On the role of electron energy distribution function in double frequency heating of electron cyclotron resonance ion source plasmas.

Double frequency heating (DFH) is a tool to improve the output of highly charged ions particularly from modern electron cyclotron resonance ion source installations with very high RF-frequencies. In order to gain information on the DFH-mechanism and on the role of the lower injected frequency we have carried out a series of dedicated experiments where we have put emphasis on the creation of a discrete resonance surface also for this lower frequency. Our well-established method of inserting an emissive MD (metal-dielectric) liner into the plasma chamber of the source is used in these experiments as a tool of investigation.

The impact of plasma-wall interaction on the gas mixing efficiency in electron cyclotron resonance ion source.

It is generally accepted that different effects are necessary to explain the gas mixing method of increasing the output of highly charged ions from an ECRIS. The two most important effects are the mass effect and the dilution effect. Their relative weights have not been determined experimentally yet, but it is generally assumed that the mass effect is dominant in standard ECRIS installations with stainless steel plasma chambers.

The influence of the extraction voltage on the energetic electron population of an electron cyclotron resonance ion source plasma.

An influence of the extraction voltage on the high energy slope of bremsstrahlung radiation spectra has been reported in ECRIS experiments, which is not well understood so far. In order to provide more detailed data on this effect, we have measured bremsstrahlung radiation spectra accompanying especially the evolution of highly charge ions (i.e.

Enhanced confinement in electron cyclotron resonance ion source plasma.

Power loss by plasma-wall interactions may become a limitation for the performance of ECR and fusion plasma devices. Based on our research to optimize the performance of electron cyclotron resonance ion source (ECRIS) devices by the use of metal-dielectric (MD) structures, the development of the method presented here, allows to significantly improve the confinement of plasma electrons and hence to reduce losses. Dedicated measurements were performed at the Frankfurt 14 GHz ECRIS using argon and helium as working gas and high temperature resistive material for the MD structures.

Metal-dielectric structures for high power electron cyclotron resonance ion source.

Metal-dielectric (MD)-structures in electron cyclotron resonance ion source (ECRIS) devices (partially) restore the plasma ambipolarity and supply cold electrons to the plasma. Both effects lead to an enhancement of the plasma electron density and temperature and significantly increase the performance of this type of ion source. At the same time, MD-structures are well suited to reduce the heat load on cold masses by Bremsstrahlung radiation.