1. APEX Studies: Accelerating w. Near 3 rd Order Resonance Vincent, Al, Michiko, Steve, Don, Yun, Guillaume, Mei, Todd, Wolfram, Greg, …

2. Goal  Accelerate full intensity beams(>1.0x10^9 bunch intensity, 111x111) to store energy with vertical betatron tune at ~0.325(0.342) or closer to 1/3  Demonstrate the reproducibility of the ramp

3. Motivation 7/10 resonance 11/16 resonance 3/4 resonance Working pt for 250 GeV run

4. Current Status: Au104third  Developed ramp Au104third  Working point at Qx=31.31(Yellow),31.36(Blue), Qy=32.325(Yellow), Qy=32.343(Blue  Beta* at IP6 and IP8 gets squeezed from 10m at injection to 0.7m at store during acceleration  23 Blue bunches and 56 Yellow bunches made to store energy with ~1x10^11 bunches intensity  Blue working pt: 0.358, 0.343 and Yellow working pt: 0.31, 0.325  Bunch intensity is about ~1.x10^11  Tried 111x111 ramp, but failed due to permit pull triggered by beam losses in Blue  Correlated with beta* squeeze below 1m.

5. Status of Au104third development 23 blue by 56 yellow bunches 0.3% lower energy than store

6. Remaining Issues Losses creep up when beta* goes ~1.2m and below

7. Remaining Issues 111 blue by 111 yellow bunches Qy in Blue = 0.342

8. Current Status: Au104third2  Design the ramp to Au104third2  beta* squeeze from 1.7m to 0.7m is stopped for the final part of the ramp  Test Au104third2 by Don and other ps experts without beam  QPA table was tunned for this ramp  No beam work yet

9. Plans for coming APEX session  Switch from the current physics ramp Au106 to Au104third2: 2 hours  Develop Au104third2 with 6x6 in each ring with tune/coupling feedback  Once achieve >90% transmission efficiency, increase the number of bunches until 111 per ring. Orbit correction and optical adjustment when needed  Repeat the ramp for 4-5 times.

10. APEX Studies: Spin tune Change due to Orbital Angle at Snakes Vadim, Mei, Thomas

11. Spin tune versus snake orbit angle Example of measurements done in Blue at 250 GeV Making use of the depolarization by 0.75 (second order) spin resonance: - vertical betatron tune is put sufficiently close to 0.75 (in this example, Q y = 0.73) -gradual change of the snake orbit angles causes the spin tune shift from ½ and therefore the shift of spin resonance from 0.75 -the depolarization is observed when the spin resonance shifted to the location of Q y Making use of the depolarization by 0.75 (second order) spin resonance: - vertical betatron tune is put sufficiently close to 0.75 (in this example, Q y = 0.73) -gradual change of the snake orbit angles causes the spin tune shift from ½ and therefore the shift of spin resonance from 0.75 -the depolarization is observed when the spin resonance shifted to the location of Q y Goals: To verify analytical formulas for spin tune dependence on snake orbit angle To verify the value of the spin tune itself Goals: To verify analytical formulas for spin tune dependence on snake orbit angle To verify the value of the spin tune itself Horizontal orbit angle measured, using BPMs, at 3 o’clock snake minus similar angle measured at 9 o’clock snake Prepared by Vadim

12. Spin tune versus snake orbit angle (2) Spin tune shift due to a snake error Orbit angle measurement error: BPM offsets, quad misalignments shift - measured snake orbit angle difference Conversion of the measured orbit angles to the spin tune shift, using the analytical formula works very well! The depolarization happens at the locations of the vertical betatron tunes during the measurements (dashed lines) Conversion of the measured orbit angles to the spin tune shift, using the analytical formula works very well! The depolarization happens at the locations of the vertical betatron tunes during the measurements (dashed lines) Measurements done at two different energies allows to calculate  sp and  0 (for Blue beam):  sp = 4.4 (+-2.5) 10 -3 - consistent with small energy dependence of spin rotation by the snakes  0 = 17 (+-15) murad - consistent with reversed BPM offsets (~24 murad) Measurements done at two different energies allows to calculate  sp and  0 (for Blue beam):  sp = 4.4 (+-2.5) 10 -3 - consistent with small energy dependence of spin rotation by the snakes  0 = 17 (+-15) murad - consistent with reversed BPM offsets (~24 murad) 250 GeV 100 GeV Prepared by Vadim