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RHIC Spin Flipper Commissiong Results and Future Plans

RHIC Spin Flipper Commissiong Results and Future Plans. RSC Meeting, June 17 2002, Mei Bai. RHIC polarized proton setup Spin manipulation using a dipole with horizontal oscillating magnetic field Rhic spin flipper commissioning Future plans. RHIC spin flipper. 12:00 o’clock.

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RHIC Spin Flipper Commissiong Results and Future Plans

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  1. RHIC Spin Flipper Commissiong Results and Future Plans RSC Meeting, June 17 2002, Mei Bai

  2. RHIC polarized proton setup • Spin manipulation using a dipole with horizontal oscillating magnetic field • Rhic spin flipper commissioning • Future plans

  3. RHIC spin flipper

  4. 12:00 o’clock BRAHMS & PP2PP (p) PHOBOS 2:00 o’clock 10:00 o’clock RHIC PHENIX (p) 8:00 o’clock 4:00 o’clock STAR (p) 6:00 o’clock Siberian snakes U-line High Intensity Source AtR BAF (NASA) m g-2 HEP/NP Pol. Proton Source LINAC AGS Siberian snakes BOOSTER TtB line TANDEMS Au source RHIC polarized proton setup • Two full snakes apart from each other by 180 in phase • Stable spin direction in which the spin precesses around is vertical. • Spin precession frequency and is independent of beam energy. In RHIC, the two snakes’ axes are perpendicular to each other and the nominal spin tune is 1/2. 1,2is the angle between the snake axis and the beam direction

  5. y z x Spin motion in the presence of the ac dipole • Thomas BMT equation where A spin resonance then happens when The strength of this resonance is For BmL=100 Gauss-m and 100 GeV/c pp, the resonance strength is 0.00046.

  6. y z x Spin manipulation using ac dipole • In the frame which rotates at the same frequency as the drive frequency, the stable spin direction becomes where: and • fixed drive frequency -- measure the spin tune • crossing through the resonance -- spin flipping where ; time to achieve 99.9% spin flip  1 sec

  7. 0.5 v 6000 0.49 200,000 200,000 6000 6000 6000 0.47 Spin flipper commissioning ------- Blue Ring • Setup: • snake: • inner current=325.06A • outter current=106.11A the predicted spin tune equals to 0.48. • Spin flipper: • amplitude: • frequency 0.00110.000164 0.001950.0002 Bm 0.000840.0002 turns • Conclusions: • spin flip efficiency  • yellow beam • The fact that we measured negative asymmetry after we spin- • flipped twice in Blue is very hard to understand. This is also • consistent with the fact that the yellow beam was actually fully • depolarized. while we were spin flipping the blue beam. This • suggests that the yellow beam spin tune is away from 0.5. m turns

  8. Spin flipper commissioning ------- Blue Ring (continue) • Effect of Spin tune spread • spin tune spread: • particles with different betatron oscillation amplitude have different spin precession tune • to achieve full spin flip, spin tune spread should be less than the spin flipper tune sweeping range. • Spin precession tune too close to the resonance during the amplitude ramping

  9. 0.5 v 6000 0.49 200,000 200,000 6000 6000 6000 0.47 Spin flipper commissioning --------- Yellow Ring • Setup: • snake: • inner current=106.9A • outer current=323.5A predicted spin tune equals to 0.48. • Spin flipper: • amplitude: • frequency: Bm turns m • Conclusions: • No spin flip was achieved in Yellow. Instead, the yellow beam • was partially depolarized. This could be because spin tune with • the snake setting of (inner106.9A, outer323.5A) doesn’t equal • to 0.48. turns

  10. Problems during RHIC pp 2002 • Spin flipper • The  0.2mm coherent betatron oscillation caused snake quench twice at injection due to the limitation of the aperture. • The resolution of the snake WFG. • No spin tune measurement • Not enough time

  11. Plans for the next run • Measure the spin flipping efficiency in both blue and yellow ring • this allows us to assess how well the spin flipper behaves • prefer to do the measurement at store. • No new instrumentation is needed provided the RHIC CNI polarimeter will be available • Measure the spin precession tune to calibrate the snake setting • The alternative way to measure the spin tune by measuring the beam polarization before and after turning on the ac dipole at a fixed frequency is to measure the asymmetry while sweeping the ac dipole frequency. The zero crossing of the measured asymmetry is where the spin tune locates. However, this requires to upgrade the current RHIC CNI polarimeter to allow one to measure the beam polarization continuously in couple of seconds.

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