Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session UI01: Magnetic Confinement Fusion VI
2:00 PM–5:00 PM,
Thursday, October 20, 2022
Room: Ballroom 100 A
Chair: Sebastian De Pascuale, Oak Ridge National Lab
Abstract: UI01.00003 : Low recycling, low collisionality and high performance with lithium conditioning in LTX-β*
3:00 PM–3:30 PM
Presenter:
Anurag Maan
(PPPL)
Authors:
Anurag Maan
(PPPL)
Dennis P Boyle
(Princeton Plasma Physics Laboratory)
George J Wilkie
(Princeton Plasma Physics Laboratory)
Manaure Francisquez
(Princeton Plasma Physics Laboratory)
Dick Majeski
(Princeton Plasma Physics Laboratory)
Robert Kaita
(Princeton Plasma Physics Laboratory)
Santanu Banerjee
(Princeton Plasma Physics Laboratory)
Drew B Elliott
(Oak Ridge National Lab)
William J Capecchi
(University of Wisconsin - Madison)
Christopher J Hansen
(University of Washington)
Shigeyuki Kubota
(University of California, Los Angeles)
Elizabeth Perez
(University of Illinois, Urbana Champaign)
Filippo Scotti
(Lawrence Livermore Natl Lab)
Vlad Soukhanovskii
(Lawrence Livermore Natl Lab)
We report the first observation of access to global recycling (Rw) near 0.5 from the plasma-facing components in the Lithium Tokamak eXperiment Beta (LTX-??), significantly below the minimum Rw ~ 0.85 reported in other devices using Li conditioning. We also observe that with increasing Li coating thickness, the effective particle confinement time ??p* is reduced while energy confinement ??E (at fixed density) increases, with ??E ~ ??p* at the lowest recycling coefficients. Flat Te profiles, first reported in LTX, have been sustained for multiple ??E – another clear signature of access to the low recycling regime. LTX-?? operates with near complete coverage of lithium on its all-metal PFCs, and has achieved LTX-record central Te,i at high plasma currents due to an ohmic power supply upgrade. In a series of experiments with varied Li wall conditioning, estimates of the recycling coefficient have been made using a Lyman-?? array and DEGAS2 modeling. We observe a progressive reduction in Lyman-?? emission with increased lithiumization and an increase in edge Te. The particle flux to the limiting surfaces appears to be significantly reduced in comparison to fluid SOL models, indicating that a large fraction of the SOL ions are mirror trapped. TRANSP calculated collisionality drops more than an order of magnitude below the banana regime boundary, indicating the importance of kinetic effects. Full-f 1x2v gyrokinetic simulations of SOL field lines with the GKEYLL code indicate that the fraction of ions trapped along field lines increases as collisionality drops, as a result of increased lithium evaporation. Predictions of the impact of high trapped ion fraction from GKEYLL are being evaluated with available experimental data. Finally neutral beam heating was implemented in LTX-?? to supplement the ohmic heating, and increases in Te have been measured.
*DE-AC02-09CH11466, DE-AC52-07NA27344. Chris Hansen acknowledges support from USDoE award DE-SC001923
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