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.