Stripping cross-sections for fast, low charge state ions

The n-body classical trajectory Monte Carlo method has been used to estimate the cross-sections for electron loss from fast, low charge state ions after collision with BeF ₂. The two ions investigated were 20 MeV/u (2.6 GeV) Xe ^q+ and 40 MeV/u (8.4 GeV) Bi ^q+, q=1-12. The systems were chosen because of their relevance to the HYLIFE-II scenario. Single and multiple electron loss cross-sections for up to 10 stripped electrons were computed for each ion charge state. Multiple electron loss accounts for up to 50% of the total cross-section for these low charge state systems. To simulate the charge state evolution of the ions in a reactor focusing chamber, the calculated cross-sections were incorporated into rate equations assuming a BeF ₂ target density of 5×10 ¹³ molecules/cm ³. At a position 3 m into the reactor chamber, incident Xe ⁺ and Bi ⁺ charge states are reduced to less than 1% of the total flux with the dominant charge states being Xe ⁸⁺ and Bi ⁶⁺, respectively.