Calculations of charge state distributions of ions passing through the HIPPO gas jet target

We will present calculated charge state distributions of ions passing through the HIPPO helium gas jet target of St. George, a recoil separator at Notre Dame’s Nuclear Science Laboratory. The operation of St. George involves directing a heavy ion beam through HIPPO and using a series of magnets to allow alpha-capture reaction products of a selected charge state to reach the detection system and reject the much more abundant unreacted beam. Charge state efficiency, i.e. the fraction of reaction products that are in the selected charge state, plays a crucial role in the overall efficiency of St. George. To evaluate this efficiency, we use the BREIT code[1] to calculate the charge state distribution of reaction products after passing through the appropriate thickness of helium. This program uses user-supplied cross sections for electron capture and electron loss. Through a comparison between calculated and experimental charge state distributions for different thicknesses of helium gas, we are gaining insight into the accuracy of the BREIT code in predicting charge state distributions.

[1] N. Winckler et al., Nucl. Inst. & Meth. Phys. Res. B 392, 67 (2003).