NDLI: First results of a heavy neutral beam probe for space potential measurements of low temperature plasmas

Content Provider	IEEE Xplore Digital Library
Author	Garcia de Gorordo, A. Hallock, G.A. Gentle, K.W.
Copyright Year	2013
Description	Author affiliation: Univ. of Texas at Austin, Austin, TX, USA (Garcia de Gorordo, A.; Hallock, G.A.; Gentle, K.W.)
Abstract	Summary form only given. A Heavy Neutral Beam Probe (HNBP) has been developed for measuring the space potential of the $Helimak^{1}$ low temperature $(T_{e}$ ~ 10 eV) plasma experiment; the HNBP is a variation on the well known Heavy Ion Beam Probe (HIBP) $^{2}$ The HNBP consists of a Na ion beam that was chopped (modulated) before entering a heat pipe neutralizer consisting of Cs vapor; the beam next enters a toroidal magnetic field region where the probing atoms are ionized; the Na ions then follow a path to a calibrated energy analyzer. The calibration and first results have been obtained and will be presented. The Texas Helimak experiment approximates a sheared cylindrical slab intended to study turbulent-driven transport. The dominant magnetic field is toroidal with a weak vertical component. Vertical propagation of turbulence in Helimak is on the order of 1000 m/s and radial electric fields are thought to play a strong role. The HNBP is capable of radial potential measurements, shedding light on sheared flow turbulence. Heavy ion beam probing of low temperature plasmas is difficult because the signal depends on electron impact ionization of the probing beam. With low electron temperature and density $(n_{e}$ ~ 1011 $cm^{-3}),$ the signal expected was in the range of 1-10 nA, and the pure electronics noise was ~2 nA (rms). Because of the very low signal levels that were expected, a phase-sensitive signal processing scheme was implemented to recover the signal from the noise. The modulation was initially implemented as a triangular sweep in order to locate the signal. Once found, an on-off modulation scheme was implemented to increase total signal strength. The detected signal and interpretation will be presented along with noise characterization.
Starting Page	1
Ending Page	1
File Size	96750
Page Count	1
File Format	PDF
ISBN	9781467351713
ISSN	07309244
DOI	10.1109/PLASMA.2013.6635067
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2013-06-16
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Temperature measurement Particle beams Plasma measurements Plasma temperature Particle beam measurements Probes
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Condensed Matter Physics Electrical and Electronic Engineering

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