1 / 17

Erosion/redeposition analysis of CMOD Molybdenum divertor and NSTX Liquid Lithium Divertor

Erosion/redeposition analysis of CMOD Molybdenum divertor and NSTX Liquid Lithium Divertor. J.N. Brooks, J.P. Allain Purdue University PFC Meeting MIT, July 8-10, 2009. CMOD Mo tile divertor erosion/redeposition analysis [ w/ D. Whyte, R. Ochoukov (MIT) ].

reid
Télécharger la présentation

Erosion/redeposition analysis of CMOD Molybdenum divertor and NSTX Liquid Lithium Divertor

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Erosion/redeposition analysis of CMOD Molybdenum divertor and NSTX Liquid Lithium Divertor J.N. Brooks, J.P. Allain Purdue University PFC Meeting MIT, July 8-10, 2009

  2. CMOD Mo tile divertor erosion/redeposition analysis [ w/ D. Whyte, R. Ochoukov (MIT) ] • Puzzling results for Mo tile erosion--high net sputtering erosion in apparent contradiction of some models. • REDEP code package (rigorous) analysis of outer divertor conducted. • {New probe diagnostic being implemented-MIT.} • Sheath BPH-3D code applied to very near tangential (~0.6°) magnetic field geometry. • D, B, Mo on Mo, sputtering erosion/transport analyzed, for 600, 800, 1000, 1100 KA shots, and for OH and RF phases. Uses TRIM-SP sputter yield and velocity distribution simulations. • RF induced sheath effect studied. W.R. Wampler et al. J. Nuc.Mat. 266-269(1999)217.

  3. Predicted Mo erosion along CMOD divertor Erosion, nm Erosion, nm Net erosion Gross erosion

  4. Code/data comparison- CMOD divertor Net Erosion DATA (post-exposure tile study-Wampler et al.) WBC • Reasonable code/data agreement

  5. Code/data comparison-CMOD divertor Gross Erosion • Poor code/data agreement (higher code values)

  6. Goals-determine: • Surface temperature limit set by lithium sputtering/runaway and/or evaporation • Lithium density in plasma edge/sol; core plasma contamination potential • Flux of sputtered lithium to carbon surfaces and D-pumping capability. REDEP/WBC NSTX Liquid Lithium Divertor Analysis[with D. Stotler, R. Maingi et al.]

  7. REDEP/WBC LLD Analysis

  8. REDEP/WBC LLD Analysis continued

  9. BPHI-3D Code- NSTX Sheath Analysis at Liquid Lithium Divertor • No magnetic sheath predicted; Debye sheath only

  10. REDEP/WBC code package--computation of sputtered particle transport 3-D, fully kinetic, Monte Carlo, treats multiple (~100) processes: • Sputtering of plasma facing surface from D-T, He, self-sputtering, etc. • Atom launched with given energy, azimuthal angle, elevation angle • Elastic collisions between atom and near-surface plasma • Electron impact ionization of atom→impurity ion • Ionization of impurity ion to higher charge states • Charge-exchange of ion with D0 etc. • Recombination (usually low) • q(E +VxB) Lorentz force motion of impurity ion • Ion collisions with plasma • Anomalous diffusion (e.g., Bohm) • Convective force motion of ion • Transport of atom/ion to core plasma, and/or to surfaces • Upon hitting surface: redeposited ion can stick, reflect, or self-sputter • Tritium co-deposition at surface, with redeposited material • Chemical sputtering of carbon; atomic & hydrocarbon A&M processes

  11. Interesting erosion/redeposition physics for sputtered lithium in the NSTX low-recycle plasma regime studied • Large sputtered-atom ionization mean free path, order of 10 cm • Large Li+1 gyroradius ( ~5 mm), due to relatively low B field • Low collisionality, due to high Te, low Ne •  Kinetic, sub-gyro orbit analysis required (i.e. WBC code)

  12. WBC Simulation of LLD sputtered lithium transport: 50 trajectories shown; 2-D view UEDGE/NSTX GRID • Long mean free paths seen for ionization; subsequent long, complex, ion transport

  13. WBC Simulation of LLD sputtered lithium transport: 50 trajectories shown; 3-D view x = distance along divertor (strike point at zero), y=distance along toroidal field

  14. Gross and net lithium erosion rates along LLD

  15. Liquid Lithium Divertor: Li Transport Results

  16. LLD redeposited lithium ion parameters

  17. CMOD Molybdenum divertor Analysis • Analysis completed for complex, ~1200 sec campaign, with 8 plasma conditions. • Acceptable code/data comparison for net Mo erosion, not good for gross erosion-puzzling result. • RF sheath significant but not a major effect. • Gross rate data via Mo photon emission being re-analyzed (Whyte et al.), WBC analysis will continue as needed. • NSTX Liquid Lithium Divertor Analysis • Results are encouraging- • --Moderate lithium sputtering; no runaway • --About 50% of the lithium is transported to carbon surfaces • --LLD could apparently handle much higher heat flux • Several model enhancements being implemented • Higher temperature case analysis, at ~5.0 seconds • Carbon sputtering of lithium and C/Li material mixing; MD modeling of Li-D-C system (w/ P. Krstic ORNL) • Higher power case-will need further UEDGE analysis Conclusions

More Related