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Title: Demonstration of Tokamak Discharge Shutdown with Shell Pellet Payload Impurity Dispersal

Journal Article · · Physical Review Letters
 [1];  [2];  [3];  [2];  [2];  [4];  [1]
  1. Univ. of California - San Diego, La Jolla, CA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
+ Show Author Affiliations

The first rapid tokamak discharge shutdown using dispersive core payload deposition with shell pellets has been achieved in the DIII-D tokamak. Shell pellets are being investigated as a possible new path toward achieving tokamak disruption mitigation with both low conducted wall heat loads and slow current quench. Conventional disruption mitigation injects radiating impurities into the outer edge of the tokamak plasma, which tends to result in poor impurity assimilation and creates a strong edge cooling and outward heat flow, thus requiring undesirable high-$$Z$$ impurities to achieve low conducted heat loads. The shell pellet technique aims to produce a hollow temperature profile by using a thin, low-ablation shell surrounding a dispersive payload, giving a greatly increased impurity ablation (and radiation) rate when the payload is released in the plasma core. This principle was demonstrated successfully using 3.6 mm outer diameter, 40 μm thickness diamond shells holding boron powder. The pellets caused rapid (<10 ms) discharge shutdown with low conducted divertor heat fluence (~0.1 MJ/m2). Confirmation of massive release of the boron powder payload into the plasma core was obtained spectroscopically. Some evidence for the formation of a hollow temperature profile during the shutdown was observed. Furthermore, these first results open a new avenue for disruption mitigation research, hopefully enabling development of highly effective methods of avoiding disruption wall damage in future reactor-scale tokamaks.

Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
AC52-07NA27344; FG02-07ER54917; FC02-04ER54698; AC05-00OR22725
OSTI ID:
1542705
Alternate ID(s):
OSTI ID: 1494388
Report Number(s):
LLNL-JRNL-779527; PRLTAO; 959496
Journal Information:
Physical Review Letters, Vol. 122, Issue 6; ISSN 0031-9007
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 24 works
Citation information provided by
Web of Science

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Cited By (5)

Numerical estimation of the oxygen impurity transport in the Aditya tokamak journal February 2020
Axisymmetric benchmarks of impurity dynamics in extended-magnetohydrodynamic simulations journal April 2019
The effect of resonant magnetic perturbation on the electron density threshold of runaway electron generation during disruptions on J-TEXT journal December 2019
Hollow pellet injection for magnetic fusion journal June 2019
First observation of plasma healing via helical equilibrium in tokamak disruptions journal July 2019

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