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Accelerator Seminar


"Spin-Manipulating Polarized Protons and Deuterons."

Vasiliy Morozov,
University of Michigan



    Polarized beam experiments have been an important part of the research programs in many accelerators and storage rings. An arrangement of magnets called a Siberian snake can be used to preserve the beam's polarization during acceleration to high energy. After acceleration, frequent reversals of the stored beam's polarization direction can significantly reduce the systematic errors in any spin asymmetry measurements. We used an rf-dipole magnet to spin-flip, with 99.9% efficiency, a 120-MeV horizontally polarized proton beam stored in the IUCF Cooler Ring in the presence of a nearly, but not exactly, full Siberian snake. We then attempted spin-flipping with the Siberian snake's strength set at exactly 100% but observed only complete depolarization. We will briefly discuss one approach to this problem and a possible solution proposed in M. Bai and T. Roser, Phys. Rev. ST-AB 11, 091001 (2008).
     Polarized deuteron experiments have recently become an accessible and interesting area of subatomic physics. We used rf magnets to study the spin manipulation of stored polarized deuterons first at IUCF and later at COSY. We spin-flipped the deuterons' vector polarization with up to 97% efficiency. We also found experimentally and then explained theoretically interesting behavior of the deuterons' tensor polarization. We tested Chao's matrix formalism for describing the spin dynamics near a single spin resonance, which allows analytic calculation of the beam polarization's behavior inside a resonance. Our measurements of the 1.85 GeV/c deuterons' polarization near and inside the resonance agreed precisely with the Chao formalism's predicted oscillations. We tested Kondratenko's proposal to overcome depolarizing resonances by ramping through them with a crossing pattern, which should force the depolarizing spin-phase components to cancel themselves. Our deuteron data demonstrated a rather substantial reduction in the depolarization compared to the tune jump at the same rate. We will also discuss a possible improvement on this technique recently suggested by Kondratenko, which should make it more practical.


Thursday, May 28, 2009

3:30 p.m. - 4:30 p.m.
CEBAF Center, Room L102/104

Talk Slides: (Slides)

For more information, please contact Dr. Alex Bogacz or Anne-Marie Valente.