A. Gavron

Composite charged particle detectors with logarithmic energy response for large dynamic range energy measurements

Abstract We have developed an array of detectors to identify charged particles produced in heavy ion reactions. The array, which consists of eight individual detector modules and a forward hodoscope, subtends a solid angle of 0.58π and covers 62% of the reaction plane in laboratory coordinates. Each of the eight identical modules has an active area which extends 13° above and below the array plane with additional limited coverage between 13° and 26°. Each module measures the position, energy and velocity of charged particles over a dynamic range which extends from minimum ionizing protons with energies up to 200 MeV to highly ionizing fission fragments with Coulomb-like energies. Position and time-of-flight are measured with low pressure multiwire proportional counters (MWPC). Total energies for heavier ions are obtained from large ion chambers. Energy and position measurements for more energetic lighter ions which pass through the ion chambers are made with segmented phoswich arrays. The forward angle hodoscope is a 34-element array of phoswich detectors mounted symmetrically around the beam axis. These detectors are sensitive to beam velocity particles ( E / A > 10–40 MeV / A ) and capable of elemental resolution from protons to Z = 23.

Simulations of neutron response and background rejection for a scintillating-fiber detector☆

Abstract We address the problem of detection of fast neutrons at energies of 5–30 MeV in the presence of strong backgrounds of low-energy neutrons and gammas. In an organic scintillator, the neutrons are detected mainly as recoil protons from n-p scattering; the gammas produce electrons primarily by Compton scattering. The recoil protons and electrons can be distinguished because the light output per unit distance near the end of a proton track is much higher than that for an electron. This difference could be used to reject gamma backgrounds such as those in a reactor environment by constructing a segmented detector from a bundle of scintillating fibers connected to a readout device. We present the results of extensive simulations for a module composed of 6400 fibers, each 250 μm square, arranged into a 2×2×2 cm3 bundle. Considered were fast neutrons with energies of 3, 7, 14 and 28 MeV and backgrounds composed of neutrons and gammas with energy distributions characteristic of delayed emission from a fission source. The simulations indicate that the detector can obtain a good compromise between outstanding background rejection and reasonable detection efficiency for the neutrons of interest.

The design and construction of a Pb/scintillator sampling calorimeter with wavelength shifter fiber optic readout

Abstract A Pb/scintillator sampling calorimeter covering the pseudorapidity interval of η = 0.83 to 4.20 has been designed and constructed for Experiment 814 of Brookhaven National Laboratory. The calorimeter uses wavelength shifting optical fibers for readout. Such fibers allow the construction of a highly granular and longitudinally compact device. A novel scheme for coupling a fiber to a scintillator plate has been designed that yields a high photoelectron response. Longitudinally, the calorimeter has a depth of four interaction lengths divided into two electromagnetic sections and two hadronic sections of 0.4, 0.4, 1.6, and 1.6 interaction lengths, respectively.

Response of the participant calorimeter to 1.5–6.8 GeV/c electrons and hadrons

Abstract The Participant Calorimeter for Experiment 814 at BNL is a lead-scintillator sampling calorimeter. The response of the calorimeter to beams of e, μ, π and p from 1.56 to 6.8 GeV/c is presented. The design and performance of two gain monitoring systems are described, one system measures the response of single scintillator plates in the calorimeter. The calorimeter electromagnetic energy resolution varies from 24 to 32% √E for different towers. For hadron energies over 5 GeV the σh/E = 43±3%/√E, and e/h = 1.02±0.07.

Measurements and calculations of the gamma response of neutron scintillators

Abstract By adapting routines from existing simulation programs for the interaction of neutrons and gammas with organic scintillators, a code has been produced to calculate the response of multi-element detectors to neutrons below 200 MeV and gammas below 10 MeV. The approach for the gamma calculations is similar to the macroscopic model used for neutron interactions. To test the approximations concerning gamma multiple-scattering and electron range-energy relations, measurements were made for the response of plastic scintillators to gammas at energies up to 1.3 MeV. The measurements focus on count rates and light-output distributions, and their analysis includes discussions of energy-to-light conversion and detector resolution. All measurements and calculations are in good agreement. The conclusions are discussed in terms of calculations of detection efficiencies for neutrons at energies of 1–200 MeV.

Response of a sampling calorimeter to low energy pions, muons, and positrons

Abstract Measurements of the response of the participant calorimeter to 250–400 MeV/c π+, μ−, and e+ are described. The participant calorimeter is a Pb/Fe/scintillator sampling calorimeter with a novel wavelength shifting fiber optic readout which is used in experiment 814 at Brookhaven National Laboratory. The e+/π+ response ratio at 250–400 MeV/c is larger than it is at higher momenta. Previous measurements of the e/π response ratio with sampling calorimeters found that the value decreased as the particle energies were reduced below about 1 GeV. This difference is attributed to the different absorption probabilities for π+ and π− at low momentum.

A neutron detector for use in strong gamma backgrounds

Abstract We describe the simulation of a new concept for a neutron detector system involving polyethylene radiators and multiwire proportional detectors which detect protons produced by neutron interactions in the radiators. The detector system is relatively insensitive to gamma radiation as long as the individual proportional counters maintain their stability. The detector system has a linear energy response and good energy resolution from threshold (determined by the radiator thickness) up to approximately 20 MeV. By detecting events in which two proton tracks are produced, the detector system can be used for imaging with a spatial resolution of ∼9°.

Heavy ion fission — an inherently non-equilibrium process?

Abstract Recent measurements of neutron emission in coincidence with fission fragments indicate a strong enhancement of the neutron multiplicity preceeding fission compared with statistical model calculations. This enhancement has enabled the determination of the reduced nuclear dissipation coefficient β which, in turn, indicates that nuclear collective motion is overdamped. We examine some possible sources of error in this determination and speculate on the consequences of the obtained value of β.

Calorimeter/absorber optimization for a RHIC dimuon experiment

The RD-10 R&D effort on calorimeter/absorber optimization for a RHIC experiment has an extended run in 1991 using the A2 test beam at the AGS. Measurements were made of the leakage of particles behind various hadron calorimeters. Behavior of the calorimeter/absorber as a muon-identifier was studied. First comparisons of results from test measurements to calculated results using the GHEISHA code were made.

Multiple scattering calculations in particle transport codes using truncated Rutherford scattering

Abstract Multiple Coulomb scattering is incorporated into numerous particle transport codes using various approximation techniques. We present a new technique that incorporates the Rutherford scattering process directly into the transport code as an additional interaction process. We avoid divergent values of the cross section by introducing a cutoff angle, and examine the effect of its value on the results we obtain.