The Effects of Electron Energy Distribution and Ionization Cross Section Uncertainty on Charge Breeder Ion Source Diagnostics with Pulsed 1+ Injection

The consecutive transients (CT) method is a plasma diagnostic technique of charge breeder electron cyclotron resonance ion source plasmas. It is based on the short-pulse injection of singly charged ions and the measurement of the resulting transients of the extracted multi-charged ion beams. Here, we study the origin of the large uncertainty bounds yielded by the method to reveal avenues to improve its accuracy. We investigate effects of the assumed electron energy distribution (EED) and the uncertainty inherited from the ionization cross section data of K4+-K12+ ions on the resulting plasma electron density n(e), average energy < E-e >, and the characteristic times of ion confinement tau(q), electron impact ionization tau(q)(inz), and charge exchange tau(q)(cx) provided by the CT method. The role of the EED was probed with Kappa and double-Maxwellian distributions, the latter resulting in a shift of the n(e) and < Ee > distributions. The uncertainty of the ionization cross section sigma(inz)(q -> q+1) was artificially curtailed to investigate its impact on values and uncertainties of the plasma parameters. It is demonstrated that the hypothetical perfect knowledge of sigma(inz)(q -> q+1) significantly reduces the uncertainties of tau(q), tau(q)(inz), and tau(q)(cx), which motivates the need for improved cross section data.