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Measurements of ${\mathrm{H}}^{\ensuremath{-}}$ stripping and ${\mathrm{H}}^{0}$ excited-state production for a wide range of foil thicknesses and experimental conditions are reported. An 800-MeV ${\mathrm{H}}^{\ensuremath{-}}$ beam was passed through carbon or aluminum oxide foils of thicknesses ranging from 10 to 550 \ensuremath{\mu}g/${\mathrm{cm}}^{2}$ 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 ${\mathrm{H}}^{0}$ atoms emerging in excited states with $ng2$ 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 ${\mathrm{H}}^{\ensuremath{-}}$ in carbon is found to be (1.8\ifmmode\pm\else\textpm\fi{}0.9)%.

The frequency dependence of the complex permeability of the ferrite (at room temperature and 125 /spl deg/C) used in the inductors at PSR has been determined by comparing the S/sub 11/ parameters from a jig containing ferrite and a MAFIA (a program package for the computation of electromagnetic fields) simulation of the jig. Both the frequency response and the longitudinal impedance of the inductive inserts were obtained by simulating the inductor cavity in MAFIA using the ferrite properties from the aforementioned fit. Experimental observations of the longitudinal instability caused by the ferrite inductors at room temperature in a bunched coasting beam have been made. Comparisons of observed and simulated growth times, resonant frequencies, and width of the instability will be discussed.

The beam diagnostics for the Los Alamos Proton Storage Ring (PSR) are being upgraded in several areas, including the closed-orbit beam-position system, the high-frequency longitudinal and transverse beam diagnostics, and the extraction-line beam-position monitoring system. The closed-orbit beam-position measuring system is based on detecting the 201 MHz modulation on the injected beam, which disappears in about 10 mu s, due primarily to the beam's momentum spread (about +or-0.1%), and the consequent spread in the revolution frequencies. Thus, although the first few turns of the injected beam are monitored with the system, the main body of the stored beam, which has lost its 201 MHz component, is not. In order to monitor the position of the stored beam, the ring beam-position system is being redesigned to operate at the revolution frequency, 2.8 MHz. >

A project to upgrade the short-pulse spallation source target at the Los Alamos Neutron Scattering Center (LANSCE) is in progress. This upgrade will reduce the target change out time from about a year to about three weeks and permit the proton beam current to be raised to 200 /spl mu/A. The project includes a new target-moderator-reflector system, a new suite of moderators for four new flight paths, improved auxiliary systems, remote handling capability, and a new crane and service building. The project has also supported calculations and experiments for target neutronics, rod-target thermo-hydraulics, and corrosion-related measurements in a proton beam. The final engineering design is now complete and the project has begun fabrication and procurement. Installation will begin in the fall of this year.

Three projects have been initiated since 1994 to improve the performance of the accelerator and target facilities for the Los Alamos Neutron Science Center (LANSCE). The LANSCE Reliability Improvement Project (LRIP) was separated into two phases. Phase I, completed in 1995, targeted near-term improvements to beam reliability and availability that could be completed in one-year's time. Phase II, now underway and scheduled for completion in May 1998, consists of two projects: (a) implementation of direct H injection for the Proton Storage Ring (PSR) and (b) an upgrade of the target/moderator system for the short pulse spallation neutron (SPSS) source. The latter will reduce the target change-out time from about 10 months to about three weeks. The third project, the SPSS Enhancement Project, is aimed at increasing the PSR output beam current to 200 /spl mu/A at 30 Hz and providing up to seven new neutron scattering instruments.

In a Fermilab-Los Alamos collaboration, inductances constructed of ferrite cores sufficient to cancel a large fraction of the space charge potential-well distortion were installed in the Los Alamos Proton Storage Ring (PSR) as one means of raising the threshold for the two-stream e-p instability. When operating at higher intensities and with sufficient inductance added for full space-charge compensation, an unacceptable longitudinal self-bunching, microwave-like, instability was encountered. Heating the cores to /spl sim/130/spl deg/C proved to be an effective cure, and was found to be a means for tuning the inductance over a limited but useful range. The heated inductors were an essential ingredient in achieving a record accumulation of 9.7 /spl mu/C/pulse. An engineered version of the inductors is now installed for routine operation of the PSR. A summary of the inductor characteristics, theory of operation, experimental results, and interpretation will be presented.

