Title: Ion Fluxes and Neutral Gas Ionization Efficiency of the 100-kW Light-Ion Helicon Plasma Source Concept for the Material Plasma Exposure eXperiment

Abstract

Linear plasma devices are cost-effective alternatives for testing materials under reactor-relevant divertor plasma conditions. In this work, we describe how an intense radio-frequency (RF) plasma source concept for the Material Plasma Exposure eXperiment (MPEX) is under development at Oak Ridge National Laboratory. The source concept, Proto-MPEX, aims to produce high-density background deuterium helicon plasmas $\left(n_e>3\times {10}^{19}{m}^{-3}\right)$ that are subsequently heated with additional RF and microwave systems to deliver reactor-relevant conditions for studies on plasma-material interaction. In this work, we focus on the plasma-producing stage and its effectiveness in converting input neutral gas into plasma, namely, the neutral gas ionization efficiency. We provide a direct quantitative measurement of the ionization efficiency by measuring the total ion flux arriving at the target region relative to the neutral gas injected at the source. Using 80 kW at 13.56 MHz and a source magnetic field of 0.05 T, the helicon plasma source delivers ion fluxes up to $1\times {10}^{24}{m}^{-2}{s}^{-1}$ and heat fluxes greater than 1 $MW{m}^{-2}$ to a target plate located 2 m away from the source. Under these conditions, we observe that the plasma source converts ~89% of the input neutral gas into plasma that arrives at the target as ion flux at a rate of ${}_{}5\times {10}^{20}{s}^{-1}$. We demonstrate that because of the large pumping capacity of the plasma, neutral gas pumping systems are required only in the target region to maintain optimal plasma operation.

Authors:

Caneses Marin, Juan  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-6123-2081"

Piotrowicz, Pawel A. ^[2]; Biewer, Theodore  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-7456-3509"

Goulding, Richard  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-1776-7983"

Lau, Cornwall  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-8576-5867"

Showers, Melissa A. ^[3]; Rapp, Juergen  ^[1]

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• Search DOE PAGES for ORCID "0000-0003-2785-9280"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Illinois at Urbana-Champaign, IL (United States). Center for Plasma-Material Interactions
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)

Publication Date:

Fri Jun 28 00:00:00 EDT 2019

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:

1648975

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Fusion Science and Technology

Additional Journal Information:

Journal Volume: 75; Journal Issue: 7; Journal ID: ISSN 1536-1055

Publisher:

American Nuclear Society

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Material Plasma Exposure eXperiment; plasma-material-interaction facility; plasma sources