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Title: Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years

Abstract

High-speed injection of solid fuel was first proposed in 1954 as a possible solution to the problem of transporting fresh fuel across the confining magnetic fields into the plasma of a fusion reactor. While it took a few decades, the use of cryogenic pellets (typically H2 and D2) on fusion experiments became common place; most tokamaks and stellarators are now equipped with a pellet injector(s). These devices operate at low temperatures (~10 to 20 K) and most often use a simple light gas gun to accelerate macroscopic-size pellets (~0.4- to 6-mm diameter) to speeds of ~100 to 1000 m/s. Before the advantages of pellet injection from the magnetic high-field side (HFS) of a tokamak were recognized in 1997, development focused on increasing the pellet speed to achieve deeper plasma penetration and higher fueling efficiency. The HFS injection technique typically dictates slower pellets (~100 to 300 m/s) to survive transport through the curved guide tubes that route the pellets to the plasma from the inside wall of the device. Two other key operating parameters for plasma fueling are the pellet-injection repetition rate and time duration—a single pellet is adequate for some experiments and a steady-state injection rate of up to ~50more » Hz is appropriate for others. In addition to plasma fueling, cryogenic pellets have often been used for particle transport and impurity studies in fusion experiments (most often with neon pellets). During the past two decades, a few new applications for cryogenic pellets have been developed and used successfully in plasma experiments: (1) one for edge-localized mode mitigation, (2) one for plasma disruption mitigation (requires large pellets that are shattered before injection into the plasma), and (3) another in which pure argon pellets are used to trigger runaway electrons in the plasma for scientific studies. Here in this paper, a brief history and the key developments in this technology during the past 25 years are presented and discussed.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, 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:
1460225
Grant/Contract Number:  
AC05-00OR22725; FC02-04ER54698
Resource Type:
Accepted Manuscript
Journal Name:
Fusion Science and Technology
Additional Journal Information:
Journal Volume: 73; Journal Issue: 4; Journal ID: ISSN 1536-1055
Publisher:
American Nuclear Society
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Cryogenic pellet; plasma fueling; disruption mitigation; ELM mitigation; runaway electrons

Citation Formats

Combs, Stephen Kirk, and Baylor, Larry R. Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years. United States: N. p., 2018. Web. doi:10.1080/15361055.2017.1421367.
Combs, Stephen Kirk, & Baylor, Larry R. Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years. United States. doi:10.1080/15361055.2017.1421367.
Combs, Stephen Kirk, and Baylor, Larry R. Wed . "Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years". United States. doi:10.1080/15361055.2017.1421367. https://www.osti.gov/servlets/purl/1460225.
@article{osti_1460225,
title = {Pellet-Injector Technology—Brief History and Key Developments in the Last 25 Years},
author = {Combs, Stephen Kirk and Baylor, Larry R.},
abstractNote = {High-speed injection of solid fuel was first proposed in 1954 as a possible solution to the problem of transporting fresh fuel across the confining magnetic fields into the plasma of a fusion reactor. While it took a few decades, the use of cryogenic pellets (typically H2 and D2) on fusion experiments became common place; most tokamaks and stellarators are now equipped with a pellet injector(s). These devices operate at low temperatures (~10 to 20 K) and most often use a simple light gas gun to accelerate macroscopic-size pellets (~0.4- to 6-mm diameter) to speeds of ~100 to 1000 m/s. Before the advantages of pellet injection from the magnetic high-field side (HFS) of a tokamak were recognized in 1997, development focused on increasing the pellet speed to achieve deeper plasma penetration and higher fueling efficiency. The HFS injection technique typically dictates slower pellets (~100 to 300 m/s) to survive transport through the curved guide tubes that route the pellets to the plasma from the inside wall of the device. Two other key operating parameters for plasma fueling are the pellet-injection repetition rate and time duration—a single pellet is adequate for some experiments and a steady-state injection rate of up to ~50 Hz is appropriate for others. In addition to plasma fueling, cryogenic pellets have often been used for particle transport and impurity studies in fusion experiments (most often with neon pellets). During the past two decades, a few new applications for cryogenic pellets have been developed and used successfully in plasma experiments: (1) one for edge-localized mode mitigation, (2) one for plasma disruption mitigation (requires large pellets that are shattered before injection into the plasma), and (3) another in which pure argon pellets are used to trigger runaway electrons in the plasma for scientific studies. Here in this paper, a brief history and the key developments in this technology during the past 25 years are presented and discussed.},
doi = {10.1080/15361055.2017.1421367},
journal = {Fusion Science and Technology},
number = 4,
volume = 73,
place = {United States},
year = {2018},
month = {2}
}

