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Title: A comparison of ion beam measurements by retarding field energy analyzer and laser induced fluorescence in helicon plasma devices

Both Laser-Induced Fluorescence (LIF) and Retarding Field Energy Analyzers (RFEA) have been applied to the investigation of beams formed in inductively coupled helicon plasmas. While the LIF technique provides a direct measurement of the velocity distribution in the plasma, the RFEA measures ion flux as a function of a retarding potential. In this paper, we present a method to compare the two techniques, by converting the LIF velocity distribution to an equivalent of a RFEA measurement. We applied this method to compare new LIF and RFEA measurements in two different experiments; the Hot Helicon Experiment (HELIX) - Large Experiment on Instabilities and Anisotropies (LEIA) at West Virginia University and Njord at University of Tromsø. We find good agreement between beam energies of the two methods. In agreement with earlier observations, the RFEA is found to measure ion beams with densities too low for the LIF to resolve. In addition, we present measurements of the axial development of the ion beam in both experiments. Beam densities drop exponentially with distance from the source, both in LIF and RFEA measurements. The effective quenching cross section from LIF in LEIA is found to be σ{sub b,*}=4×10{sup −19} m{sup 2}, and the effective beam collisionalmore » cross sections by RFEA in Njord to be σ{sub b}=1.7×10{sup −18} m{sup 2}.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [2]
  1. Department of Physics and Technology, UiT The Arctic University of Norway, 9037 Tromsø (Norway)
  2. Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22408253
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANISOTROPY; COMPARATIVE EVALUATIONS; CROSS SECTIONS; FLUORESCENCE; ION BEAMS; LASERS; PLASMA; PLASMA INSTABILITY; QUENCHING