Advancing local helicity injection for non-solenoidal tokamak startup

Bongard, Michael W.; Bodner, Grant M.; Burke, Marcus G.; Fonck, Raymond J.; Pachicano, Jessica L.; Perry, Justin M.; Pierren, Christopher; Reusch, Joshua A.; Rhodes, Alexander T.; Richner, Nathan J.; Rodriguez Sanchez, Cuauhtemoc; Schaefer, Carolyn E.; Weberski, Justin D.

doi:10.1088/1741-4326/ab17e3

Title: Advancing local helicity injection for non-solenoidal tokamak startup

Journal Article · Wed May 22 00:00:00 EDT 2019 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ab17e3· OSTI ID:1515411

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

Experiments on the A ~ 1 PEGASUS ST are advancing the physics and technology basis of Local Helicity Injection (LHI). LHI injects helicity with relatively intense electron current sources in the plasma edge. It creates high toroidal current, toroidally-averaged tokamak-like plasmas that have been efficiently transitioned to Ohmically driven tokamak plasmas. Tradeoffs between physics and engineering goals are tested with LHI systems on the low-field-side and the high-field-side of PEGASUS, producing plasmas predominantly driven by non-solenoidal induction and DC helicity drive, respectively. An extensive LHI source development campaign comparing active arc sources, passive and gas-effused electrode sources lead to the selection of active arc sources for present and next-step LHI deployments. LHI plasmas with net toroidal current I_p=0.225 MA, T_e>100 eV, and n_e ~ 10¹⁹ m^-3 are attained to date. A predictive 0D power-balance model describes experimental I_p (t) and partitions the active current drive sources. High-frequency MHD activity is found to be present during LHI current drive, in addition to n=1 modes previously found in NIMROD simulation and experiment. A new system of reduced MHD activity was detected where n=1 activity is suppressed, LHI CD efficiency improves, and long-pulse plasmas are sustained with V_IND ~ 0.

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

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FG02-96ER54375

OSTI ID:: 1515411

Journal Information:: Nuclear Fusion, Vol. 59, Issue 7; Related Information: M.W. Bongard, G.M. Bodner, M.G. Burke, R.J. Fonck, J.L. Pachicano, J.M. Perry, C. Pierren, J.A. Reusch, A.T. Rhodes, N.J. Richner, C. Rodriguez Sanchez, C.E. Schaefer, and J.D. Weberski, "Public Data Set: Advancing Local Helicity Injection for Non-Solenoidal Tokamak Startup," DOI: 10.18138/1489772; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 12 works

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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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