Electron trajectories and inhomogeneity effects in a Daly detector

Abstract

Some characteristics have been studied of a Daly detector. Numerical calculations of electron trajectories in a simplified model prove that detection of ions with very different energies by means of a detector with a fixed converter is only possible when relatively large dimensions are given to the scintillator. Experimental verification of the numerical results has been carried out by means of a specially designed detector with an adjustable converter. For the chosen configurations the numerical and experimental findings agree reasonably well. The influence of inhomogeneities in the converter surface, the scintillator and the cathode of the photomultiplier on the detection efficiency has also been investigated. In the chosen set-up variations in the counting losses upon displacement of the ion image across the converter are of the same order as their mean values. Strong inhomogeneities are introduced, when relatively high ion current densities ( approximately 10^-15 A mm^-2) are applied for some hours on to a fixed converter, and consequently high electron current intensities on to the corresponding scintillator area. There is some evidence that under these extreme conditions degradation of the applied plastic scintillator occurs.