The lifetime of 800-MeV ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ 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 ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ions. The unstripped ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ ions, neutral ${\mathrm{H}}^{0}$ atoms, and protons were detected 5.5 m from the magnet. This spectrum was analyzed to determine the lifetime of the ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ 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 ${\mathrm{H}}^{\mathrm{\ensuremath{-}}}$ is briefly discussed.

An experiment has been performed to demonstrate the feasibility of proton computed tomography. The proton energy loss was used to measure the projections of the relative stopping power of the phantom. High quality reconstructions were obtained from scans of 19 cm and 30 cm diameter performance phantoms. Comparison with reconstructions from an EMI CT-5005 X-ray scanner showed the proton technique is more dose efficient by a large factor.

The conserved-vector-current hypothesis, together with measured nuclear-beta-decay rates, predicts a value of the rate for the decay ..pi../sup +/..--> pi../sup 0/e/sup +/..nu.. of 0.4027 +- 0.0018 s/sup -1/. With use of a decay-in-flight technique the authors have made the most precise measurement to date of this rate, obtaining the value 0.398 +- 0.015 s/sup -1/, in good agreement with the prediction.

The conserved-vector-current hypothesis, together with measured nuclear beta-decay rates, predicts a value of the rate for the decay ..pi../sup +/..--> pi../sup 0/e/sup +/..nu.. of 0.4027 +- 0.0018 s/sup -1/. Using a decay-in-flight technique we have made the most precise measurement to date of this rate, obtaining the value 0.394 +- 0.015 s/sup -1/, in good agreement with the prediction. This differs slightly from the value previously reported in W. K. McFarlane et al., Phys. Rev. Lett. 51, 249 (1983).

The (..pi../sup +/, p) reaction has been studied at T/sub ..pi../ = 90 and 180 MeV on /sup 12/C, and at T/sub ..pi../ = 90 and 170 MeV on /sup 13/C. The resolution was sufficient to resolve many single levels in the residual nuclei, and angular distributions were obtained between laboratory angles of 10/sup 0/ and 115/sup 0/. A comparison between the present (..pi.., p) data and existing high-energy (p,d) data in terms of a model assuming intermediate pion exchange in the (p,d) reaction indicates that the (..pi..,p) reaction is an important subprocess in the (p,d) reaction. The present data also suggest that pion rescattering is likely to be a fundamental part of the (..pi.., p) reaction mechanism.

A new search for three-photon decays of the neutral pion has been made. No signal in excess of background was observed. The upper limit for the ..pi../sup 0/ ..-->.. 3..gamma.. branching ratio is 3.8 x 10/sup -7/ (90% confidence level).

The experimental procedure and results of a comparative study of the imaging characteristics of proton and X-ray CT scans are presented. Scans of a human brain and heart are discussed. The proton produced images are found to be similar in information content while providing a decided dose advantage.

A precise measurement of the differential cross section at zero degrees for the pion charge-exchange reaction ..pi../sup -/p ..-->.. ..pi../sup 0/n at p/sub ..pi../ = 522 MeV/c has been made. The result is dsigma/d/OMEGA(0/sup 0/) = 4.32 +- 0.11 mb/sr. 12 references.

In an experiment at the Princeton-Pennsylvania Accelerator, the relative rate $\frac{{{K}_{e2}}^{+}}{{{K}_{\ensuremath{\mu}2}}^{+}}$ was measured to be (${1.8}_{\ensuremath{-}0.6}^{+0.8}$) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}5}$. Combining this with previous measurements gives a world average of (${1.9}_{\ensuremath{-}0.4}^{+0.5}$) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}5}$, which agrees with the universal $V\ensuremath{-}A$ theory prediction of 2.09 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}5}$.