Using Rutherford backscattering spectroscopy to characterize targets for the Multi-Terawatt (MTW) Laser at LLE*

Rutherford backscattering spectroscopy (RBS) is a useful technique for determining elemental composition and thickness of a target.  In RBS, light ion beams from an accelerator are incident on the target to be studied.  A surface barrier detector is used to study the energy spectrum of the scattered ions.  The energy of the scattered ions depends on the elements in the target, and the width of each peak is related to the elemental layer thickness.  The computer program SIMNRA is used to analyze the scattered ion spectra.   RBS experiments have been performed using the 1.7 MV Pelletron accelerator at SUNY Geneseo to characterize samples from the Multi-Terawatt (MTW) laser at the Laboratory for Laser Energetics (LLE).  Hydrogen and helium beams of several MeV were used determine the composition and thickness of aluminum (Al) and aluminum-iron (Al-Fe) foils, each backed by a plastic layer.  We have been able to measure the layer thickness of each target, as well as determine the ratio of aluminum-to-iron in the Al-Fe target.  The SIMNRA software also allows surface roughness effects to be included in the analysis.