P. V. Pancella

Analyzing powers and spin correlation coefficients for p+d elastic scattering at 135 and 200 MeV

The proton and deuteron analyzing powers and ten of the possible 12 spin correlation coefficients have been measured for p+d elastic scattering at proton bombarding energies of 135 and 200 MeV. The results are compared with Faddeev calculations using two different NN potentials. The qualitative features of the extensive data set on the spin dependence in p+d elastic scattering over a wide range of angles presented here are remarkably well explained by two-nucleon force predictions without inclusion of a three-nucleon force. The remaining discrepancies are, in general, not alleviated when theoretical three-nucleon forces are included in the calculations.

MoNA—The Modular Neutron Array

The Modular Neutron Array (MoNA), a highly efficient time-of-flight neutron detector, is being constructed for use at the National Superconducting Cyclotron Laboratory. The modular design of the detector provides significant flexibility and allows the bulk of the assembly and testing to be done by undergraduates at nine of the schools participating in the project.

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.

Test of a windowless storage cell target in a proton storage ring

Abstract Stored ion beams offer the possibility to use polarized internal targets that consist of a source of polarized atoms in conjunction with a long, narrow, windowless target cell to enhance the target thickness. In this paper, we discuss the effect of such a cell on the performance of the storage ring, based on measurements carried out with the Indiana Cooler. A prototype target cell was constructed and was operated with a controlled flow of H 2 target gas in a beam of stored protons. Detection of protons scattered at angles from 4° to 15° in coincidence with the associated recoil particles was used to identify elastic scattering. The results show that the presence of a 25 cm long target cell with a rectangular opening of 6.4 mm by 7.9 mm is compatible with operation of the Cooler ring. This demonstrates the feasibility of an important component of experiments with stored, polarized beams and carrier-free polarized, internal targets.

Performance of a polarized-hydrogen storage cell target

Abstract A storage cell has been constructed for use as an internal polarized gas target in the storage ring at the Indiana University Cyclotron Facility. The storage cell has thin teflon walls which allow for detection of low energy recoil particles. We report on nuclear polarization measurements of hydrogen atoms, produced by an atomic beam source, in this storage cell. The results indicate that a target polarization in excess of 0.70 is achieved. We discuss the design and construction details of a storage cell target and the polarization results which are based on low-energy pp spin correlation measurements using the University of Wisconsin tandem accelerator.

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.

Polarized internal gas target for hydrogen and deuterium at the IUCF Cooler Ring

Abstract A polarized internal gas target has been constructed and used at the IUCF Cooler Ring. Polarized hydrogen atoms produced by a high-intensity atomic beam source are injected into a target cell whose Teflon walls are thin enough to allow low-energy recoil particles to be detected in coincidence with forward scattered particles. An average proton target polarization of 0.740±0.013 has been measured.

Interaction of stored, cooled proton beams with fiber targets

Abstract The use of thin fibers as internal targets for nuclear physics experiments in storage rings is discussed. We have measured the lifetime and the energy spread of stored, electron-cooled beams in the presence of an internal carbon fiber target. Measurements have been carried out in the Indiana Cooler with proton beams between 100 MeV and 300 MeV. The effect of the inhomogeneous fiber target on the beam is the same as that of a homogeneous gas target of equivalent thickness within the accuracy of the measurement. The measurements are compared with a Monte Carlo simulation of the stored beam. It is demonstrated that charging of the fiber target can significantly affect the lifetime and energy spread of the stored beam.

Differential cross sections for pp-->pn pi + near threshold.

Differential cross sections from kinematically complete measurements of {ital pp}{r_arrow}{ital pn}{pi}{sup +} production are presented for proton beam energies of 294.2, 299.5, and 319.5 MeV. Total cross sections are given for 294.2, 299.5, 306.5, 314.3, and 319.5 MeV. The two angular distributions close to threshold are dominated by {ital s} wave contributions. Total cross sections within the first 30 MeV of threshold show qualitative agreement with an early theoretical prediction based on PCAC.