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Title: Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation

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 refrig- erator (temperatures ~8-20 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 ~5-8 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 premixed 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,more » 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 ~100-800 m/s have been recorded. The data and results from laboratory testing are presented and discussed, and a simple model for the pellet solidification process is described.« less

Authors:
 [1];  [1];  [2];  [1];  [1];  [1];  [1];  [1];  [1];  [3];  [4]
+ Show Author Affiliations
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Florida, Gainesville, FL (United States)
  3. Washington State Univ., Pullman, WA (United States)
  4. Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1327580
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
IEEE Transactions on Plasma Science
Additional Journal Information:
Journal Volume: 44; Journal Issue: 9; Journal ID: ISSN 0093-3813
Publisher:
IEEE
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Argon; cryogenic pellet; deuterium; disruption mitigation; neon; plasma; shattered; cameras; electron tubes

Citation Formats

Combs, Stephen Kirk, Meitner, S. J., Gebhart, T. E., Baylor, Larry R., Caughman, John B., Fehling, Dan T., Foust, Charles R., Ha, Tam T., Lyttle, Mark S., Fisher, J. T., and Younkin, T. R. Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation. United States: N. p., 2016. Web. doi:10.1109/TPS.2016.2578461.
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Combs, Stephen Kirk, Meitner, S. J., Gebhart, T. E., Baylor, Larry R., Caughman, John B., Fehling, Dan T., Foust, Charles R., Ha, Tam T., Lyttle, Mark S., Fisher, J. T., & Younkin, T. R. Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation. United States. https://doi.org/10.1109/TPS.2016.2578461
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Combs, Stephen Kirk, Meitner, S. J., Gebhart, T. E., Baylor, Larry R., Caughman, John B., Fehling, Dan T., Foust, Charles R., Ha, Tam T., Lyttle, Mark S., Fisher, J. T., and Younkin, T. R. Fri . "Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation". United States. https://doi.org/10.1109/TPS.2016.2578461. https://www.osti.gov/servlets/purl/1327580.
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@article{osti_1327580,
title = {Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation},
author = {Combs, Stephen Kirk and Meitner, S. J. and Gebhart, T. E. and Baylor, Larry R. and Caughman, John B. and Fehling, Dan T. and Foust, Charles R. and Ha, Tam T. and Lyttle, Mark S. and Fisher, J. T. and Younkin, T. R.},
abstractNote = {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 refrig- erator (temperatures ~8-20 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 ~5-8 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 premixed 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 ~100-800 m/s have been recorded. The data and results from laboratory testing are presented and discussed, and a simple model for the pellet solidification process is described.},
doi = {10.1109/TPS.2016.2578461},
journal = {IEEE Transactions on Plasma Science},
number = 9,
volume = 44,
place = {United States},
year = {Fri Jan 01 00:00:00 EST 2016},
month = {Fri Jan 01 00:00:00 EST 2016}
}
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https://doi.org/10.1109/TPS.2016.2578461
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Works referencing / citing this record:

Innovations in Technology and Science R&D for ITER
journal, January 2019

  • Campbell, David J.; Akiyama, Tsuyoshi; Barnsley, Robin
  • Journal of Fusion Energy, Vol. 38, Issue 1
  • DOI: 10.1007/s10894-018-0187-9

Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years
journal, December 2017

Development of Solenoid-Driven and Pneumatic Punches for Launching High- Z Cryogenic Pellets for Tokamak Disruption Mitigation Experiments
journal, May 2019

Shattered pellet injection technology design and characterization for disruption mitigation experiments
journal, April 2019

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