The performance of Electron Cyclotron Resonance Ion Sources (ECRIS), producing high charge state ions from a great variety of elements, has improved dramatically over the past decades, thus enabling significant advances in accelerator-based nuclear physics. The order-of-magnitude performance leaps of ECR ion sources result from improvements to the magnetic plasma confinement, increases in the microwave heating frequency and techniques to stabilize the plasma at high densities. Parallel to the technical development of the ion sources themselves significant effort has been directed into development of their plasma diagnostic tools. We review recent results of ECRIS plasma diagnostics including e.g. wall and plasma bremsstrahlung, optical emission spectroscopy, measurement of the electron energy distribution as well as various time-resolved measurements on conventional and charge breeder ion sources yielding information on ion confinement and production times. Particular attention will be given to techniques used for studying plasma instabilities. The plasma diagnostics experiments and their results are compared to those obtained with fusion mirror machines, being direct ancestors of modern ECR ion sources. The data obtained mostly with the second-generation ECR ion sources operating at frequencies from 10 to 18 GHz are assessed to answer questions such as: “What can we learn from these experiments for the next generation sources?”, and “Which plasma diagnostics experiments should be carried out with the high-performance 3rd generation sources operating at frequencies higher than 20 GHz to pave the way for the next generation sources?”. Finally, we present a conceptual design of a permanent magnet ion source with quadrupole magnetic field topology and describe how this device could be used for validating certain trends emerging from the plasma diagnostics experiments with conventional minimum-B sources and how this information could open the door for source designs based on higher frequencies and stronger magnetic fields.
|Category of your contribution||Fundamental processes in ion source, plasma|