skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

Plasmas in the Pegasus spherical tokamak are initiated and grown by the non-solenoidal local helicity injection (LHI) current drive technique. The LHI system consists of three adjacent electron current sources that inject multiple helical current filaments that can reconnect with each other. Anomalously high impurity ion temperatures are observed during LHI with T i,OV ≤ 650 eV, which is in contrast to T i,OV ≤ 70 eV from Ohmic heating alone. Spatial profiles of T i,OV indicate an edge localized heating source, with T i,OV ~ 650 eV near the outboard major radius of the injectors and dropping to ~150 eV near the plasma magnetic axis. Experiments without a background tokamak plasma indicate the ion heating results from magnetic reconnection between adjacent injected current filaments. In these experiments, the HeII T i perpendicular to the magnetic field is found to scale with the reconnecting field strength, local density, and guide field, while $${{T}_{\text{i},\parallel}}$$ experiences little change, in agreement with two-fluid reconnection theory. In conclusion, this ion heating is not expected to significantly impact the LHI plasma performance in Pegasus, as it does not contribute significantly to the electron heating. However, estimates of the power transfer to the bulk ion are quite large, and thus LHI current drive provides an auxiliary ion heating mechanism to the tokamak plasma.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  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) (SC-24)
OSTI Identifier:
1361014
Grant/Contract Number:  
FG02-96ER54375
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 7; Related Information: M.G. Burke, J.L. Barr, M.W. Bongard, R.J. Fonck, E.T. Hinson, J.M. Perry, J.A. Reusch, and D.J. Schlossberg, "Public Data Set: Continuous, Edge Localized Ion Heating During Non-Solenoidal Plasma Startup and Sustainment in a Low Aspect Ratio Tokamak," DOI: 10.18138/1336395; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamaks; ion heating; magnetic reconnection; non-solenoidal tokamak plasma startup; helicity injection

Citation Formats

Burke, Marcus G., Barr, Jayson L., Bongard, Michael W., Fonck, Raymond J., Hinson, Edward T., Perry, Justin M., Reusch, Joshua A., and Schlossberg, David J. Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa6f2b.
Burke, Marcus G., Barr, Jayson L., Bongard, Michael W., Fonck, Raymond J., Hinson, Edward T., Perry, Justin M., Reusch, Joshua A., & Schlossberg, David J. Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak. United States. doi:10.1088/1741-4326/aa6f2b.
Burke, Marcus G., Barr, Jayson L., Bongard, Michael W., Fonck, Raymond J., Hinson, Edward T., Perry, Justin M., Reusch, Joshua A., and Schlossberg, David J. Tue . "Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak". United States. doi:10.1088/1741-4326/aa6f2b. https://www.osti.gov/servlets/purl/1361014.
@article{osti_1361014,
title = {Continuous, edge localized ion heating during non-solenoidal plasma startup and sustainment in a low aspect ratio tokamak},
author = {Burke, Marcus G. and Barr, Jayson L. and Bongard, Michael W. and Fonck, Raymond J. and Hinson, Edward T. and Perry, Justin M. and Reusch, Joshua A. and Schlossberg, David J.},
abstractNote = {Plasmas in the Pegasus spherical tokamak are initiated and grown by the non-solenoidal local helicity injection (LHI) current drive technique. The LHI system consists of three adjacent electron current sources that inject multiple helical current filaments that can reconnect with each other. Anomalously high impurity ion temperatures are observed during LHI with Ti,OV ≤ 650 eV, which is in contrast to Ti,OV ≤ 70 eV from Ohmic heating alone. Spatial profiles of Ti,OV indicate an edge localized heating source, with Ti,OV ~ 650 eV near the outboard major radius of the injectors and dropping to ~150 eV near the plasma magnetic axis. Experiments without a background tokamak plasma indicate the ion heating results from magnetic reconnection between adjacent injected current filaments. In these experiments, the HeII T i perpendicular to the magnetic field is found to scale with the reconnecting field strength, local density, and guide field, while ${{T}_{\text{i},\parallel}}$ experiences little change, in agreement with two-fluid reconnection theory. In conclusion, this ion heating is not expected to significantly impact the LHI plasma performance in Pegasus, as it does not contribute significantly to the electron heating. However, estimates of the power transfer to the bulk ion are quite large, and thus LHI current drive provides an auxiliary ion heating mechanism to the tokamak plasma.},
doi = {10.1088/1741-4326/aa6f2b},
journal = {Nuclear Fusion},
number = 7,
volume = 57,
place = {United States},
year = {Tue May 16 00:00:00 EDT 2017},
month = {Tue May 16 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 2 works
Citation information provided by
Web of Science

Save / Share: