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Title: A multichannel magnetic probe system for analysing magnetic fluctuations in helical axis plasmas

The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger et al., Fusion Technol. 17, 123 (1990)] plasmas has motivated the installation of a sixteen former, tri-axis helical magnetic probe Mirnov array (HMA). The new array complements two existing poloidal Mirnov arrays by providing polarisation information, higher frequency response, and improved toroidal resolution. The helical placement is ideal for helical axis plasmas because it positions the array as close as possible to the plasma in regions of varying degrees of favourable curvature in the magnetohydrodynamic sense, but almost constant magnetic angle. This makes phase variation with probe position near linear, greatly simplifying the analysis of the data. Several of the issues involved in the design, installation, data analysis, and calibration of this unique array are presented including probe coil design, frequency response measurements, mode number identification, orientation calculations, and mapping probe coil positions to magnetic coordinates. Details of specially designed digitally programmable pre-amplifiers, which allow gains and filters to be changed as part of the data acquisition initialisation sequence and stored with the probe signals, are also presented. The low shear heliac geometry [R. Jiménez-Gómez et al., Nucl. Fusion 51, 033001 (2011)], flexibility of the H-1NFmore » heliac, and wealth of information provided by the HMA create a unique opportunity for detailed study of Alfvén eigenmodes, which could be a serious issue for future fusion reactors.« less
Authors:
; ; ; ; ; ;  [1]
  1. Plasma Research Laboratory, Research School of Physical Sciences and Engineering, The Australian National University, Canberra, ACT 0200 (Australia)
Publication Date:
OSTI Identifier:
22220342
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 84; Journal Issue: 9; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLIFIERS; CALIBRATION; DATA ACQUISITION; DATA ANALYSIS; DESIGN; FLUCTUATIONS; GAIN; GEOMETRY; INSTALLATION; MAGNETIC PROBES; MAGNETOHYDRODYNAMICS; MAPPING; PLASMA; PLASMA CONFINEMENT; POLARIZATION; RESOLUTION; STELLARATORS; THERMONUCLEAR REACTORS