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Title: Applications of high-speed dust injection to magnetic fusion

Abstract

It is now an established fact that a significant amount of dust is produced in magnetic fusion devices due to plasma-wall interactions. Dust inventory must be controlled, in particular for the next-generation steady-state fusion machines like ITER, as it can pose significant safety hazards and degrade performance. Safety concerns are due to tritium retention, dust radioactivity, toxicity, and flammability. Performance concerns include high-Z impurities carried by dust to the fusion core that can reduce plasma temperature and may even induce sudden termination of the plasma. We have recognized that dust transport, dust-plasma interactions in magnetic fusion devices can be effectively studied experimentally by injection of dust with known properties into fusion plasmas. Other applications of injected dust include diagnosis of fusion plasmas and edge localized mode (ELM)'s pacing. In diagnostic applications, dust can be regarded as a source of transient neutrals before complete ionization. ELM's pacing is a promising scheme to prevent disruptions and type I ELM's that can cause catastrophic damage to fusion machines. Different implementation schemes are available depending on applications of dust injection. One of the simplest dust injection schemes is through gravitational acceleration of dust in vacuum. Experiments at Los Alamos and Princeton will be described,more » both of which use piezoelectric shakers to deliver dust to plasma. In Princeton experiments, spherical particles (40 micron) have been dropped in a systematic and reproducible manner using a computer-controlled piezoelectric bending actuator operating at an acoustic (0,2) resonance. The circular actuator was constructed with a 2.5 mm diameter central hole. At resonance ({approx} 2 kHz) an applied sinusoidal voltage has been used to control the flux of particles exiting the hole. A simple screw throttle located {approx}1mm above the hole has been used to set the magnitude of the flux achieved for a given voltage. Particle fluxes ranging from a few tens of particle per second up to thousands of particles per second have been achieved using this simple device. To achieve higher dust injection speed, another key consideration is how to accelerate dust at controlled amount. In addition to gravity, other possible acceleration mechanisms include electrostatic, electromagnetic, gas-dragged, plasma-dragged, and laser-ablation-based acceleration. Features and limitations of the different acceleration methods will be discussed. We will also describe laboratory experiments on dust acceleration.« less

Authors:
 [1];  [2]
  1. Los Alamos National Laboratory
  2. Max Planck Institute for Extraterrestrial Physics, Germany
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
DOE/LANL
OSTI Identifier:
1048374
Report Number(s):
LA-UR-12-23930
TRN: US1204258
DOE Contract Number:  
AC52-06NA25396
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; ACTUATORS; BENDING; DUSTS; EDGE LOCALIZED MODES; ELECTRON TEMPERATURE; FLAMMABILITY; IMPLEMENTATION; IMPURITIES; ION TEMPERATURE; IONIZATION; PLASMA; RADIOACTIVITY; RESONANCE; RETENTION; SAFETY; TOXICITY; TRANSIENTS; TRITIUM; WALL EFFECTS

Citation Formats

Wang, Zhehui, and Li, Yangfang. Applications of high-speed dust injection to magnetic fusion. United States: N. p., 2012. Web. doi:10.2172/1048374.
Wang, Zhehui, & Li, Yangfang. Applications of high-speed dust injection to magnetic fusion. United States. doi:10.2172/1048374.
Wang, Zhehui, and Li, Yangfang. Wed . "Applications of high-speed dust injection to magnetic fusion". United States. doi:10.2172/1048374. https://www.osti.gov/servlets/purl/1048374.
@article{osti_1048374,
title = {Applications of high-speed dust injection to magnetic fusion},
author = {Wang, Zhehui and Li, Yangfang},
abstractNote = {It is now an established fact that a significant amount of dust is produced in magnetic fusion devices due to plasma-wall interactions. Dust inventory must be controlled, in particular for the next-generation steady-state fusion machines like ITER, as it can pose significant safety hazards and degrade performance. Safety concerns are due to tritium retention, dust radioactivity, toxicity, and flammability. Performance concerns include high-Z impurities carried by dust to the fusion core that can reduce plasma temperature and may even induce sudden termination of the plasma. We have recognized that dust transport, dust-plasma interactions in magnetic fusion devices can be effectively studied experimentally by injection of dust with known properties into fusion plasmas. Other applications of injected dust include diagnosis of fusion plasmas and edge localized mode (ELM)'s pacing. In diagnostic applications, dust can be regarded as a source of transient neutrals before complete ionization. ELM's pacing is a promising scheme to prevent disruptions and type I ELM's that can cause catastrophic damage to fusion machines. Different implementation schemes are available depending on applications of dust injection. One of the simplest dust injection schemes is through gravitational acceleration of dust in vacuum. Experiments at Los Alamos and Princeton will be described, both of which use piezoelectric shakers to deliver dust to plasma. In Princeton experiments, spherical particles (40 micron) have been dropped in a systematic and reproducible manner using a computer-controlled piezoelectric bending actuator operating at an acoustic (0,2) resonance. The circular actuator was constructed with a 2.5 mm diameter central hole. At resonance ({approx} 2 kHz) an applied sinusoidal voltage has been used to control the flux of particles exiting the hole. A simple screw throttle located {approx}1mm above the hole has been used to set the magnitude of the flux achieved for a given voltage. Particle fluxes ranging from a few tens of particle per second up to thousands of particles per second have been achieved using this simple device. To achieve higher dust injection speed, another key consideration is how to accelerate dust at controlled amount. In addition to gravity, other possible acceleration mechanisms include electrostatic, electromagnetic, gas-dragged, plasma-dragged, and laser-ablation-based acceleration. Features and limitations of the different acceleration methods will be discussed. We will also describe laboratory experiments on dust acceleration.},
doi = {10.2172/1048374},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Aug 08 00:00:00 EDT 2012},
month = {Wed Aug 08 00:00:00 EDT 2012}
}

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