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Supported by. Office of Science. XP 1043 – thermal transport in the SOL (FY10 Joint Research Target). College W&M Colorado Sch Mines Columbia U CompX General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U

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  1. Supported by Office of Science XP 1043 – thermal transport in the SOL (FY10 Joint Research Target) College W&M Colorado Sch Mines Columbia U CompX General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics New York U Old Dominion U ORNL PPPL PSI Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Washington U Wisconsin R. Maingi, A.G. McLean, T.K. Gray, J-W. Ahn 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 JAEA Hebrew U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep U Quebec NSTX Mini Results Review Princeton, NJ Sept. 29, 2010

  2. FY2010 JRT on SOL heat transport included analysis of data, development of two-color IR camera, and modeling • Data analyzed from old XPs: 434, 814, 816, 923 (no lithium) • Good Ip, PNBI, flux expansion scans • Mix of low and high triangularity discharges • Presented at PSI and IAEA (T.K. Gray) • Two-color IR camera technique developed (A.G. McLean) • Presented at RSI conference • Comprehensive dataset obtained with two-color camera • Mostly high triangularity discharges, two lithium rates • Modeling done with SOLT code (Myra) and XGC-0 with neoclassical transport (Park, Pankin, Chang) • Oct. 2010 4Q report nearing completion

  3. Complete dataset obtained with 300 mg lithium evaporated between discharges • Goal 1: measure SOL heat flux footprint at high d • NBI scan: 2-6 MW in 1 MW increments at 1.2, 0.8 MA • Ip scan 0.7 – 1.3 MA at 4 MW and Bt=0.45 T • Bt scan from 0.33-0.55 T at 0.8 MA, 4 MW • Made a great dataset for tE scaling analysis • Goal 2: measure heat flux footprint in C-Mod/DIII-D low k, near-DN shape • Got Ip between 0.72-0.8 MA, few NBI levels • Goal 3: measure heat flux footprint as a function of drsep • High d: got data at drsep= 0, -2.5, -5, -7.5, -1 cm • Low d: got data at drsep= -0.7, -1.3 cm • Camera timing and multiple resets complicating analysis

  4. Very nice dataset obtained with 150 mg lithium evaporated between discharges after camera reset problem resolved • Goal 1: measure SOL heat flux footprint at high d • Ip scan 0.7 – 1.3 MA at 4 MW and Bt=0.45 T • Bt scan 0.35, 0.45, 0.55 T at 0.8 MA, 4 MW • Some comparison between 3 and 4 MW discharges • Goal 2: measure heat flux footprint in C-Mod/DIII-D low k, near-DN shape • Got Ip at 0.75 MA, 2 & 3 MW comparison • Goal 3: measure heat flux footprint as a function of drsep • High d: got good data at drsep= 0 and (-20)mm • Analysis in progress with existing 1-D calculation • Implementation of 2-D calculation, and appropriate frame averaging will be implemented during down time

  5. Analysis of existing NSTX data highlighted important empirical dependences • Divertor heat flux footprint width mapped to midplane (lqmid) decreases rapidly with Ip • lqmidindependent of PSOL in low radiated power regimes, and contracts very weakly with flux expansion • Means high flux expansion, from e.g. snowflake or reduced X-point height, can be used to spread the heat flux in the divertor • lqmidprojected at 3 mm for NSTX-Upgrade, with qpeak ~ 24 MW/m2 with flux expansion = 30 • Have not projected to NSTX-U based on “snowflake” yet

  6. Peak heat flux decreases inversely with flux expansion with roughly constant lqmid in NSTX lqdiv increases with flux expansion lqmid stays approximately constant during the scan Gray, PSI10

  7. Heat flux width lqmid largely independent of Ploss in attached plasmas in NSTX Radiative/ Detached Attached Radiative/ Detached Attached • ~ 0.5, fexp ~ 6, Ip= 0.8 MA Peak divertor heat flux increases with Ploss Apparent change in slope near Ploss=4 MW in these conditions, as divertor transitions from a radiative/detached divertor to an attached divertor lqmid relatively independent of Ploss in high heat flux regime All data in this talk averaged over ELMs and before lithium coatings Gray, PSI10

  8. Heat flux width lqmid largely independent of Ploss in attached plasmas in NSTX Radiative/ Detached Attached Radiative/ Detached Attached • ~ 0.5, fexp ~ 6, Ip= 0.8 MA + d ~ 0.7, fexp ~ 16, Ip= 1.2 MA Narrow Ploss plot range Add in high d data Apparent Ip or q95 effect Gray, PSI10

  9. Heat flux width decreases strongly with Ip in NSTX d~ 0.5 fexp~6 PNBI=4 MW • Combined data from dedicated Ip scans in low d and high d discharges • Ip dependence also in DIII-D, JET • Different PNBI and fexp, but previous slides shows no Ploss or fexp effect on lqmid • q95, l|| different • Power law fit: lqmid ~ 3 +/- 0.5 mm @ 2 MA d ~ 0.7 fexp~16 PNBI=6 MW lqmid = 0.91Ip-1.6 Gray, PSI10

  10. New data with lithium confirms main dependences in the absence of lithium • Divertor heat flux footprint width contracts with Ip • lqmidindependent of PSOL in low radiated power regimes, and independent of Bt • lqmiddecreases by ~ 50% in ELM-free discharges enabled through lithium conditioning (analysis in progress) • Analysis of drsep dependence in progress also

  11. Strong inverse Ip dependence of SOL widths observed in discharges with lithium wall coatings • Outer divertor peak heat flux increases with Ip, because both lqdiv and lqmid contract • Data from 150 mg lithium • Consistent with no lithium results • Qualitatively consistent with 300 mg lithium results • Intensity calibration preliminary! 1.2 MA (#141245) 1.0 MA (#141256) 0.8 MA (#141255) preliminary 1.2 MA (#141245) 1.0 MA (#141256) 0.8 MA (#141255) preliminary

  12. SOL width independent of PSOL and Bt • Outer divertor peak heat flux increases with NBI power, but lqdiv and lqmid stay constant • Consistent with no lithium results • Outer divertor peak heat flux, lqdiv and lqmid insensitive to Bt • Intensity calibration preliminary! 6 MW (#138246) 3 MW (#138235) preliminary 0.33 T (#138568) 0.40 T (#138564) preliminary

  13. Drsep and lithium dependences

  14. SUPPLEMENTARY INFORMATION

  15. Divertor peak heat flux evolves during discharge in NSTX Ip flat-top at 0.25 sec (L-H transition at 0.13 sec) Stored energy usually flat-tops after Ip flat-top Density ramps throughout the discharge (large drsep, small ELMs) Peak divertor temperature rise flattens as density rises Outer divertor heat flux peaks when WMHD flat-tops; rolls over as density rises Total outer divertor power relatively constant (i.e. profile broadens) Ip Pheat/10 [MW] WMHD ne DTpeakdiv qpeakdiv Pdiv Use highest values for projections

  16. Simplest 0-D heat flux projection based on power balance extrapolates from measured NSTX heat flux profiles • IR thermography measures heat flux profile qdivout(r) for calculation of divertor power loading: • Define characteristic divertor heat flux scale length, : • Assume related* to characteristic midplane scale length through flux expansion fexp: • Project NSTX-U qpeakdiv: Ip=2 MA, Ploss=10 MW, Bt=1 T, fexp=30 • For Ploss extrapolation, use • Determine dependence of lqmid on external parameters (Ip, Ploss, Bt, flux expansion) from NSTX data (FY10 Joint Research Target) *Loarte, JNM 1999

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