Achieving High Spin-Flip Efficiency with an RF Magnet and Discovery of Spin-Resonance Strength Formulae Problem.

[摘要] Frequent polarization reversals, or spin-flips, of a beam in high energy storage rings, may be a powerful tool for greatly reducing the systematic errors of spin asymmetry measurements in scattering experiments. A spin-flipping technique using an artificially induced spin-depolarizing resonance, created by an rf magnet with a horizontal magnetic field, is being developed to allow such polarization reversals in a well-controlled way. We used a new ferrite rf dipole to study the spin flipping of a 2.1 GeV/c vertically polarized proton beam stored in the COSY Cooler Synchrotron in Jϋlich, Germany. We swept the rf dipole;;s frequency through an rf-induced spin resonance to flip the beam;;s polarization direction. After determining the resonance;;s frequency, we varied the frequency;;s range and ramp time, and the number of flips. At the rf dipole;;s maximum strength and its optimum frequency range and ramp time, we measured a proton spin-flip efficiency of 99.92 ± 0.04 %. This result, along with previous similar IUCF results at lower energy, indicate that due to the Lorentz invariance of an rf-dipole;;s transverse ∫Bdl and the weak energy dependence of its spin-resonance strength, a small rf dipole should allow efficient spin flipping in very high energies in rings such as the 250 GeV RHIC or even the 7 TeV LHC.The accurate prediction of a spin-depolarizing resonance strength remains a challenge. We earlier analyzed all available data on the spin-flipping of stored beams of polarized protons, electrons and deuterons. We found 10-20-fold deviations of the measured rf-induced resonance strength from the theoretically predicted strength. Therefore, we recently studied these resonance strength deviations experimentally by varying the rf dipole;;s voltage, and the size, momentum spread and vertical betatron tune with a 2.1 GeV/c polarized proton beam stored in COSY. We found no dependence of the resonance strength on the beam;;s size or momentum spread. We did find enhancements of more than 100 when the rf spin resonance was near an intrinsic proton spin resonance.We studied the resonance strength deviations experimentally by using 1.85 GeV/c vertically polarized deuterons stored in COSY with an rf dipole and then an rf solenoid.

[发布机构] University of Michigan

[效力级别] Resonance Strength

[关键词] Spin-flip;Resonance Strength;Physics;Science;Physics