TY - JOUR
T1 - A multichannel magnetic probe system for analysing magnetic fluctuations in helical axis plasmas
AU - Haskey, S. R.
AU - Blackwell, B. D.
AU - Seiwald, B.
AU - Hole, M. J.
AU - Pretty, D. G.
AU - Howard, J.
AU - Wach, J.
PY - 2013/9
Y1 - 2013/9
N2 - The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger, 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, Nucl. Fusion 51, 033001 (2011)]10.1088/0029-5515/ 51/3/033001
AB - The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger, 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, Nucl. Fusion 51, 033001 (2011)]10.1088/0029-5515/ 51/3/033001
UR - http://www.scopus.com/inward/record.url?scp=84885153224&partnerID=8YFLogxK
U2 - 10.1063/1.4819250
DO - 10.1063/1.4819250
M3 - Article
SN - 0034-6748
VL - 84
JO - Review of Scientific Instruments
JF - Review of Scientific Instruments
IS - 9
M1 - 093501
ER -