08 LBNL is going to explore the use of bladders in place of
the bellows. Tests are planned to test if the bladders can be used at
4.2K. The bladders are expected to fail at some point during
pressurization but there will be 3-4 bladders in place of the bellows.
So even if one bladder fails during a test another bladder is ready to
replace it for the test to continue.

[NHMFL Test Date]{.underline}: At this time, the tests at NHMFL are
planned for the week of [Nov. 16, 2008, in FY09.]{.underline}

##  

# 3. PROGRAM MANAGEMENT

## 3.1 Administration

## 3.1.1.4 Toohig Fellowship

*S. Peggs, BNL*

There are currently 3 Toohig Fellows (TFs) -- Rama Calaga (BNL), Helene
Felice (LBNL) and Riccardo de Maria (BNL).

Calaga -- the first ever TF - will cease being a TF before the end of
FY08, in order to take a post-doctoral position at BNL, partially funded
by the Collider-Accelerator Department and partly by LARP. His intention
on the LARP side is to work on Crab Cavity R&D, in support of a
potential future upgrade of the LHC. In the slightly more than 2 years
that Calaga has been a TF, he has spent more than 50% of his time at
CERN, based in the ABP group of the AB department, supervised by Oliver
Bruning. He has been involved in many activities, both theoretical and
operational. He has spent much time in the SPS control room.

Felice -- chronologically the second TF -- is based in the
superconducting magnet group at LBNL. She spends a significant amount of
time at CERN, although less than 50%. Most recently she has been working
with Gijs de Rijk et al at CERN, on the testing and re-testing of TQS
model quadrupoles. She is also working on design issues for the upcoming
HQ series of HQ Nb3Sn quadrupoles that LARP will soon begin to build and
test. She is task leader for "Instrumentation and Quench Protection".

De Maria has only recently become a TF, and is still in the process of
defining his interests in detail. One major focus area is the nascent
LARP involvement in PS2 studies, calculations and design. He has begun
to work on the imaginary gamma-T lattice option for the PS2. He has also
begun to look into the Fermilab Main Injector (upgraded) and the KEK
J-PARC accelerator as important PS2 analogs.

Very recently an offer was made to a fourth potential TF, who has
provisionally accepted a position, but who has yet to visit the LARP
laboratories in order to see if a mutually satisfactory supervisor and
broad topic can be defined. Whether or not that person accepts, it also
possible that another excellent candidate will also be offered a TF
position.

The TF Committee, which seeks and evaluates TF candidates (according to
the rules in the LARP Research Program Management Plan), is currently
chaired by Angelika Drees (BNL). More information is available at
<http://www.interactions.org/toohig> .

## 3.2 Commissioning

## 3.2.2.1 Long Term Visitor (LTV) Program

*S. Peggs, BNL*

The first batch of Long Term Visitors (LTVs) are about to go to CERN.
They are Eliane Gianfelice (FNAL), Steve Peggs (BNL), and James Strait
(FNAL). Gianfelice will go for a period of about 4 months, while Peggs
and Strait will be in residence at CERN for approximately 12 months.
This is a new program which has long been under deliberation, and so it
is too soon to report on how well (or poorly) it is functioning.

An LTV is a visitor to CERN from a U,S. DOE-supported institution who
will spend more than 4 contiguous months at CERN to help with one or
more aspects of the LHC accelerator and its injectors, including
upgrades.

CERN chooses candidate LTVs from a pool of applicants supplied by LARP.
The administrator of LARP LTVs compiles the LARP list in conjunction
with the head of LARP. This list will contain a primary task and a
contact person for each applicant.

CERN selection is made by a committee that presently consists of Paul
Collier, Roger Bailey, Mike Lamont, Oliver Brüning, and the machine
coordinators. LTV applications are sent to the LARP LTV administrator
(currently Peter Limon), in order to enter the "pool" of LARP-approved
candidates. The LTV administrator (a task leader in LARP parlance) is
supported in his evaluations and deliberations by the Long Term Visitor
Advisory Committee, LTVAC, which he chairs.

