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Title: Results from the CDX-U Lithium Wall and NSTX Lithium Pallet Injection and Evaporation Experiments

Abstract

CDX-U has been operated with the vacuum vessel wall and limiter surfaces nearly completely coated with lithium, producing dramatic improvements to plasma performance. Discharges achieved global energy confinement times up to 6 ms, exceeding previous CDX-U results by a factor of 5, and ITER98P(y,1) scaling by 2-3. Lithium wall coatings up to 1000 {angstrom} thick were applied between discharges by electron-beam-induced evaporation of a lithium-filled limiter and vapor deposition from a resistively heated oven. The e-beam power was modest (1.6 kW) but it produced up to 60 MW/m2 power density in a 0.3 cm{sup 2} spot; the duration was up to 300 s. Convective transport of heat away from the beam spot was so effective that the entire lithium inventory (140 g) was heated to evaporation (400-500 C) and there was no observable hot spot on the lithium surface within the beam footprint. These results are promising for use of lithium plasma-facing components in reactor scale devices. Lithium coating has also been applied to NSTX carbon plasma-facing surfaces, to control the density rise during long-duration H-modes for non-inductive current sustainment. First, lithium pellets were injected into sequences of Ohmically heated helium plasmas in both center stack limiter (CSL) and lowermore » single-null divertor (LSND) configurations to deposit a total of 25-30 mg of lithium on the respective plasma contact areas. In both cases, the first subsequent L mode, deuterium discharge with NBI showed a reduction in the volume-average density by a factor {approx}3 compared to similar discharges before the lithium coating. Recently, a lithium evaporator was installed aimed toward the graphite tiles of the lower center stack and divertor. Twelve depositions, ranging from about 10 mg to 5 g of lithium, were performed. The effects on LSND L-mode, double-null divertor (DND) H-mode, and DND reversed-shear plasmas were variable but, immediately after coating, there were decreases in the density and significant increases in electron and ion temperature, neutron rate, confinement time, and edge flow velocity, and reductions in H-mode ELM frequency. For several days of operation after lithium coating, the ratio of oxygen to carbon emission was lower than with boronization.« less

Authors:
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Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
897942
Report Number(s):
UCRL-CONF-225210
TRN: US200706%%139
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: 21st IAEA Fusion Energy Conference, Chengdu, China, Oct 16 - Oct 21, 2006
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CONFINEMENT TIME; DEUTERIUM; EVAPORATION; GRAPHITE; HELIUM; HOT SPOTS; IAEA; ION TEMPERATURE; LITHIUM; POWER DENSITY; REVERSED SHEAR; THERMONUCLEAR REACTORS

Citation Formats

Majeski, R, Kugel, H, Bell, M, Bell, R, Beiersdorfer, P, Bush, C, Doerner, R, Gates, D, Gray, T, Kaita, R, LeBlanc, B, Maingi, R, Mansfield, D, Menard, J, Mueller, D, Paul, S, Raman, R, Roquemore, A, Skinner, C, Sabbagh, S, Souskhanovskii, V, Spaleta, J, Stevenson, T, Timberlake, J, and Zakharov, L. Results from the CDX-U Lithium Wall and NSTX Lithium Pallet Injection and Evaporation Experiments. United States: N. p., 2006. Web.
Majeski, R, Kugel, H, Bell, M, Bell, R, Beiersdorfer, P, Bush, C, Doerner, R, Gates, D, Gray, T, Kaita, R, LeBlanc, B, Maingi, R, Mansfield, D, Menard, J, Mueller, D, Paul, S, Raman, R, Roquemore, A, Skinner, C, Sabbagh, S, Souskhanovskii, V, Spaleta, J, Stevenson, T, Timberlake, J, & Zakharov, L. Results from the CDX-U Lithium Wall and NSTX Lithium Pallet Injection and Evaporation Experiments. United States.
Majeski, R, Kugel, H, Bell, M, Bell, R, Beiersdorfer, P, Bush, C, Doerner, R, Gates, D, Gray, T, Kaita, R, LeBlanc, B, Maingi, R, Mansfield, D, Menard, J, Mueller, D, Paul, S, Raman, R, Roquemore, A, Skinner, C, Sabbagh, S, Souskhanovskii, V, Spaleta, J, Stevenson, T, Timberlake, J, and Zakharov, L. Thu . "Results from the CDX-U Lithium Wall and NSTX Lithium Pallet Injection and Evaporation Experiments". United States. https://www.osti.gov/servlets/purl/897942.
@article{osti_897942,
title = {Results from the CDX-U Lithium Wall and NSTX Lithium Pallet Injection and Evaporation Experiments},
author = {Majeski, R and Kugel, H and Bell, M and Bell, R and Beiersdorfer, P and Bush, C and Doerner, R and Gates, D and Gray, T and Kaita, R and LeBlanc, B and Maingi, R and Mansfield, D and Menard, J and Mueller, D and Paul, S and Raman, R and Roquemore, A and Skinner, C and Sabbagh, S and Souskhanovskii, V and Spaleta, J and Stevenson, T and Timberlake, J and Zakharov, L},
abstractNote = {CDX-U has been operated with the vacuum vessel wall and limiter surfaces nearly completely coated with lithium, producing dramatic improvements to plasma performance. Discharges achieved global energy confinement times up to 6 ms, exceeding previous CDX-U results by a factor of 5, and ITER98P(y,1) scaling by 2-3. Lithium wall coatings up to 1000 {angstrom} thick were applied between discharges by electron-beam-induced evaporation of a lithium-filled limiter and vapor deposition from a resistively heated oven. The e-beam power was modest (1.6 kW) but it produced up to 60 MW/m2 power density in a 0.3 cm{sup 2} spot; the duration was up to 300 s. Convective transport of heat away from the beam spot was so effective that the entire lithium inventory (140 g) was heated to evaporation (400-500 C) and there was no observable hot spot on the lithium surface within the beam footprint. These results are promising for use of lithium plasma-facing components in reactor scale devices. Lithium coating has also been applied to NSTX carbon plasma-facing surfaces, to control the density rise during long-duration H-modes for non-inductive current sustainment. First, lithium pellets were injected into sequences of Ohmically heated helium plasmas in both center stack limiter (CSL) and lower single-null divertor (LSND) configurations to deposit a total of 25-30 mg of lithium on the respective plasma contact areas. In both cases, the first subsequent L mode, deuterium discharge with NBI showed a reduction in the volume-average density by a factor {approx}3 compared to similar discharges before the lithium coating. Recently, a lithium evaporator was installed aimed toward the graphite tiles of the lower center stack and divertor. Twelve depositions, ranging from about 10 mg to 5 g of lithium, were performed. The effects on LSND L-mode, double-null divertor (DND) H-mode, and DND reversed-shear plasmas were variable but, immediately after coating, there were decreases in the density and significant increases in electron and ion temperature, neutron rate, confinement time, and edge flow velocity, and reductions in H-mode ELM frequency. For several days of operation after lithium coating, the ratio of oxygen to carbon emission was lower than with boronization.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2006},
month = {10}
}

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