Study of gasdynamic electron cyclotron resonance plasma vacuum ultraviolet emission to optimize negative hydrogen ion production efficiency

Negative hydrogen ion sources are used as injectors into accelerators and drive the neutral beam heating in ITER. Certain processes in low-temperature hydrogen plasmas are accompanied by the emission of vacuum ultraviolet (VUV) emission. Studying the VUV radiation, therefore, provides volumetric rates of plasma-chemical processes and plasma parameters. In the past, we have used gasdynamic ECR discharge for volumetric negative ion production and investigated the dependencies between the extracted H− current density and various ion source parameters. It was shown that it is possible to reach up to 80 mA/cm2 of negative ion current density with a two electrode extraction. We report experimental studies on negative hydrogen ion production in a high-density gasdynamic ECR discharge plasma consisting of two simple mirror traps together with the results of VUV emission measurements. The VUV-power was measured in three ranges—Lyα, Lyman band, and molecular continuum—varying the source control parameters near their optima for H− production. It was shown that the molecular continuum emission VUV power is the highest in the first chamber while Lyα emission prevails in the second one. Modifications for the experimental scheme for further optimization of negative hydrogen ion production are suggested.peerReviewe

Efficiency investigation of a negative hydrogen ion beam production with the use of the gasdynamic ECR plasma source

Negative hydrogen ion sources are of great demand in modern physics as injectors into accelerators and drivers for neutral beam injectors for fusion devices. It has been shown earlier that the use of the gasdynamic ECR discharge provides the opportunity to extract up to 80 mA/cm2 of negative ion current density. We studied experimentally the volumetric negative hydrogen ion production and vacuum ultraviolet emission in a gasdynamic ECR discharge. The high-density plasma was sustained by the pulsed 37 GHz / 100 kW gyrotron radiation in a magnetic configuration consisting of two consecutive simple mirror traps. The future prospects of the volumetric H– source based on the gasdynamic ECR discharge related to the transition from pulsed to continuous operating mode with the use of an improved magnetic confinement system are discussed. Numerical simulation of the negative hydrogen ion beam extraction at the continuous operating mode facility was performed. Optimal configuration of the extraction electrodes and the electron damping magnets was found.peerReviewe

Status of new developments in the field of high-current gasdynamic ECR ion sources at the IAP RAS

The experimental and theoretical research carried out in the past at the Institute of Applied Physics (IAP RAS) resulted in development of a new type of electron cyclotron resonance ion source (ECRIS) – the gasdynamic ECRIS. The gasdynamic ECRIS features a confinement mechanism in a magnetic trap that is different from Geller’s classical ECRIS confinement i.e. the quasi-gasdynamic one similar to that in fusion mirror traps . Such ion source type has demonstrated good performance producing high current (100-300 mA) multi-charged ion beams with moderate average charge (Z=4-5 for argon) and especially high efficiency for low emittance hydrogen and deuterium beam formation (500 emA current, current density up to 700 emA/cm2 and RMS emittance below 0.07 π·mm·mrad). Experimental studies of gasdynamic ECRIS in a pulsed mode were performed at SMIS 37 facility.The obtained high-level results have stimulated a wide spectrum of research activities devoted to further extension of the gasdynamic ECR source principles to related fields of research and applications. The present report overviews recent investigations at the Ion Sources Laboratory connected with ECR plasma heating by powerful millimeter wave gyrotron radiation. Novel ideas such as using a magnetic field generated by a single coil for plasma quasigasdynamic confinement for proton beams production, applications of a dense ECR plasma for H- generation, development of a new CW gasdynamic ECR source with 28 GHz gyrotron heating among others are discussed.peerReviewe