***3.3 Joint Interaction Region Studies***

*A. Zlobin, FNAL*

LARP Joint IR Studies (JIRS) begin in FY08, extending and bringing
together connected tasks that were previously performed either in
Accelerator Systems or in Magnet Systems. The main goal is to improve
efficiency and communication between accelerator and magnet tasks and
turn them into integrated studies. The JIRS scope of work is described
in The mission of LARP "Joint Interaction Region Studies". According to
this document JIRS will provide guidance to LARP magnet R&D based on
integrated studies of magnet and accelerator issues.

JIRS directions include:

1.  **QA - accelerator quality Nb3Sn quadrupole suitable for LHC Phase I
    upgrade.**

JIRS will define and evaluate a list of potential QA locations at CERN
in full communication with CERN; develop specifications for QA magnets
based on at least one of the potential locations; examine the
possibility of using LQ or HQ designs and tooling to build QA. JIRS will
also identify bench tests on QA or LQ or HQ to demonstrate accelerator
quality performance (except radiation), to be performed within LARP or
at CERN.

2.  **QB - Nb3Sn quadrupole prototype for Phase II upgrade.**

JIRS will perform preliminary studies to generate a set of parameters
for QB magnets based on 1 (or more) upgrade scenarios to guide magnet
studies, well before CERN states the QB length, aperture, gradient and
peak coil field; estimate and simulate correction system parameters and
possible issues in a QB implementation.

3.  **Slim magnets - IR magnets inside ATLAS, CMS detectors.**

JIRS will list and evaluate "sample straw man" parameters and operation
conditions for slim magnets located inside ATLAS and/or CMS. The
usefulness of conventional (NbTi) or alternative (Nb3Sn, Nb3Al or HTS)
magnet technologies in terms of operational margin, life-time, etc. has
to be also evaluated.

4.  **Other studies.** Additional works have been also included in the
    FY08 working plan

-   Analysis of IR optics layout with crab cavities

-   Design study of separation dipole D1 for Phase I upgrade and D1-D4
    for Phase I-b for local crab cavity options

FY08 Joint IR Studies tasks and budget are shown in Table 1. The total
budget of 340k\$ supports efforts of \~1 FTE.

Table 3.3.1 JIRS WBS and budget.

+------+------------------------+----------+-----+-----+------+------+
|      |                        |          | Tot | B   | F    | L    |
|      |                        |          | al, | NL, | NAL, | BNL, |
|      |                        |          |     |     |      |      |
|      |                        |          | k\$ | k\$ | k\$  | k\$  |
+------+------------------------+----------+-----+-----+------+------+
| 3.3  | Joint IR Studies       | Zlobin   | *   | *   | **2  | **   |
|      |                        |          | *34 | *12 | 00** | 20** |
|      |                        |          | 0** | 0** |      |      |
+------+------------------------+----------+-----+-----+------+------+
| 3    | Simulation             |          |     |     |      |      |
| .3.1 |                        |          |     |     |      |      |
+------+------------------------+----------+-----+-----+------+------+
| 3.3  | Operating margins      | Mokhov   | **8 |     | 80   |      |
| .1.1 |                        |          | 0** |     |      |      |
+------+------------------------+----------+-----+-----+------+------+
| 3.3  | Accel. Quality &       | R        | **4 | 40  |      |      |
| .1.2 | Tracking               | ob.-Dem. | 0** |     |      |      |
+------+------------------------+----------+-----+-----+------+------+
| 3    | Studies                |          |     |     |      |      |
| .3.2 |                        |          |     |     |      |      |
+------+------------------------+----------+-----+-----+------+------+
| 3.3  | Optics & layout        | J        | *   | 40  | 80   |      |
| .2.1 |                        | ohnstone | *12 |     |      |      |
|      |                        |          | 0** |     |      |      |
+------+------------------------+----------+-----+-----+------+------+
| 3.3  | Magnet feasibility     | Wanderer | *   | 40  | 40   | 20   |
| .2.2 | studies                |          | *10 |     |      |      |
|      |                        |          | 0** |     |      |      |
+------+------------------------+----------+-----+-----+------+------+

In the first part of FY08 JIRS focused on the investigation of
possibilities of using Nb3Sn quadrupoles in the LHC Phase I upgrade
planned at CERN. The results obtained during these studies were
presented and discussed within US-LARP collaboration and with CERN:

-   Discussions at CERN with LHC Interaction Upgrade Working Group
    (LIUWG) - March-April

    -   LBM optics provides sufficient aperture with baseline NbTi 90 mm
        Q1 and 130 mm Q2-Q3. It allows using higher G and shorter Nb3Sn
        90 mm Q1 and 110 mm Q3's.

