Lithium Surface Coatings for Improved Plasma Performance in NSTX Page: 4 of 30
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
I. INTRODUCTION
The National Spherical Torus Experiment [1] (NSTX) research on lithium-coated
plasma facing components (PFC) is the latest step in a research program to develop
liquid lithium for providing a self-healing plasma facing surface in a DT reactor. [2] The
initial NSTX lithium research is aimed towards sustaining the current non-inductively in
H-mode plasmas, which requires control of both secular density rises and impurity
influxes. Motivated by the long range potential of lithium PFCs, NSTX has been
investigating lithium coatings for density control and impurity control as part of a
phased, three-part approach to lithium PFCs: first with lithium pellet injection, then with
lithium evaporators, and finally with a liquid lithium divertor. This phased approach is
allowing NSTX control systems, diagnostics, and research to be adapted to lithium-
improved wall conditions. Under these conditions, deuterium ions and neutrals incident
on solid lithium PFCs can react to form lithium deuteride (LiD), which remains in the
lithium unavailable for recycling. This is in contrast to molecular deuterium, which is not
gettered, and can recycle. This behavior of ions and neutrals provides a pumping effect
over the plasma wetted area for a wide range in plasma density and shape, and this is
the basis for the control of wall recycling and impurities being investigated in this work.
II. EXPERIMENT DESCRIPTION
NSTX capabilities presently include Ro < 0.85 m, a < 0.67 m, R/a > 1.26, k < 2.7,
d < 0.8, IP < 1.5 MA, BT < 0.3T, and 1.5 sec maximum pulse length. Copper passive
stabilizer plates, graphite power handling surfaces, 7 MW of deuterium Neutral Beam
heating, 6 MW of 30 MHz High Harmonic Fast Wave (HHFW) for heating and current
drive at 10-20 OlCRF provide additional experimental versatility. The 0.2 m radius center
stack (CS) is clad with alternating vertical columns of 1.3 cm thick graphite (Union
Carbide, Type ATJ) tiles between columns of 2-D Carbon Fiber Composite (CFC)
(Allied Signal, Type 865-19-4) tiles. The inner divertor tiles are 5.1 cm thick graphite; the
outer divertor and passive stabilizer plate tiles are 2.5 cm thick graphite. The plasma
facing components (PFCs) are conditioned as required using bakeout at 350 , He Glow
Discharge Cleaning (HeGDC) and boronization. [3] A sabot-style Lithium Pellet Injector
(LPI) can inject lithium, other low-Z pellets, or powders into edge plasmas. [4] The2
Upcoming Pages
Here’s what’s next.
Search Inside
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Kugel, H. W.; Ahn, J.-W.; Allain, J. P.; Bell, R.; Boedo, J.; Bush, C. et al. Lithium Surface Coatings for Improved Plasma Performance in NSTX, report, February 19, 2008; Princeton, New Jersey. (https://digital.library.unt.edu/ark:/67531/metadc935488/m1/4/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.