Electron cyclotron resonance plasmas and electron cyclotron resonance ion sources: Physics and technology (invited)

Abstract

Electron cyclotron resonance (ECR) ion sources are scientific instruments particularly useful for physics: they are extensively used in atomic, nuclear, and high energy physics, for the production of multicharged beams. Moreover, these sources are also of fundamental interest for plasma physics, because of the very particular properties of the ECR plasma. This article describes the state of the art on the physics of the ECR plasma related to multiply charged ion sources. In Sec. I, we describe the general aspects of ECR ion sources. Physics related to the electrons is presented in Sec. II: we discuss there the problems of heating and confinement. In Sec. III, the problem of ion production and confinement is presented. A numerical code is presented, and some particular and important effects, specific to ECR ion sources, are shown in Sec. IV. Eventually, in Sec. V, technological aspects of ECR are presented and different types of sources are shown.

Simulation of electron distribution features in the ionization process of an electron cyclotron resonance discharge

“…Due to the potential in production of high-intensity multicharged ion beams, [5][6][7] ECR sources are attracting considerable attention for accelerators, atomic physics experiments, and industrial applications. In contrast to the experimental investigations, numerical simulations of ECR discharge, such as the ionizing characteristics, are less studied.…”

Dynamic regimes of cyclotron instability in the afterglow mode of minimum-Belectron cyclotron resonance ion source plasma

“…The density was not measured in the present afterglow experiment but can be estimated from well-known parameters of steady-state ECRIS plasma discharge. Experiments [22,24] and simulations [25,26] on ECRIS plasmas sustained by 14-18 GHz microwave radiation imply that their electron density, n e , is below 10 12 cm -3 as a maximum i.e. well below the critical density of 2.4 x 10 12 cm -3 .…”

The effect of plasma electrode collar structure on the performance of the JYFL 14GHz electron cyclotron resonance ion source

“…the ions are not magnetized, if on an average f ii =f ci 4 1, where f ii is the ion-ion collision frequency. In ECRIS plasma the f ii can be estimated with the equation presented by Melin et al [6] and Girard et al [6,29], showing that f ii ∝Q 2 Q eff n e =T 3=2 i , where Q is the charge state of the ion, Q eff the effective (mean) charge state of the ion population in the plasma, n e the electron density and T i the ion temperature. Using reasonable assumptions, obtained from experiments with ECRIS plasmas [6,29], the collision frequencies of 40 Ar charge states 1+ and 12+ are 4:3 Â 10 5 and 6:2 Â 10 7 s −1 , for example.…”

“…In ECRIS plasma the f ii can be estimated with the equation presented by Melin et al [6] and Girard et al [6,29], showing that f ii ∝Q 2 Q eff n e =T 3=2 i , where Q is the charge state of the ion, Q eff the effective (mean) charge state of the ion population in the plasma, n e the electron density and T i the ion temperature. Using reasonable assumptions, obtained from experiments with ECRIS plasmas [6,29], the collision frequencies of 40 Ar charge states 1+ and 12+ are 4:3 Â 10 5 and 6:2 Â 10 7 s −1 , for example. The corresponding ion gyrofrequencies range from 1:9 Â 10 5 to 3:8 Â 10 5 s −1 for 1+ and from 2:3 Â 10 6 to 4:6 Â 10 6 s −1 for 12+, when the magnetic field varies between 0.5 and 1 T. With 0.5 T the collision frequency is more than an order of magnitude higher than the gyrofrequency with charge states Q ≥5þ.…”