Polarization Build - up of a Stored Proton Beam by Interaction with a Purely Electron - Polarized Deuterium Gas Target

This experiment is a part of the A-region activities by the PINTEX collaboration. Its aim is the investigation of a possible depolarization of the stored polarized proton beam in presence of an internal gas target. The proposed depolarization mechanism is based on a coupling to a nearby depolarizing resonance. Depolarizing resonances occur at discrete beam energies when the precession frequency of the magnetic moment of a stored particle is an integer multiple of the frequency of some nonvertical perturbing field. The depolarization mechanism is coupling to an intrinsic resonance (caused by transverse field components of focussing quadrupoles). The precession frequency Gy forb of the magnetic moment of a proton (G = 1.793) is for these resonances synchronous with the vertical betatron frequency Y, forb. For particles on the stable orbit, a nearby intrinsic resonance has no effect. Particles not on the st able orbit carry out betatron oscillations of amplitude z = (EP,)-'/~, where E is the particle emittance and P, the vertical betatron function. For such a article the spin closed-orbit vector is tilted away from the vertical direction by an angle a = (I'Is) JG, where I' is the strength of the closest intrinsic resonance, evaluated at an emittance and 6 = IGy Y, f rnl with m an integer, chosen to make 6 as small as possible. If a proton on the stable orbit is scattered by a target atom but remains within the acceptance of the storage ring, its trajectory is suddenly bent away from that orbit and the particle undergoes betatron oscillations. As mentioned above, the spin closed orbit is now tilted away from the vertical direction by an angle a. The direction of the magnetic moment of that proton remains vertical. Only the projection on the tilted spin closed orbit is conserved, resulting in a partial loss of vertical polarization of A P I P = a2, or, in terms of the scattering angle O,,