First field test of a novel optical gas analyser in the exhaust of Wendelstein 7-X

Journal Article · Thu Mar 26 00:00:00 UTC 2026 · Plasma Physics and Controlled Fusion

DOI: https://doi.org/10.1088/1361-6587/ae52b0 · OSTI ID:3028572

Schlisio, Georg  ^[1]; Brindley, J. ^[2]; Law, M.  ^[2]; Klepper, C. Christopher  ^[3]; Delabie, Ephrem G.  ^[3]; Bräuer, T. ^[1]; Pölöskei, P. Zs  ^[1]; Boumendjel, Y. M.  ^[1]; Siddiki, F. B. T.  ^[4]; Krychowiak, M.  ^[1]

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1. Max Planck Institute for Plasma Physics, Greifswald (Germany)
2. Gencoa Ltd., Liverpool (United Kingdom)
3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
4. University of Wisconsin, Madison, WI (United States); Max Planck Institute for Plasma Physics, Greifswald (Germany)

A novel optical gas analyser, designed for isotope-resolved exhaust composition measurement, was field-tested at Wendelstein 7-X (W7-X) to validate its laboratory-proven concept under operational fusion experiment conditions. The system, Optix, comprises a cold cathode remote plasma generator and a high-resolution Fabry–Perot spectrometer and was deployed in the exhaust line of W7-X during the OP2.3 campaign. The injection of ³He and ⁴He for minority ion-cyclotron heating provided a test case for helium isotope discrimination. Despite limitations due to background gas and low partial pressures of the target species, isotope-resolved spectral signatures were successfully observed, demonstrating the fundamental viability of the Optix approach. Additionally, the spectrometer was evaluated for plasma emission measurements from both core and edge sightlines. While helium line emission was detectable, interpretation was hindered by complex background signals, highlighting the benefits of controlled remote plasma generators for spectroscopy. This first deployment provides critical insight into pressure requirements, spectral resolution, and operational constraints, informing future applications of optical exhaust diagnostics in fusion devices.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 3028572
• Journal Information: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 3 Vol. 68; ISSN 0741-3335; ISSN 1361-6587
• Publisher: IOP ScienceCopyright Statement
• Country of Publication: United States
• Language: English