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SLAC's Increased Involvement in the LHC

SLAC's traditional electron and photon based science program has been diversifying to the high-energy frontier over the last few years, with efforts on both the accelerator and the ATLAS detector at CERN's Large Hadron Collider (LHC). Both of these efforts are expected to ramp up over the next few years. On the accelerator side, Tom Markiewicz has become the Accelerator Systems leader for the U.S. LHC Accelerator Research Program (LARP) and also heads the newly created LARP department in the Accelerator Research Division (ARD).

Underscoring this increased involvement in the LHC, SLAC recently hosted the 9th LARP Collaboration Meeting on October 17-19, 2007. About 60 participants from Brookhaven National Laboratory (BNL), CERN, Fermi National Accelerator Laboratory, Lawrence Berkeley National Laboratory (LBNL) and the University of Texas joined their SLAC colleagues in animated discussions of current and future work. At a session devoted to new proposals, SLAC speakers presented eight proposals for new efforts that would leverage SLAC experience and expertise to the benefit of the LHC and U.S. Accelerator R&D. SLAC is actively working with LARP management to find a way to permit at least some of these efforts to go forward.

LARP efforts are currently divided into four areas: the development of a new generation of superconducting magnets based on Nb3Sn cable (as opposed to the usual NbTi material); research into accelerator system devices and studies in support of higher luminosity at the LHC; support of LHC hardware and beam commissioning; and integrated planning for any U.S. participation in LHC luminosity upgrade projects.

The magnet group, a joint effort with Fermilab, LBNL and BNL collaborators, has made several Nb3Sn magnets that approach the field limit of the conductor with predictable harmonics. Their near term goals are to extend the development to long magnets (4m) and to larger aperture, higher gradient magnets, as well as to improve the quality and design of the Nb3Sn cable strands. Perhaps the most controversial part of the meeting was sparked by a "challenge" from CERN. The U.S. was challenged to provide several accelerator quality Nb3Sn magnets roughly four years from now as part one of a two-phase LHC luminosity upgrade. This would require a rapid acceleration of the current R&D program and a major new commitment of U.S. resources.

The Accelerator Systems group has efforts in instrumentation, collimation and accelerator physics. Instrumentation currently being installed will measure luminosity and beam parameters, excite controlled beam orbit variations for a variety of diagnostic purposes and incorporate several flavors of feedback. Accelerator physics efforts include compensation of beam-beam effects with wires or with a device in use at Fermilab called an electron lens, as well as continued studies on how the beam-beam interaction and electron cloud can limit LHC performance. SLAC has been also developing a second generation rotating collimator for the LHC. (See related SLAC Today stories from September 7, 2006, December 8, 2006 and July 27, 2007.) The first full-scale device should be ready for tests by the end of the year. If successful, SLAC may be asked to build upwards of 30 collimators as part of the LHC upgrades.

Whatever the final details, it is clear that the next few years will see a significant increase in SLAC's involvement with hadrons and the LHC.

Tom Markiewicz and Nan Phinney, SLAC Today, November 29, 2007