J.B. Cumming

An excitation function of K− and K+ production in Au+Au reactions at the AGS

Abstract Mid-rapidity spectra and yields of K− and K+ have been measured for Au+Au collisions at 4, 6, 8, and 10.7 AGeV. The K− yield increases faster with beam energy than for K+ and hence the K−/K+ ratio increases with beam energy. This ratio is studied as a function of both s and s − s th which allows the direct comparison of the kaon yields with respect to the production threshold in p+p reactions. For equal s − s th the measured ratio K−/K+=0.2 at energies above threshold in contrast to the K−/K+ ratio of near unity observed at energies below threshold. The use of the K−/K+ ratio to test the predicted changes of kaon properties in dense nuclear matter is discussed.

A Single arm spectrometer detector system for high-energy heavy ion experiments

The recent availability of 14.6 GeV/c per nucleon 16O and 28Si ions from the Brookhaven National Laboratory Tandem-AGS accelerator facility has prompted the design, construction and operation of a large-solid-angle (25 msr) magnetic spectrometer with particle identification from ∼0.5 to ∼4.7 GeV/c. A small-solid-angle Cherenkov counter complex views the target through the magnet and extends the particle identification up to ∼15 GeV/c. This experiment (E-802) employs event characterization detectors, a charged-particle multiplicity array, a highly segmented lead-glass detector, and a zero degree calorimeter. The facility measures momentum spectra of identified heavy-ion-produced hadrons with high resolution (Δp/p≤0.005) as a function of collision centrality given by triggers from the event characterization detectors. Construction and performance details of the spectrometer components and auxiliary detectors are described.

Absolute cross section for the C12(p, pn)C11 reaction at 50 MeV

Abstract Absolute cross sections for the C 12 (p, pn)C 11 reaction at proton energies between 21 and 50.5 MeV were measured at the Brookhaven Linac. Beam intensity was measured with a Faraday cup and the C 11 induced in polyethylene foils was assayed in a calibrated well-type scintillation counter. Corrections for C 11 gas loss from the foils were applied. The C 12 (p, pn)C 11 cross section at 50.5 MeV is 86.4±2.6 mb. Absolute cross sections for Na 22 and Na 22 production from aluminium were also measured at several energies.

Measurement of energy emission from O+A and p+A collisions at 14.5 GeV/c per nucleon with a lead-glass array

Abstract The first data from a 16O beam of total energy 232 GeV at the BNL Tandem-AGS are reported. A lead-glass array covering the laboratory pseudo-rapidity interval 1.25

Recent results from E802 and E859

Abstract Recent single-particle inclusive measurements and two-particle correlation data from E802 and its succesor, E859, are presented. The K + / π + ratio observed for collisions of 14.6 A·GeV 28 Si ions on various targets is presented as a function of both forward and transverse energy. Source sizes are determined via interferometry using π + , π − , K + and proton pairs.

Measurement of energy and charged particle emission in the central rapidity region from O+A and p+A collisions at 14.5 GeV/c per nucleon and preliminary results from Si+A collisions

The first data from a16O beam of total energy 232 GeV at the BNL Tandem-AGS are discussed. Preliminary results from a28Si beam of total energy 406 GeV are also shown. The full complement of E802, including a magnetic spectrometer, was used for the28Si measurement. A different experimental arrangement was used for16O. Comparison measurements with proton beams are presented for both configurations.

Au+Au reactions at the AGS: Experiments E866 and E917

Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2--10.7 AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.Particle production and correlation functions from Au+Au reactions have been measured as a function of both beam energy (2-10.7AGeV) and impact parameter. These results are used to probe the dynamics of heavy-ion reactions, confront hadronic models over a wide range of conditions and to search for the onset of new phenomena.

Performance and promise of the Compton suppression well counter

Abstract Determination of gamma-ray activities in small environmental samples poses a challenge to measurement technologies: to achieve the lowest possible detection limits, an instrument must combine high efficiency with superior peak-to-background characteristics. These requirements are simultaneously met by a Compton-suppression well counter (CSWC) of intrinsic germanium. The Brookhaven CSWC has a 5-cm deep, 1-cm diameter well and active volume of ∼ 125 cm 3 . It is positioned in the 3.3-in through-hole of 10 × 12 in NaI(Tl) crystal. This CSWC was first assembled in the mid 1980s, and used in several research studies: double β − decay of 48 Ca, the radioactivity of 180m Ta, and high-sensitivity neutron activation analysis of iridium in rocks and minerals. More recently it has been employed in environmental radioactivity research on the transport of the members of the uranium and thorium series in natural soils. The counter typically measures samples of ∼ 3 g of soil, has a peak-to-Compton ratio of ∼ 300:1, and a sensitivity for 235 U of ∼ 50 ng. It can detect gamma rays of less than 30 keV, hence can be used to measure environmentally significant nuclides like 210 Pb, 230 Th and 241 Am in small soil samples or soil fractions. Because of the simple geometry self-absorption corrections are straightforward. The paper will discuss the performance of this device, and the projected performance of an advanced model which will incorporate a number of changes materially increasing the sensitivity.

A novel approach to the determination of iridium via Ge-coincidence/NaI(Tl)-anticoincidence gamma-ray spectrometry

Iridium has proven to be a useful fingerprint of extraterrestrial material, and neutron activation analysis is the method of choice for its determination because of the high thermal cross section (910 b) of 191Ir (37.3% natural abundance) and the favorable decay characteristics of the product nuclide. However, radiochemical separations are frequently required for the determination of iridium at low concentrations (in the ppb range). The present work describes a precise, nondestructive neutron-activation procedure that is capable of analyzing samples of both high (ppm) and low (ppb) Ir content. Advantage is taken of the fact that the principal gamma lines of 73.8-d 192Ir are in various coincidences with one another. Instead of conventional gamma-gamma coincidence spectrometry with two Ge detectors, we utilize the 784.6- and 920.9-keV sum peaks which are generated when an iridium containing sample is placed in the well of a highly-efficient HPGe detector. The well-type detector is positioned centrally in a large annular NaI(Tl) detector which is operated in an anticoincidence mode. This improves the quality of the gamma spectra by suppressing the Compton backgrounds due to nuclides such as 60Co by a factor of 4–6 in the regions of interest without affecting the intensities of the two sum peaks. The sensitivity of this method under our experimental conditions (20-mg sample irradiated at 1.5 × 1014 n cm−2 s−1 for 5 min and counted 3–4 weeks after irradiation) is ∼5 ppb Ir in a relatively unfavorable matrix such as peridotite.

On the determination of iridium in diverse geological samples employing HPGe-coincidence/NaI(Tl)-anticoincidence spectrometry

Abstract We report the Ir content of a variety of geological samples determined by the HPGe-coincidence/ NaI(Tl)-anticoincidence gamma ray spectrometry (henceforth referred to as coincidence/anticoincidence technique) and by the conventional Instrumental Neutron Activation Analysis (INAA). The coincidence/ anticoincidence technique is well suited for nondestructive measurement of the Ir content in diverse types of small (