    -   Symmetric optics has potentially aperture problems at the Q2's
        and Q3 even with baseline 130mm NbTi magnets. Q1 can be replaced
        with higher gradient and shorter 90-110 mm Nb3Sn without
        reducing triplet aperture. Replacing the Q3 with a 110mm Nb3Sn
        magnet needs further study.

-   Presentation to LHC upgrade construction project committee -- April
    1, 2008.

    -   JIRS recommended that US-LARP pursues development of the 110 mm
        aperture Nb3Sn quadrupoles as QA. It has greatest flexibility
        for installation options in Phase I and paves the way toward IR
        quadrupoles for the Phase II upgrade. Construction project
        should consider using 90-110 mm Nb3Sn quadrupoles to replace Q1
        or Q3 in LBM or Symmetric optics.

-   Presentation and discussion of JIRS results at LARP collaboration
    meeting -- April 2008

The JIRS results will be summarized and published in two papers
submitted to European Particle Accelerator Conference (EPAC'2008) --
June, 2008:

-   ID: 4291  Optics Implications of Implementing Nb3Sn Magnets in the
    LHC Phase I Upgrade

-   ID: 3477  Nb3Sn Quadrupoles in the LHC IR Phase I Upgrade

JIRS next steps include**:**

-   Study new version of LHC Phase I optics and NbTi magnet parameters

-   Re-iterate Nb3Sn magnet parameters consistent with new optics

-   Studies of the effect of field quality in Nb3Sn quadrupoles.

## 3.3.1 Simulations

## 3.3.1.1 Operating Margins 

*N. Mokhov, FNAL*

**Statement of work for FY08**: Based on realistic energy deposition
calculations estimate the operational performance margins for Nb3Sn
quadrupoles installed in the LHC high-luminosity insertions for the
Phase-I upgrade.

**Status and plans:**

The LARP JIRS project aims at investigation of potential of replacing
one (on each side of IP) of the NbTi quadrupoles with a Nb3Sn one in the
LHC Phase I upgrade of high-luminosity IRs. Based on realistic energy
deposition calculations, an attempt is made to derive operational
margins for the quads in various configurations.

Simulations are done with MARS15 (2008), and DPMJET-3 as an event
generator for 7x7 TeV pp-collisions at the luminosity of 2.5x10^34^
cm^-2^ s^-1^, using LowBetaMax and Symmetric optics configurations. IP5
(R) is considered, with a full crossing angle of 450 μrad, segmented
3-mm thick absorbers -- stainless steel or tungsten - possibly cooled at
LN-temperature, as proposed in our paper PRSTAB, 9, 10001 (2006) and
Proc. WAMDO06 Workshop, CARE-Conf-06-049-HHH, p. 80 (2006). Apertures of
the TAS absorber studied are 42 and 55 mm. All details -- 3D geometry
and materials of all the components in the cryostat - of the baseline
130-mm NbTi quadrupoles and proposed 90, 110 and 130-mm Nb3Sn
quadrupoles along with the OPERA-calculated 2-D magnetic maps (200, 180
and 125 T/m, ∆x = ∆y = 2 mm) were implemented into the MARS15 model of
the IP5 triplet. Design goals on the peak power density are defined as
one third of the quench limits: 0.53 and 1.66 mW/g for NbTi and Nb3Sn
coils, respectively.

Figure 3.3.1.1.1 shows MARS15 model and tracks in the symmetric optics
triplet with a 130-mm NbTi baseline Q1 quadrupole replaced with the
90-mm aperture Nb3Sn one. An example of the calculated distribution of
peak power density in the inner coils along the hybrid triplet of the
LowBetaMax optics is shown in Figure 3.3.1.1.2.

