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Title: Radially scanning magnetic probes to study local helicity injection dynamics

Abstract

Two new magnetic probes have been deployed on the Pegasus spherical tokamak to study the dynamics of local helicity injection non-solenoidal plasma start-up and current drive. The magnetic radial array probe consists of 15 pickup coils (~5 × 8 mm each) that measure Bz(R) over a 15 cm linear extent. The coils consist of traces embedded in a printed circuit board. Three coil designs are utilized to balance frequency response and coil sensitivity. Helmholtz coil measurements are used to measure coil and full assembly bandwidths (~2 MHz and ~200 kHz, respectively) and sensitivities (0.18/0.35/0.96 mV T-1 s). The magnetic radial scanning probe is an array of Hall effect sensors that measure field strength (|B|177 mT) and direction at 8 spatial points (ΔR = 1.5 cm), supporting the studies of equilibrium field structure and low-frequency (≤5 kHz) current dynamics. It uses commercial surface-mount Hall effect sensors with chip-integrated amplifiers and compensators that are mounted in a 3-D printed frame. Helmholtz coil measurements indicate negligible cross-field gain nonlinearity and provide absolute calibration of the diagnostic. Both probes are constructed as an electrostatically shielded insertable air-side assembly that mounts within a radially translatable ultrahigh vacuum assembly from an existing probe.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
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  1. Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics
Publication Date:
Research Org.:
Univ. of Wisconsin, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1461755
Alternate Identifier(s):
OSTI ID: 1460027
Grant/Contract Number:  
FG02-96ER54375
Resource Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 89; Journal Issue: 10; Related Information: N.J. Richner, M.W. Bongard, R.J. Fonck, J.A. Reusch, and C.E. Schaefer, "Public Data Set: Radially Scanning Magnetic Probes to Study Local Helicity Injection Dynamics," DOI: 10.18138/1432455; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; magnetic probe; helicity injection; local helicity injection; spherical tokamak; tokamak startup; electromagnetic interactions; plasma confinement; data acquisition; coils; electrical circuits; semiconductor devices; carbon based materials

Citation Formats

Richner, Nathan J., Bongard, Michael W., Fonck, Raymond J., Reusch, Joshua A., and Schaefer, Carolyn E. Radially scanning magnetic probes to study local helicity injection dynamics. United States: N. p., 2018. Web. doi:10.1063/1.5036527.
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Richner, Nathan J., Bongard, Michael W., Fonck, Raymond J., Reusch, Joshua A., & Schaefer, Carolyn E. Radially scanning magnetic probes to study local helicity injection dynamics. United States. https://doi.org/10.1063/1.5036527
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Richner, Nathan J., Bongard, Michael W., Fonck, Raymond J., Reusch, Joshua A., and Schaefer, Carolyn E. Thu . "Radially scanning magnetic probes to study local helicity injection dynamics". United States. https://doi.org/10.1063/1.5036527. https://www.osti.gov/servlets/purl/1461755.
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@article{osti_1461755,
title = {Radially scanning magnetic probes to study local helicity injection dynamics},
author = {Richner, Nathan J. and Bongard, Michael W. and Fonck, Raymond J. and Reusch, Joshua A. and Schaefer, Carolyn E.},
abstractNote = {Two new magnetic probes have been deployed on the Pegasus spherical tokamak to study the dynamics of local helicity injection non-solenoidal plasma start-up and current drive. The magnetic radial array probe consists of 15 pickup coils (~5 × 8 mm each) that measure Bz(R) over a 15 cm linear extent. The coils consist of traces embedded in a printed circuit board. Three coil designs are utilized to balance frequency response and coil sensitivity. Helmholtz coil measurements are used to measure coil and full assembly bandwidths (~2 MHz and ~200 kHz, respectively) and sensitivities (0.18/0.35/0.96 mV T-1 s). The magnetic radial scanning probe is an array of Hall effect sensors that measure field strength (|B|177 mT) and direction at 8 spatial points (ΔR = 1.5 cm), supporting the studies of equilibrium field structure and low-frequency (≤5 kHz) current dynamics. It uses commercial surface-mount Hall effect sensors with chip-integrated amplifiers and compensators that are mounted in a 3-D printed frame. Helmholtz coil measurements indicate negligible cross-field gain nonlinearity and provide absolute calibration of the diagnostic. Both probes are constructed as an electrostatically shielded insertable air-side assembly that mounts within a radially translatable ultrahigh vacuum assembly from an existing probe.},
doi = {10.1063/1.5036527},
journal = {Review of Scientific Instruments},
number = 10,
volume = 89,
place = {United States},
year = {Thu Jul 12 00:00:00 EDT 2018},
month = {Thu Jul 12 00:00:00 EDT 2018}
}
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Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
https://doi.org/10.1063/1.5036527
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Citation Metrics:
Cited by: 2 works
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Figures / Tables:

Figure 1 Figure 1: Schematic of the probe and mechanical assembly (not to scale). (a) The mechanical housing/vacuum assembly, rotatable mount, and linear translation stage. (b) The insertable magnetic probe assembly. (c) An expanded view of the sensor assembly and electrostatic shielding.
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Works referenced in this record:

