Solenoidfree Plasma Startup in NSTX using Transient CHI

1
Liquid Lithium Implications for CHI R. Raman,
T.R. Jarboe Univ. of Washington Li Divertor
Meeting 10 May 2006 B252, PPPL
College WM Colorado Sch Mines Columbia
U Comp-X General Atomics INEL Johns Hopkins
U LANL LLNL Lodestar MIT Nova Photonics New York
U Old Dominion U ORNL PPPL PSI Princeton
U SNL Think Tank, Inc. UC Davis UC
Irvine UCLA UCSD U Colorado U Maryland U
Rochester U Washington U Wisconsin
Culham Sci Ctr U St. Andrews York U Chubu U Fukui
U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu
Tokai U NIFS Niigata U U Tokyo JAERI Hebrew
U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST
ENEA, Frascati CEA, Cadarache IPP, Jülich IPP,
Garching ASCR, Czech Rep
2
CHI Can Benefit From Liquid Lithium

• Once a CHI discharge has formed, it is desirable
  to reduce the electron density
• Allows plasma to heat up
• Eases coupling to RF Current Drive and ECH
  heating
• Li is very well suited for this purpose as it
  pumps atomic hydrogen
• No need to inject much larger amounts of neutral
  gas
• For the purpose of plasma start-up, probably even
  a pure Li plasma is OK (Zakharov)

3
Liquid Li System Design That Incorporates CHI
Needs Would Allow NSTX to Considerably Extend CHI
Capability for Increasing the Magnitude of the
Solenoid-free Plasma Start-up Current

• Reduced Recycling
• Higher Voltage capability with reduced absorber
  arcing

4
Key Elements of Proposed Design Previously Tested
on DIII-D using a Divertor Ring Electrode
Li on top of divertor plates
(1) Li would pump the Absorber region, Improving
the DIII-D design and reducing absorber
arcing. (2) Allows NSTX divertor tiles to be
baked to full temperature (no O-rings needed)
after new design validation. (3) Allows 4kV CHI
capability, considerably increasing CHI
potential, while maintaining present 2kV TF
insulation limits.
Here we have an opportunity to design a truly
novel divertor, allowing exploration of new
areas of important and interesting research that,
in addition to developing Li capability, can
simultaneously enhance NSTX capability for
solenoid-free plasma start-up.