![](media/image4.wmf){width="5.401388888888889in"
height="3.2381944444444444in"}

**Figure 3.3.1.1.1 Particle tracks in the MARS15 model of the Symmetric
optics hybrid triplet.**

![](media/image5.png){width="4.803472222222222in"
height="4.065972222222222in"}

**Figure 3.3.1.1.2 Peak power density in the inner coils along the
hybrid triplet of the LowBetaMax optics. Red histogram is for the left
coils, blue one is for the right coils.**

At this stage, results of full simulations for three hybrid triplet
configurations - two LowBetaMax and one Symmetric optics -- allow us to
derive the following conclusions:

1.  There are always four pronounced peaks in longitudinal distributions
    of maximum power density in the first SC cable (averaged over the
    cable area at the azimuthal maxima): close to Q1 non-IP end, Q2a IP
    end, Q2b non-IP end and Q3 IP end (see also LHC PR 633, 2003).

2.  For the configurations considered all the peaks are safely below the
    design limits (for 55-mm TAS).

3.  Increasing TAS aperture from 42 to 55mm, increases first peak by 10%
    and heat load to the cold components by 75 W.

4.  3-mm tungsten absorbers in Q1 provides reduction of peaks by a
    factor of about 3 and 2 in Q1 and Q2, respectively, compared to the
    stainless steel ones.

5.  Peak in Q3 is practically insensitive to the configuration.

6.  Compared to the nominal case, dynamic heat loads to the SC quads are
    certainly higher at 2.5x10^34^ cm^-2^s^-1^ and enlarged TAS
    aperture, but -- because of larger quad apertures and use of
    absorbers - seem to be manageable, especially with high-Z absorbers
    cooled at LN2.

7.  Using Nb3Sn for Q1 or Q3 instead of NbTi substantially increases
    operational margins, frees space for instrumentation between quads,
    and provides verification of this new technology for Phase II.

***3.3.1.3 Accelerator Quality & Tracking***

*G. Robert-Demolaize, BNL*

**Statement of work for FY08**

The Accelerator Quality & Tracking (AQT) task has to:

-   provide a set of tracking tools that would allow working in a "plug
    and play" way once new sets of data are available,

-   develop reference error tables for field harmonics and mechanical
    settings for all QA locations,

-   perform analysis of the QA field quality and alignment on beam
    dynamics and provide feedback for magnet design and correction
    system,

-   start working on QB magnet design for the full LHC upgrade scenario.

**Status and plans:**

The primary goal so far was the development of all required numerical
tools to perform tracking studies. The common format for all AQT studies
is chosen as MAD-X, so as to be comparable to previous CERN results.
JIRS is currently working on two basic schemes for the IR1/IR5
luminosity upgrade, referred to as LowBetaMax and Symmetric. The layouts
studied so far in AQT are:

-   LowBetaMax: a) 130-mm NbTi Q1 with L = 7.06 m and K1 = 167.2 T/m, b)
    130-mm Nb3Sn Q1 with L= 5.65 m (the magnetic center is moved by 1 m
    towards the IP) and K1 = 208.9 T/m, and c) 110-mm Nb3Sn Q3 with two
    modules of L = 3.00 m (spaced by 1.8 m) and K1 = 176.2 T/m

-   Symmetric: a) 130-mm NbTi Q3 with L= 9.2 m and K1 = 121.9 T/m, b)
    110-mm Nb3Sn Q3 with two modules of L = 3.19 m (spaced by 0.9 m) and
    K1 = 177.7 T/m.

For each of these cases, only the IR5 layout is provided; it is then
converted into MAD-X format, in order to check that the optics function
are comparable to the ones obtained in the original format. For the
LowBetaMax cases, the calculated values of the main optics functions are
reported in Table 3.3.1.2.1 (using the thick lens model). Compared to
the original values, the differences from the MAD-X model are on the
order of 10^−3^ for beta_max but can go up to a full unit in
chromaticity dQ~x,y~ in the Ti Q1 case.

Table 3.3.1.2.1: Calculated optics functions for the IR5 for three
LowBetaMax optics.

