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NSTX_U Design Point Studies C Neumeyer 5/4/6

NSTX_U Design Point Studies C Neumeyer 5/4/6. Use of KCOOL to determine SS water cooled capacity… a. TF inner leg J limit b. TF outer leg I limit 2) Plasma shape based on J Menard equilibrium 3) Scan of design points for t_flat ≥ 10s using… a. LN2 (adiabatic 80K to 100C)

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NSTX_U Design Point Studies C Neumeyer 5/4/6

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  1. NSTX_U Design Point Studies C Neumeyer 5/4/6 Use of KCOOL to determine SS water cooled capacity… a. TF inner leg J limit b. TF outer leg I limit 2) Plasma shape based on J Menard equilibrium 3) Scan of design points for t_flat ≥ 10s using… a. LN2 (adiabatic 80K to 100C) b. Sub-cooling (adiabatic -50C to 100C) c. Water cooling (active cooling Tmax = 100C)

  2. TF Inner Leg Water Cooling via KCOOL Steady state: J_cu = 10.1kA/cm2 J_avg = 5.6 kA/cm2 Assumptions: 35% water fraction, 10% insulation fraction, 2 circular coolant passages per turn 10m/s limit on water flow velocity, 100C max T_cu No credit taken for counterflow option

  3. TF Outer Leg Water Cooling via KCOOL Steady state: 121.5kA Pulsed: Assumptions: Existing conductor & cooling hole dimensions except tap added at midplane to create two cooling circuits per outer leg 2) 10m/s limit on water flow velocity, 100C max T_cu

  4. Plasma Shape Seems a bit close based on simplified (non-divertor) shape model Assumptions: Per J Menard, =2.8, =0.6 R0+a_100 =1.474m is 10cm inboard of HHFW antenna guards R0 = 0.903m

  5. Constraints on Scans • Bt flat top for entire Ip≠0 duration • Ip_dot ramp-up = 5MA/s • Ip_dot ramp-down = 10MA/s • Solenoid provides 100% of ramp-up flux based on Hirschman-Neilson • w/Li=0.5 and CE=0.25 • T_max OH & TF conductor = 100C • _max OH & TF conductor = 138MPA (20ksi) • |I_oh| ≤ 24kA, V_oh=+/-8kV (2 anti-parallel strings of 8 PSS) • 36 turn TF coil • V_tf=+/-2kV (2 series x 6 parallel PSS) • Solutions optimized for maximum Ip • Note: Cases run with Ti=Te. However since they are limited by magnetics there • is minimal dependency on confinement model. This assumption was tested at high Ip cases.

  6. Cases Optimizer aims to maximize Ip in each case

  7. Ip vs. Pulse Length

  8. Bt vs. Pulse Length Note: Outer Leg is not limiting

  9. Solenoid Flux vs. Pulse Length

  10. Summary Comments Results do not quite reach Ip and Bt levels from Masa’s strawman Solenoid flux requirement may be less than assumed, need to compare formula used vs. experimental results TF outer legs suit design points arrived at herein but need further enhancement in cooling (method TBD) to go higher in Bt Need to look at outer PF coils long pulse and steady state limits Design points arrived at herein are not strongly coupled to Ti=Te (or not) assumption, because magnetics is limiting and Paux=10MW appears to be sufficient for supplemental NICD during flat top

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