RHIC LowEnergy Operations Todd Satogata Weekly Experiment Meeting

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. Mac. Kay, 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 March 4, 2008 T. Satogata RHIC Low-Energy Plans

Cho, , Scien ce, 312 (14 Apr 2006) A. Cho 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 Me. V, corresponding to heavy ion collisions with c. m. energy in the range s. NN = 5 - 50 Ge. V. ” § 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, “crit. RHIC”) March 4, 2008 T. Satogata RHIC Low-Energy Plans 2

Low Energy Test Run and Lowest Energy Parameters § Several staged low energy tests Gold 2007 -8 Gold 2008? s. NN [Ge. V] 9. 183 5. 2 5. 0 Beam energy [Ge. V] 4. 59 2. 6 2. 5 Beam kinetic energy [Ge. V] 3. 660 1. 669 1. 569 Relativistic 4. 93 2. 79 2. 68 Relativistic 0. 979 0. 934 0. 928 Momentum [Ge. V/c] 4. 496 2. 428 2. 320 B [T-m] 37. 40 20. 19 19. 30 Injection current scaling 0. 384 0. 207 0. 198 Main dipole current [A] 217. 7 117. 5 112. 3 Main quad current [A] 202. 6 109. 4 104. 6 Revolution frequency [Hz] 76571 73010 72570 RF harmonic number 366 384 387 RF frequency [MHz] 28. 03 28. 08 Max beam size 95% [mm] 15. 32 20. 85 21. 32 March 4, 2008 § § 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) § § § T. Satogata 2007 9 Ge. V setup “in the can” Test RF/timing fixes Reproduce 2007 Au test; physics Explore near lowest energy Establish lowest energy baseline RHIC Low-Energy Plans 3

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=360 120 bunch fill pattern Yellow Blue h Allowed s. NN [Ge. V] 360 16. 7 -107 375 6. 3 -6. 7 363 11. 4 -15. 0 378 5. 8 -6. 1 366 9. 0 -10. 5 381 5. 45 -5. 7 369 7. 7 -8. 6 384 5. 15 -5. 38 372 6. 9 -7. 4 387 4. 91 -5. 1 March 4, 2008 § Must raise harmonic number § Retuning cavities is a prohibitive effort § Collisions at both experiments require h(mod 3)=0; Experiment DAQs also requires h(mod 3)=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 T. Satogata RHIC Low-Energy Plans 4

Challenges: Chromaticity and Stability Defocusing sextupole strength should sum to negative § Low-energy transverse beam stability requires negative chromaticity § Sextupole component of main dipoles drives vertical chromaticity beyond unipolar power supply tuning range § Below s. NN = 9. 3 Ge. V/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. . . March 4, 2008 T. Satogata RHIC Low-Energy Plans 5

STAR BBC Coinc 1500 +/-6 mm Vernier Scan Uncogging 2007 Gold Test Run: STAR Vernier Scans +/-9 mm Vernier Scan 0 35 Au Beam [e 9] Few losses from scan! 0 § Measured beam size ~ 4 mm at *=10 m § 700 -1000 Hz BBC coincidences March 4, 2008 <10% backgrounds Peak luminosity ~1. 5 x 10 24 cm-2 s-1 T. Satogata RHIC Low-Energy Plans 6

The Fly In The Ointment P. Sorensen/STAR Dec 19 2007 § STAR s. NN=9. 2 Ge. V 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” March 4, 2008 T. Satogata RHIC Low-Energy Plans 7

Mar 2008 Low Energy Test Run Plan and Objectives § 6/7 Mar: Tandem/Booster/AGS Au PPM setup § 10 Mar 08: 00 -12: 00 ish § § 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: 00 ish-11 Mar 12: 00 ish § Restore s. NN=9. 2 Ge. V 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 s. NN=9. 2 Ge. V data at both experiments § 11 Mar 12: 00 ish-12 Mar 08: 00 (end of run) § Install s. NN=5. 0 Ge. V setup (or s. NN=5. 2 Ge. V 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? March 4, 2008 T. Satogata RHIC Low-Energy Plans 8