Outline. Introduction of spin dynamics. RHIC polarized proton 250GeV development. Conclusion

Transcription

1 Accelerating Polaried Protons to 250 GeV Mei Bai Collider Accelerator Department Brookhaven National Laborator

2 Outline Introduction of spin dnamics RHIC polaried proton 250GeV development Conclusion

3 ds dt Spin vector in particle s rest frame Spin motion in circular accelerator: Thomas BMT Equation e S [ G B (1 G) B// ] S m B In a perfect accelerator, spin vector precesses around the bending dipole field direction: vertical Spin tune Qs: number of precessions in one orbital revolution. In general, Q s G

4 polaried proton acceleration challenges: preserve polariation Depolariation(polariation loss) mechanism Come from the horiontal magnetic field which kicks the spin vector awa from its vertical direction Spin depolariing resonance : coherent build-up of perturbations on the spin vector when the spin vector gets kicked at the same frequenc as its precession frequenc x Initial x 1 st full betatron Oscillation period x 2nd full betatron Oscillation period

5 spin depolariing resonance Imperfection resonance Source: dipole errors, quadrupole misalignments Resonance location: G = k k is an integer Intrinsic resonance Source: horiontal focusing field from betatron oscillation Resonance location: G = kp±q, P is the periodicit of the accelerator, Q is the vertical betatron tune For protons, imperfection spin resonances are spaced b 523 MeV The higher energ, the stronger the depolariing resonance

6 preserve polariation: Siberian snake(s) Use one or a group of snakes to make the spin tune to be at ½ Break the coherent buildup of the perturbations on the spin vector

7 However,

8 6Q Q s k -x -x -x -x -x -x

9 snake depolariation resonance mq Q When m is an even number Disappears in the two snake case like RHIC if the closed orbit is perfect s k Store working pt. Ramp working pt. 3/4 5/6 7/8 When m is an odd number Driven b the intrinsic spin resonances 5/8

10 Accelerate RHIC polaried protons to 250 GeV

11 BRAHMS(p) Absolute Polarimeter (H jet) RHIC pc Polarimeters Siberian Snakes Spin flipper PHENIX (p) STAR (p) Spin Rotators (longitudinal polariation) Spin Rotators Solenoid Partial Siberian Snake (longitudinal polariation) Pol. H Source LINAC 200 MeV Polarimeter BOOSTER AGS Helical Partial Siberian Snake AGS Polarimeters Strong AGS Snake

12 RHIC pp design parameter Achieved performance for phsics runs Parameter Unit p-p relativistic, injection 25.9 relativistic, store no of bunches, n b 112 ions per bunch, N b emittance e N x, 95% mm-mrad 20 average luminosit cm -2 s polariation,store % 70 p-p ~65

13 Preserving Polariation in RHIC Optimie the snake setting to have spin tune at 1/2 Precise vertical closed orbit control Minimie the vertical closed orbit distortion to reduce the strength of even order snake resonances Precise optics control Minimie the linear coupling Keep both horiontal and vertical tune with the window where no harmful snake resonances Avoid store the at an energ nearb a strong intrinsic spin resonance

14 RHIC intrinsic resonance spectrum Design goal Achieved Phsics Run Intrinsic spin resonance Qx =28.73, Q =29.72, emit= 10

15 Polaried proton at 250 GeV 250 GeV injection Polariation at 250 GeV Polariation at injection

16 RHIC pp polariation ramp measurement Resonance around 138 GeV 0.01 Asmmetr d Beam Energ [GeV]

17 Orbit/Tunes during the 250 GeV acceleration G =5x81+(Q-12) G =5x81-(Q-6) G =3x81+(Q-12)

18 Snake resonance observed in RHIC ¼ snake resonance Coupled 3/14 snake resonance Maximum vertical tune Horiontal tune 3/14

19 Conclusion RHIC has achieved 100% polariation transmission efficienc at 100 GeV The first effort of accelerating polaried proton to 250 GeV ields a polariation of 46% The polariation as a function of energ during the acceleration shows the polariation loss at energ of 136 GeV, a strong resonance at G =3x81+(Q-12) More time will be need to explore the polariation loss as a function of the betatron tune and orbit distortion at the three strong resonances.

20 Acknowledgement L. Ahrens, I.G. Alekseev, J. Alessi, J. Beebe-Wang, M. Blaskiewic, A. Bravar, J.M. Brennan, D. Bruno, G. Bunce, J. Butler, P. Cameron, R. Connoll, J. Delong, T. D Ottavio, A. Drees, W. Fischer, G. Ganetis, C. Gardner, J. Glenn, T. Haes, H-C. Hseuh. H. Huang, P. Ingrassia, U. Iriso-Ari, O. Jinnouchi, J. Laster, R. Lee, A. Luccio, Y. Luo, W.W. MacKa, Y. Makdisi, G. Marr, A. Marusic, G. McIntre, R. Michnoff, C. Montag, J. Morris, A. Nicoletti, P. Oddo, B. Oerter, J. Piacentino, F. Pilat, V. Ptitsn, T. Roser, T. Satogata, K. Smith, D.N. Svirida, S. Tepikian, R. Tomas, D. Trbojevic, N. Tsoupas, J. Tuoolo, K. Vetter, M. Milinski. A. Zaltsman, A. Zelinski, K. Zeno, S.Y. Zhang.