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The design, construction, and performance of a segmented-target, cathode-strip, tracking-detector is discussed. The chamber was made of low- Z materials in order to allow photons to leave the target region. It was used to determine the reaction vertex of stopping kaons, and was successfully operated in a high-intensity kaon beamline at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The vertical and horizontal resolutions of the stopping kaon reaction positions were σ X ∼0.454 mm and σ Y ∼1.180 mm , respectively. The uncertainty in the longitudinal ( Z ) direction is given by one-half the thickness of a target segment.

The capability has successfully been developed at the Los Alamos Nuclear Science Center (LANSCE) to utilize a spatially and temporally prepared 800 MeV proton beam to produce proton radiographs. A series of proton bursts are transmitted through a dynamic object and transported, via a unique magnetic lens system, to an image plane. The magnetic lens system permits correcting for the e⁄ects of multiple coulomb scattering which would otherwise completely blur the spatially transmitted information at the image plane. The proton radiographs are recorded either on a time integrating film plate or with a recently developed multi-frame electronic imaging camera system. The latter technique permits obtaining a time dependent series of proton radiographs with time intervals (modulo 358 ns) up to many microseconds and variable time intervals between images. One electronically shuttered, intensified, CCD camera is required per image. These cameras can detect single protons interacting with a scintillating fiber optic array in the image plane but also have a dynamic range which permits recording radiographs with better than 5% statistics for observation of detailed density variations in the object. A number of tests have been carried out to characterize the quality of the proton radiography system for absolute mass determination, resolution, and dynamic range. Initial dynamic experiments characterized the temporal and spatial behavior of shock propagation in a high explosive sample with up to six images per experiment. Based on experience with the prototype system, a number of upgrades are being implemented including the anticipated capability for enhanced mass discrimination through di⁄erential multiple coulomb scattering radiographs and more images with improved imaging techniques. ( 1999 Published by Elsevier Science B.V. All rights reserved.

Double-differential cross sections and analyzing powers A{sub y} for the ({rvec p},n) reactions on {sup 3}He and {sup 4}He were measured at 200 MeV between {theta}{sub lab}=0{degree} and 44{degree}. The neutron spectra from {sup 3}He({rvec p},n) are dominated by the quasifree scattering peak and show no evidence for resonances in the three-proton system. The spectra from {sup 4}He({rvec p},n) exhibit strong resonance behavior in the p{sup 3}He system at low relative p{sup 3}He energies owing to the excitation of known L=1 resonances in {sup 4}Li, but there is no distinct quasifree peak in the measured spectra. The experimental A{sub y} for {sup 3}He({rvec p},n), averaged over the experimental range of neutron energies, are similar to those for free nucleon-nucleon (NN) scattering, whereas for {sup 4}He({rvec p},n) the A{sub y} are generally larger than the free values. The cross sections at far forward angles for both {sup 3}He and {sup 4}He appear to be suppressed relative to the free {ital NN} cross sections by Pauli blocking. At most angles, the shapes of the cross section spectra from both {sup 3}He and {sup 4}He are reproduced by distorted-wave impulse approximation (DWIA) calculations using a quasifree scattering model. Specifically for {sup 4}He({rvec p},n),more » the model requires the use of an optical potential which has a strong L=1 potential resonance corresponding to the low-lying L=1 states in {sup 4}Li. {copyright} {ital 1998} {ital The American Physical Society}« less

Asymmetries ${A}_{y}$ for ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ elastic scattering from polarized ${}^{3}$He were measured at incident energies passing through the $\ensuremath{\pi}$ nucleon ${P}_{33},$ or $\ensuremath{\Delta}$(1232), resonance. The data were taken at the Clinton P. Anderson Meson Physics Facility using the high-energy pion channel ${P}^{3}$ and a large acceptance spectrometer to detect the scattered pions. The polarized ${}^{3}$He target, originally developed at TRIUMF, was modified for these experiments by the addition of diode lasers. Completely unexpected negative asymmetries were observed at and below the resonance in ${\ensuremath{\pi}}^{+}$ scattering near $50\ifmmode^\circ\else\textdegree\fi{}$--60$\ifmmode^\circ\else\textdegree\fi{}$, which cannot be reproduced by multiple scattering theory and Faddeev wave functions. A hybrid model, which adds a $\ensuremath{\Delta}$-neutron spin-spin interaction term to the conventional calculations, provides a good description of the ${\ensuremath{\pi}}^{+}$ data. For ${\ensuremath{\pi}}^{\ensuremath{-}}$ scattering this term predicts a negligible effect on ${A}_{y}$ and the data do not show the anomalous ${A}_{y}$ seen with ${\ensuremath{\pi}}^{+}$.

