US LHC Accelerator Research Program (LARP)BackgroundProposed in 2003 to coordinate efforts at US labs related to the LHC accelerator (as opposed to CMS or ATLAS)

Originally FNAL, BNL, and LBNLSLAC joined shortly thereafterSome work (AC Dipole) supported at UT Austin

LARP GoalsAdvance International Cooperation in High Energy Accelerators Advance High Energy Physics oBy helping the LHC integrate luminosity as quickly as possibleAdvance U.S. Accelerator Science and Technology LARP includes projects related to initial operation, but a significant part of the program concerns the LHC upgrades Current Budget: $12-13M/year.

Magnet SystemsThe goal of the LARP magnet program is to demonstrate the viability of magnets based on Nb3Sn superconductor on a timescale which would allow them to be utilized on the LHC Phase II upgrade in approximately 2020.

Nb3Sn allows larger gradients/apertures and/or larger temperature margins than traditional NbTi, but it has never been used to make accelerator quality magnets before.

Eric Prebys*

*Fermi National Accelerator Lab, PO 500, Batavia IL, 60510

Luminosity MonitorAn ionization detector installed in the neutral absorbers on each side of the ATLAS and CMS interaction regions.

Rate and radiation levels have made the design challenging.

Personnel ProgramsLARP funds two programs to support US personnel working at CERN.

Accelerator SystemsAccelerator Systems includes

Instrumentation o Schottky Monitoro Tune Trackero AC Dipoleo Luminosity Monitor Collimationo Rotatable Collimatorso Crystal Collimation Studies Accelerator Physicso Beam-beamo Space Chargeo Electron Cloudo PS2 (new synchrotron for CERN)

o Crab Cavities

Rotatable CollimatorsThese collimators have multiple facets, such that damaged surfaces can be rotated away in the event of catastrophic beam loss.

1.0x1012

0.8

0.6

0.4

0.2

0.0

[m**-3]

5x101143210

bunch population (xnpnom)

Groebner multip. design

extr., 50 GeV inj., 4 GeV

PS2 aver. EC density vs. NbLHC25 beam, tri-gaussian bunch profile

avdenrun avdenrun#1

AC DipoleThis device drives small oscillations in the beam in order to measure both linear and non-linear lattice terms.

Toohig FellowshipA competitive postdoctoral fellowship open to recent PhD recipients.

Successful candidates are expected to spend approximately half of their time at CERN and half at the LARP host lab of their choice.

Crab CavitiesCrab cavities are superconducting RF cavities which deflect bunches such that they collide head on, even when the beams cross at an

angle. This technology has recently been endorsed by CERN for

the Phase II upgrade.

Long Term Visitors (LTV) ProgramThis program provides support for more senior personnel to spend extended periods at CERN, doing accelerator related R&D or helping to commission the LHC.

Salary is provided by the home institution, while LARP pays relocation and cost of living expenses.

PS2 The PS2 has been proposed to replace the 50 year old PS. LARP is taking part in a number of studies, including the effects of electron cloud and space charge.

www.uslarp.org

Challenging MaterialWhereas NbTi remains pliable in its superconducting state, Nb3Sn becomes brittle during the required heated reaction steps.

Cables must therefore be wound on a mandrill, baked, and then carefully transferred to the magnet.

Design ComparisonLARP has investigated two designs for the magnets:

YokeGap

Collar-YokePreloadShim

ControlSpacer

Skin

Collar

YokeCollaringKey

Inner poleOuter polepiece

Coil MidplaneShim

CollarTraditional magnet design.

Pre-load provided by a series of collars which hold coils in place.

ShellNew conceptPre-load produced by inflatable bladder, and maintained keys, which are inserted..

Nominal ChoicePushing all ParametersLARP magnet subprograms investigate all aspects of magnet design:

Aluminum collar

Bladder location

Aluminum shellMaster key

Loading keys

Yoke-shell alignment

Pole alignment key

Quench heater

Coil

Long Quad (LQ)

The long quad program has produced a 4m magnet with a 90mm aperture and a design gradient of 200 T/m based on a shell design. It is

scheduled to be tested next month.

Technical Quad (TQ)1m magnets with 90mm apertures were produced with both collar and shell designs. All reached gradients of >200 T/m.

High Gradient Quad (HQ)A 1m magnet with a 120mm aperture and a design gradient of 200 T/m based on the shell approach is being built and is scheduled to be tested in FY10.