SI DETECTOR PULSE-HEIGHT SHIFT AND MULTIPLE-SCATTERING PROBLEMS IN HEAVY-ION ELASTIC RECOIL DETECTION ANALYSIS

In recent years, a number of groups around the world have optimised an d used heavy ion elastic recoil detection analysis (HIERDA) to study m aterials science problems, which are intractable with other techniques , but HIERDA remains a technique with many unresolved issues. There is no standard methodology for analysing HIERDA spectra and extracting a ccurate depth profiling information. While 'slab' analyses for systems where all the isotopes are resolved work well, other cases with overl apping signals are more difficult to analyse. In attempting to develop a general methodology, a number of physical problems arise which are discussed here. Firstly, there is the problem of the response stabilit y of the Si energy detector as used in both time of flight and energy (ToF-E) and Delta E-E type spectrometers. The problem is worse for ToF -E systems than those using gas ionisation chambers as the radiation d amage of the silicon detector is greater in this case. The second prob lem involves the effects of multiple and plural scattering that are pr obably best estimated using Monte Carlo simulation of the spectra. (C) 1998 Elsevier Science Ltd. All rights reserved.