An upgrade is in progress to the Los Alamos Proton Storage Ring (PSR) to allow direct injection of the H/sup -/ beam into the ring and provide a beam bump system to move the circulating beam off the stripper foil. The primary benefits of this upgrade are matching the transverse phase space of the injected beam to the PSR acceptance and reduction of foil hits by the circulating beam by a factor of ten. Foil thickness is optimized to minimize the combination of circulating-beam losses plus losses due to excited H/sup 0/ states produced at injection. An overall factor of five reduction in losses is expected. The project comprises extensive modifications of the injection line, the injection section of the ring, and the waste-beam transport line. We will discuss the goals of the project, present an overview of the technical design, and describe the status of the implementation plan.

The interaction of 800-MeV H ions with a thin foil produces protons, the ground state and excited states of neutral H atoms, and unstripped H 2 ions. We investigated the distributions of individual H 0 Stark states within the n53 and 4 levels produced by C and Al 2O3 foil stripping of H 2 ions. Foils of various thicknesses were placed upstream of a magnet with a linearly increasing transverse field along the beam direction producing a motional electric field strong enough to ionize H 0 states withn>3. We consider three questions: ~i! What are the populations of individual H 0 Stark states produced in the interaction of 800-MeV H 2 ions with thin C and Al2O3 foils, ~ii ! how do the relative population distributions change with foil thickness, and ~iii ! how is the population distribution produced in an Al 2O3 foil modified when the foil is placed in a magnetic field? A simple qualitative model is presented to explain the major trends. @S1050-2947 ~98!02212-4#

The peak intensity of the PSR is limited by a fast transverse instability. In 1996 we started a project to upgrade the PSR to 200 /spl mu/A at 30 Hz, which requires operation above the instability threshold achieved with our present RF system. We have, therefore, resumed our experimental program to understand and control the instability. In this paper we will present our latest data.

A design for extremely low mass, high-resolution multiwire proportional chambers (MWPC) was achieved by the MEGA collaboration in its experiment to search for the lepton family number violating decay μ→eγ. To extend the present branching ratio limit by over an order of magnitude, these MWPCs were operated in high particle fluxes. They showed minimal effects of aging, and evidenced spatial and energy resolutions for the orbiting positrons from muon decay which were consistent with our design parameters. The unique features of these chambers, their assembly into the MEGA positron spectrometer, and their performance during the experiment are described in this paper.

The interaction of 800-MeV H- ions with a thin foil produces protons, the ground state and excited states of neutral H-0 atoms, and unstripped H- ions. We investigated the distributions of individual H-0 Stark states within the n=3 and 4 levels produced by C and Al2O3 foil stripping of H- ions. Foils of various thicknesses were placed upstream of a magnet with a linearly increasing transverse field along the beam direction producing a motional electric field strong enough to ionize H-0 states with n greater than or equal to 3. We consider three questions: (i) What are the populations of individual H-0 Stark states produced in the interaction of 800-MeV H- ions with thin C and Al2O3 foils, (ii) how do the relative population distributions change with foil thickness, and (iii) how is the population distribution produced in an Al2O3 foil modified when the foil is placed in a magnetic field? A simple qualitative model is presented to explain the major trends. [S1050-2947(98)02212-4].

Measurements of H- stripping and H-0 excited-state production for a wide range of foil thicknesses and experimental conditions are reported. An 800-MeV H- beam was passed through carbon or aluminum oxide foils of thicknesses ranging from 10 to 550 mu g/cm(2) and the excited states produced were analyzed by field. stripping in a special magnet downstream of the foil. The foil thicknesses were independently determined. The H-0 atoms emerging in excited states with n>2 can be stripped to protons in fields of up to 1.3 T The yield of excited states as a function of foil thickness and the cross sections for the various interactions are presented. The cross-section ratio of double to single ionization of H- in carbon is found to be (1.8+/-0.9)%.

