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Title: Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment

Abstract

External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ∼5 ms. The addition of the external copper coils effectively increases this time to ∼7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M. C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each externalmore » coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.« less

Authors:
; ; ; ; ; ;  [1]
  1. Tri Alpha Energy, P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States)
Publication Date:
OSTI Identifier:
22596562
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 87; Journal Issue: 11; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BALANCES; BEAMS; CONFINEMENT TIME; COPPER; FIELD-REVERSED THETA PINCH DEVICES; INDUCTANCE; MAGNETIC FIELDS; PLASMA; PROBES; ROGOWSKI COIL; SKIN; SOLENOIDS; STAINLESS STEELS; SURFACES; WALLS

Citation Formats

Roche, T., E-mail: troche@trialphaenergy.com, Thompson, M. C., Mendoza, R., Allfrey, I., Garate, E., Romero, J., and Douglass, J. Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment. United States: N. p., 2016. Web. doi:10.1063/1.4960061.
Roche, T., E-mail: troche@trialphaenergy.com, Thompson, M. C., Mendoza, R., Allfrey, I., Garate, E., Romero, J., & Douglass, J. Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment. United States. doi:10.1063/1.4960061.
Roche, T., E-mail: troche@trialphaenergy.com, Thompson, M. C., Mendoza, R., Allfrey, I., Garate, E., Romero, J., and Douglass, J. Tue . "Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment". United States. doi:10.1063/1.4960061.
@article{osti_22596562,
title = {Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment},
author = {Roche, T., E-mail: troche@trialphaenergy.com and Thompson, M. C. and Mendoza, R. and Allfrey, I. and Garate, E. and Romero, J. and Douglass, J.},
abstractNote = {External flux conserving coils were installed onto the exterior of the C-2U [M. W. Binderbauer et al., Phys. Plasmas 22, 056110 (2015)] confinement vessel to increase the flux confinement time of the system. The 0.5 in. stainless steel vessel wall has a skin time of ∼5 ms. The addition of the external copper coils effectively increases this time to ∼7 ms. This led to better-confined/longer-lived field-reversed configuration (FRC) plasmas. The fringing fields generated by the external coils have the side effect of rendering external field measurements invalid. Such measurements were key to the previous method of excluded flux calculation [M. C. Thompson et al., Rev. Sci. Instrum. 83, 10D709 (2012)]. A new array of B-dot probes and Rogowski coils were installed to better determine the amount of flux leaked out of the system and ultimately provide a more robust measurement of plasma parameters related to pressure balance including the excluded flux radius. The B-dot probes are surface mountable chip inductors with inductance of 33 μH capable of measuring the DC magnetic field and transient field, due to resistive current decay in the wall/coils, when coupled with active integrators. The Rogowski coils measure the total change in current in each external coil (150 A/2 ms). Currents were also actively driven in the external coils. This renders the assumption of total flux conservation invalid which further complicates the analysis process. The ultimate solution to these issues and the record breaking resultant FRC lifetimes will be presented.},
doi = {10.1063/1.4960061},
journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 11,
volume = 87,
place = {United States},
year = {2016},
month = {11}
}