F. Sperisen

Siberian snake experiments at the IUCF Cooler Ring

Recent polarized proton beam experiments in the IUCF Cooler Ring found an evidence for a second-order snake depolarizing resonance, when the vertical betatron tune was inadvertently set near a quarter-integer. We have also studied the possibility of spin-flipping the beam polarization in the presence of a full Siberian snake using an RF solenoid. By varying the rf solenoids ramp time and frequency range, we reached a spin-flip efficiency of about 97%.

Angular distribution of the longitudinalp→p→spin correlation parameterAzzat 197.4 MeV

A polarized proton beam with a large longitudinal polarization component of 0.545{+-}0.005 (96% of the total polarization) was prepared in a storage ring (IUCF-Cooler). This was achieved by means of spin precession solenoids in two of the six straight sections of the ring. A polarized hydrogen storage cell target internal to the ring was used to measure the longitudinal spin correlation coefficient A{sub zz} in pp elastic scattering over the laboratory angular range 5.5 degree sign -43.5 degree sign ({theta}{sub c.m.}=11.5 degree sign -90 degree sign ) with statistical errors of typically 0.025. The absolute normalization was determined to an accuracy of 2.0% by use of the identity A{sub yy}-A{sub xx}-A{sub zz}{identical_to}1 at {theta}{sub c.m.}=90 degree sign . The identity also allows a reduction of the scale factor uncertainty of the previously published analyzing powers and spin correlation coefficients. The results are compared to recent pp partial wave analyses and NN potential models. (c) 2000 The American Physical Society.

Polarized internal gas target for hydrogen and deuterium at the IUCF cooler ring

A polarized internal H gas storage cell target has been successfully operated in the IUCF cooler ring. A target thickness for atomic hydrogen has been measured to be 3.5±0.3×1013/cm2 in a single spin state. Target polarization (0.75±0.01) showed no sign of deterioration after two weeks of operation with an average beam current of 100 μA. Detection of p‐p elastic events at 200 MeV bombarding energy has been demonstrated by use of coincidences between silicon detectors near the beam and a forward detector array. This target is presently being used to measure p‐p elastic scattering spin correlation coefficients at 200 MeV.

Measurement of Coulomb-Nuclear Interference in the pp Analyzing Power Ay at the IUCF Cooler Ring

We report here a measurement of the analyzing power Ay in 185 MeV elastic proton-proton (pp) scattering at forward angles (2.5°–10.5° in the laboratory). In this angular range the Coulomb and nuclear amplitudes are of similar magnitude and measurements of polarization observables allow separation of the real and imaginary components of the nuclear amplitudes by their interference with the known Coulomb amplitude.[1] Precise measurements at such small angles can be difficult due to the presence of beam halo or scattering from target materials other than hydrogen. In the present experiment we have used both a windowless gas jet target and coincident detection of the low energy proton at large angles to eliminate these backgrounds.