BNL, Upton, Long Island, New York, USA
Polarization transmission during the AGS acceleration cycle is critical for the RHIC polarized proton program, driving strong interest on the exploration of the polarization losses in the AGS. Intrinsic spin resonances are the main source of depolarization in the AGS. This results in the formation of a polarization profile since the strength of such depolarizing resonance depends on the Courant Snyder invariant of each particle. The Zgoubi code and the AGS Zgoubi on-line model now allow to explore the formation of the polarization profile during the acceleration cycle using multi-particle trackings with realistic beam and machine conditions. This paper introduces the specificities of these simulations and compares some of the latest simulated and experimental results.
BNL, Upton, Long Island, New York, USA
To search for the critical point in the QCD phase diagram, Au-Au collisions at beam energies between 2.5 and 15 GeV are required. While RHIC has successfully operated at 3.85 and 5.75 GeV, the performance achieved at 2.5 GeV is not sufficient for a meaningful physics program. We report on dedicated beam experiments performed to understand and improve this situation.
BNL, Upton, Long Island, New York, USA
The AGS tune jump system accelerates the crossing of 82 horizontal intrinsic resonances using two fast pulsed quadrupoles. Timing of the tune jumps requires accurate tune and energy measurements. Although cross calibration using measurements of the beam revolution frequency shows good accuracy for most of the AGS energy range it is not adequately sensitive as the beam becomes highly relativistic. This drives a strong interest for a new independent energy measurement method. Reduction in the vertical tune across vertical intrinsic spin resonances can induce important depolarization of the beam. Therefore it was proposed to use the negative vertical tune shift created by this tune jump system to calibrate the energy measurement at few locations along the AGS acceleration cycle. The fast tune jump, of ΔQ≈-0.02 within 100μs in the vertical plane, allows to accurately locate the spin resonant condition, independently from orbit or field conditions. Simulations using the AGS Zgoubi on-line model facilitates the interpretation of the experimental results. This paper introduces the experimental procedure and shows some of the latest results.