![](media/image6.png){width="5.147222222222222in"
height="0.7604166666666666in"}

In order to perform tracking studies for each considered scenario (and
both Symmetric and LowBetaMax options), the new layout of the IR5
insertion has to be implemented into the rest of the LHC lattice. This
"upgraded" lattice is then re-matched to the nominal tunes and
chromaticities, and converted to the thin lens model using the tools
developed by Riccardo DeMaria. Then the parameters of the triplet
magnets for each upgrade scenario are plugged into the corresponding
scripts for installation of the new and/or modified magnets in both IR1
and IR5 insertions.

Figure 3.3.1.2.1 shows an example of the display of both magnet
gradients and twiss functions in IR5 for the Symmetric NbTi Q3 case as
described above. In addition to the "perfect" model, error tables based
on measurements of the harmonics of each magnet type (NbTi or Nb3Sn
quads) will be included and would make it possible to study the effect
of the various possibilities of magnet aperture (90, 110 and 130 mm).

![](media/image7.png){width="4.375in" height="2.65625in"}

Figure 3.3.1.2.1: Variations of \_x and Dx along IR5 for a Symmetric
optic case with a NbTi Q3 magnet of 130 mm aperture (K1 = 121.9 T/m).

With the lattice set up, one can use the CERN SixTrack run environment
for detailed tracking. An AQT account is being opened specifically on
the CERN computing resources for these studies, that would allow
calculating e.g. the dynamic aperture for each scenario. Another
relevant parameter to study is the shape of the tune footprint; new
numerical tools had to be created in order to obtain footprints like the
one seen in Figure 3.2.1.2.2. The required numerical models are finally
set up and all scenarios can now be analyzed through them. The first
task of AQT is therefore achieved,

![](media/image8.png){width="3.7472222222222222in"
height="2.4277777777777776in"}

Figure 3.2.1.2.2: Sample tune footprint for a Symmetric optics with a
NbTi Q3 magnet

of 130 mm aperture (K1 = 121.9 T/m).

The optics are considered as ideal, i.e. no multipole errors are
included. Beam-beam events are only considered at IP1 and IP5, with
Np=1.15E+11 but additional tools might be needed depending on
preliminary analysis of the first tracking results. Most of the effort
was invested in ensuring the compatibility with CERN and LARP existing
tools, which will help on the long term when the final upgrade layout
will be selected from comparisons between all proposed solutions. Future
plans include the treatment of recent measurement of Nb3Sn harmonics for
both LowBetaMax and Symmetric.

## 3.3.2 Studies

***3.3.2.1 Optics & Layout***

*J. Johnstone, FNAL*

Statement of work in FY08:

\(1\) The 'LowBetaMax'(LBM) and 'Symmetric' (SYM) LHC Phase 1 upgrade
optics will be developed in collaboration with CERN personnel, with
particular emphasis on analyzing the feasibility of replacing the
baseline NbTi Q1 or Q3 with Nb3Sn magnets of the same slot length to
attain higher luminosity through the greater heat margin, and; (2)
Develop a layout for a local IR crab cavity (CC) insertion, specifying
magnet parameters for new separation/recombination dipoles plus the
dogleg dipoles required to provide adequate beam separation in the
cavities.

Status and plans:

\(1\) Preliminary collision optics have been designed for β\* = 25cm for
both the LBM and SYM triplet configurations assuming NbTi magnets in
appropriate combinations of 90mm and 130mm apertures. Variations of
these models were designed such that Nb3Sn magnets were completely
interchangeable with either the Q1 or Q3. Six such variations were
created to begin exploring the magnet parameter space of length,
aperture, gradient, and number of modules. Table 3.3.2.1.1 lists magnet
parameters for 4 of these models.

Table 3.3.2.1.1. Magnet parameters for 4 examples of the 8 IR
configurations studied. The preferred solution is represented by the
right hand entries.

