APEX Report: February 26-27, 2008 Fulvia Pilat Time Meeting, March 4, 2008

Feb : Background, steering, and collimation 55 bunches PHENIX 8 kHz at start Blue then yellow collimation STAR re-steering Beta* squeeze (Satogata + team)

 *=0.65m APEX Conclusions Goal: Commission pp83lowbeta,  *=0.65m in IR6/8 for operations There are presently no show-stoppers for adoption for run_fy09 This is equivalent to  *=0.40m at 250 GeV Ramp efficiencies are good: 93-95% in both rings Nonlinear chrom correction works, but needs careful ramp tuning Sextupoles are the main cause of failed pp83lowbeta ramps Ramp system checks on sextupole ramping speed would help Collimation worked with no beam decay penalty Experiments agree that backgrounds were reasonable 55 bunches, PHENIX peak 8-10 kHz, emittance pi um STAR consistent after steering, with singles correction Open issues: Luminosity and beam lifetime: how much worse? Yellow dispersion/optics

Goal: measure spin coherent oscillation excited by a vertical ac dipole with a tune close to the spin tune A new design of RHIC spin flipper is scheduled to be installed during summer shut down. This will allow us to bench mark our model of the new design RHIC spin flipper Ac dipole 1:Ac dipole 2: Spin rotator 1: Axis: vertical Angle  0 : 90 o Spin rotator 2: Axis: vertical Angle  0 : -45 o Spin rotator 2: Axis: vertical Angle  0 : -45 o M. Bai, T. Roser

Q sf =0.495Q sf =0.49 Q sf =0.495 Q sf =0.493 Q sf =0.491 AC dipole current readback[A] polarization vs. ac dipole tune indicates the blue spin tune is around 0.495

Summary Highlight: first data set from previous APEX session indicates coherent precession a quick polarization vs. ac dipole tune indicates the blue spin tune is around This is consistent with the result of quick tune scan at injection early in the run But: The three data sets we took during this session were not ideal due to a thicker blue target. Since the total amount of events is limited by the WFD(80Million), the thicker the target, the less revolutions and bigger error bars. Thin target: 16,075,851 revolutions Thick target: 7,523,654 revolutions Since all the blue vertical thin targets are gone, would be good to repeat two measurements in Yellow. Estimate: ~1 hour.

APEX: February 27 RF phasing Litvinenko, Abreu, Ptitsyn, etc….. 2 test ramps with 6 and 12 bunches; Injected with 80º shift to 70º at before ramping and decrease the phase to 0º at the first 70 seconds of the ramp; Long. emittance blows at injections due to dynamic loading which causes a dipole oscillation of the bunches; Comparison between the efficacy of the method was difficult due to emittance blown-up.

Injection with 80 º Comparison of bunch length for two ramps with and without rf phasing 9949 (no rf phasing); 9956 (rf phasing) Bunch length increase

APEX Schedule March 5, :30am1pm6am7am11:30am Injection BBQ 8:30am End of physics store Chromaticity Feedback Cameron +team Long Vernier Scan Fischer +team Coherent spin precession Bai Injection Impedance localization Blaskiewicz Bai Ramps BBQ Chromaticity Feedback Cameron +team Radial Feedback Schultheiss Hoff