Investigation into the gas mixing effect in ECRIS plasma using Kα and optical diagnostics

Method for estimating charge breeder ECR ion source plasma parameters with short pulse 1+ injection of metal ions

“…Similar conclusion, i.e. increase of n e with the neutral gas pressure, has been drawn when probing ECRIS plasmas with diamagnetic loop [11], K-alpha x-ray emission [24] or 1+ in-flight ionisation in a charge breeder [34]. The behavior of the charge breeding efficiency with the buffer gas pressure can be explained as follows: as the neutral gas feed rate is increased, the enhanced charge exchange rate limits the high charge state ion production whereas ions with low or medium charge state first benefit from the increased plasma density (electron impact ionisation rate) and only at very high neutral gas pressure their production is limited by the charge exchange.…”

“…the increase of the plasma density with the neutral gas pressure. Importantly, these trends are similar to those inferred from other diagnostics such as diamagnetic loop experiments and K-alpha emission [11,24]. The advantage of the CT method over other diagnostics techniques arises from its simplicity; practically all charge breeders are readily equipped with 1+ beam pulsing and N+ beam current (transient) detection apparatus.…”

“…Refs. [11,24,25]), (ii) the support gas feed rate (pressure) which acts on the neutral and electron densities (see e.g. Refs.…”

“…Refs. [24,26]), (iii) the magnetic field minimum B min as it affects the tail of the EED and the occurrence of kinetic plasma instabilities [27][28][29], and (iv) the extraction magnetic field B ext , which allegedly affects the trapping of the hot electrons and the global plasma confinement [30]. For each parameter sweep, a 500 −900 nA K + beam was produced with the 1+ ion source.…”