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Dual-pass upgrade to the Thomson scattering diagnostic on the Prototype-Material Plasma Exposure eXperiment (Proto-MPEX)

Conference ·
DOI:https://doi.org/10.1063/1.5039370· OSTI ID:1607299
 [1];  [1];  [1]
  1. ORNL
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The Thomson scattering (TS) diagnostic on the Prototype-Material Plasma Exposure eXperiment has been upgraded to measure electron temperature (Te) and density (ne) simultaneously at two axial locations. After the first pass through the vacuum vessel, the exiting laser beamline is re-collimated in the atmosphere and rerouted into the vacuum vessel for the second pass. The upgrade will help diagnose axial Te and ne gradients between the “central chamber” and the target region which are located 1 m and 2.5 m, respectively, downstream from the Helicon radio-frequency source. The TS measurements have given Te ≈ 4–15 eV and ne ≈ 2–4 × 1019 m-3 at the central chamber and Te ≈ 1–2 eV and ne ≈ 1–2 × 1019 m-3 at the target region. The upgrade also increases the number of sampling points at the target region from 3 fibers to 5 fibers, measuring 3 cm radially across the plasma column, and 25 fibers in the central chamber, radially spanning 8 cm. The intensified CCD camera is double triggered for each laser pulse in order to measure (1) the TS and laser stray light and (2) the plasma background light that contains nuisance emission lines and bremsstrahlung. Subtracting the background light from the TS photons improves the temperature and density measurements. Details of the diagnostic setup, axial and radial measurements, and areas for further optimization are discussed.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
DOE Contract Number:
AC05-00OR22725
OSTI ID:
1607299
Country of Publication:
United States
Language:
English

References (10)

The Challenges of Plasma Material Interactions in Nuclear Fusion Devices and Potential Solutions journal June 2017
Plasma flow measurements in the Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) and comparison with B2.5-Eirene modeling journal May 2018
Preface: Proceedings of the 20th Topical Conference on High-Temperature Plasma Diagnostics, Atlanta, Georgia, USA, 1–5 June 2014 journal November 2014
Advanced Thomson scattering system for high-flux linear plasma generator journal December 2012
Laser Thomson scattering system applicable to low-temperature plasma in the divertor simulator MAP-II journal November 2005
Developing the science and technology for the Material Plasma Exposure eXperiment journal July 2017
First results from the Thomson scattering diagnostic on proto-MPEX journal August 2016
Thomson scattering of plasma turbulence on PSI-2 journal August 2017
High resolution Thomson scattering system for steady-state linear plasma sources journal January 2018
Laser light scattering in laboratory plasmas journal January 1969

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Related Subjects

Linear device
dual-pass Thomson Scattering
electron density
electron temperature