Influence of the secondary electrons emitted by a cylindrical metal-dielectric structure on the Frankfurt 14 GHz electron cyclotron resonance ion source performances

Abstract

Previous research allowed us to develop highly efficient electron emissive metal-dielectric (MD) structures, which are suitable to be used as sources of secondary electrons in electron cyclotron resonance ion sources (ECRIS). First tests have been performed replacing the stainless steel disk of the Frankfurt 14 GHz ECRIS by a MD structure. This method was recently extended by inserting a MD cylinder (150 mm long and 58 mm in diameter) into this source. The experiments were performed with pure argon as source gas and with gas mixing (argon+oxygen). In this contribution, the performance with MD cylinder is compared to that of the standard source (stainless steel plasma chamber) and to the case, where a cylinder of technical aluminum was installed. With the MD cylinder the yield of highly charged ions from the ECRIS are significantly enhanced. For Ar16+ ion current enhancement factors of up to 50 were obtained.

The influence of ambipolarity on plasma confinement and on the performance of electron cyclotron resonance ion sources

“…It was not the aim to reach the ultimate performance of the source, e.g., by adding other methods, e.g., gas mixing. To what extent this scenario of an ambipolar source with optimized compensation of electron losses can still be improved by applying other methods ͑e.g., gas mixing͒ may be object of future experiments and can be concluded from a study that we have carried out earlier 9 where we have shown that gas mixing in addition to an installed MD liner only gains another factor of not more than 2 compared to the use of the MD liner with pure argon gas.…”

Plasma diagnostics at electron cyclotron resonance ion sources by injection of laser ablated fluxes of metal atoms

“…7 In its present configuration, a metal-dielectric structure (Al 2 O 3 /Al) is inserted into the plasma chamber, 8 which assists us in increasing the output of the highest charge states, at the same time decreasing the output of ions with lower charge states ͑Zр8 for argon͒. The biased disk has been replaced by a л3 mm stainless steel rod inserted axially into the plasma chamber from the microwave injection side of the source.…”