Results and interpretation of high frequency experiments at 28 GHz in ECR ion sources, future prospects

Abstract

For the needs of future heavy ion accelerators, electron cyclotron resonance ion sources (ECRISs) should be able to deliver higher intensities and higher charge states. The 1e mA level intensity has already been reached by room temperature ECRIS for medium charge states of light elements (O6+, Ar8+). However, such level of intensity for heavy elements (like Pb27+ for CERN/LHC and GSI) requires more powerful ECRIS with higher electron densities (up to 1013 cm−3). On the other hand, an optimized magnetic configuration system has to be used in order to obtain the suitable compromise between the electron confinement and the high flux ion losses. Before the design of the future “high intensity ECRIS,” experiments have been performed with the superconducting SERSE source both at 18 and 28 GHz. After an overview of major results recently obtained, some scaling laws will be presented. Our results show that much larger intensities and charges can be reached with ECRIS. Then, we will show how the next ECRIS generation will look like, based on the scaling laws derived in the above-mentioned experiments.

Limitation of the ECRIS performance by kinetic plasma instabilities (invited)

“…1 demonstrate that the best performance is achieved at 0.7 ≤ B min /B ECR ≤ 0.8, which corresponds approximately the value derived from the semiempirical scaling. 2 The drop of the performance at higher B min /B ECR -ratio is accompanied by the appearance of periodic beam current fluctuations at least in the case of SuSI and JYFL 14 GHz A-ECR. It has been shown 4 that the optimum B min /B ECR -ratio is independent on the extraction mirror field B ext , for example, which indicates that the decrease of the source performance at B min /B ECR ≥ 0.8 is not due to changing plasma confinement.…”

Three-dimensional simulations of ion dynamics in the plasma of an electron cyclotron resonance ion source

“…This development is mainly done by following the semiempirical scaling laws [2]-increasing both the confining magnetic fields of the ECRIS trap and the frequency of the microwave radiation that heats the electrons in the source plasma. Extracted ion currents can be increased by applying various special techniques [3] such as gas mixing, wall coating, afterglow, and other effects.…”

GTS-LHC: A New Source For The LHC Ion Injector Chain

“…This source, the Grenoble Test Source (GTS) [10] [11], uses a traditional minimum-B configuration optimised to obtain a better compromise between plasma confinement and ion losses. The principles of this optimisation was one of the spin-offs of the Innovative ECRIS collaboration [12]. Apart from the improved magnetic field configuration and a larger plasma chamber this source could be adapted into the existing infrastructure in the ion linac building with a minimum of expenditure and modification.…”