Limitations of electron cyclotron resonance ion source performances set by kinetic plasma instabilities

Journal Article · Sun Feb 15 00:00:00 EST 2015 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4906804· OSTI ID:22392353

Laulainen, J.; Komppula, J.; Kronholm, R.; Kalvas, T.; Koivisto, H. ^[1]; Izotov, I.; Mansfeld, D. ^[2]; Skalyga, V. ^[2]

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1. Department of Physics, University of Jyväskylä, 40500 Jyväskylä (Finland)
2. Institute of Applied Physics, RAS, 46 Ul‘yanova St., 603950 Nizhny Novgorod (Russian Federation)

Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropy of the electron energy distribution function stemming from the resonant nature of the electron heating process. Electron cyclotron plasma instabilities are related to non-linear interaction between plasma waves and energetic electrons resulting to strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents observed in several laboratories. It is demonstrated with a minimum-B 14 GHz ECRIS operating on helium, oxygen, and argon plasmas that kinetic instabilities restrict the parameter space available for the optimization of high charge state ion currents. The most critical parameter in terms of plasma stability is the strength of the solenoid magnetic field. It is demonstrated that due to the instabilities the optimum B{sub min}-field in single frequency heating mode is often ≤0.8B{sub ECR}, which is the value suggested by the semiempirical scaling laws guiding the design of modern ECRISs. It is argued that the effect can be attributed not only to the absolute magnitude of the magnetic field but also to the variation of the average magnetic field gradient on the resonance surface.

• OSTI ID: 22392353
• Journal Information: Review of Scientific Instruments, Vol. 86, Issue 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
BEAM CURRENTS
ECR ION SOURCES
ENERGY SPECTRA
GHZ RANGE
MAGNETIC FIELDS
MICROWAVE RADIATION
PERIODICITY
PLASMA INSTABILITY
PLASMA WAVES
SOLENOIDS
TAIL ELECTRONS