Dynamic simulations of the interchange instability, ion production, and electron heating processes in an electron cyclotron resonance ion source plasma

Simulations hitherto performed with electron cyclotron resonance (ECR) ion sources (ECRIS) were mostly to predict physical quantities in their steady states. This article explores the time-dependent phenomena such as: interch ange instability, ion production, and electron heating in order to simulate the time variations of hot-electron density, ion-trapping potential well, and core-electron temperature. This study has identified that the oscillati ons of around 1 Hz observable for these plasma parameters are a consequence of the interchange instability suffered by the hot electrons in the outer radial edge of an ECR shell. A pulsation of the ion-trapping potential well was found to take place under the unstable regime, thereby increasing the extractable ion current whenever the depth of the well is reduced due to th e instability-triggered loss of electrons from the confinement. This findin g may be exploited as a new method to obtain pulsed ion beams without pulsi ng the rf power. This article presents a formula for the best operating con dition to achieve the highest steady ion beam currents out of an ECRIS. A s elf-consistent core-electron temperature was also predicted as a function o f time. (C) 2000 American Institute of Physics. [S0034-6748(00)69702-2].