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Design Point Studies for next step device National High-heat-flux Advanced Torus Experiment NHTX

Design Point Studies for next step device National High-heat-flux Advanced Torus Experiment NHTX. C Neumeyer 6/8/6. Outline. Background Method Physics Assumptions and Plasma Shapes Engineering Assumptions and Issues - TF inner leg cooling - Heat removal from machine

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Design Point Studies for next step device National High-heat-flux Advanced Torus Experiment NHTX

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  1. Design Point Studies for next step device National High-heat-flux Advanced Torus Experiment NHTX C Neumeyer 6/8/6

  2. Outline • Background • Method • Physics Assumptions and Plasma Shapes • Engineering Assumptions and Issues • - TF inner leg cooling • - Heat removal from machine • - Divertor heat removal • - Power supply utilization • Results • Conclusions

  3. Background: Options Studied • NSTX Center Stack Upgrade ~ 10s pulse • - adiabatic water cooled, sub-cooled, LN2 • - Paux= 10-20MW • - full, partial inductive • - OH coil, iron core • NSTX Center Stack Upgrade ~ 20-60s pulse • - active water cooled • - retain VV, PF coils, TF outer legs • NSTX Upgrade ~ 60s pulse • - replace center stack, PF, TF outer legs • - retain existing VV (kappa*a <=1.3m) • NSTX Replacement ~ 60s pulse • - all new machine Attractive mission: Ip ~ 4MA Bt ~ 1.5T Paux ~ 38MW

  4. Highlights of New Machine • High P/R • - plasma should accept Paux = 32MW NBI + 6MW RF = 38MW • Non-Inductive Sustainment • - solenoid sized for ramp-up flux only • Long Pulse • - active water cooling, 60 second pulse • Full Use of PPPL/TFTR Infrastructure • - full MG energy + grid power • - full PS capacity • - full NBI capacity • Some Incremental Infrastructure Required • - water flow • - 138kV substation

  5. Methodology • XL-based “systems code” using non-linear optimizer (‘Solver”) • Jardin/Kessel physics algorithms used for NSST were starting point • Continued evolution with Peng, Rutherford, Kessel for CTF studies • - See PPPL Report 4165 “Spherical Torus Design Point Studies” • Engineering & physics algorithms tailored to subject situation

  6. Physics Assumptions Solutions maximize Ip*Paux

  7. Range of Cross Sections = 3.674/SQRT(A_100) =0.6 Z=1.3m ~ limit of existing VV Simple limiter shape model: R0+a=1.473

  8. Limiter model vs. Divertor separatrix flux surface from J. Menard equilibria @ A=1.8

  9. Engineering Assumptions

  10. TF Inner Leg Cooling fPacking depends on J_avg and dZ Typical T v. t Adiabatic Cu H20 Possible x-section KCOOL model

  11. Machine Heat Removal TFTR ratings (may not be available anymore TBD)… Water tank = 33000 gallons (adequate) Cooling power = 20MW (adequate) Component cooling = 3300 GPM (~ 1/6 of requirement)

  12. Divertor Heat Removal 4” dia pipes are adequate for divertor supply/return manifolds (assume full power capacity on top and bottom)

  13. Power Supplies Use PS at 15kA per PSS (continuous rating of SCRs) Rep rate limited to ~ 1200s min due to 3.25kA rms rating Xfmrs OK (8 hrs) 5 parallel 750MCM per PSS ~ 50 parallel 1000MCM cables req’d for 200kA-60s/1200s

  14. Results (1)

  15. Results (2)

  16. Results (3)

  17. Results (4) NSTX New

  18. Conclusions • Sweet spot ~ A=1.8 should be pursued • Much work remains to • - develop and prove out physics and engineering aspects of design • - optimize water cooling aspects • Highlighted challenges • - TF bundle torsion and joint • - large water flows • - 200MW from grid • - restoration of MG capability

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