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RHIC Low-Energy Operations Todd Satogata Weekly Experiment Meeting March 4, 2008

RHIC Low-Energy Operations Todd Satogata Weekly Experiment Meeting March 4, 2008. With help from: L. Ahrens, M. Bai, J.M. Brennan, D. Bruno, J. Butler, X. Chang, W. Christie, A. Drees, A. Fedotov, W. Fischer, J. Gullotta, P. Harvey, T. Hayes, W. Jappe, R.C. Lee, W. W. MacKay,

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RHIC Low-Energy Operations Todd Satogata Weekly Experiment Meeting March 4, 2008

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  1. RHIC Low-Energy OperationsTodd SatogataWeekly Experiment MeetingMarch 4, 2008 With help from: L. Ahrens, M. Bai, J.M. Brennan, D. Bruno, J. Butler, X. Chang, W. Christie, A. Drees, A. Fedotov, W. Fischer, J. Gullotta, P. Harvey, T. Hayes, W. Jappe, R.C. Lee, W. W. MacKay, N. Malitsky, G. Marr, R. Michnoff, B. Oerter, E. Pozdeyev, F. Severino, K. Smith, P. Sorensen, S. Tepikian, N. Tsoupas and surely others too! • A (brief) history of RHIC low energy • Challenges and resolutions • Planning and schedule

  2. Searching For The QCD Critical Point: Lots of Interest • Two Years Ago: RIKEN workshop at BNL, Mar 9-10 2006 • “...a growing body of theoretical and experimental evidence that the critical point on the QCD phase diagram, if it exists, should appear on the QGP transition boundary at baryo-chemical potential ~100 - 500 MeV, corresponding to heavy ion collisions with c.m. energy in the range sNN = 5 - 50 GeV.” • Critical Point and Onset of Deconfinement Workshop at GSI, Jul 9-13 2007 • 141 registered participants from 3 continents; 66 presentations • 160 papers on “QCD critical point” in Google Scholar • 112/160 mention RHIC low energy (or, as George Stephens puts it, “critRHIC”) A. Cho, Science, 312 (14 Apr 2006) T. Satogata RHIC Low-Energy Plans

  3. Low Energy Test Run and Lowest Energy Parameters • Several staged low energy tests • Systematically address challenges • Leverage available beams • Establish luminosity scaling • Permit time for upgrade strategy • 2006 proton test run a success! • 2007 Au test run (1 day) • Leverage proton test rigidity setup • Test RF/timing changes • Measure luminosity • Test experiment DAQs • 2008 Au test run (March 10-12) • 2007 9 GeV setup “in the can” • Test RF/timing fixes • Reproduce 2007 Au test; physics • Explore near lowest energy • Establish lowest energy baseline T. Satogata RHIC Low-Energy Plans

  4. Challenges: RHIC RF Harmonic Number • Nominal RHIC RF: h=360 bunches • RHIC RF tuning range: 28-28.17 MHz • With lower energy, RHIC RF frequency cannot fall low enough to maintain h=360 • Must raise harmonic number • Retuning cavities is a prohibitive effort • Collisions at both experiments require h(mod3)=0; Experiment DAQs also requires h(mod3)=0 • All beam-synchronous clocks are driven by this clock • All RHIC single-bunch instrumentation • Abort system (needs to find gap) • Experiment DAQ clocks • A problem during Run-7 testing • Fixed, Tested in August 2007 • BPM clock decoding fix complete h=360 120 bunch fill pattern Yellow Blue T. Satogata RHIC Low-Energy Plans

  5. Challenges: Chromaticity and Stability • Low-energy transverse beam stability requires negative chromaticity • Sextupole component of main dipoles drives vertical chromaticity beyond unipolar power supply tuning range • Below sNN = 9.3 GeV/u, we require 1 day of maintenance to flip defocusing sextupole power supply leads at power supplies • Strong octupoles were used to stabilize beam during the 2006/7 test runs • But that adversely affected beam lifetime... Defocusing sextupole strength should sum to negative T. Satogata RHIC Low-Energy Plans

  6. 2007 Gold Test Run: STAR Vernier Scans 1500 • Measured beam size ~ 4mm at *=10m <10% backgrounds • 700-1000 Hz BBC coincidences Peak luminosity ~1.5 x 1024 cm-2 s-1 Uncogging +/-6mm Vernier Scan +/-9mm Vernier Scan STAR BBC Coinc 0 35 Few losses from scan! Au Beam [e9] 0 T. Satogata RHIC Low-Energy Plans

  7. The Fly In The Ointment P. Sorensen/STAR Dec 19 2007 • STAR sNN=9.2 GeV saw 18 primary vertices/2500 events • Believe that 2007 BBC coincidences were not collisions • But their trigger clocks at the time were also “a bit woogidy” T. Satogata RHIC Low-Energy Plans

  8. Mar 2008 Low Energy Test Run Plan and Objectives • 6/7 Mar: Tandem/Booster/AGS Au PPM setup • 10 Mar 08:00-12:00ish • Swap defocusing sextupole leads (at power supplies only) • Set up h=366 RF/clock; test experiment triggers, instrumentation • Test h=387/h=384 RF/clock; test experiment triggers, instrumentation • Optimize Tandem/NSRL dual-species operation • 10 Mar 12:00ish-11 Mar 12:00ish • Restore sNN=9.2 GeV ramp/setup; check/adjust for PHENIX BBC • Machine tuning, lifetime optimization • Vernier scans (with STAR BBCx&&CTB triggers) • Measure cross sections, luminosity, lumi lifetime with experiments • Acquire sNN=9.2 GeV data at both experiments • 11 Mar 12:00ish-12 Mar 08:00 (end of run) • Install sNN=5.0 GeV setup (or sNN=5.2 GeV if h=387 problems) • Machine tuning, lifetime optimization • Measure inj efficiency, beam lifetime; evaluate chrom, beam optics • Evaluate collision/background signals; collect short data run? T. Satogata RHIC Low-Energy Plans

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