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Works referenced in this record:

A new centrifuge pellet injector for fusion experiments
journal, April 1993

  • Andelfinger, C.; Buchelt, E.; Cierpka, P.
  • Review of Scientific Instruments, Vol. 64, Issue 4
  • DOI: 10.1063/1.1144101

Fueling efficiency of pellet injection on DIII-D
journal, March 1999


Experimental Study of the Propellant Gas Load Required for Pellet Injection with ITER-Relevant Operating Parameters
journal, September 2015

  • Combs, S. K.; Baylor, L. R.; Foust, C. R.
  • Fusion Science and Technology, Vol. 68, Issue 2
  • DOI: 10.13182/FST14-925

Disruption Mitigation System Developments and Design for ITER
journal, September 2015

  • Baylor, L. R.; Barbier, C. C.; Carmichael, J. R.
  • Fusion Science and Technology, Vol. 68, Issue 2
  • DOI: 10.13182/FST14-926

Pellet fueling technology development leading to efficient fueling of ITER burning plasmas
journal, May 2005

  • Baylor, L. R.; Combs, S. K.; Jernigan, T. C.
  • Physics of Plasmas, Vol. 12, Issue 5
  • DOI: 10.1063/1.1865052

ELM pace making and mitigation by pellet injection in ASDEX Upgrade
journal, April 2004


A pellet injector of the HL-2A tokamak
journal, September 2013

  • Vinyar, I. V.; Lukin, A. Ya.; Skoblikov, S. V.
  • Instruments and Experimental Techniques, Vol. 56, Issue 5
  • DOI: 10.1134/S0020441213050102

Improved core fueling with high field side pellet injection in the DIII-D tokamak
journal, May 2000

  • Baylor, L. R.; Jernigan, T. C.; Combs, S. K.
  • Physics of Plasmas, Vol. 7, Issue 5
  • DOI: 10.1063/1.874011

Development of a Two-Stage Pneumatic Repeating Pellet Injector for the Refueling of Long-Pulse Magnetic Confinement Fusion Devices
journal, December 1997

  • Frattolillo, Antonio; Migliori, Silvio; Combs, Stephen K.
  • Fusion Technology, Vol. 32, Issue 4
  • DOI: 10.13182/FST97-A19907

A three‐barrel repeating pneumatic pellet injector for plasma fueling of the Joint European Torus
journal, May 1988

  • Combs, S. K.; Milora, S. L.; Baylor, L. R.
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 6, Issue 3
  • DOI: 10.1116/1.575242

Pellet fuelling of ELMy H mode discharges on ASDEX Upgrade
journal, November 1996


Results from Laboratory Testing of a New Four-Barrel Pellet Injector for the TJ-II Stellarator
journal, September 2013

  • Combs, S. K.; Foust, C. R.; McGill, J. M.
  • Fusion Science and Technology, Vol. 64, Issue 3
  • DOI: 10.13182/FST13-A19144

High density operation in H mode discharges by inboard launch pellet refuelling
journal, February 2000


The JET high frequency pellet injector project
journal, October 2007


Development of a Diagnostic Twin Screw Extruder to Characterize Fuel Production for Tokamaks
journal, September 2013

