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tcsu_magnetics_paper.pdf2011-08-26 16:14:07Katherine Velas
tcsu_magnetics_poster.pdf2011-08-22 16:22:13Katherine Velas

Three-Axis Magnetic Field Measurements in the TCSU RMF Current Drive Experiment

Author: Katherine M. Velas
Requested Type: Poster Only
Submitted: 2011-06-07 17:11:54

Co-authors: Richard D. Milroy

Contact Info:
RPPL, University of Washington
120 AERB
Seattle, WA   98195-2
USA

Abstract Text:
A 3-axis probe was installed on TCSU shortly before its final shutdown. The probe is wound with 2 mil gold plated tungsten wire using a Kapton form. It is covered in a gold electrostatic shield and housed in a thin-wall stainless steel tube, which acts as the vacuum boundary. Teflon provides high voltage insulation and a boron nitride jacket provides the plasma-facing surface. The construction ensures a short field penetration time. The probe assembly has a 5 mm outside diameter, is UHV compatible, and can be baked to 200 degrees C. The probe has 90 windings that simultaneously measure Br, Btheta, and Bz at 30 radial positions and is fully translatable. Moving the probe to multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field.

Initially, data has been processed with a 10 kHz low pass filter to capture the steady field. Higher frequency content has more shot-to-shot variability making it difficult to map these axially. Plans include using a band pass filter to isolate the RMF frequency, which is consistent between shots. It is anticipated that the RMF field, in conjunction with the steady field, will yield a map of the full 3D rotating field structure.

Measurements were made for odd-parity RMF antennas and even-parity RMF antennas at multiple bias field configurations and multiple RMF frequencies. The 3-axis probe measurements are used to calculate the end-shorting torque, which opposes the RMF torque. Data from even- and odd-parity experiments will be compared.

The NIMROD code has been adapted to simulate the TCSU experiment, using boundary conditions adjusted to match both even- and odd-parity experimental conditions [1]. A comparison of the steady n=0 components of the calculated fields to the 3-axis probe measurements shows agreement in the magnetic field structure of the FRC as well as in the toroidal field in the jet region.

[1] R.D. Milroy, C.C. Kim and C.R. Sovinec, "Extended MHD simulations of FRC formation and sustainment with RMF current drive", Phys. Plasmas, 17, 062502 (2010).

Characterization: A1,A3

Comments:

University of Washington

Workshop on Innovation in Fusion Science (ICC2011) and
US-Japan Workshop on Compact Torus Plasma
August 16-19, 2011
Seattle, Washington

ICC 2011