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R Raman, B.A. Nelson, D. Mueller1, T.R. Jarboe, M.G. Bell1, J. Menard1, R. Maqueda2 et al.

University of Washington, Seattle1Princeton Plasma Physics Laboratory

2Nova Photonics

Transient CHI StartupXP606 Summary

NSTX Results ReviewPPPL, Princeton, NJ,

26-28 July 2006

Supported byOffice ofScience

College W&MColorado Sch MinesColumbia UComp-XGeneral AtomicsINELJohns Hopkins ULANLLLNLLodestarMITNova PhotonicsNew York UOld Dominion UORNLPPPLPSIPrinceton USNLThink Tank, Inc.UC DavisUC IrvineUCLAUCSDU ColoradoU MarylandU RochesterU WashingtonU Wisconsin

Culham Sci CtrU St. Andrews

York UChubu UFukui U

Hiroshima UHyogo UKyoto U

Kyushu UKyushu Tokai U

NIFSNiigata UU Tokyo

JAERIHebrew UIoffe Inst

RRC Kurchatov InstTRINITI

KBSIKAIST

ENEA, FrascatiCEA, Cadarache

IPP, JülichIPP, Garching

ASCR, Czech Rep

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Implementation of CHI in NSTX

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Hardware improvements since 2005

•Branch 5 plenum volume increased from 0.9cc to 1.2cc-Previously operated most discharges at highest regulator pressure

•MOV ratings increased to support operation up to 1.75kV

-New capacitor snubber installed-Noise spikes during voltage application generally do not exceed 1.8kA

•Response time of capacitor bank current monitor improved

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Parameters partially explored this year

•Varied capacitor bank size-20, 25, 35, 45mF

•Varied injector flux and toroidal field -PF1B from 4400 to 6000A -TF from 0.3T to 0.55T

•Operated most resent discharges at ~1.75kV -1.6 to 1.85kV- ~250V increase from 2005

•Generated up to 160kA of closed flux current -Several discharges contained 150kA -60kA produced in 2005

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Dramatic improvement in closed flux current generation from 2005

120874: 2006 results118326: 2005 results

LRDFIT (J. Menard)

Inj. current

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Movie of a high current discharge

Fast Camera:R. Maqueda &L. Roquemore

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Compared to 2005 results, equilibrium reconstructions are much more robust during the current decay phase after injector current is zero

Plasma and Injector current

EFIT (S. Sabbagh)

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Electron temperature magnitude and time-evolution for Ip ~ 70kA discharges, as in 2005

120814: Black: 8ms, Red: 12ms

120842: Black: 8ms, Red: 10ms

Thomson (B. LeBlanc)

Profile becomes less hollow with timePlasma and Injector current

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Effect of increased edge neutral pressure on current persistence is similar to that seen on HIT-II

119166: Beams conditioning, NBI valve open119167: NBI valve closed119168: NBI valve open, No NB conditioning

Plasma current Vessel neutral pressure

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On HIT-II increased electron density lowers Ip

Discharges repeated without between shot wall conditioning. Two plasma Injector sources for shots 25731 to 25742. One source for remaining shots.

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MOV’s clamp the injector voltage at about 1.75kV

The capacitor bank is discharged into an open load with the snubber disconnected. The MOV’s significantly conduct starting at 1.7kV.

Capacitor Bank Charge Voltage:121699: 1.5kV, 121703:1.7kV, 121704:1.8kV, 121705:1.85kV, 121706: 1.9kV, 121709: 2.0kV

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Record startup current produced in NSTX

• 160 kA produced using transient CHI– Verifies high current feasibility of CHI startup

• High current discharges not yet optimized– Extension to about 300kA should be possible with

present system at 2kV

• Hardware improvements needed– Higher voltage MOVs to allow 2kV operation– Higher power DC charging power supply– 200kW ECH to heat the CHI plasma