<table>
<colgroup>
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 7%" />
</colgroup>
<tbody>
<tr class="odd">
<td rowspan="3"></td>
<td colspan="6">LowBetaMax</td>
<td colspan="6">Symmetric</td>
</tr>
<tr class="even">
<td colspan="3">NbTi</td>
<td colspan="3">Nb3Sn Q3</td>
<td colspan="3">NbTi</td>
<td colspan="3">Nb3Sn Q3</td>
</tr>
<tr class="odd">
<td>ID mm</td>
<td>L<sub>mag</sub> m</td>
<td>G<sub>nom</sub> T/m</td>
<td>ID mm</td>
<td>L<sub>mag</sub> m</td>
<td>G<sub>nom</sub> T/m</td>
<td>ID mm</td>
<td>L<sub>mag</sub> m</td>
<td>G<sub>nom</sub> T/m</td>
<td>ID mm</td>
<td><p>L<sub>mag</sub></p>
<p>m</p></td>
<td>G<sub>nom</sub> T/m</td>
</tr>
<tr class="even">
<td>Q1</td>
<td>90</td>
<td>7.060</td>
<td>167.2</td>
<td>90</td>
<td>7.060</td>
<td>167.2</td>
<td>130</td>
<td>9.200</td>
<td>121.9</td>
<td>130</td>
<td>9.200</td>
<td>121.9</td>
</tr>
<tr class="odd">
<td>Q2a</td>
<td>130</td>
<td>7.787</td>
<td>121.4</td>
<td>130</td>
<td>7.787</td>
<td>121.4</td>
<td>130</td>
<td>7.800</td>
<td>121.9</td>
<td>130</td>
<td>7.800</td>
<td>121.9</td>
</tr>
<tr class="even">
<td>Q2b</td>
<td>130</td>
<td>7.787</td>
<td>121.4</td>
<td>130</td>
<td>7.787</td>
<td>121.4</td>
<td>130</td>
<td>7.800</td>
<td>121.9</td>
<td>130</td>
<td>7.800</td>
<td>121.9</td>
</tr>
<tr class="odd">
<td>Q3</td>
<td>130</td>
<td>8.711</td>
<td>121.4</td>
<td>110</td>
<td>2*3.000</td>
<td>176.2</td>
<td>130</td>
<td>9.200</td>
<td>121.9</td>
<td>110</td>
<td>2*3.190</td>
<td>175.7</td>
</tr>
</tbody>
</table>

In the preferred solution the Q3 NbTi magnet in the SYM design was
replaced by 2 short (3.19m) Nb3Sn magnet modules having 110mm aperture.
This model appears to be close to optimal for reproducing the NbTi Q3
R-matrix, ease of manufacturing, convenience of installation, and
providing adequate aperture consistent with the 1E35 luminosity
anticipated after the Phase 2 LHC upgrade (see also *3.3.1.1* *Operating
Margins*). The magnet apertures and beam envelope for this case are
shown in Fig. 3.3.2.1.1.

![](media/image9.png){width="4.855555555555555in"
height="1.792361111111111in"}

> **Figure 3.3.2.1.1. IR5 magnet apertures for the SYM model with a
> 110mm Nb3Sn Q3s, and the 9σ beam envelope for β\* = 25cm and 225 μrad
> half-crossing angle.**

The physical apertures are reduced from the coil ID by corrections for
the beam pipe, beam screen, etc. The 9σ beam envelope in the crossing
plane reflects a 225 μrad half-crossing angle (10σ separation at the
first parasitic crossing), and is inflated using a prescription that
takes into account optical mismatches, beam jitter, momentum errors,
etc.

\(2\) A model local crab cavity dogleg insertion has been designed that
would replace the baseline D1-D2 separation/recombination dipole
configuration. The 6 resistive D1 magnets would be replaced by four
180mm bore, superconducting RHIC DX magnets, with 1m separating them.
The 3 magnets completing the dogleg were assumed to be 9.45m SC, double
bore magnets. This design provides 17.55m of longitudinal space for the
cavities, with the beams separated by 270mm. The CC insertion fits
exactly within the baseline D1-D2 slot of 104.1m. Magnet parameters for
the CC insert are listed in Table 3.3.2.1.2.

Table 3.3.2.1.2. Magnet parameters and beam separation through the CC
dogleg insertion.

