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AGS Run-9 Preparations, Status and Plans

AGS Run-9 Preparations, Status and Plans. Haixin Huang. Dec. 16, 2008. Strategy to Overcome Polarization Loss. There are significant emittance growth in the injector chain: Emittance growth in the LEBT/MEBT of linac. Multiple scattering at stripping foil at LtB. BtA optics mismatch.

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AGS Run-9 Preparations, Status and Plans

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  1. AGS Run-9 Preparations, Status and Plans • Haixin Huang Dec. 16, 2008

  2. Strategy to Overcome Polarization Loss • There are significant emittance growth in the injector chain: • Emittance growth in the LEBT/MEBT of linac. • Multiple scattering at stripping foil at LtB. • BtA optics mismatch. • The plan is to solve these emittance growth problem one by one: • LEBT/MEBT upgrade (currently under testing) • Change the LtB foil; manipulate beta function at the foil to reduce the emittance growth (Will test it after Jan. 12) • BtA study to better understand the BtA line and AGS optical model. (data analysis underway) • Setup AGS injection with vertical tune in the spin tune gap (>8.95). (Working on the modeling) • Installation of two tune jump quads to mitigate the polarization loss due to horizontal resonances. • Change RF setup from h=12 to h=6 to reduce space charge effect (more important due to expected smaller emittances). Haixin Huang

  3. AGS/Booster Setup (1) • LINAC beam transfer line upgrade is finished. The expected benefit is to reduce horizontal emittances at the AGS by about 30% ( will have a learning curve to find the optimized parameters). • Use faster Booster acceleration rate. It was lowered since NSRL running due to P/S limit. We can run it faster now. It should not affect polarization. • Start Booster on Jan. 12. With LEBT/MEBT upgrade, it is worthwhile to check the emittances at the BtA. The new LtB foil test and the beta function manipulation at LtB foil will be the major work. • Start the three weeks of setup before blue ready for beam: Jan. 19 • Start with injection with front porch. • CSNK 2.1T+ WSNK 1.53T as usual. • Injection optics: injection with dwell field but high vertical tune (>8.95). It is worth of trying to see if it is feasible. • Horizontal tune will be set close to 8.70 throughout the ramp to make tune jump setup easier. Haixin Huang

  4. AGS/Booster Setup (2) • The emittance dependence on intensity hints some space charge or instability related to brightness of the beam. H=6 for AGS injection to reduce the emittance growth. Lower the RF voltage near injection would also help. However, due to limited resources from RF group for RHIC LLRF upgrade, AGS RF setup will be the same as last year (h=12) at beginning, then we will switch to H=6 when RHIC is up running. • BtA tuning historically was not based on model but experience: lack of a good BtA model. A BtA beam study was aimed to get a good model of BtA and ultimately change the BtA setup strategy. Verify model of BtA line before the run (with beam) and achieve a better match at AGS injection. This would help to reduce AGS emittances.Apply the knowledge gained from BtA studies to get a matched optics. • Horizontal tune jump will be commissioned after mid-March. The gain on polarization during 250GeV run is hoped from smaller emittance out of linac and better matching at AGS injection. Haixin Huang

  5. Spin Tune and Qy vs Gg (Courtesy of Nick)

  6. Tune Jump for Horizontal Resonances • Add two fast quad for this purpose. • Minimum change of nx 0.04 change in 100 ms-> requires dB/dx of 0.5T/m and 300Gauss. This will quadruple the crossing speed. • Operation issue: has to be dead-reckoning of timing. For practical operation, we need to maintain the horizontal tune and radius constant throughout the ramp. • Benefit on polarization transfer efficiency (horizontal 16pi beam): • Crossing Pf/Pi(peak) Pf/Pi(whole) • regular speed 0.9030.815 • Double speed 0.950 0.903 • 4X speed 0.975 0.950 Haixin Huang

  7. Tune Jump Pulse Trains 1400A peak current Haixin Huang

  8. Horizontal Tune Jump Status • Ceramic chambers have been ordered and probably arrive by the end of the year. Coating is needed (4 weeks). • Cables have been pulled. • Control hardware preparation has started. Application is under development. • P/S is modified from existing ones. A test showed that it met the specs. • Magnet coil and assembly have started bidding process. • Expect to get the magnet coils around mid of Feb. They will be first assembled by CAD and then tested by magnet division on their quality. • The hope is that they can be installed sometime in mid-March for commissioning. But it is an aggressive schedule. Haixin Huang

  9. Tune Jump Power Supply Test (Courtesy of Jian-lin Mi) 4ms Power supply test showed that it met the requirements(1400A peak, 240A rms): 1500A, 245A Haixin Huang

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