High resolution techniques for nuclear reaction narrow resonance width measurements and for shallow depth profiling

Abstract

Numerous problems must be solved in order to measure and use efficiently and with high precision narrow nuclear reaction resonances with widths below some hundreds of eV for proton beams. The various techniques typically involved will be reviewed systematically, with emphasis on thier most critical stages. Their routine use will be described for high resolution depth profiling in the vicinity of the surface, i.e. in the range of some tens to hundreds of Å. It will be shown that many existing facilities may be used for this purpose, specialised and highly sophisticated equipment being necessary only for advanced metrology. The discussion will cover: beam energy spread from single-ended and tandem accelerators and its optimization for proton and 15N beams; target preparation and contamination problems and in particular the contruction of standard targets for overall energy resolution measurements using well known resonances; the peculiar mathematical properties of the Breit-Wigner resonance line shape, in particular with respect to convolution with Gaussians; ion-target interactions, including Doppler effects, energy straggling and Lewis effect; data fitting using particle-solid interaction theories. Examples will be given of experiments relating to nuclei as 1H, 15N, 18O, 27Al.