Recent developments in support of the shattered pellet technique for disruption mitigation

S. K. Combs, S. J. Meitner, T. E. Gebhart, L. R. Baylor, J. B.O. Caughman, D. T. Fehling, C. R. Foust, T. Ha, M. S. Lyttle, J. T. Fisher, T. R. Younkin

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

The technology for producing, accelerating, and shattering large pellets (before injection into plasmas) for disruption mitigation has been under development at the Oak Ridge National Laboratory for several years, including a system on DIII-D that has been used to provide some significant experimental results. The original proof-of-principle testing was carried out using a pipe gun injector cooled by a cryogenic refrigerator (temperatures ∼8 to 20 K) and equipped with a stainless steel tube to produce 16.5 mm pellets composed of either pure D2, pure Ne, or a dual layer with a thin outer shell of D2 and core of Ne. Recently, significant progress has been made in the laboratory using that same pipe gun and a new injector that is an ITER test apparatus cooled with liquid helium. The new injector operates at ∼5 to 8 K, which is similar to temperatures expected with cooling provided by the flow of supercritical helium on ITER. An alternative technique for producing/solidifying large pellets directly from a pre-mixed gas has now been successfully tested in the laboratory. Also, two additional pellet sizes have been tested recently (nominal 24.4 and 34.0 mm diameters). With larger pellets, the number of injectors required for ITER disruption mitigation can be reduced, resulting in less cost and a smaller footprint for the hardware. An attractive option is longer pellets, and 24.4 mm pellets with a length/diameter ratio of ∼3 have been successfully tested. Since pellet speed is the key parameter in determining the response time of a shattered pellet system to a plasma disruption event, recent tests have concentrated on documenting the speeds with different hardware configurations and operating parameters; speeds of ∼100 to 800 m/s have been recorded. The data and results from laboratory testing are presented and discussed.

Original languageEnglish
Title of host publication2015 IEEE 26th Symposium on Fusion Engineering, SOFE 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781479982646
DOIs
StatePublished - May 31 2016
Event26th IEEE Symposium on Fusion Engineering, SOFE 2015 - Austin, United States
Duration: May 31 2015Jun 4 2015

Publication series

NameProceedings - Symposium on Fusion Engineering
Volume2016-May

Conference

Conference26th IEEE Symposium on Fusion Engineering, SOFE 2015
Country/TerritoryUnited States
CityAustin
Period05/31/1506/4/15

Keywords

  • deuterium
  • disruption mitigation
  • neon
  • plasma
  • shattered pellet

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