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Understanding and predicting the dynamics of tokamak discharges during startup and rampdowna)
a)Paper TI3 4, Bull. Am. Phys. Soc. 54, 255 (2009).
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View: Figures


Image of FIG. 1.
FIG. 1.

DIII-D experimental simulation of a complete ITER discharge. (a) (V/m, solid black) and normalized current (dash); (b) normalized (dash), (gray) and EC power (solid black); (c) flux consumption and divertor ; and (d) neutral beam power (gray), OH power (solid black), and electron density (, dash). Discharge uses the full-bore startup scenario, diverting at 0.28 s, and the ITER prescribed rampdown scenario. Flux shapes at selected times during the discharge evolution are also shown.

Image of FIG. 2.
FIG. 2.

Breakdown with only OH. (a) Vacuum contours of mod in Gauss at and (b) initial intensity viewed by a fast framing camera at , 3 ms after breakdown, (No. 138138). and .

Image of FIG. 3.
FIG. 3.

Plasma formation and initial startup using a fast framing camera viewing line emission (No. 135899). Time (millisecond), plasma current (kiloampere), and inductive loop voltage (volt) are shown at the bottom of each frame. Parameters are and .

Image of FIG. 4.
FIG. 4.

Abel inversion (at ) of fast camera data in Fig. 3. EC second harmonic radius is shown as a horizontal dotted line.

Image of FIG. 5.
FIG. 5.

(a) Peak line integrated density during the preionization phase and (b) initial current at as a function of vertical field at breakdown. Plotted are radial EC launch with deuterium fill gas (diamond), oblique launch, 24 deg, with deuterium (square), and radial launch with helium (triangle). Two Ohmic discharges (solid squares) that did not burnthrough are also shown. Discharge conditions are and .

Image of FIG. 6.
FIG. 6.

Burnthrough times of selected low impurities for OH startup and startup with EC assist. Times are referenced to start time of heating power, either OH (a) or EC (b).

Image of FIG. 7.
FIG. 7.

(a) Comparison of flux consumption from the start of inductive voltage to current flattop for three discharges: OH only, EC, and NB during the entire current ramp. Plotted are (a) inductive flux, (b) resistive flux, (c) Ejima coefficient (defined in text), and (d) average power during the current ramp.

Image of FIG. 8.
FIG. 8.

Comparison of DIII-D experimental simulation of ITER (black) to ITER modeling (gray) using the DINA code. (a) Elongation, (b) , (c) , and (d) density. [Adapted from Fig. 3 of the Institute of Publishing “Experimental Simulation of ITER Rampdown in DIII-D” (Ref. 12).]

Image of FIG. 9.
FIG. 9.

Stability analysis during rampdown (No. 136327) of an ITER-like discharge. (a) Plasma current, (b) vertical location of current centroid, , (c) growth rate of the mode, and (d) controllability parameter, .


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Understanding and predicting the dynamics of tokamak discharges during startup and rampdowna)