  -------------- ------------- ------------ ------------- ----------------
  Magnet         Lmag, m       B, T         S, m          Beam Sep'n, mm

  D1 (4\*DX)     4\*3.70       4\*4.3       0             0

                                            17.8          48.5

  D11            9.45          6.734        53.71         244

                                            63.16         270

  D12            9.45          6.734        80.71         270

                                            90.16         244

  D2             9.45          6.734        94.65         220

                                            104.10        194
  -------------- ------------- ------------ ------------- ----------------

Since there are no focusing elements between the D1-D2 dipoles,
replacing the baseline separation/recombination scheme with the CC
dogleg does not impact the optics, and is almost entirely de-coupled
from any assumptions regarding the IR triplet configuration. The
location of the insertion within the LS is illustrated in Fig.
3.3.2.1.2, with the corresponding collision lattice functions for the
SYM triplet layout.

![](media/image10.wmf){width="4.723611111111111in"
height="3.0118055555555556in"}

> **Figure 3.3.2.1.2. Location of the CC insertion dogleg dipoles within
> the high luminosity IR straight, and representative Phase 1 collision
> optics (β\* = 25cm).**

***3.3.2.2 Magnet Feasibility Studies***

*P. Wanderer, BNL*

Statement of work in FY08:

Sub-task 1: Establish QA specifications based on its potential location.
Perform QA design studies including conductor, structural materials,
etc. Examine the possibility of using LQ or HQ-derived designs and
tooling to build QA magnets. Identify bench tests on QA or LQ or HQ
magnets that would help explore and demonstrate accelerator quality
performance.

Status and plans:

Sub-task 1 has received by far the most attending of the three
sub-tasks, but not in the way planned at the beginning of the FY. As
FY08 progressed and CERN's plans for the Phase I upgrade became more
specific (especially with respect to timetable, it was concluded that
the most effective use of resources was to wait for the IR quad
specifications that will be listed in the Phase I Conceptual Design
Report, rather than develop specifications independently of the LIUWG
(LHC Interaction Upgrade Working Group) at CERN.

This has led to the description of the QA design being "slot compatible"
with the CERN NbTi quads. The meaning of "slot compatible" includes:
same or smaller cold mass length and diameter; compatible with the
planned corrector system; integral gradient the same within \~ 10% but
possibly from two separate cold masses; same quench protection system;
compatible with cryogenic system (i.e., heat exchanger).

**Table 3.3.2.2.**1. Summary of basic magnet parameters.

  ---------------- ----------------------------------------------------- ----------------------------------------------------- ----------------------------------------------------- ----------------------------------------------------- ----------------------------------------------------- ------------------------------------------
                   TQC-90                                                IRQ-90                                                IRQ-110                                               HQ-110                                                IRQ-130                                               HQ-134

  Coil             ![](media/image11.png){width="0.6340277777777777in"   ![](media/image12.png){width="0.6319444444444444in"   ![](media/image13.png){width="0.6451388888888889in"   ![](media/image14.png){width="0.6326388888888889in"   ![](media/image15.png){width="0.6194444444444445in"   ![](media/image16.png){width="0.58125in"
  cross-section    height="0.6111111111111112in"}                        height="0.6111111111111112in"}                        height="0.6368055555555555in"}                        height="0.6104166666666667in"}                        height="0.6166666666666667in"}                        height="0.5791666666666667in"}

  Coil ID, mm      90                                                                                                          110                                                                                                         130                                                   134

  Strand OD, mm    0.7                                                   0.7                                                   0.7                                                   0.8                                                   0.7                                                   0.8

  Cable width,mm   10.05                                                 15.14                                                 15.10                                                 15.15                                                 15.10                                                 15.15

  J~c~(12T),       2.5                                                                                                                                                                                                                                                                           
  kA/mm^2^                                                                                                                                                                                                                                                                                       

  B~max~(1.9K), T  12.9                                                  13.8                                                  14.4                                                  14.5                                                  14.5                                                  15.0

  G~max~(1.9K),    248                                                   268                                                   229                                                   229                                                   193                                                   193
  T/m                                                                                                                                                                                                                                                                                            

  G~nom~(12.5kA)   208.3                                                 185.6                                                 179.7                                                 168.0                                                 155.9                                                 144.5

  G~max~/Gnom      1.19                                                  1.44                                                  1.28                                                  1.37                                                  1.24                                                  1.34

  W(12.5kA),kJ/m   358                                                   384                                                   674                                                   595                                                   923                                                   857

