H.O. Meyer

Polarizing a Stored Proton Beam by Spin-Flip?

We discuss polarizing a proton beam in a storage ring, either by selective removal or by spin flip of the stored ions. Prompted by recent, conflicting calculations, we have carried out a measurement of the spin-flip cross section in low-energy electron–proton scattering. The experiment uses the cooling electron beam at COSY as an electron target. The measured cross sections are too small for making spin flip a viable tool in polarizing a stored beam. This invalidates a recent proposal to use co-moving polarized positrons to polarize a stored antiproton beam.

Dependence of {rvec {ital p}}{rvec {ital p}} {r_arrow} {ital pp{pi}}thinsp{sup 0} near Threshold on the Spin of the Colliding Nucleons

A polarized internal atomic hydrogen target and a stored, polarized beam are used to measure the spin-dependent total cross section Delta_sigma_T/sigma_tot, as well as the polar integrals of the spin correlation coefficient combination A_xx-A_yy, and the analyzing power A_y for pp->pp pi0 at four bombarding energies between 325 and 400 MeV. This experiment is made possible by the use of a cooled beam in a storage ring. The polarization observables are used to study the contribution from individual partial waves.

Measurement of Partial-Wave Contributions in pp{yields}pp{pi}{sup 0}

We report a measurement of the spin-dependent total cross section ratios {delta}{sigma}{sub T}/{sigma}{sub tot} and {delta}{sigma}{sub L}/{sigma}{sub tot} of the pp{yields}pp{pi}{sup 0} reaction between 325 and 400 MeV. The experiment was carried out with a polarized internal target in a storage ring. Nonvertical beam polarization was obtained by the use of solenoidal spin rotators. Near threshold, the knowledge of both spin-dependent total cross sections is sufficient to deduce the strength of certain participating partial waves, free of any model. (c) 1999 The American Physical Society.

Spin-dependent scattering of polarized protons from a polarized 3He internal gas target

We describe the first experiment to use a polarized internal gas target and polarized beam in a storage ring. A laser optically pumped polarized 3He internal gas target has been used with circulating beams of 197–414 MeV polarized protons to carry out an extensive set of measurements of spin dependent scattering. A large acceptance non-magnetic detector system consisting of wire-chambers, scintillators and microstrip detectors was used to detect protons, neutrons, deuterons, and 3He nuclei from the beam-target interaction. It is demonstrated that these techniques result in low backgrounds (< 1%) due to scattering from species other than the polarized target gas and allow detection of low energy recoiling nuclei. Specific issues such as interfacing the experiment to the storage ring and monitoring the luminosity and polarizations are discussed in detail.

Evidence for Two-Nucleon Processes in A(p,Pi-)A+1

Possible signatures of two-nucleon pion production processes in reactions A(p/sub pol/,..pi../sup -/)A+1 near threshold are identified: a dependence of the analyzing power on the total angular momentum, and a simple scaling of the cross section with subshell occupancy for the struck target neutron. Measurements for /sup 12,13,14/C(p/sub pol/,..pi../sup -/) exhibit these expected features, supporting the view that the fundamental NN..-->..NN..pi.. processes dominate in nuclear pion production.

Evidence for two-nucleon processes in A(p/sub pol/,. pi. /sup -/)A+1

Possible signatures of two-nucleon pion production processes in reactions A(p/sub pol/,..pi../sup -/)A+1 near threshold are identified: a dependence of the analyzing power on the total angular momentum, and a simple scaling of the cross section with subshell occupancy for the struck target neutron. Measurements for /sup 12,13,14/C(p/sub pol/,..pi../sup -/) exhibit these expected features, supporting the view that the fundamental NN..-->..NN..pi.. processes dominate in nuclear pion production.

Polarization reversal of stored proton beams in the Indiana Cooler

A spin flipper of reliable and robust long‐term operation was developed and has been used successfully at the Indiana University Cooler Storage Ring. To reverse the polarization of the stored beam, the frequency of a rf solenoid is swept adiabatically across a depolarizing resonance frequency. Depolarizing sidebands to the resonance are eliminated by shorting out the ring’s bunching rf cavity prior to the frequency sweep. With the spin flipper it is no longer necessary to dump the stored beam and to refill the ring with protons of opposite spin state. Rather, beam accumulation continues without reversing the spin at injection, and instead the polarization of the stored beam is flipped periodically. Thus the luminosity is significantly increased when the flipper is used.

Multiwire proportional chamber for the IUCF cooler ring

Abstract The design and construction of a multiwire proportional chamber for experiments with the Indiana Cooler is described. The novel features of this device are an opening in the center of the sensitive area and fast high-voltage switching, both required by experimental demands. Data are presented on the performance of this chamber which is currently in use for the first nuclear physics experiment with an internal target in a stored, cooled beam.

Measurement of spin correlation coefficients in p→p→→d π+

The spin correlation coefficent combinations

Spin correlation coefficients in from 325 to 400 MeV

{A}_{\mathrm{xx}}{+A}_{\mathrm{yy}}