The effects of electron energy distribution and ionization cross section uncertainty on charge breeder ion source diagnostics with pulsed 1+ injection

Abstract

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 ne, average energy ⟨Ee⟩, and the characteristic times of ion confinement τq, electron impact ionization τinzq, and charge exchange τcxq 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 ne and ⟨Ee⟩ distributions. The uncertainty of the ionization cross section σq→q+1inz was artificially curtailed to investigate its impact on values and uncertainties of the plasma parameters. It is demonstrated that the hypothetical perfect knowledge of σq→q+1inz significantly reduces the uncertainties of τq, τinzq, and τcxq, which motivates the need for improved cross section data.