Simplifying position-sensitive gas-ionization detectors for heavy ion elastic recoil detection

Heavy ion elastic recoil detection is an effective tool for materials analy sis. This has been facilitated by the development of novel detection system s, including large solid-angle gas-ionization detectors with position-sensi tivity. With such detectors the exposure of the sample to the beam is reduc ed, however, data analysis can be complex. This paper reports on a detailed investigation of a detector design commonly used. The results of this work have led to suggestions for design-modifications, which considerably simpl ify detector operation and data analysis. The modifications have been imple mented and tested. With the modified detector, the total energy information can be obtained by adding the signals from the anode electrodes, but also directly from a grid-electrode, obviating the need for the relative calibra tion of the anode electrodes. The subdivision of the energy loss electrode, together with a carefully chosen position of the entrance window to mainta in optimum resolution for two Delta E signals, enable light and heavy ions to be resolved at the same gas pressure. The placement of a sawtooth electr ode within the anode gives position information, which is linear and indepe ndent of atomic number and ion energy. Protons can be identified simultaneo usly with heavy ions by combining the information from the grid and residua l energy signals, both amplified with high gain. (C) 2000 Elsevier Science B.V. All rights reserved.