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Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas
Plasma probes are simple and inexpensive diagnostic tools for fast measurements of relevant plasma parameters. While in earlier times being employed mainly in relatively cold laboratory plasmas, plasma probes are now routinely used even in toroidal magnetic fusion experiments, albeit only in the edg...
Autores principales: | , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
MDPI
2020
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7599483/ https://www.ncbi.nlm.nih.gov/pubmed/33065961 http://dx.doi.org/10.3390/ma13204524 |
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author | Ionita, Codrina Schrittwieser, Roman Xu, Guosheng Yan, Ning Wang, Huiqian Naulin, Volker Rasmussen, Jens Juul Steinmüller-Nethl, Doris |
author_facet | Ionita, Codrina Schrittwieser, Roman Xu, Guosheng Yan, Ning Wang, Huiqian Naulin, Volker Rasmussen, Jens Juul Steinmüller-Nethl, Doris |
author_sort | Ionita, Codrina |
collection | PubMed |
description | Plasma probes are simple and inexpensive diagnostic tools for fast measurements of relevant plasma parameters. While in earlier times being employed mainly in relatively cold laboratory plasmas, plasma probes are now routinely used even in toroidal magnetic fusion experiments, albeit only in the edge region, i.e., the so-called scrape-off layer (SOL), where temperature and density of the plasma are lower. To further avoid overheating and other damages, in medium-size tokamak (MST) probes are inserted only momentarily by probe manipulators, with usually no more than a 0.1 s per insertion during an average MST discharge of a few seconds. However, in such hot and high-density plasmas, their usage is limited due to the strong particle fluxes onto the probes and their casing which can damage the probes by sputtering and heating and by possible chemical reactions between plasma particles and the probe material. In an attempt to make probes more resilient against these detrimental effects, we tested two graphite probe heads (i.e., probe casings with probes inserted) coated with a layer of electrically isolating ultra-nano-crystalline diamond (UNCD) in the edge plasma region of the Experimental Advanced Superconducting Tokamak (EAST) in Hefei, People’s Republic of China. The probe heads, equipped with various graphite probe pins, were inserted frequently even into the deep SOL up to a distance of 15 mm inside the last closed flux surface (LCFS) in low- and high-confinement regimes (L-mode and H-mode). Here, we concentrate on results most relevant for the ability to protect the graphite probe casings by UNCD against harmful effects from the plasma. We found that the UNCD coating also prevented almost completely the sputtering of graphite from the probe casings and thereby the subsequent risk of re-deposition on the boron nitride isolations between probe pins and probe casings by a layer of conductive graphite. After numerous insertions into the SOL, first signs of detachment of the UNCD layer were noticed. |
format | Online Article Text |
id | pubmed-7599483 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2020 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-75994832020-11-01 Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas Ionita, Codrina Schrittwieser, Roman Xu, Guosheng Yan, Ning Wang, Huiqian Naulin, Volker Rasmussen, Jens Juul Steinmüller-Nethl, Doris Materials (Basel) Article Plasma probes are simple and inexpensive diagnostic tools for fast measurements of relevant plasma parameters. While in earlier times being employed mainly in relatively cold laboratory plasmas, plasma probes are now routinely used even in toroidal magnetic fusion experiments, albeit only in the edge region, i.e., the so-called scrape-off layer (SOL), where temperature and density of the plasma are lower. To further avoid overheating and other damages, in medium-size tokamak (MST) probes are inserted only momentarily by probe manipulators, with usually no more than a 0.1 s per insertion during an average MST discharge of a few seconds. However, in such hot and high-density plasmas, their usage is limited due to the strong particle fluxes onto the probes and their casing which can damage the probes by sputtering and heating and by possible chemical reactions between plasma particles and the probe material. In an attempt to make probes more resilient against these detrimental effects, we tested two graphite probe heads (i.e., probe casings with probes inserted) coated with a layer of electrically isolating ultra-nano-crystalline diamond (UNCD) in the edge plasma region of the Experimental Advanced Superconducting Tokamak (EAST) in Hefei, People’s Republic of China. The probe heads, equipped with various graphite probe pins, were inserted frequently even into the deep SOL up to a distance of 15 mm inside the last closed flux surface (LCFS) in low- and high-confinement regimes (L-mode and H-mode). Here, we concentrate on results most relevant for the ability to protect the graphite probe casings by UNCD against harmful effects from the plasma. We found that the UNCD coating also prevented almost completely the sputtering of graphite from the probe casings and thereby the subsequent risk of re-deposition on the boron nitride isolations between probe pins and probe casings by a layer of conductive graphite. After numerous insertions into the SOL, first signs of detachment of the UNCD layer were noticed. MDPI 2020-10-13 /pmc/articles/PMC7599483/ /pubmed/33065961 http://dx.doi.org/10.3390/ma13204524 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Ionita, Codrina Schrittwieser, Roman Xu, Guosheng Yan, Ning Wang, Huiqian Naulin, Volker Rasmussen, Jens Juul Steinmüller-Nethl, Doris Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas |
title | Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas |
title_full | Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas |
title_fullStr | Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas |
title_full_unstemmed | Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas |
title_short | Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas |
title_sort | diamond-coated plasma probes for hot and hazardous plasmas |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7599483/ https://www.ncbi.nlm.nih.gov/pubmed/33065961 http://dx.doi.org/10.3390/ma13204524 |
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