Public Data Set: Radially Scanning Magnetic Probes to Study Local Helicity Injection Dynamics
dataset, July 2018

  • Richner, Nathan; Bongard, Michael; Fonck, Raymond
  • Pegasus-Supplementary information for journal article at DOI: 10.1063/1.5036527, 1 file (9.4 MB)
  • DOI: 10.18138/1432455

Hall probe measurements of the poloidal magnetic field in Compact Toroidal Hybrid plasmas
journal, September 2014

  • Stevenson, B. A.; Knowlton, S. F.; Hartwell, G. J.
  • Review of Scientific Instruments, Vol. 85, Issue 9
  • DOI: 10.1063/1.4894209

Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak
journal, May 2017

  • Burke, M. G.; Barr, J. L.; Bongard, M. W.
  • Nuclear Fusion, Vol. 57, Issue 7, Article No. 076010
  • DOI: 10.1088/1741-4326/aa6f2b

High spatial resolution Hall sensor array for edge plasma magnetic field measurements
journal, September 2005

  • Liu, Yuhong; Maurer, David A.; Navratil, Gerald A.
  • Review of Scientific Instruments, Vol. 76, Issue 9
  • DOI: 10.1063/1.2018628

The upgraded Pegasus Toroidal Experiment
journal, July 2006

H-mode plasmas at very low aspect ratio on the Pegasus Toroidal Experiment
journal, September 2016

Development of internal magnetic probe for current density profile measurement in Versatile Experiment Spherical Torus
journal, November 2014

  • Yang, J.; Lee, J. W.; Jung, B. K.
  • Review of Scientific Instruments, Vol. 85, Issue 11
  • DOI: 10.1063/1.4886429

A Hall sensor array for internal current profile constraint
journal, October 2010

  • Bongard, M. W.; Fonck, R. J.; Lewicki, B. T.
  • Review of Scientific Instruments, Vol. 81, Issue 10
  • DOI: 10.1063/1.3475539

Non-inductively driven tokamak plasmas at near-unity βt in the P egasus toroidal experiment
journal, May 2018

  • Reusch, J. A.; Bodner, G. M.; Bongard, M. W.
  • Physics of Plasmas, Vol. 25, Issue 5
  • DOI: 10.1063/1.5017966

Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torus
journal, October 2012

  • Jeong-hun, Yang; Chung, Kyoung-Jae; An, YoungHwa
  • Review of Scientific Instruments, Vol. 83, Issue 10
  • DOI: 10.1063/1.4739224

Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak
journal, October 2008

  • Ďuran, Ivan; Hronová, Olena; Stöckel, Jan
  • Review of Scientific Instruments, Vol. 79, Issue 10
  • DOI: 10.1063/1.2971209

Measurements of magnetic field fluctuations using an array of Hall detectors on the TEXTOR tokamak
journal, October 2002

  • Ďuran, I.; Stöckel, J.; Mank, G.
  • Review of Scientific Instruments, Vol. 73, Issue 10
  • DOI: 10.1063/1.1502018

Public Data Set: Advancing Local Helicity Injection for Non-Solenoidal Tokamak Startup
dataset, January 2019

  • Bongard, Michael; Bodner, Grant; Burke, Marcus
  • University of Wisconsin-Madison
  • DOI: 10.18138/1489772

Hall Effect Devices
journal, May 1959

Hall Effect Devices
journal, October 2004

Public Data Set: Advancing Local Helicity Injection for Non-Solenoidal Tokamak Startup
dataset, January 2019

  • Bongard, Michael; Bodner, Grant; Burke, Marcus
  • University of Wisconsin-Madison
  • DOI: 10.18138/1489772
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    Works referencing / citing this record:

    Public Data Set: Radially Scanning Magnetic Probes to Study Local Helicity Injection Dynamics
    dataset, July 2018

    • Richner, Nathan; Bongard, Michael; Fonck, Raymond
    • Pegasus-Supplementary information for journal article at DOI: 10.1063/1.5036527, 1 file (9.4 MB)
    • DOI: 10.18138/1432455

    Public Data Set: Spatial Heterodyne Spectroscopy for High Speed Measurements of Stark Split Neutral Beam Emission in a High Temperature Plasma
    dataset, January 2018

    • Burke, Marcus; Fonck, Raymond; McKee, George
    • University of Wisconsin-Madison
    • DOI: 10.18138/1435641

    Public Data Set: Advancing Local Helicity Injection for Non-Solenoidal Tokamak Startup
    dataset, January 2019

    • Bongard, Michael; Bodner, Grant; Burke, Marcus
    • University of Wisconsin-Madison
    • DOI: 10.18138/1489772
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      Figures / Tables found in this record:

      Figure 1 (p. 3)figure
      Figure 2 (p. 3)figure
      Figure 3 (p. 4)figure
      Figure 4 (p. 4)figure
      Figure 5 (p. 4)figure
      Figure 6 (p. 5)figure
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      Figure 8 (p. 6)figure
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