  J~cu~, A/mm^2^   2407                                                  1546                                                  1585                                                  1345                                                  1585                                                  1345
  ---------------- ----------------------------------------------------- ----------------------------------------------------- ----------------------------------------------------- ----------------------------------------------------- ----------------------------------------------------- ------------------------------------------

The design studies that have taken place prior to and during FY08 have
covered the wide range of possible apertures. The main parameters of
analyzed magnets are summarized in Table 3.3.2.2.1. The Table shows that
the TQ models have insufficient margin (less than 20%), poor field
quality and difficult quench protection to be used in Phase I upgrade.
Models with 15 mm cable can provide larger margin and could be used as
Q1 or Q3 in both LBM and Symmetric optics (see Optics & Layouts and
Operation margin Task reports). As CERN's interest in large apertures
became clearer, the work shifted to the large-aperture (130 mm), two
layer version. In the last couple of months, CERN discussions have moved
to diameters near 110 mm, and HQ designs are now being developed for
that aperture too.

Field quality was measured and analyzed in 5 TQ models. The results are
summarized in Table 3.3.2.2.2. Comparison with present NbTi LHC IR
quadrupoles shows that Nb3Sn magnets have a factor of 3 larger harmonics
RMS spread. The effect of that is being studied by the Tracking and
Simulation Task.

**Table 3.3.2.2.**2. TQ harmonics at 45 T/m and Rref = 22.5 mm.

  ------- --------- --------- --------- --------- --------- ---------- ---------
  **n**   **TQC**                       **TQS**             **Mean**   **RMS**

          **01**    **02E**   **02A**   **01**    **02**               

  b~3~    0.99      -0.01     -3.40     -1.49     1.90      -0.40      1.87

  b~4~    -0.07     0.41      2.07      -1.13     1.28      0.51       1.10

  b~5~    2.89      4.65      -5.33     -0.83     2.66      0.81       3.55

  b~6~    -6.28     -7.12     -7.03     -6.33     -6.75     -6.70      0.35

  b~7~    0.13      -0.10     -0.11     0.19      0.00      0.02       0.12

  b~8~    -0.06     0.08      0.20      -0.05     -0.29     -0.02      0.16

  b~9~    -0.04     -0.07     0.21      0.12      0.15      0.07       0.11

  b~10~   0.02      0.24      0.12      0.22      0.10      0.14       0.08

  a~3~    -1.54     0.43      -2.95     3.64      2.55      0.43       2.46

  a~4~    -0.63     -2.33     4.38      -3.34     -5.87     -1.56      3.42

  a~5~    5.00      8.35      6.83      -0.78     -0.38     3.81       3.74

  a~6~    0.03      0.52      -1.58     -0.26     -0.08     -0.27      0.70

  a~7~    0.07      -0.50     -0.22     -0.29     -0.15     -0.22      0.19

  a~8~    0.12      0.26      -0.48     -0.16     -0.56     -0.16      0.32

  a~9~    -0.04     -0.24     -0.33     -0.01     -0.05     -0.14      0.13

  a~10~   -0.01     0.04      0.03      0.02      -0.09     0.00       0.05
  ------- --------- --------- --------- --------- --------- ---------- ---------

\* calculated values subtracted from b6 and b10.

Some of the bench tests needed for this task have taken place. The
primary example is the testing of 1m TQ magnets. The tests include
training at 4.5 K and 1.9 K, quench origin and propagation, quench
protection, field quality, and strain. Other needed bench tests are now
budgeted for FY08 or FY09. These are tests of the strain tolerance of
the strand (at NIST) and cable (at the National High Magnetic Field Lab
in Florida and at CERN). So far, magnets have not been thermally cycled
to room temperature and back more than once.

Sub-task 2. With the design of the Phase I upgrade not yet set, trying
to design the optics and QB magnets for the Phase II upgrade has not
taken place. It is useful to note that the work in next year or two will
give us a good idea of the achievable range of apertures and gradients.

Sub-task 3. Upgrade plans for ATLAS and CMS are not well-formed at this
time, so no work has been done on slim magnets in FY08. However, CERN
has recently expressed strong interest in the US supplying a
large-aperture dipole. The list of options for this magnet includes a
dipole based on the DX dipole built for RHIC.