The response of position-sensitive detectors to fission fragments and other heavy ions

Abstract

Position-sensitive surface barrier detectors have been used for the measurement of energy and angular distributions of fission fragments and other heavy ions. The techniques used to calibrate such detectors are described. It is possible to determine the position of an incident ion with a resolution of about 0.25 mm for a 50 mm detector length, the position response being independent of the energy of the ion. However, the position response curve is non-linear, showing its largest curvature at one end of the detector. The pulse height versus energy calibration was determined for a variety of heavy ions produced by elastic scattering of 32S and 16O. The ions Ni, Ag and Au exhibited pulse-height defects, which were measured as a function of ion energy, and were found to be approximately equal to those for a “heavy ion” type surface barrier detector. The pulse height versus energy calibration is a function of position, but is linear at a given position. In spite of the slow rise time of the pulses, it was possible to obtain fast timing signals, with a resolution of 3.5 nsec (fwhm) at a fixed position and fixed energy. The time dependence on position, however, is very large with about 50 nsec difference between the center of the detector and the ends.