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Proton Beam Scrubbing Study in RHIC

Proton Beam Scrubbing Study in RHIC. H. Huang, W. Fisher, T. Roser, S.Y. Zhang. 13 th IFCA Beam Dynamics Workshop On Beam Induced Pressure Rise. December 12, 2003. RHIC Rings. 6 IRs, about 700 m warm sections. Outer ring. IR 12. IR 10. IR 2. Inner ring. RHIC. IR 8. IR 4. IR 6.

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Proton Beam Scrubbing Study in RHIC

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  1. Proton Beam Scrubbing Study in RHIC • H. Huang, W. Fisher, T. Roser, S.Y. Zhang 13th IFCA Beam Dynamics Workshop On Beam Induced Pressure Rise December 12, 2003

  2. RHIC Rings 6 IRs, about 700 m warm sections Outer ring IR 12 IR 10 IR 2 Inner ring RHIC IR 8 IR 4 IR 6 Haixin Huang

  3. Pressure Rise Observation at RHIC Injection • Pressure rise of several decades has been observed at injection for nominal operation conditions. • Pressure rise is not evenly distributed, but happens mostly at warm sections and IRs. • The pressure rise patterns are different for gold and proton beams. They are also different for different injection patterns (55 vs. 110 bunches) • The pressure rise drops when energy ramp starts. 5 x 10-6 Torr Haixin Huang

  4. RHIC pressure rise distribution (Au beam) 1e-5 4 Bo3, 1.5e-6 Torr 1e-7 2 1e-9 0 1e-5 4 IR12, 6e-6 Torr 1e-7 2 1e-9 0 2 4 6 8 10 12 4 1e-5 1e-7 2 Yi11, 6e-7 Torr 1e-9 0 Gold Beam Ramp 1797 Haixin Huang

  5. 1e-6 Torr 1e-9 Torr Proton Beam Ramp 2237, 110-bunch, 1/16/02 Ramp 2158, 55-bunch, 1/6/02 Ramp 2189, 55-bunch, 1/10/02 Haixin Huang

  6. Increase Bunch IntensitybyBeam Scrubbing Results from other accelerators ·       SPS 2000 - Scrubbing at P=7 x 10-7 Torr, in 24 hrs, total dose 0.1mC/mm2, pressure rise was reduced by a factor of 5. ·       SPS 2002 - Scrubbing at P=5 x 10-6 Torr, in 24 hrs, total dose 0.5mC/mm2, pressure rise was reduced by a factor of 100. ·      PSR - Dose in 24 hrs is about 0.035mC/mm2, estimated from the e-current on the wall. Mild pressure rise and threshold increase. The differences between RHIC from SPS: • The pressure rises are localized, species dependent, bunch pattern sensitive. • The pressure rises are in field free area. Haixin Huang

  7. RHIC Beam Scrubbing Study Instead of days, we only have a few hours available for beam study. Hope to answer questions such as: • Will scrubbing work for RHIC? • Do we need to repeat the process for many local pressure rises? • How efficient is the scrubbing if it works? Method: • Use 110 bunch pattern in one ring. Starting from 21011proton/bunch . Fill RHIC manually to monitor the pressure rise (1Hz signals). • Increase bunch number to keep pressure (P=5 10-6Torr). When the pressure drops, dump the beam and refill. Haixin Huang

  8. Pressure Rise at Bo2. 120*1011 90*1011 80*1011 4.6*10-6Torr Haixin Huang

  9. Pressure Rise at Warm Sections Group 1 Group 2 Group 3 Group 4 Haixin Huang

  10. High, Medium and Low Pressure Rises Constant pressure 2.5 times Haixin Huang

  11. Beam Scrubbing Effect Kicker, RF region Warm Sections IR Regions Scrubbing effect=dose/(peak pressure at fill 3) Dose, 1e-6 Torr*hour Haixin Huang

  12. Summary(1) • Consistent scrubbing effects seen at locations with pressure rise higher than 10-7Torr. The higher the pressure rise, the stronger the scrubbing effect. • Higher intensity (120*1011) achieved at the end of the study demonstrated that it is feasible to use beam scrubbing to reach the enhanced design proton intensity. • SPS beam scrubbing results: pressure rise of 5*10-6 Torr for 24 hrs  dose of 120*10-6Torr*hour resulted 100 times pressure rise reduction. RHIC study results: dose of 3.2*10-6 Torr*hour resulted 2.5 pressure rise reduction. Haixin Huang

  13. Summary (2) • A 4 hours beam scrubbing (two beams) will result 15 times pressure reduction, which may be enough for 110*1011 proton beam. • With two beams, IRs will be the hot spots. Need to evaluate the potential damages to the physics experiment detectors. • Poor beam life time caused large loss in the ring. 30 BPM electronics in the tunnel failed on the day of scrubbing. It is under evaluation if the scrubbing can be done without damage to BPM electronics before all of them moving out of tunnel. Haixin Huang

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