Status of RHIC Polarization Studies

Summary of Polarization Studies during Run09 Tune scans: – Nearby 0.7 – Near integer tune Polarization ramp measurement – 28/56 bunches – At both working points Spin tune as function of horizontal orbital angle at snake – 100 GeV and 250 GeV

Polarization Status: 250 GeV polarization were lost beyond 100 GeV to 250 GeV Average polarization transmission efficiency: ~80% Best polarization achieved w.o. rotator: ~54%

Polarization ramp measurement: nearInt polarization were lost beyond 100 GeV to 250 GeV Average polarization transmission efficiency: ~80% Best polarization achieved w.o. rotator: ~54%

Tune Scan of 250GeV: gg260, gg381, gg422 7/10 resonance 11/16 resonance 3/4 resonance Working pt for 250 GeV run

Investigating polarization at near Integer Orbit deteriorated rms ~0.5mm Orbit rms ~ 0.2mm Zero the snake orb angle

What did we learn from near integer tune study Polarization transmission efficiency reached plateau for Qy = and above, as expected However, it didn’t exceed what was achieved at working point close to 2/3 resonance, and the best achieved polarization is only 50%, also below what we had with the other working point, not as expected. Possible speculations – Stronger intrinsic resonance strength – Stronger imperfection resonance due to closed orbit distortion No information on closed orbit at defocusing quads where there are no bpms – Need detailed studies to see the above effects More realistic model of RHIC for simulation Data of measured spin direction w.o. rotator to check whether stable spin direction is vertical

Status of spin tracking using zgoubi A matured code developed at F. Moet and S. Valero.Calculate beam dynamics as well as spin dynamics by integrating through magnetic field. The original version has no snakes. Provide cross-check with spin tracking using spink Currently, – Testing the spin tracking of zgoubi Compared the net spin rotation through a RHIC dipole by zgoubi – Agreed up to 10^-4 degrees for a hard edge magnet and 10^-3 degrees with fridge field included Check the main depolarization resonances at RHIC with no snake Repeat with snakes. Currently, snakes are represented as two perfect 180 degree spin rotators which are perfect drift for orbital motion. Add ac dipole – Bench mark zgoubi with experimental data Polarization tune scan data in RUN09 Spin flipper data in RUN09 – Detailed spin tracking with closed orbit errors

Spin Flipper Status New design: localize the ac ipole driven oscillation within spin flipper Add three new ac dipoles. Increase the DC dipole current to 1500 Amps Rotating field strength: Ac dipole DC dipole

Spin Flipper Status Plan for RUN03 is to test the closure ac dipole bump Adding the ac dipole in the middle of the the spin flipper Expect magnet coil early Nov. Expect magnet stand mid of Oct. Installation will begin once it is available. Vacuum work including installation of the ceramic pipe first week of Nov. Magnet will be installed during maintainence Measure the residual coherent oscillation beyond spin flipper

How to achieve >50% polarization at 250 GeV? Polarization transmission efficiency –Explore the possibility of accelerating polarized protons at working point between –250 GeV tune scan data indicates a polarization transmission efficiency of 90% and more can be achieved –Assuming polarization at RHIC injection reaches >60%, the polarization at 250 GeV can reach > 50% Polarization lifetime: detailed data analysis -What’s impact of Blue PHENIX rotator setting on spin tune? -Did the local orbit at rotators matter? Should demonstrate the correlation from the data Optimize the snake setting (current and orbital angle) at store based on the spin tune measurement Revisit spin tracking -Bench making spin tracking code(s) using experimental data

Spin tune as function of H orbital angle between snakes Measurements were done at 100 GeV as well as 250 GeV These data sets will allow us to distinguish the contribution to the spin tune shift from snake imperfection and from horizontal angle between snakes

Spin tune as function of H orbital angle between snakes Blue Qy = 0.74

Spin tune as function of H orbital angle between snakes Yellow Qy = 0.744

Polarization Lifetime: 250 GeV Polarization lifetime is very sensitive to the PHENIX rotator setting

Investigating polarization at near Integer Orbit deteriorated rms ~0.5mm Orbit rms ~ 0.2mm Zero the snake orb angle