Impedance of an intense plasma-cathode electron source for tokamak startup

Hinson, Edward Thomas; Barr, Jayson L.; Bongard, Michael W.; Burke, Marcus Galen; Fonck, Raymond J.; Perry, Justin M.

doi:10.1063/1.4952628

Title: Impedance of an intense plasma-cathode electron source for tokamak startup

Journal Article · Tue May 31 00:00:00 EDT 2016 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4952628· OSTI ID:1255444

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Univ. of Wisconsin-Madison, Madison, WI (United States)

In this study, an impedance model is formulated and tested for the ~1kV, ~1kA/cm², arc-plasma cathode electron source used for local helicity injection tokamak startup. A double layer sheath is established between the high-density arc plasma (n_arc ≈ 10²¹ m^-3) within the electron source, and the less dense external tokamak edge plasma (n_edge ≈ 10¹⁸ m^-3) into which current is injected at the applied injector voltage, V_inj. Experiments on the Pegasus spherical tokamak show the injected current, I_inj, increases with V_inj according to the standard double layer scaling I_inj ~ V_inj^3/2 at low current and transitions to I_inj ~ V_inj^1/2 at high currents. In this high current regime, sheath expansion and/or space charge neutralization impose limits on the beam density n_b ~ I_inj/V_inj^1/2. For low tokamak edge density n_edge and high I_inj, the inferred beam density n_b is consistent with the requirement n_b ≤ n_edge imposed by space-charge neutralization of the beam in the tokamak edge plasma. At sufficient edge density, n_b ~ n_arc is observed, consistent with a limit to n_b imposed by expansion of the double layer sheath. These results suggest that n_arc is a viable control actuator for the source impedance.

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Research Organization:: Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: FG02-96ER54375

OSTI ID:: 1255444

Alternate ID(s):: OSTI ID: 1255165

Journal Information:: Physics of Plasmas, Vol. 23, Issue 5; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 8 works

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References (42)

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Public Data Set: Continuous, Edge Localized Ion Heating During Non-Solenoidal Plasma Startup and Sustainment in a Low Aspect Ratio Tokamak Burke, Marcus; Barr, Jayson; Bongard, Michael https://doi.org/10.18138/1336395	dataset	January 2017
Public Data Set: A Power-Balance Model for Local Helicity Injection Startup in a Spherical Tokamak Barr, J. L.; Bongard, M. W.; Burke, M. G. Pegasus Public Data Sets https://doi.org/10.18138/1345037	dataset	May 2018
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Public Data Set: Initiation and Sustainment of Tokamak Plasmas with Local Helicity Injection as the Majority Current Drive Perry, Justin; Bodner, Grant; Bongard, Michael Pegasus-Supplementary information for journal article at DOI: https://doi.org/10.1088/1741-4326/aac72e, 1 file (17.1 MB) https://doi.org/10.18138/1419641	dataset	July 2018
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Public Data Set: Advancing Local Helicity Injection for Non-Solenoidal Tokamak Startup Bongard, Michael; Bodner, Grant; Burke, Marcus University of Wisconsin-Madison https://doi.org/10.18138/1489772	dataset	January 2019
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Cited By (14)

Non-inductively driven tokamak plasmas at near-unity βt in the P egasus toroidal experiment Reusch, J. A.; Bodner, G. M.; Bongard, M. W. Physics of Plasmas, Vol. 25, Issue 5 https://doi.org/10.1063/1.5017966	journal	May 2018
Public Data Set: Impedance of an Intense Plasma-Cathode Electron Source for Tokamak Plasma Startup Hinson, Edward; Barr, Jayson; Bongard, Michael Pegasus-Supplementary information for journal article at DOI: 10.1063/1.4952628, 1 file (11.2 MB) https://doi.org/10.18138/1235552	dataset	October 0168
Public Data Set: H-mode Plasmas at Very Low Aspect Ratio on the Pegasus Toroidal Experiment Thome, Kathreen; Bongard, Michael; Barr, Jayson https://doi.org/10.18138/1236495	dataset	January 2016
Public Data Set: On Virial Analysis at Low Aspect Ratio Bongard, Michael; Barr, Jayson; Fonck, Raymond Pegasus-Supplementary information for journal article at DOI: 10.1063/1.4959808, 1 file (440 KB) https://doi.org/10.18138/1240359	dataset	July 2016
Public Data Set: A Novel, Cost-Effective, Multi-Point Thomson Scattering System on the Pegasus Toroidal Experiment Schlossberg, D. J.; Bodner, G. M.; Reusch, J. A. AIP - Review of Scientific Instruments, Vol. 87, Issue 11, 49.6 MB https://doi.org/10.18138/1257860	dataset	September 2016
Public Data Set: Control and Automation of the Pegasus Multi-point Thomson Scattering System Bodner, Grant; Bongard, Michael; Fonck, Raymond Pegasus, 13 files https://doi.org/10.18138/1257971	dataset	January 2016
Public Data Set: Erratum: "Multi-point, high-speed passive ion velocity distribution diagnostic on the Pegasus Toroidal Experiment" [Rev. Sci. Instrum. 83, 10D516 (2012)] Burke, Marcus; Fonck, Raymond; Bongard, Michael https://doi.org/10.18138/1259852	dataset	January 2016
Public Data Set: Continuous, Edge Localized Ion Heating During Non-Solenoidal Plasma Startup and Sustainment in a Low Aspect Ratio Tokamak Burke, Marcus; Barr, Jayson; Bongard, Michael https://doi.org/10.18138/1336395	dataset	January 2017
Public Data Set: A Power-Balance Model for Local Helicity Injection Startup in a Spherical Tokamak Barr, J. L.; Bongard, M. W.; Burke, M. G. Pegasus Public Data Sets https://doi.org/10.18138/1345037	dataset	May 2018
Public Data Set: Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment Reusch, Joshua; Bodner, Grant; Bongard, Michael Pegasus-Supplementary information for journal article at DOI: 10.1063/1.5017966, 1 file (5.1 MB) https://doi.org/10.18138/1410490	dataset	March 2018
Public Data Set: Initiation and Sustainment of Tokamak Plasmas with Local Helicity Injection as the Majority Current Drive Perry, Justin; Bodner, Grant; Bongard, Michael Pegasus-Supplementary information for journal article at DOI: https://doi.org/10.1088/1741-4326/aac72e, 1 file (17.1 MB) https://doi.org/10.18138/1419641	dataset	July 2018
Public Data Set: Radially Scanning Magnetic Probes to Study Local Helicity Injection Dynamics Richner, Nathan; Bongard, Michael; Fonck, Raymond Pegasus-Supplementary information for journal article at DOI: 10.1063/1.5036527, 1 file (9.4 MB) https://doi.org/10.18138/1432455	dataset	July 2018
Public Data Set: Spatial Heterodyne Spectroscopy for High Speed Measurements of Stark Split Neutral Beam Emission in a High Temperature Plasma Burke, Marcus; Fonck, Raymond; McKee, George University of Wisconsin-Madison https://doi.org/10.18138/1435641	dataset	January 2018
Public Data Set: Advancing Local Helicity Injection for Non-Solenoidal Tokamak Startup Bongard, Michael; Bodner, Grant; Burke, Marcus University of Wisconsin-Madison https://doi.org/10.18138/1489772	dataset	January 2019

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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Title: Impedance of an intense plasma-cathode electron source for tokamak startup

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References (42)

Cited By (14)

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