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Title: DESIGN AND COMMISSIONING OF A THREE-BARREL SHATTERED PELLET INJECTOR FOR DIII-D DISRUPTION MITIGATION STUDIES

Abstract

Disruptions are sudden unplanned terminations of tokamak plasmas that can lead to high thermal loads and runaway electrons (RE). Unmitigated disruptions in ITER are predicted to dissipate hundreds of MJ of thermal energy and generate multi-MeV runaway electrons. This intense heat and energetic particle beams can cause localized melting of the plasma facing components. Reliable and fast acting disruption mitigation (DM) techniques are therefore a critical requirement for ITER to safeguard the machine from damage. The proven method for DM centers on injecting a large quantity of impurity particles into the plasma to quickly increase density and radiate the thermal energy to mitigate thermal effects. Additionally, if the particle injection can achieve a critical density, it can create collisional drag which suppresses the formation of REs. The particle injection methods attempted have been shell pellet injection, massive gas injection, and shattered pellet injection (SPI). The SPI technique has been successfully used on DIII-D [1] to study thermal mitigation using a single-barrel SPI system that can more efficiently reach the critical density required for successful disruption mitigation than the other injection approaches. Recently, a new three-barrel second SPI (SPI-II) system has been developed for use on DIII-D to study injection effectsmore » from multiple toroidal locations and pellet timing. The SPI-II system is a liquid helium cooled pipe gun that has two 7 mm and one 8.5 mm pellet sizes. The pellet sizes are determined by the inner diameter of the pipe gun barrels which can easily be changed for different pellet sizes. The three pellets can be formed and fired individually or simultaneously. The SPI-II has provisions for making and firing pure species pellets with deuterium, neon, or argon and also deuterium layered pellets with a core of neon. The pellets are fired into a bent tube near the plasma edge which shatters them from the impact. This paper will describe the design and commissioning of the SPI-II system. Measured pellet speeds and shattered pellet fragment sizes will be reported.« less

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1394137
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 22nd Topical Meeting on the Technology of Fusion Energy (TOFE) http://tofe2016.ans.org/ - Philadelphia, Pennsylvania, United States of America - 8/22/2016 12:00:00 AM-
Country of Publication:
United States
Language:
English

Citation Formats

Meitner, Steven, Baylor, Larry, Commaux, Nicolas JC, Shiraki, Daisuke, Combs, Stephen Kirk, Bjorholm, Thomas, Ha, Tam, and McGinnis, William. DESIGN AND COMMISSIONING OF A THREE-BARREL SHATTERED PELLET INJECTOR FOR DIII-D DISRUPTION MITIGATION STUDIES. United States: N. p., 2017. Web. doi:10.1080/15361055.2017.1333854.
Meitner, Steven, Baylor, Larry, Commaux, Nicolas JC, Shiraki, Daisuke, Combs, Stephen Kirk, Bjorholm, Thomas, Ha, Tam, & McGinnis, William. DESIGN AND COMMISSIONING OF A THREE-BARREL SHATTERED PELLET INJECTOR FOR DIII-D DISRUPTION MITIGATION STUDIES. United States. https://doi.org/10.1080/15361055.2017.1333854
Meitner, Steven, Baylor, Larry, Commaux, Nicolas JC, Shiraki, Daisuke, Combs, Stephen Kirk, Bjorholm, Thomas, Ha, Tam, and McGinnis, William. 2017. "DESIGN AND COMMISSIONING OF A THREE-BARREL SHATTERED PELLET INJECTOR FOR DIII-D DISRUPTION MITIGATION STUDIES". United States. https://doi.org/10.1080/15361055.2017.1333854. https://www.osti.gov/servlets/purl/1394137.
@article{osti_1394137,
title = {DESIGN AND COMMISSIONING OF A THREE-BARREL SHATTERED PELLET INJECTOR FOR DIII-D DISRUPTION MITIGATION STUDIES},
author = {Meitner, Steven and Baylor, Larry and Commaux, Nicolas JC and Shiraki, Daisuke and Combs, Stephen Kirk and Bjorholm, Thomas and Ha, Tam and McGinnis, William},
abstractNote = {Disruptions are sudden unplanned terminations of tokamak plasmas that can lead to high thermal loads and runaway electrons (RE). Unmitigated disruptions in ITER are predicted to dissipate hundreds of MJ of thermal energy and generate multi-MeV runaway electrons. This intense heat and energetic particle beams can cause localized melting of the plasma facing components. Reliable and fast acting disruption mitigation (DM) techniques are therefore a critical requirement for ITER to safeguard the machine from damage. The proven method for DM centers on injecting a large quantity of impurity particles into the plasma to quickly increase density and radiate the thermal energy to mitigate thermal effects. Additionally, if the particle injection can achieve a critical density, it can create collisional drag which suppresses the formation of REs. The particle injection methods attempted have been shell pellet injection, massive gas injection, and shattered pellet injection (SPI). The SPI technique has been successfully used on DIII-D [1] to study thermal mitigation using a single-barrel SPI system that can more efficiently reach the critical density required for successful disruption mitigation than the other injection approaches. Recently, a new three-barrel second SPI (SPI-II) system has been developed for use on DIII-D to study injection effects from multiple toroidal locations and pellet timing. The SPI-II system is a liquid helium cooled pipe gun that has two 7 mm and one 8.5 mm pellet sizes. The pellet sizes are determined by the inner diameter of the pipe gun barrels which can easily be changed for different pellet sizes. The three pellets can be formed and fired individually or simultaneously. The SPI-II has provisions for making and firing pure species pellets with deuterium, neon, or argon and also deuterium layered pellets with a core of neon. The pellets are fired into a bent tube near the plasma edge which shatters them from the impact. This paper will describe the design and commissioning of the SPI-II system. Measured pellet speeds and shattered pellet fragment sizes will be reported.},
doi = {10.1080/15361055.2017.1333854},
url = {https://www.osti.gov/biblio/1394137}, journal = {},
issn = {1536--1055},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {7}
}

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