RHIC Spin Flipper Commissioning Plan

1. RHIC Spin Flipper Commissioning Plan M. Bai, T. Roser, C. Dawson, Y. Makdisi, W. Meng, S. Nayak, P. Oddo, C. Pai, P. Pile, P. Rosa, J. Tuozzolo Spin 2010, Julich, Germany

2. Outline • Introduction • How to excite an isolated spin resonance in the presence of full snakes? • Commissioning Results • From RUN 2009 • From RUN 2010 • Plan for RHIC pp Run 11 • Summary

3. Spin Flipping • A single RF dipole or RF solenoid • Excite two resonances at Qs = Qrf and Qs=1-Qrf • Works when Qs != 0.5, proved at IUCF and COSY • But won’t work when Qs = 0.5, like at RHIC Qrf Qspin 0.5

4. Exciting an isolated resonance: RF spin rotator with rotating field y beam z x

5. Exciting an isolated resonance: RF spin rotator with rotating field • Drive a single isolated spin resonance • Induce spin flip with spin tune at ½ • Non-destructive spin tune measurement

6. Non-destructive Spin Tune Measurement

7. Implement an RF spin rotator with rotating field • Schematic layout rf dipole 1: rf dipole 2: Spin rotator: Axis: vertical Angle -0 Spin rotator: Axis: vertical Angle 0 Spin rotator: Axis: vertical Angle -0 where for each rf dipole, Spin flipper strength:

8. Simulation of spin flipping with a rotating field • RHIC 1m beta* lattice • Single particle with spin tune at 0.5 • vertical betatron amplitude at 6 mm-mrad • on-momentum • simulation code: zgoubi • Spin flipper: • Amplitude: 200Gauss-m • Tune: 0.49 -> 0.51 • Sweep in 20,000 turns

9. Location of RHIC Spin Flipper(Blue) Location of RHIC spin flipper(Blue) -167.493o 208.03o IP10 2 15oSpin rotator Sector 9 -15oSpin rotator

10. Commissioning results from RUN09 • Confirmed closure of DC dipole H bump. The difference orbit is 0.07mm in horizontal and 0.02mm in vertical with DC dipoles at 500Amps • They are transparent to the polarization • Before turning on: • 49.9+-5% • At 500Amp: • 46+-5% • Back to zero current: • 48.9+-5%

11. Commissioning results from RUN09 • Observed global ac dipole driven coherent betatron oscillation effects with nominal spin flipper setup at 100 GeV, • on collision rates • Depolarized Yellow beam • Non-negligible effect on spin motion of Blue beam

12. Commissioning results from RUN09 • Measured single ac dipole effect at injection • Polarization as function of spin tune with one ac dipole on at tune of 0.49, oscillating amplitude of current: 10 amps • Measured the global ac dipole driven coherent oscillation effect on spin motion at injection • Two ac dipoles on at tune of 0.49, current amplitude for each ac dipole 10 amps, and 180o phase difference in between • Measured polarization as function of spin tune

