skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Advanced Field-Aligned ICRF Antennas for Improved Breakdown Resistance

Abstract

To make a viable tokamak reactor concept, efficient, robust steady state current drive is required. RF power is among the leading contenders due to its high efficiency and penetration to the plasma core without density limits. To minimize impact on tritium breeding, high power density RF antennas are desired. At present, electrical breakdown limits the power density to ~10 MW/m2. Recent results at MIT utilizing an Inconel based field aligned ICRF antenna showed significantly increased load tolerance, reduced impurity contamination, and reduced RF enhanced heat flux associated with ICRF antenna operation compared to standard ICRF antennas. However, a field-aligned antenna results in a smaller antenna area compared to a standard antenna due to geometrical constraints. To increase the power density, a field-aligned antenna must have a higher voltage and power limit. Emerging experimental results suggest that materials with higher tolerance to surface fatigue and melting temperature lead to higher breakdown limits. The ability to produce high density, well-bonded refractory metal coatings on Inconel based substrates has recently been demonstrated by Plasma Processes using electroforming (EL-Form) techniques and testing at MIT has confirmed improved breakdown resistance. In addition, the ability to additively manufacture (AM) an ICRF antenna will enable the developmentmore » of more complex antenna designs that could lead to further improved electrical performance. Therefore, during this investigation, an advanced field-aligned ICRF antenna is being developed by combining AM techniques to produce an antenna with complex features such as internal cooling channels and the deposition of innovative EL-Form refractory metal coatings to improve breakdown resistance. During Phase I, AM Inconel 625 material was produced and EL-Form molybdenum was successfully deposited on the AM Inconel 625. Unlike previous efforts to produce a high quality surface finish on tungsten coatings, the EL-Form Mo on AM Inconel was successfully polished to a fine surface finish, i.e., approximately 5 times better than previously achieved on polished tungsten coated electrodes. This high surface finish is necessary for optimum breakdown resistance. At the conclusion of Phase I, EL-Form Mo coated AM Inconel 625 electrodes with a high quality surface finish were delivered to MIT for inspection and testing. During Phase II, the techniques developed during Phase I will be optimized to produce Inconel 625 field aligned antenna straps with EL-Form Mo coatings. Tests of these advanced ICRF components will then be performed to yielding critical data on performance.« less

Authors:
 [1]
  1. Plasma Processes, LLC
Publication Date:
Research Org.:
Plasma Processes, LLC
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1508337
Report Number(s):
DOE-PLASMA-0018735
DOE Contract Number:  
SC0018735
Type / Phase:
SBIR (Phase I)
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 36 MATERIALS SCIENCE; Fusion, Plasma Heating, ICRF antenna, Breakdown Resistance, Additive Manufacturing, Direct Metal Laser Sintering, EL-Form, Molybdenum, Tungsten

Citation Formats

O'Dell, John Scott. Advanced Field-Aligned ICRF Antennas for Improved Breakdown Resistance. United States: N. p., 2019. Web.
O'Dell, John Scott. Advanced Field-Aligned ICRF Antennas for Improved Breakdown Resistance. United States.
O'Dell, John Scott. Tue . "Advanced Field-Aligned ICRF Antennas for Improved Breakdown Resistance". United States.
@article{osti_1508337,
title = {Advanced Field-Aligned ICRF Antennas for Improved Breakdown Resistance},
author = {O'Dell, John Scott},
abstractNote = {To make a viable tokamak reactor concept, efficient, robust steady state current drive is required. RF power is among the leading contenders due to its high efficiency and penetration to the plasma core without density limits. To minimize impact on tritium breeding, high power density RF antennas are desired. At present, electrical breakdown limits the power density to ~10 MW/m2. Recent results at MIT utilizing an Inconel based field aligned ICRF antenna showed significantly increased load tolerance, reduced impurity contamination, and reduced RF enhanced heat flux associated with ICRF antenna operation compared to standard ICRF antennas. However, a field-aligned antenna results in a smaller antenna area compared to a standard antenna due to geometrical constraints. To increase the power density, a field-aligned antenna must have a higher voltage and power limit. Emerging experimental results suggest that materials with higher tolerance to surface fatigue and melting temperature lead to higher breakdown limits. The ability to produce high density, well-bonded refractory metal coatings on Inconel based substrates has recently been demonstrated by Plasma Processes using electroforming (EL-Form) techniques and testing at MIT has confirmed improved breakdown resistance. In addition, the ability to additively manufacture (AM) an ICRF antenna will enable the development of more complex antenna designs that could lead to further improved electrical performance. Therefore, during this investigation, an advanced field-aligned ICRF antenna is being developed by combining AM techniques to produce an antenna with complex features such as internal cooling channels and the deposition of innovative EL-Form refractory metal coatings to improve breakdown resistance. During Phase I, AM Inconel 625 material was produced and EL-Form molybdenum was successfully deposited on the AM Inconel 625. Unlike previous efforts to produce a high quality surface finish on tungsten coatings, the EL-Form Mo on AM Inconel was successfully polished to a fine surface finish, i.e., approximately 5 times better than previously achieved on polished tungsten coated electrodes. This high surface finish is necessary for optimum breakdown resistance. At the conclusion of Phase I, EL-Form Mo coated AM Inconel 625 electrodes with a high quality surface finish were delivered to MIT for inspection and testing. During Phase II, the techniques developed during Phase I will be optimized to produce Inconel 625 field aligned antenna straps with EL-Form Mo coatings. Tests of these advanced ICRF components will then be performed to yielding critical data on performance.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {4}
}

Technical Report:
This technical report may be released as soon as October 28, 2023
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that may hold this item. Keep in mind that many technical reports are not cataloged in WorldCat.

Save / Share: