Diagnostics of a charge breeder electron cyclotron resonance ion source helium plasma with the injection of 23 Na 1+ ions

This work describes the utilization of an injected 23Na1þ ion beam as a diagnostics of the helium plasma of a charge breeder electron cyclotron resonance ion source. The obtained data allows estimating the upper limit for the ion-ion collision mean-free path of the incident sodium ions, the lower limit of ion-ion collision frequencies for all charge states of the sodium ions and the lower limit of the helium plasma density. The ion-ion collision frequencies of high charge state ions are shown to be at least on the order of 1–10 MHz and the plasma density is estimated to be on the order of 1011 cm−3 or higher. The experimental results are compared to simulations of the 23Na1þ capture into the helium plasma. The results indicate that the lower breeding efficiency of light ions in comparison to heavier elements is probably due to different capture efficiencies in which the in-flight ionization of the incident 1þ ions plays a vital role.