David Richard Swenson

A combined polarized target/ionization chamber for measuring the spin dependence of nuclear muon capture in laser polarized muonic 3He

Abstract We describe a device used in experiment 1231 at LAMPF and in e683 at TRIUMF to study the spin dependence of the reaction μ − + 3 He → 3 H + v μ . In order to study the spin dependence, we needed to form and polarize muonic 3He and in the same volume detect the 1.9 MeV tritons created in the reaction. Furthermore, the recoil direction of the tritons had to be determined. The apparatus served both as a polarized target and as a detector. The detector, a gridded ion chamber, was incorporated inside a 51 polarized target that was filled with 8 atm of 3He and 100 Torr of N2 and rubidium metal. At the operating temperature of the device (205–230°C) the rubidium number density was approximately 1015 atoms/cm3. Muons that stopped in the target formed muonic helium atoms, which were then polarized by collisions with optically pumped Rb vapor. Two high-powered GaAlAs diode laser arrays were used to polarize the Rb in the 100 cm3 fiducial volume located inside the ion chamber. The ion chamber produced clean signals from the reaction tritons despite having to operate under the extreme conditions required for efficient optical pumping. The direction of the tritons was determined by analyzing the shapes of the ionization pulses. The muon polarization was measured using the decay electron asymmetry.

Volume H/sup -/ ion source development at LAMPF

One method of increasing the intensity of the LAMPF proton Storage Ring is to use a brighter H/sup -/ ion source. To develop such a source, the performance of the small LBL dipole filter and the BNL toroidal filter volume H/sup -/ sources are being investigated. Results of testing a new high-duty-factor design of the BNL toroidal filter volume source are discussed. Results of experiments to reduce the electron to H/sup -/ ratio and modulate the beam intensity in the small LBL source are presented.<<ETX>>

Systematic errors from an optically pumped polarized ion source

Abstract The systematic errors that arise in polarization measurements have been examined using the LAMPF optically pumped polarized ion source (OPPIS). Knowledge of these is important in planning precise experiments such as charge symmetry breaking or parity violation measurements.

Performance of the LAMPF optically pumped polarized ion source

In 1992, the LAMPF optically pumped polarized ion source (OPPIS) was used in experiments demanding a wide range of currents and polarizations. OPPIS was operated in different configurations to meet the differing current and polarization requirements for each experiment. We describe methods used to increase beam polarization at the expense of current for experiments that were count rate limited. OPPIS can be operated at 50 μA, giving 56% polarization, 25 μA with 65% polarization, or 2 μA with 77% polarization. The source reliability in 1992 was excellent, easily exceeding 95%. Contributions to experimental systematic errors made by the source were measured in 1992. We speculate about further improvements that can be made to OPPIS.

DEVELOPMENT OF A TOROIDAL-FILTER H- ION SOURCE

High brightness H− ion beams will be required for the next generation of accelerator‐driven, neutron spallation sources. Volume H− ion sources have the potential for providing these beams at a high duty factor with moderate beam currents and with the long‐term operational stability and reliability needed. We report on the results of a continuing study of the Los Alamos National Laboratory version of a toroidal‐filter, volume H− ion source which was designed to provide such beams. The H− beam current, emittance, and electron loading have been measured with the source equipped with a 3‐ and a 10‐mm‐diam emission aperture and with several configurations of the plasma filter. The results are compared to beam simulations.

Development of a volume H/sup -/ ion source for LAMPF

We have continued the development of a toroidal-filter volume H/sup -/ ion source with the goal of providing a better ion source for the proton storage ring at the Los Alamos Neutron Scattering Center (LANSCE). A prototype source has produced H/sup -/ beam currents of 6.3 mA from a 3-mm-diameter emission aperture (89 mA/cm/sup 2/) and 18 mA from a 10-mm-diameter emission aperture (23 mA/cm/sup 2/). These results were achieved when cesium was added to tile discharge. The cesium increased the H/sup -/ current by a factor of 2-3 while the extracted electron current was strongly suppressed. The magnetic filter can be configured so that the electron to H/sup -/ ratio is 2:1 and is weakly dependent on operating parameters, with only a moderate loss of H/sup -/ current. Tests indicate there is essentially no explicit dependence of extracted beam current on duty factor up to 10% duty-factor. Emittance data were taken for various operating conditions in a mass-analyzed beam line and a comparison is made to the surface conversion H/sup -/ ion source now in operation for the storage ring.

Polarization diagnostics and optical pumping development for OPPIS at LAMPF

We report improvement of the polarization diagnostics and their use in the development of the Optically Pumped Polarized Ion Source (OPPIS).