PPPL-3356 is available in <a href="PPPL-3356.pdf">pdf</a> or 
<a href="PPPL-3356.ps">postscript</a> formats.

<p>
<b>A Fast Shutdown Technique for Large Tokamaks</b></p>

<p><b>Authors:</b> S.C. Jardin, G.L. Schmidt, E.D. Fredrickson, K.W. Hill, J. Hyun, B.J. Merrill, and R. Sayer</p>

<p>
<b>Date:</b> September 1999</p>

<p><b>Published in:</b> Nucl. Fusion <b>40</b> (May 2000) 923-933.</p>

<p>
A practical method is proposed for the fast shutdown of a large, ignited tokamak. The method consists of injecting a rapid series of 30-50 deuterium pellets doped with a small (0.0005%) concentration of Krypton impurity, and simultaneously ramping the plasma current and shaping fields down over a period of several seconds using the poloidal field system. Detailed modeling with the Tokamak Simulation Code using a newly developed pellet mass deposition model shows that this method should terminate the discharge in a controlled and stable way without producing significant numbers of runaway electrons. A partial prototyping of this technique was accomplished in TFTR.
</p>