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Profiles Variations in NSTX-U and their Potential Impact on Equilibrium and Stability

NSTX-U. Supported by. Profiles Variations in NSTX-U and their Potential Impact on Equilibrium and Stability. Magnetoboss. Coll of Wm & Mary Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Lehigh U Nova Photonics ORNL PPPL Princeton U Purdue U

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Profiles Variations in NSTX-U and their Potential Impact on Equilibrium and Stability

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  1. NSTX-U Supported by Profiles Variations in NSTX-U and their Potential Impact on Equilibrium and Stability Magnetoboss Coll of Wm & Mary Columbia U CompX General Atomics FIU INL Johns Hopkins U LANL LLNL Lodestar MIT Lehigh U Nova Photonics ORNL PPPL Princeton U Purdue U SNL Think Tank, Inc. UC Davis UC Irvine UCLA UCSD U Colorado U Illinois U Maryland U Rochester U Tennessee U Tulsa U Washington U Wisconsin X Science LLC Culham Sci Ctr York U Chubu U Fukui U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu Tokai U NIFS Niigata U U Tokyo JAEA Inst for Nucl Res, Kiev Ioffe Inst TRINITI Chonbuk Natl U NFRI KAIST POSTECH Seoul Natl U ASIPP CIEMAT FOM Inst DIFFER ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching ASCR, Czech Rep 12/6/2013

  2. What was done… • ISOLVER-TRANSP • Scale existing electron density profiles, use Zeff=2 to derive ion density profiles. • Use Chang-Hinton model for ion transport, scale electron temperature to give a desired H98 or HST. • NUBEAM for the beam heating, torque, and current drive. • ISOLVER to compute self-consistent internal equilibrium • Run simulations long enough that the simulations reach steady state, and only use the steady state part of the solution. • Stand-alone ISOLVER • Used input pressure and current (ff’) profiles from various NSTX shots. • Range of shots taken to give a wide range in li. • Auto-generate thousands of equilibria with different shapes to look for trends in the PF requirements.

  3. For Relaxed Scenarios, the Thermal Pressure Peaking Strongly Impacts the Equilibrium Parameters 1.0 MA, 1.0 T, Pinj=12.6 MW, near non-inductive 1.6 MA, 1.0 T, Pinj=10.2 MW, partial inductive 1.2 MA, 0.55 T, Pinj=12.4 MW, high bT All: fGW=0.7, H98y,2=1 • Concerns: n=0 stability and control (VDE, boundary) and n=1 (core kink/tearing) • Regardless of the target, too much thermal pressure peaking will drive li too high. • And values above 2.3 will probably be unacceptable for n=0 (next slide) • (note, li reaches approximate steady state faster than qmin). • When pushing to higher IN (or lower q95), broader thermal profiles will allow the final qmin to equilibrate above 1.

  4. Vertical Stability May Provide Limitations on Global Stability With Narrower Profiles • Empirically, IPF-3U/IPF-5<0.25 Leads to a VDE. • (These had ~9 kA of PF-5 Before the VDE) • Use stand-alone ISOLVER simulation of NSTX-U • Scan many values of d, k, dr-sep, for each of a large number of profile shapes. • Plot the PF-3 to PF-5 ratio for all the cases Vertical Control Good Vertical Control Bad

  5. Rules For NBCD… fGW~0.55 • Call the sources by the tangency radius • 50 cm: old source C • 60 cm: old source B • 70 cm: old source A • New beams at 110 cm, 120 cm, 130 cm • Highest core NBCD efficiency: • 110 cm, 120 cm • Highest mid-radius NBCD efficiency: • 130 cm • Lowest total NBCD efficiency: 50 cm • Then 60 cm, then 70 cm • Want to maximize NBCD? • Use 110 cm, 120 cm, 130 cm • But will be dominant in the core. • Want to minimize NBCD? • use 50 cm, 60 cm • Want to raise qmin with 4 sources? • use 50, 60, 70, 130 • Want to lower qmin with 4 sources? • use 60, 70, 110, 120 110 cm 70 cm 120 cm 130 cm 60 cm 50 cm fGW~1 70 cm 60 cm 120 cm 50 cm 110 cm 130 cm

  6. At BT=0.75 T, Significant Variation in the Current Profile May be Possible: fGW=0.7 4 Source Combinations at Fixed Current IP=800kA, fGW=0.74 4 Source Combinations at 100% NI Fraction

  7. At BT=0.75 T, Significant Variation in the Current Profile May be Possible: Varying fGW 4 Source Combinations at Fixed Current IP=800kA, fGW=0.74 4 Source Combinations at Fixed Current IP=800kA, fGW=0.6

  8. A Small Amount of Fast Ion Diffusion Might Be Good!

  9. It MAY be Possible to Generate Large Changes in the Rotation Profiles • Details of torque profile depend on the density. • No predictions yet, because so validated momentum transport model. • But note that I Goumiri has a very simple control-oriented model that could be used for prediction soon. fGW~1 fGW~0.55 110 cm 120 cm 120 cm 130 cm 130 cm 110 cm 70 cm 70 cm 60 cm 50 cm 60 cm 50 cm

  10. Optimized Equilibrium For Maintaining High bT(At BT=0.55 T, How Can the Plasma Current Be Maximized with qmin>1?) Target Equilibria: BT=0.55 T, IP=900-1100 kA k=2.9-2.9 bN=5.2-5.9, bT=18-22% qmin=1.2, tflat-top>>tCR Can only work for broad thermal profiles

  11. Key Experimental Questions • Can we use variations in the beams to control qmin? • How does the transport change with qmin? • Does transport get worse as qmin increases at fixed q95? • Can we use the available current drive actuators to maintain profiles consistent with vertical and n=1 stability? • Can we systematically change the rotation shear at the mid-radius/edge (not pedestal) to assess changes in confinement? • Can we optimize the NBCD, profiles, and plasma shape to maximize bN at low-q95? • Same as asking what is the highest bT that we can operate at for longer than a few tCR?

  12. Backup

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