  • Fisher, J. T.; Leachman, J. W.
  • Fusion Science and Technology, Vol. 64, Issue 3
  • DOI: 10.13182/FST13-A19146

A pneumatic injector of hydrogen pellets for the LHD stellarator
journal, October 2006

  • Vinyar, I. V.; Lukin, A. Ya.; Umov, A. P.
  • Instruments and Experimental Techniques, Vol. 49, Issue 5
  • DOI: 10.1134/S0020441206050228

Main characteristics of the fast disruption mitigation valve
journal, March 2007

  • Bozhenkov, S. A.; Finken, K. -H.; Lehnen, M.
  • Review of Scientific Instruments, Vol. 78, Issue 3
  • DOI: 10.1063/1.2712798

Effect of Parallel Flows and Toroidicity on Cross-Field Transport of Pellet Ablation Matter in Tokamak Plasmas
journal, April 2005


Pellet injectors developed at PELIN for JET, TAE and HL-2A
journal, October 2011


Small‐bore (1.8‐mm), high‐firing‐rate (10‐Hz) version of a repeating pneumatic hydrogen pellet injector
journal, March 1995

  • Combs, S. K.; Foust, C. R.; Milora, S. L.
  • Review of Scientific Instruments, Vol. 66, Issue 3
  • DOI: 10.1063/1.1145620

ORNL mock-up tests of inside launch pellet injection on JET and LHD
journal, November 2001


Plasma behaviour at high β and high density in the Madison Symmetric Torus RFP
journal, December 2008


A Technique for Producing Large Dual-Layer Pellets in Support of Disruption Mitigation Experiments
journal, August 2011

  • Combs, S. K.; Leachman, J. W.; Meitner, S. J.
  • Fusion Science and Technology, Vol. 60, Issue 2
  • DOI: 10.13182/FST60-473

Pellet Injection Technology and Its Applications on ITER
journal, September 2016

  • Baylor, L. R.; Combs, S. K.; Duckworth, R. C.
  • IEEE Transactions on Plasma Science, Vol. 44, Issue 9
  • DOI: 10.1109/TPS.2016.2550419

ELM frequency control by continuous small pellet injection in ASDEX Upgrade
journal, September 2003


Pellet fuelling
journal, June 1995


New ORNL Pellet Injection System and Installation/Initial Operations on MST
journal, September 2003

  • Combs, S. K.; Baylor, L. R.; Fehling, D. T.
  • Fusion Science and Technology, Vol. 44, Issue 2
  • DOI: 10.13182/FST03-A388

Reduction of Edge-Localized Mode Intensity Using High-Repetition-Rate Pellet Injection in Tokamak H -Mode Plasmas
journal, June 2013


High-Efficiency Plasma Refuelling by Pellet Injection from the Magnetic High-Field Side into ASDEX Upgrade
journal, August 1997


Disruptions in ITER and strategies for their control and mitigation
journal, August 2015


Pellet fuelling deposition measurements on Jet and TFTR
journal, December 1992


A pneumatic injector of deuterium pellets for the TORE-SUPRA tokamak
journal, July 2006

  • Vinyar, I. V.; Umov, A. P.; Lukin, A. Ya.
  • Instruments and Experimental Techniques, Vol. 49, Issue 4
  • DOI: 10.1134/S0020441206040257

Tritium Proof-of-Principle Pellet Injector—Phase II
journal, October 1995


Status of the JET high frequency pellet injector
journal, October 2013


Repeating pneumatic hydrogen pellet injector for plasma fueling
journal, June 1985

  • Combs, S. K.; Milora, S. L.; Foust, C. R.
  • Review of Scientific Instruments, Vol. 56, Issue 6
  • DOI: 10.1063/1.1138025

Big Dee - A Flexible Facility Operating Near Breakeven Conditions
journal, July 1985


