A sensitivity analysis was carried out using a three-dimensional grid erosion analysis code to understand the effect of doubly charged ions on the erosion of an ion acceleration grid. In the preliminary analysis, it was found that the neutral flux value estimated by assuming all the ions to be singly charged has significant errors when the doubly charged ion fraction is non-negligible. Calculations were conducted for the μ10 EM1 ion acceleration grid system, varying the doubly charged ion fraction (0, 0.1, and 0.2), and the experimental and simulation results of the acceleration grid current and acceleration grid mass loss were compared. In the case of doubly charged ion fractions of 0.1 and 0.2, which are similar to the experimental condition, the simulation results were in good quantitative agreement with the experimental data. Calculation results showed that when the doubly charged ion fraction was varied from 0.1 to 0 (0.2), the acceleration grid current and acceleration grid mass loss changed by -14% (+9.5%) and -18% (+32%), respectively. Electron backstreaming was also found to vary with the doubly charged ion fraction; it occurred 14% slower (12% faster) when the doubly charged ion fraction was varied from 0.1 to 0 (0.2). The structural failure of the deceleration grid was less sensitive than electron backstreaming; the deceleration grid eroded 8.3% slower (8.6% faster) when the doubly charged ion fraction was varied from 0.1 to 0 (0.2).
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