13. Measured Driven Betatron Oscillations Two AC dipole with opposite phase [mm] single AC dipole [mm]

14. Commissioning results from RUN09

15. Data Analysis • two isolated resonance at Qs=Qosc and 1-Qosc • non-zero spin tune spread with Gaussian distribution • resonance strength ε is from single particle spin tracking • using zgoubi • two ac dipole case, ε=0.00006 • single dipole case ε is 4 times stronger • Data Analysis: • two isolated resonance at Qs=Qosc and 1-Qosc • beam has a finite spin tune spread, i.e. different particles with different spin tunes. A Gaussian distribution centered at Qs,0 with an • rms width of d is assumed • Here, Pf,i are the polarizations with/without AC dipole(s) on. ε is the resonance strength obtained from single particle spin tracking using zgoubi. For two ac dipole case, ε=0.00006 and for single dipole case ε is 4 times stronger • The following assumptions for a reasonable match of the data • A gap of +-0.002 of the ac dipoles’ tune. Full depolarization is assumed for any spin tunes inside the gap • Spin tune spread of 0.005, or, d=0.005 • Pi =49% and 58% for the two cases, respectively • Data Analysis: • two isolated resonance at Qs=Qosc and 1-Qosc • beam has a finite spin tune spread, i.e. different particles with different spin tunes. A Gaussian distribution centered at Qs,0 with an • rms width of d is assumed • Here, Pf,i are the polarizations with/without AC dipole(s) on. ε is the resonance strength obtained from single particle spin tracking using zgoubi. For two ac dipole case, ε=0.00006 and for single dipole case ε is 4 times stronger • The following assumptions for a reasonable match of the data • A gap of +-0.002 of the ac dipoles’ tune. Full depolarization is assumed for any spin tunes inside the gap • Spin tune spread of 0.005, or, d=0.005 • Pi =49% and 58% for the two cases, respectively • Data Analysis: • two isolated resonance at Qs=Qosc and 1-Qosc • beam has a finite spin tune spread, i.e. different particles with different spin tunes. A Gaussian distribution centered at Qs,0 with an • rms width of d is assumed • Here, Pf,i are the polarizations with/without AC dipole(s) on. ε is the resonance strength obtained from single particle spin tracking using zgoubi. For two ac dipole case, ε=0.00006 and for single dipole case ε is 4 times stronger • The following assumptions for a reasonable match of the data • A gap of +-0.002 of the ac dipoles’ tune. Full depolarization is assumed for any spin tunes inside the gap • Spin tune spread of 0.005, or, d=0.005 • Pi =49% and 58% for the two cases, respectively • Data Analysis: • two isolated resonance at Qs=Qosc and 1-Qosc • beam has a finite spin tune spread, i.e. different particles with different spin tunes. A Gaussian distribution centered at Qs,0 with an • rms width of d is assumed • Here, Pf,i are the polarizations with/without AC dipole(s) on. ε is the resonance strength obtained from single particle spin tracking using zgoubi. For two ac dipole case, ε=0.00006 and for single dipole case ε is 4 times stronger • The following assumptions for a reasonable match of the data • A gap of +-0.002 of the ac dipoles’ tune. Full depolarization is assumed for any spin tunes inside the gap • Spin tune spread of 0.005, or, d=0.005 • Pi =49% and 58% for the two cases, respectively

16. Commissioning results from RUN09 • Curves are single isolated resonance models • assuming: • spin tune spread ~ 0.005 • ac dipole spectrum has sideband ~0.003 • Pi =49% and 58% for the two cases, respectively

17. Conclusions from RUN09 Commissioning • Global ac dipole driven coherent oscillation needs to be suppressed • Minimize noise of ac dipoles • -40dB or better • Minimize spin tune spread

18. New Design • Add 3 additional ac dipoles to form two closed vertical orbital bumps Ac dipole 1: Ac dipole 2: Spin rotator 2: Axis: vertical Angle -0 Spin rotator 1: Axis: vertical Angle 0 Spin rotator 0: Axis: vertical Angle 0 Spin flipper strength,

19. Commissioning result in RUN10: AC dipole bump P. Oddo

20. Commissioning Plan for Run 11 • At injection • Demonstrate closure of the two AC dipole bumps • Measure the residual coherent driven oscillation using DSA of BBQ • Minimize the ac dipole peak by scanning the ratio between the 3 ac dipoles • Demonstrate inducing single resonance • Measure polarization with spin flipper on at a fixed tune as function of spin tune

21. Commissioning Plan • Demonstrate spin flipping at injection • Minimize spin tune spread • measure the spin flipping efficiency as function of • AC dipole frequency sweep time • # of spin flips • AC dipole amplitude • At store • Check the spin flipper setting • Closure of AC dipole bumps • Minimize spin tune • Measure spin flipping efficiency

22. Summary • Commissioning of two-AC dipole design of spin flipper shows the detrimental effect of global ac dipole driven coherent oscillation • Collision rates • Depolarization on Yellow beam • Prevent from obtaining rotating field • A new design of five-Ac dipole is now implemented and scheduled to be commissioned in the coming RHIC 500 GeV polarized proton Run in 2011

23. Momentum spread for Fill 10526: S. Y. Zhang • RF voltage 150 kV • bunch intensity 1.3x10^11 • longitudinal emittance: • 1.35 evs