Theoretical and experimental study of the overdense plasma generation in a miniaturized microwave ion source

Abstract

To understand the plasma evolution mechanism of microwave ion source (MIS), a hybrid discharge heating (HDH) mode is proposed. That mode contains two parts: ignition discharge by surface wave plasma (SWP) and ionization by electron cyclotron resonance. Compared with the traditional electron cyclotron heating (ECH) mode, the HDH mode has a wider scope of application for MIS with a chamber diameter smaller than the cutoff size. The spatio-temporal evolution of electric field, power deposition, electron temperature, and electron density of a miniaturized microwave ion source (MMIS) at Peking University is investigated based on the HDH mode. In addition, the MMIS is optimized based on the theoretical results of the HDH mechanism. Preliminary experiments show that a mixed hydrogen continuous wave beam of up to 25 mA at 30 keV can be extracted with a power efficiency of 25 mA/100 W.

Improvement of miniaturized 2.45 GHz ECR plasma flood gun at PKU

“…However, no discharge occurs under off-resonant magnetic field configuration even when the microwave power reaches 100 W. The current load is measured at the extraction voltage of 0.1 kV and the discharge load is measured at 0 kV. The results can be explained by the hybrid discharge heating mode (HDH) that we proposed earlier [21]. For ECR ion source, the HDH mode divides plasma evolution into two steps, i.e.…”

A new proton injector based on PKU-type 2.45GHz PMECR ion source for BNCT facility

“…Several types of particle ion sources based on 2.45 GHz microwave have been developed here. There are standard ion sources [4,5], miniaturized ion source [6], H2 + /H3 + Cluster ion source [7], Hion source [8], low charged ion source [9] and electron source based on 2.45GHz ECR and surface plasma source (SPS e-gun) [10]. Among the above particle sources, most of them are all permanent magnet type with ceramic microwave matching method except for the SPS e-gun.…”

The High Beam to Power Efficiency Investigation of Miniaturized Microwave Ion Source

“…Using hydrogen to discharge, the maximum total current intensity is 5.8 mA (160 W) 7 . At Peking University (PKU), the researchers started the study of miniaturization of ECRIS since 2012 and developed a miniaturized ion source with the inner diameter of 30 mm and a 20 mA hydrogen beam has been produced with 180 W RF power with this source 1,2 source and their mechanisms is not sufficient, and the relevant research is still in very primary exploratory stage, which greatly limits the further improvement of the performance of the miniaturized 2.45 GHz ECR hydrogen ion source. A hybrid discharged mechanism was proposed and it well explained the processes inside the MIS 2,9 .…”

“…At Peking University (PKU), the researchers started the study of miniaturization of ECRIS since 2012 and developed a miniaturized ion source with the inner diameter of 30 mm and a 20 mA hydrogen beam has been produced with 180 W RF power with this source 1,2 source and their mechanisms is not sufficient, and the relevant research is still in very primary exploratory stage, which greatly limits the further improvement of the performance of the miniaturized 2.45 GHz ECR hydrogen ion source. A hybrid discharged mechanism was proposed and it well explained the processes inside the MIS 2,9 . The miniaturization of the ion source requires a detailed study of working parameters like input power, pressure, magnetic configuration and so on, so that the discharge performance of the ion source can be improved while the ion source is miniaturized.…”