Protecting against damage from refraction of high power microwaves in the DIII-D tokamak
Abstract
Here, several new protective systems are being installed on the DIII D tokamak to increase the safety margins for plasma operations with injected ECH power at densities approaching cutoff. Inadvertent overdense operation has previously resulted in reflection of an rf beam back into a launcher causing extensive arcing and melt damage on one waveguide line. Damage to microwave diagnostics, which are located on the same side of the tokamak as the ECH launchers, also has occurred. Developing a reliable microwave based interlock to protect the many vulnerable systems in DIII-D has proved to be difficult. Therefore, multiple protective steps have been taken to reduce the risk of damage in the future. Among these is a density interlock generated by the plasma control system, with setpoint determined by the ECH operators based on rf beam trajectories and plasma parameters. Also installed are enhanced video monitoring of the launchers, and an ambient light monitor on each of the waveguide systems, along with a Langmuir probe at the mouth of each launcher. Versatile rf monitors, measuring forward and reflected power in addition to the mode content of the rf beams, have been installed as the last miter bends in each waveguide line. Asmore »
- Authors:
-
- General Atomics, San Diego, CA (United States)
- Univ. of Texas, Austin, TX (United States)
- Univ. of California, Los Angeles, CA (United States)
- Univ. of California, Davis, CA (United States)
- Publication Date:
- Research Org.:
- General Atomics, San Diego, CA (United States)
- Sponsoring Org.:
- USDOE
- Contributing Org.:
- University of Texas-Austin, Austin, Texas, USA University of California-Los Angeles, Los Angeles, California, USA University of California-Davis, Davis, California, USA
- OSTI Identifier:
- 1372857
- Grant/Contract Number:
- FC02-04ER54698
- Resource Type:
- Accepted Manuscript
- Journal Name:
- EPJ Web of Conferences
- Additional Journal Information:
- Journal Volume: 147; Journal ID: ISSN 2100-014X
- Publisher:
- EDP Sciences
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Citation Formats
Lohr, John, Brambila, Rigo, Cengher, Mirela, Chen, Xi, Gorelov, Yuri, Grosnickle, William, Moeller, Charles, Ponce, Dan, Prater, Ron, Torrezan, Antonio, Austin, Max, Doyle, Edward, Hu, Xing, and Dormier, Calvin. Protecting against damage from refraction of high power microwaves in the DIII-D tokamak. United States: N. p., 2017.
Web. doi:10.1051/epjconf/201714703003.
Lohr, John, Brambila, Rigo, Cengher, Mirela, Chen, Xi, Gorelov, Yuri, Grosnickle, William, Moeller, Charles, Ponce, Dan, Prater, Ron, Torrezan, Antonio, Austin, Max, Doyle, Edward, Hu, Xing, & Dormier, Calvin. Protecting against damage from refraction of high power microwaves in the DIII-D tokamak. United States. https://doi.org/10.1051/epjconf/201714703003
Lohr, John, Brambila, Rigo, Cengher, Mirela, Chen, Xi, Gorelov, Yuri, Grosnickle, William, Moeller, Charles, Ponce, Dan, Prater, Ron, Torrezan, Antonio, Austin, Max, Doyle, Edward, Hu, Xing, and Dormier, Calvin. Mon .
"Protecting against damage from refraction of high power microwaves in the DIII-D tokamak". United States. https://doi.org/10.1051/epjconf/201714703003. https://www.osti.gov/servlets/purl/1372857.
@article{osti_1372857,
title = {Protecting against damage from refraction of high power microwaves in the DIII-D tokamak},
author = {Lohr, John and Brambila, Rigo and Cengher, Mirela and Chen, Xi and Gorelov, Yuri and Grosnickle, William and Moeller, Charles and Ponce, Dan and Prater, Ron and Torrezan, Antonio and Austin, Max and Doyle, Edward and Hu, Xing and Dormier, Calvin},
abstractNote = {Here, several new protective systems are being installed on the DIII D tokamak to increase the safety margins for plasma operations with injected ECH power at densities approaching cutoff. Inadvertent overdense operation has previously resulted in reflection of an rf beam back into a launcher causing extensive arcing and melt damage on one waveguide line. Damage to microwave diagnostics, which are located on the same side of the tokamak as the ECH launchers, also has occurred. Developing a reliable microwave based interlock to protect the many vulnerable systems in DIII-D has proved to be difficult. Therefore, multiple protective steps have been taken to reduce the risk of damage in the future. Among these is a density interlock generated by the plasma control system, with setpoint determined by the ECH operators based on rf beam trajectories and plasma parameters. Also installed are enhanced video monitoring of the launchers, and an ambient light monitor on each of the waveguide systems, along with a Langmuir probe at the mouth of each launcher. Versatile rf monitors, measuring forward and reflected power in addition to the mode content of the rf beams, have been installed as the last miter bends in each waveguide line. As these systems are characterized, they are being incorporated in the interlock chains, which enable the ECH injection permits. The diagnostics most susceptible to damage from the ECH waves have also been fitted with a variety of protective devices including stripline filters, thin resonant notch filters tuned to the 110 GHz injected microwave frequency, blazed grating filters and shutters. Calculations of rf beam trajectories in the plasmas are performed using the TORAY ray tracing code with input from kinetic profile diagnostics. Using these calculations, strike points for refracted beams on the vacuum vessel are calculated, which allows evaluation of the risk of damage to sensitive diagnostics and hardware.},
doi = {10.1051/epjconf/201714703003},
journal = {EPJ Web of Conferences},
number = ,
volume = 147,
place = {United States},
year = {Mon Jul 24 00:00:00 EDT 2017},
month = {Mon Jul 24 00:00:00 EDT 2017}
}
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