Double-differential cross sections ${d}^{2}\ensuremath{\sigma}∕(d\ensuremath{\Omega}d{E}_{x})$ and spectra of analyzing powers, ${A}_{y}$, for the $^{4}\mathrm{He}(\stackrel{P\vec}{p},n)$ reaction were measured at ${T}_{p}\ensuremath{\approx}100$ and $200\phantom{\rule{0.3em}{0ex}}\text{MeV}$ at forward angles between ${\ensuremath{\theta}}_{lab}=0\ifmmode^\circ\else\textdegree\fi{}$ and $44\ifmmode^\circ\else\textdegree\fi{}$, and were analyzed using wave functions from the recoil-corrected continuum shell model (RCCSM). The steep rise of the cross-section spectra just above the $p+^{3}\mathrm{He}$ rest energy threshold results from the excitation of the ${2}^{\ensuremath{-}}$ and ${1}^{\ensuremath{-}}$ resonances in $^{4}\mathrm{Li}$ and is well reproduced by the RCCSM at both incident energies. At higher excitation energies, the predicted cross sections fall off faster than the experimental values at forward angles. The absolute cross sections from the RCCSM were renormalized by factors of 1.3 and 1.6 at $100\phantom{\rule{0.3em}{0ex}}\text{MeV}$ and $200\phantom{\rule{0.3em}{0ex}}\text{MeV}$, respectively, in order to fit the cross section summed over the lowest $10\phantom{\rule{0.3em}{0ex}}\text{MeV}$ of excitation at the peak of the angular distribution. The $100\phantom{\rule{0.3em}{0ex}}\text{MeV}$ ${A}_{y}$, averaged over the lowest $10\phantom{\rule{0.3em}{0ex}}\text{MeV}$ of excitation, are well reproduced by the RCCSM but not the $200\phantom{\rule{0.3em}{0ex}}\text{MeV}$ ${A}_{y}$, nor are the details of the ${A}_{y}$ spectra well described at either energy.

The (Kstopped−,π0) strangeness and charge changing reaction was investigated by producing a BΛ12 hypernucleus from a carbon target. The branching ratio for K− capture to the ground and p-shell states of this hypernucleus was found to be (0.28±0.08)×10−3 and (0.35±0.09)×10−3, respectively, which after correction for isospin was lower than a previously measured value for the C12(Kstopped−,π−)CΛ12 reaction, but still above the theoretical predictions for the ground state. The experiment obtained a missing-mass resolution comparable to in-flight reactions, however the higher background and lower selectivity of the Kstopped− reaction limits its usefulness in the study of new hypernuclear species.

Analyzing powers for ${\ensuremath{\pi}}^{\ensuremath{-}}p$ elastic scattering have been measured at TRIUMF using the CHAOS spectrometer and a spin-polarized target. These data were collected at a bombarding energy of ${T}_{\ensuremath{\pi}}=279\mathrm{MeV}$ and cover an angular range of $53l~{\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}^{\ensuremath{\pi}}l~180\ifmmode^\circ\else\textdegree\fi{}.$ There is good agreement between these data and the latest partial wave analysis from the VPI/GWU group.

High quality analyzing powers for the ${\ensuremath{\pi}}^{\ensuremath{-}}\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}n$ reaction have been obtained with a polarized proton target over a broad angular range at incident kinetic energies of 98.1, 138.8, 165.9, and 214.4 MeV. This experiment nearly doubled the existing $\ensuremath{\pi}N$ single-charge-exchange database for energies ranging from 10 to 230 MeV, with 36 new analyzing powers. The Neutral Meson Spectrometer was used to detect the outgoing neutral pions. The data are well described by recent phase-shift analyses. When combined with high-precision and accurate cross section data at the same energies, the data can provide a good test of the degree of isospin breaking in the region of the $\ensuremath{\Delta}(1232)$ resonance. They will also be helpful for constraining the evaluation of the pion-nucleon $\ensuremath{\sigma}$ term from the scattering amplitudes.

Asymmetries for the ({pi}{sup {minus}},{pi}{sup 0}) reaction on polarized {sup 3}He were measured using a 200-MeV pion beam at LAMPF. The {pi}{sup 0}{close_quote}s were detected with the neutral meson spectrometer in coincidence with the recoiling tritons. A recoil triton detector, consisting of scintillation-counter telescopes and a wire chamber, was used to measure the time-of-flight, energy loss, and direction of the tritons. The polarized gaseous {sup 3}He target, developed at TRIUMF, was modified to run with two diode lasers; the polarization reached 65{percent}. The asymmetries between {theta}{sub lab}=60{degree} and 105{degree} were found to be strongly angle dependent. The results are compared with theoretical calculations. {copyright} {ital 1999} {ital The American Physical Society}

An intensifiedlshuttered cooled PC-based CCD camera system was designed and successfully fielded on proton radiographyexperiments at the Los Alamos National Laboratory LANSCE facility using 800-MeV protons. The four camera detectorsystem used front-illuminated full-frame CCD arrays (two 1024 x 1024 pixels and two 5 12 x 5 12 pixels) fiber opticallycoupled to either 25-mm diameter planar diode or microchannel plate image intensifiers which provided optical shuttering fortime resolved imaging of shock propagation in high explosives. The intensifiers also provided wavelength shifting and opticalgain. Typical sequences consisting of four images corresponding to consecutive exposures of about 500 ns duration for 40-usproton burst images (from a fast scintillating fiber array) separated by approximately I microsecond were taken during theradiography experiments. Camera design goals and measured performance characteristics including resolution, dynamicrange, responsivity, system detection quantum efficiency (DQE), and signal-to-noise will be discussed.KEYWORDS: high resolution, high speed, multi-frame, electro-optically shuttered, intensified, CCD camera system