Reduction of edge localized mode intensity on DIII-D by on-demand triggering with high frequency pellet injection and implications for ITER
journal, August 2013

  • Baylor, L. R.; Commaux, N.; Jernigan, T. C.
  • Physics of Plasmas, Vol. 20, Issue 8
  • DOI: 10.1063/1.4818772

Ablation of hydrogen pellets in hydrogen and helium plasmas
journal, June 1975


Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak
journal, November 1982


Solid deuterium centrifuge pellet injector
journal, April 1983

  • Foster, C. A.
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 1, Issue 2
  • DOI: 10.1116/1.572161

Repetitive fueling pellet injection in large helical device
journal, September 2003


A new pellet injector for steady state fuelling in Tore Supra
journal, September 2003


Pellet injectors for EAST and KSTAR tokamaks
journal, November 2017


Extruder system for high-throughput/steady-state hydrogen ice supply and application for pellet fueling of reactor-scale fusion experiments
journal, November 1998

  • Combs, S. K.; Foust, C. R.; Qualls, A. L.
  • Review of Scientific Instruments, Vol. 69, Issue 11
  • DOI: 10.1063/1.1149216

A New Pellet Injection System for HL-2A
journal, October 2012

  • Xu, H. B.; Zhu, G. L.; Liu, D. Q.
  • Fusion Science and Technology, Vol. 62, Issue 2
  • DOI: 10.13182/FST12-A14622

Tritium pellet injector results
journal, May 1989

  • Fisher, P. W.; Bauer, M. L.; Baylor, L. R.
  • Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 7, Issue 3
  • DOI: 10.1116/1.575823

Performance of a pneumatic hydrogen‐pellet injection system on the Joint European Torus
journal, August 1989

  • Combs, S. K.; Jernigan, T. C.; Baylor, L. R.
  • Review of Scientific Instruments, Vol. 60, Issue 8
  • DOI: 10.1063/1.1140643

Progress on the application of ELM control schemes to ITER scenarios from the non-active phase to DT operation
journal, February 2014


Pellet injection technology
journal, July 1993

  • Combs, S. K.
  • Review of Scientific Instruments, Vol. 64, Issue 7
  • DOI: 10.1063/1.1143995

Pellet delivery and survivability through curved guide tubes for fusion fueling and its implications for ITER
journal, November 2005


High‐speed repeating hydrogen pellet injector for long‐pulse magnetic confinement fusion experiments
journal, May 1996

  • Frattolillo, A.; Migliori, S.; Scaramuzzi, F.
  • Review of Scientific Instruments, Vol. 67, Issue 5
  • DOI: 10.1063/1.1146988

Development and integration of a 50 Hz pellet injection system for the Experimental Advanced Superconducting Tokamak (EAST)
journal, January 2017


Demonstration of rapid shutdown using large shattered deuterium pellet injection in DIII-D
journal, September 2010


Properties of Tritium Inferred from Pellet Injector Experiments
journal, March 1992


Fast‐opening magnetic valve for high‐pressure gas injection and applications to hydrogen pellet fueling systems
journal, September 1986

  • Milora, S. L.; Combs, S. K.; Foust, C. R.
  • Review of Scientific Instruments, Vol. 57, Issue 9
  • DOI: 10.1063/1.1138677

Control of post-disruption runaway electron beams in DIII-D
journal, May 2012

  • Eidietis, N. W.; Commaux, N.; Hollmann, E. M.
  • Physics of Plasmas, Vol. 19, Issue 5
  • DOI: 10.1063/1.3695000

Rview of pellet fueling
journal, January 1981


50 Hz deuterium pellet injector for EAST tokamak
journal, October 2015


Plasma fuelling with cryogenic pellets in the stellarator TJ-II
journal, April 2017


Thermal quench mitigation and current quench control by injection of mixed species shattered pellets in DIII-D
journal, June 2016