Improvement of beam availability is a prime objective of the present LANSCE (Los Alamos Neutron Scattering Center) Upgrade. A RAMI (reliability, availability, maintainability, and inspectability) program is being developed to identify the most cost-effective improvements to achieve the availability goal. The beam-delivery system is divided into subsystems appropriate for the modeling of availability. The availability of each subsystem is determined from operation data and assessment of individual component designs. These availability data are incorporated in an availability model to predict the benefit of improvement projects to achieve cost benefit prioritization. Examination of the data also identifies a comprehensive list of factors affecting availability. A good understanding of these factors using root-cause analysis is essential for availability improvement. In this paper, we will describe the RAMI program and the development of the availability model

The lifetime of 800-MeV H- ions against electron detachment in a static electric field was measured over a range of eight orders of magnitude in experiments at the High Resolution Atomic Beam Facility of the Los Alamos Meson Physics Facility. The ions traversed a linear gradient magnetic field of 1.3-T peak strength resulting in a 6-MV/cm peak rest-frame electric field capable of stripping a large fraction of H- ions. The unstripped H- ions, neutral H-0 atoms, and protons were detected 5.5 m from the magnet. This spectrum was analyzed to determine the lifetime of the H- ion versus electric-field strength and the results were compared with previous studies. Three parametrizations of the lifetime formula based on an existing theory were used to calculate the stripping probability. The data were fit to the lifetime formula and good agreement with theoretical predictions was found. Finally, a possible experiment for observing excited states of H- is briefly discussed.

Neutron dose equivalent rates have been measured for 800-MeV proton beam spills at the Los Alamos Meson Physics Facility. Neutron detectors were used to measure the neutron dose levels at a number of locations for each beam-spill test, and neutron energy spectra were measured for several beam-spill tests. Estimates of expected levels for various detector locations were made using a simple analytical model developed for 800-MeV proton beam spills. A comparison of measurements and model estimates indicates that the model is reasonably accurate in estimating the neutron dose equivalent rate for simple shielding geometries. The model fails for more complicated shielding geometries, where indirect contributions to the dose equivalent rate can dominate.< >

Foil stripping of H{sup {minus}} directly to H{sup +} is being considered for proton injection in the next generation of high-current proton storage rings. This technique can result in significant losses because excited states of HO, which are also produced in the foil, are field stripped in the downstream bending magnets. Without due care in the injection system design, many of the resulting protons will be outside the acceptance of the storage ring and will be quickly lost. We measured the production of such H{sup 0} excited states at the LAMPF High Resolution Atomic Beam Facility. An 800-MeV H{sup {minus}} beam was passed through carbon foils of thicknesses 70, 100, 200, and 300 {mu}g/cm{sup 2}, and the excited states were analyzed by a special magnet downstream of the foil. The magnet had a linear field gradient so that the trajectories of the outgoing protons could be used to reconstruct the field values at which the various H{sup 0} stripped. We found that about 1% of the H{sup 0} emerge in excited states which can be stripped to protons by ring-bending magnets.

First-turn beam losses in the LAMPF proton storage ring were measured as a function of the left-right position of the carbon foil used to strip neutral hydrogen atoms to H+ for proton injection into the PSR. Two foil thicknesses, 200 and 300 μg/cm2 , were tested. Results indicated that first-turn loss is caused predominately by magnetic field stripping of a small fraction of the H 0 atoms that pass through the stripper foil without being stripped to protons, and the results were not consistent with a mechanism involving protons originating from atoms in the halo of the neutral beam incident on the stripper foil

The CYGNUS extensive air-shower experiment is described. The design criteria, construction and operation details, and performance characteristics are presented. A discussion of the data analysis techniques is given. Finally, several enhancements and improvements in the apparatus are described.

One of the leading experimental projects at LAMPF has been the MEGA experiment. This is an experiment to search for the rare decay μ → eγ with a sensitivity of 10−13. A prime component of this project has been the design and construction of high-rate, low-mass MWPCs for the tracking of positrons from muon decay. With rate capabilities of 2 × 104 e+/mm2/s and a thickness of 3 × 10−4 radiation lengths, these chambers are state-of-the-art cylindrical MWPCs. Cylindrical chambers of this size (0.9 m2) and thinness have never been previously constructed. The MEGA project at LAMPF has recently succeeded in building chambers with these necessary performance characteristics as demonstrated by data taken from muon decays, cosmic rays, and sources.

The assessment of radiation shielding for the beam lines and experimental areas at the Los Alamos Meson Physics Facility (LAMPF) required a quick and simple method of estimating dose equivalent rates for primary 800-MeV proton beam spills in the forward direction. In this study, we show that forward production dose equivalent rates can be characterized by a Moyer Model formula normally used for transverse production angles. Appropriate parameters for the forward formula were determined by fitting the results of a Monte Carlo simulation.

The CYGNUS air shower array, located in Los Alamos, New Mexico, has been operating since April, 1986. The expansion of the array from 108 to 200 counters is described along with the increase in muon detection area. The new array, to be fully operational by the end of 1989, will have three times the sensitivity to UHE sources. 5 refs., 2 figs.