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TSC time dependent free-boundary simulations of the ACT1 ( aggr phys) plasma and disruptions

This study presents time-dependent simulations of the ACT1 plasma and disruptions using the TSC code. The simulation results are compared to experimental data and adjustments are made to improve agreement. The study also explores the MHD stability of the ACT1 case and investigates thermal and mechanical analyses.

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TSC time dependent free-boundary simulations of the ACT1 ( aggr phys) plasma and disruptions

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  1. TSC time dependent free-boundary simulations of the ACT1 (aggr phys) plasma and disruptions C. Kessel, PPPL ARIES Project Meeting, Jan 23-24, 2012, UCSD

  2. ARIES ACT1 (aggr phys) operating point *the case shown is not the latest, we have done better Ip = 11.25 MA R = 5.5 m a = 1.375 m κ= 2.2 δ = 0.7 IBS = 9 MA (9.4 MA*) ILH = 0.75 MA (0.8 MA*) IFW = 125 kA q(0) ~ 2 qmin ~ 2 q95 = 3.3 li(1) = 0.5 β = 10% n/nGr = 1.0 Wth = 600 MJ (625 MJ*) n(0) = 2.2 x 1020 /m3 n(0)/<n> = 1.3 βN = 5.5 Te,i(0) ~ 38 keV T(0)/<T> = 2.25 Pα = 340 MW PLH = 40 MW PIC = 15 MW Pbrem = 60 MW Pline = 42 MW Pcyc = 17 MW Zeff = 2.18 Tped = 4 keV (4.7 keV*) H98 = 1.6 Use Coppi-Tang L-mode χ model adjusting for pedestal and global τE

  3. Pedestal is slightly low, so it will be increased to ~ 5 keV, and lower Ip Radiated power is slightly high, will reduce by lowering fAr, and then lower H98 as well βN is too high, found that BT was set slightly low, but will also pursue lower T, since <σv> should not change strongly…this would hurt CD efficiency The T(0)/<T> from ASC is pretty low, probably will not meet, but will try other profiles & transport models

  4. Work to do for ACT1, and beyond Make adjustments and document final case for ACT1 Examine parameters against systems code, make corrections or understand differences…..feedback for future system studies Examine other T(rho) profiles and transport models Possibly pass thru TRANSP for ICRF/EC current drive and power deposition (is more critical to ACT2 configuration with much larger power and CD) Examine MHD stability of ACT1 case from TSC Use this case for disruption simulations Begin ACT2 case based on JSOLVER preliminary configuration Are we continuing with the 4 corners study? Is there a ACT3 and ACT4?

  5. Vertical Displacement Event (VDE) Turn off vertical position control at 1055s Plasma contacts wall at 1059 s Plasma goes from H-mode to L-mode from 1059-1060s q95 drops during this phase as plasma scrapes off on wall reaching 1.5-2 by 1060 s Thermal quench is from 1 ms long starting at 1060 s Current quench begins, but does not finish in this simulation

  6. VDE 2 (1) Turn off vertical position control at 1055s (2) Plasma contacts wall at 1059 s (3-4) Plasma goes from H-mode to L-mode from 1059-1060s (4) q95 drops during this phase as plasma scrapes off on wall reaching 1.5-2 by 1060 s (4-5) Thermal quench is from 1 ms long starting at 1060 s (4-5…6) Current quench begins, but does not finish in this simulation 1 3 4 5 4 5 6

  7. Major (or midplane) disruption (MD) Plasma disrupts right from its flattop state, no pre-disrupt evolution, at 1060 s Plasma should contact inboard wall, but this simulation has too large a time step Little vertical motion, will check with smaller time step Thermal quench t = 1059.964s 1060.439s Current quench

  8. How to work with mechanical analysis • Can take moving plasma as input to mechanical codes • Simplest is to take Ip as a wire and just provide global behavior, like Ip(t), Rp(t), Zp(t) • More accurate to use plasma currents on fixed (R,Z) grid as function of time, I(Ri,Zi,t) • For this we want to make the structure model as good as we can albeit axisymmetrically • Right now I have a double-walled VV and tungsten passive stabilizer plates…..thin segmented FW, strong-back, etc. • We can also take the eddy currents in the structures in TSC and evaluate the associated forces, at least for comparison

  9. How do we work with thermal analysis? Although we have not done this before in TSC, we can examine the heat flux on the FW while it evolves and is in contact Use a formula on the parallel heat flux q||(r, Bp, B, λpow, Wdisr) Work like this was done with the DINA code for ITER, Sugihara Nuc Fus 2007

  10. Work to do for disruption simulations • Get flattop plasma established and reduce time step prior to initiating disruption • Get disruption sequence set, ΔtTQ, Thalo, dhalo, halo onset, hyper-resistivity, ΔtCQ,…. • VDE and MD scenarios (fast Ip drop, slow Ip drop, …) • Structure models (materials, temperatures, geometry) • Post-processing of simulation….forces, heat fluxes, other data for mechanical/thermal analysis

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