  • Shiraki, D.; Commaux, N.; Baylor, L. R.
  • Physics of Plasmas, Vol. 23, Issue 6
  • DOI: 10.1063/1.4954389

Overview of recent developments in pellet injection for ITER
journal, August 2012


Tritium Proof-of-Principle Injector Experiment
journal, September 1988

  • Fisher, P. W.; Milora, S. L.; Combs, S. K.
  • Fusion Technology, Vol. 14, Issue 2P2B
  • DOI: 10.13182/FST88-A25264

Refuelling performance improvement by high speed pellet launch from the magnetic high field side
journal, August 2001


Solidification and Acceleration of Large Cryogenic Pellets Relevant for Plasma Disruption Mitigation
journal, September 2016

  • Combs, S. K.; Meitner, S. J.; Gebhart, T. E.
  • IEEE Transactions on Plasma Science, Vol. 44, Issue 9
  • DOI: 10.1109/TPS.2016.2578461

Novel rapid shutdown strategies for runaway electron suppression in DIII-D
journal, August 2011


Development of a Twin-Screw D 2 Extruder for the ITER Pellet Injection System
journal, July 2009

  • Meitner, S. J.; Baylor, L. R.; Carbajo, J. J.
  • Fusion Science and Technology, Vol. 56, Issue 1
  • DOI: 10.13182/FST09-20

Technique for measuring D2 pellet mass loss through a curved guide tube using two microwave cavity detectors
journal, July 2006

  • Combs, S. K.; Caughman, J. B. O.; Wilgen, J. B.
  • Review of Scientific Instruments, Vol. 77, Issue 7
  • DOI: 10.1063/1.2219748

Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments
journal, October 2016


A system for cryogenic hydrogen pellet high speed inboard launch into a fusion device via guiding tube transfer
journal, September 2003

  • Lang, P. T.; Cierpka, P.; Gehre, O.
  • Review of Scientific Instruments, Vol. 74, Issue 9
  • DOI: 10.1063/1.1602940

Alternative Techniques for Injecting Massive Quantities of Gas for Plasma-Disruption Mitigation
journal, March 2010

  • Combs, S. K.; Meitner, S. J.; Baylor, L. R.
  • IEEE Transactions on Plasma Science, Vol. 38, Issue 3
  • DOI: 10.1109/TPS.2009.2038781

Comparison of deuterium pellet injection from different locations on the DIII-D tokamak
journal, October 2007


First demonstration of rapid shutdown using neon shattered pellet injection for thermal quench mitigation on DIII-D
journal, March 2016


A compact flexible pellet injector for the TJ-II stellarator
journal, October 2008

  • McCarthy, K. J.; Combs, S. K.; Baylor, L. R.
  • Review of Scientific Instruments, Vol. 79, Issue 10
  • DOI: 10.1063/1.2955706

Speed limit of frozen pellets (H2, D2, and Ne) through single-loop and multiloop tubes and implications for fusion plasma research
journal, January 2001

  • Combs, S. K.; Griffith, A. E.; Foust, C. R.
  • Review of Scientific Instruments, Vol. 72, Issue 1
  • DOI: 10.1063/1.1331322

ELM triggering by local pellet perturbations in type-I ELMy H-mode plasma at JET
journal, July 2007


Diagnostic Twin Screw Extruder: Initial Measurements of Continuous Ne, H 2 , and D 2 Extrusions
journal, September 2015

  • Fisher, J. T.; Leachman, J. W.
  • Fusion Science and Technology, Vol. 68, Issue 2
  • DOI: 10.13182/FST14-970

Fast-opening, high-throughput gas valve and application for inertial fusion energy R&D
journal, January 2004

  • Combs, S. K.; Foust, C. R.; Gouge, M. J.
  • Review of Scientific Instruments, Vol. 75, Issue 1
  • DOI: 10.1063/1.1633026

ELM mitigation with pellet ELM triggering and implications for PFCs and plasma performance in ITER
journal, August 2015