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XP723: Momentum transport and the effect of rotation on confinement

XP723: Momentum transport and the effect of rotation on confinement. Make use of n=3 NRMP for rotation braking in various degrees Steady-state application: effect of v f on energy confinement; s-s momentum confinement/diffusivity (includes offset)

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XP723: Momentum transport and the effect of rotation on confinement

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  1. XP723: Momentum transport and the effect of rotation on confinement • Make use of n=3 NRMP for rotation braking in various degrees • Steady-state application: effect of vf on energy confinement; • s-s momentum confinement/diffusivity (includes offset) • Perturbative application: Transient determination of momentum • confinement/diffusivity (offset can be ignored) • Make use NTV theory to determine n=3 torque • Main goals of XP were achieved (not enough good shots to • assess reproducibility, no pCHERS) Vf at R=131 cm Vfat center IRWM

  2. Momentum Diffusivity Does Not Show Any Clear Relation to Either Ion or Electron Diffusivities • cf ~ cI indicates importance of ITG modes • ExB suppression of these modes may be the cause of the lack of this relation in NSTX Use EF/RWM coils to control rotation (Er) to reduce ExB suppression Does cf ~ cI relation return?

  3. Run Plan • Use relatively MHD quiescent discharge as baseline • Still deciding: want something that is relatively long “steady-state” (400 ms), including rotation • May want to use a discharge with optimal error field correction developed early in the run • Impurity injection element needs several hundred ms for transport assessment • Establish baseline discharge • Inject impurity in comparison shot to see if non-perturbing (if so, can use impurity injection throughout rest of XP, with comparison shots every so often to check “perturbery” • Two phases of XP • Steady-state application of EF/RWM field to test effect of rotation on energy and impurity transport, determine “steady-state” momentum diffusivity/confinement • Perturbative application of EF/RWM to determine momentum diffusivity & pinch from transients • Space transient applications to be several tf(20-50 ms)

  4. Run Plan (cont’d) • Baseline Shot Development (2-4 discharges) • Determine maximum EF/RWm current for achieving near zero rotation (Imax) • Steady-State • EF/RWM on at 300 ms • Impurity injection at 350 ms • Four conditions (2 shots/condition) – 8 discharges • Shot Condition • 1 IRWM=0 • 2 IRWM=IMAX • 3 IRWM=1/3 IMAX • 4 IRWM=2/3 IMAX

  5. Run Plan (cont’d) • Constant EF/RWM “blips” for transient analysis (total 6 discharges) Shot Condition 1 Imax 2 2/3 Imax 3 1/3 Imax __________________________ • Step-up “blips” (total 4 shots) Shot Condition 1 3 steps 2 2 steps

  6. Run Plan (cont’d) • Step-down “blips” (total 4 shots) Shot Condition • 3 steps • 2 steps Total: 26 shots (a healthy day)

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