Spatially resolved X-ray spectroscopy of an ECR plasma - indication for evaporative cooling

We have used an X-ray CCD camera in single photon counting mode and a pinhole to obtain spatially and spectrally resolved images of the plasma of an electron cyclotron resonance ion source. Software based on the CERN ROOT package was developed to process and analyse the data. Comparison of plasma images from trapped xenon to that from a xenon-argon mixture provides evidence for evaporative cooling of the ion cloud in ECR ion sources. This results in more localised and highly charged ion clouds when lighter-mass argon gas is added to a heavy-ion xenon plasma. This observation can have implications on the thermodynamics and charge state balance in astrophysical and other laboratory plasmas.