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Title: Global equilibrium in electron cyclotron resonance ion sources

Abstract

In electron cyclotron resonance ion sources (ECRISs) the neutral gas density n{sub g} is typically smaller than the plasma density, which is the opposite of many other source cases, for example, radio-frequency ion source for H (plus or minus) production. For the latter, a global model of equilibrium between ambipolar diffusion and ionization gives a firm prediction of the electron temperature T{sub h}. With the purpose of obtaining firm predictions also for ECRIS plasmas, the difficulty of a highly charged ion distribution and of a more complicated model of ambipolar potential {phi} is here taken into account. Using an approximate solution for the highly charged ion density, the global balance equations are written and discussed as a function of {phi}, of the gas density n{sub g}, and of the electron temperature T{sub h}. Some examples of the application of equilibrium balance laws to a typical ECRIS are given.

Authors:
 [1]
  1. INFN-LNL, Viale dell'Universita 2, 35020 Legnaro, Padova (Italy)
Publication Date:
OSTI Identifier:
20778980
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 77; Journal Issue: 3; Conference: 11. international conference on ion sources, Caen (France), 12-16 Sep 2005; Other Information: DOI: 10.1063/1.2169701; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMBIPOLAR DIFFUSION; DENSITY; ECR ION SOURCES; ELECTRON TEMPERATURE; EQUATIONS; EQUILIBRIUM; FORECASTING; ION DENSITY; ION TEMPERATURE; IONS; MATHEMATICAL SOLUTIONS; PLASMA DENSITY; RADIOWAVE RADIATION

Citation Formats

Cavenago, M. Global equilibrium in electron cyclotron resonance ion sources. United States: N. p., 2006. Web. doi:10.1063/1.2169701.
Cavenago, M. Global equilibrium in electron cyclotron resonance ion sources. United States. doi:10.1063/1.2169701.
Cavenago, M. Wed . "Global equilibrium in electron cyclotron resonance ion sources". United States. doi:10.1063/1.2169701.
@article{osti_20778980,
title = {Global equilibrium in electron cyclotron resonance ion sources},
author = {Cavenago, M.},
abstractNote = {In electron cyclotron resonance ion sources (ECRISs) the neutral gas density n{sub g} is typically smaller than the plasma density, which is the opposite of many other source cases, for example, radio-frequency ion source for H (plus or minus) production. For the latter, a global model of equilibrium between ambipolar diffusion and ionization gives a firm prediction of the electron temperature T{sub h}. With the purpose of obtaining firm predictions also for ECRIS plasmas, the difficulty of a highly charged ion distribution and of a more complicated model of ambipolar potential {phi} is here taken into account. Using an approximate solution for the highly charged ion density, the global balance equations are written and discussed as a function of {phi}, of the gas density n{sub g}, and of the electron temperature T{sub h}. Some examples of the application of equilibrium balance laws to a typical ECRIS are given.},
doi = {10.1063/1.2169701},
journal = {Review of Scientific Instruments},
number = 3,
volume = 77,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • The major infrastructures of nuclear physics in Europe adopted the technology of electron cyclotron resonance (ECR) ion sources for the production of heavy-ion beams. Most of them use 14 GHz electron cyclotron resonance ion sources (ECRISs), except at INFN-LNS, where an 18 GHz superconducting ECRIS is in operation. In the past five years it was demonstrated, in the frame of the EU-FP5 RTD project called ''Innovative ECRIS,'' that further enhancement of the performances requires a higher frequency (28 GHz and above) and a higher magnetic field (above 2.2 T) for the hexapolar field. Within the EU-FP6 a joint research activitymore » named ISIBHI has been established to build by 2008 two different ion sources, the A-PHOENIX source at LPSC Grenoble, reported in another contribution, and the multipurpose superconducting ECRIS (MS-ECRIS), based on fully superconducting magnets, able to operate in High B mode at a frequency of 28 GHz or higher. Such a development represents a significant step compared to existing devices, and an increase of typically a factor of 10 for the intensity is expected (e.g., 1 emA for medium charge states of heavy ions, or hundreds of e{mu}A of fully stripped light ions, or even 1 e{mu}A of charge states above 50{sup +} for the heaviest species). The challenging issue is the very high level of magnetic field, never achieved by a minimum B trap magnet system; the maximum magnetic field of MS-ECRIS will be higher than 4 or 5 T for the axial field and close to 2.7 T for the hexapolar field. The detailed description of the MS-ECRIS project and of its major constraints will be given along with the general issues of the developments under way.« less
  • Multiple frequency heating is one of the most effective techniques to improve the performance of Electron Cyclotron Resonance (ECR) ion sources. The method increases the beam current and average charge state of the extracted ions and enhances the temporal stability of the ion beams. It is demonstrated in this paper that the stabilizing effect of two-frequency heating is connected with the suppression of electron cyclotron instability. Experimental data show that the interaction between the secondary microwave radiation and the hot electron component of ECR ion source plasmas plays a crucial role in mitigation of the instabilities.
  • A numerical simulation of the effect of selective light ion cyclotron resonance heating on the charge state distribution of an electron cyclotron resonance (ECR) source running in a gas mixture is presented which gives good agreement with experiments recently performed in this laboratory. It is shown that heating results in enhanced transport of the heated species out of the plasma. Applying this to light ions increases containment of the heavy ones. Applying this method to highly charged ions may yield improvement of the yields of the heated species in the pulsed afterglow mode of ECR ion sources. Numerical simulation showsmore » that the respective ion pulses can be compressed, i.e., shortened and increased in amplitude. Thus higher pulse repetition frequencies seem feasible. This may be of interest in applications. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.« less
  • The experiments described here were performed at a 5 GHz electron-cyclotron-resonance ion source with a magnetic hexapole. The discharge was run in argon. By launching a fast magnetoacoustic wave from the high-field side (end on) we heated hydrogen ions{emdash}present in traces from the residual gas{emdash}at their fundamental ion cyclotron resonance (ICR) frequency of 2.2 MHz with 5 W only. As a consequence the currents of Ar{sup {ital q}+} ions extracted from the source were significantly increased for {ital q}{ge}5 while the currents of lower charged argon ions were decreased, indicating an enhanced plasma confinement. However, a reduction of the hydrogenmore » content in the residual gas resulted in a reversal of the effect of ICR heating. {copyright} {ital 1996 American Institute of Physics.}« less
  • Electron cyclotron resonance ion source (ECRIS) development has progressed with multiple-frequency plasma heating, higher mirror magnetic fields, and better technique to provide extra cold electrons. Such techniques greatly enhance the production of highly charged ions from ECRISs. So far at continuous wave (CW) mode operation, up to 300 e{mu}A of O{sup 7+} and 1.15 emA of O{sup 6+}, more than 100 e{mu}A of intermediate heavy ions for charge states up to Ar{sup 13+}, Ca{sup 13+}, Fe{sup 13+}, Co{sup 14+}, and Kr{sup 18+}, and tens of e{mu}A of heavy ions with charge states to Kr{sup 26+}, Xe{sup 28+}, Au{sup 35+}, Bi{supmore » 34+}, and U{sup 34+} were produced from ECRISs. At an intensity of at least 1 e{mu}A, the maximum charge state available for the heavy ions are Xe{sup 36+}, Au{sup 46+}, Bi{sup 47+}, and U{sup 48+}. An order of magnitude enhancement for fully stripped argon ions (I{ge}60enA) were also achieved. This article will review the ECR ion source progress and discuss key requirement for ECRISs to produce the highly charged ion beams. {copyright} {ital 1998 American Institute of Physics.}« less