APEX Report:February 26-27, 2008

Fulvia Pilat

Time Meeting, March 4, 2008

Feb 28 2008: 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 20-30 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:)cos( sfQBL

Ac dipole 2:)sin( sfQBL

Spin rotator 1:Axis: verticalAngle 0: 90o

Spin rotator 2:Axis: verticalAngle 0: -45o

Spin rotator 2:Axis: verticalAngle 0: -45o

M. Bai, T. Roser

Qsf=0.495 Qsf=0.49

Qsf=0.49Qsf=0.495

Qsf=0.495

Qsf=0.493 Qsf=0.493 Qsf=0.491

AC

dip

ole

curr

ent

read

back

[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 0.495. 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 27RF phasingLitvinenko, 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, 2008

9:30am 1pm6am 7am 11:30am

InjectionInjectionBBQ

8:30am

End of physics store

08-33ChromaticityFeedbackCameron+team

08-41LongVernierScanFischer+team

07-03Coherentspin precessionBai

Injection

08-04ImpedancelocalizationBlaskiewiczBai

RampsBBQ

08-33ChromaticityFeedbackCameron+team

08-38RadialFeedbackSchultheissHoff