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Motivation: Li Flux (powder) >> Li Flux (Evaporation).

Can We Use Lithium More Aggressively and More Effectively for the Control of NSTX Density ?. Motivation: Li Flux (powder) >> Li Flux (Evaporation). Powder deposition allows quick On and Off. LITER inflexible - so far.

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Motivation: Li Flux (powder) >> Li Flux (Evaporation).

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  1. Can We Use Lithium More Aggressively and More Effectively for the Control of NSTX Density ? • Motivation: • Li Flux (powder) >> Li Flux (Evaporation). • Powder deposition allows quick On and Off. LITER inflexible - so far. • Lithium power injection experiment success? Did no harm - LPI not the right technology. • Most contemporary Lithium is most effective at reducing ne. LITER did little to reduce ne. • HGDC good for operations LITER and HGDC incompatible - trapped He. • There is another CHEAP technology for the flexible deposition of Lithium.

  2. Jim Irby and the MIT Team

  3. Los Alamos Injector Schematic (Tricos, Wurden and Wang) PZT Shaker 150 – 300 Watts Powder Metal Mesh Plasmadynamic hyperfine dust injector for the National Spherical Torus Experiment Catalin M Tricos et al Rev Scientific Instruments 77,10E304 (2006)

  4. Energy Required to Fully Ionize 1 mg of Li Diameter of particle: 50 mm Mass of particle: 3.67 e-5 mg Number of particles: 28.6 e3 /mg Number of Atoms: 8.68 e19 /mg Energy to Melt: 0.001 kJ/mg Energy to Vaporize: 0.026 kJ/mg Total to Gas: 0.027 kJ/mg Ionization Energies: 0.075 1.05 1.70 kJ/mg Total all States: 2.83 kJ/mg Total Energy Lost: 2.86 kJ/mg (NSTX ~ 250 kJ)

  5. Inboard Candidate Outboard Candidate Three Candidate Locations Shaker Lower Divertor Candidate

  6. Extremely Aggressive Experiment with Upper Single Null Shaker Inboard Candidate Outboard Candidate N.B. Lithium Powder Injected into Outer Strike Point !

  7. Powder Injector Uses • A dropper system could be exploited in several ways - which might ameliorate • the NSTX density rise problem • Continuous real-time injection into SOL of LSN discharge. • Injection into vacuum vessel before plasma breakdown. • (1) Mid-air breakdown or • (2) after dusting the lower divertor. • Injection into last few seconds of HGDC – spreading Lithium while trapping minimal He. • Continuous real-time injection into SOL / strike point of USN discharge. • would not increase non-inductive current fraction as compared to LSN operation. Might • demonstrate density pump-out.*Represents extremely aggressive attempt at pump-out. • * Other reasons for USN Operation (1) Most Lithium upstairs anyway (2) Locating • LITER downstairs could greatly simplify its operation and would allow for Snout Mode • Operation – much more timely deposition of Lithium.

  8. LPI Lithium Powder Li Powder Injected into the SOL Appears to Migrate Preferentially Toward Upper X point – Outside Vessel Center Stack Gas Feed Lower Divertor

  9. Other Potential Uses for a Powder Injection Capability • Injection of other powders – like Boron or Carbon • Boron into HGDC – briefly - covering Iron between shots • Carbon into HGDC – briefly – artificial blooms - density pump-out ? • Physics tests - best place, best amount of Lithium for ELMS reduction. • Does (say) 5 mg into outer strike point USN affect ELMs ? • Is spreading more Lithium around the machine - during HGC-important ? • Can we optimize ELMS ?

  10. Extremely Aggressive Experiment with Upper Single Null Shaker Inboard Candidate Outboard Candidate N.B. Lithium Powder Injected into Outer Strike Point !

  11. 1 2 3 4 Inboard Organ Pipes (Upper)

  12. Organ Pipe Flange (Seen Between TF Busses)

  13. LITERPort

  14. Needed for Outboard Option

  15. Inboard and Outboard Candidates

  16. What We Need to Implement Powder Injector • A timely decision to proceed • (2) A timely decision on candidate location • (3) Drill hole in carbon tile • (4) Install tube and gate valve

  17. Maximum Drop Rate / Hole Mass = 1/2gt2XMass/Sphere sec Sphere Dia Mass/Sphere = 3.7 x 10-5 mg Sphere Dia = 50 mm Mass = 3.6 mg max flux thru one hole sec g = 9.8 m/sec

  18. Hole Diameter = 1.5 Time Particle Diameter (Enough of Traffic Jam to Guarantee Powder Shut Off ?) Dp = 50 mm Dh = 1.5 X Dp = 76 mm

  19. Total Max Flux = Max Flux (Number Holes Exposed) Hole Maximum Total Flux vs Plate Radius 600 160 500 120 400 Plate Radius Number Holes Exposed 80 Flux (mg / sec) 300 Buck Beers Stainless Plate 76 mm hole diameter 23% Open Area 200 40 100 0 0 0 0.2 0.4 0.6 0.8 1.0 Plate Radius (mm)

  20. Possible Tactics to Encourage a Traffic Jam …

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