Journal
JOURNAL OF INSTRUMENTATION
Volume 16, Issue 5, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1748-0221/16/05/P05018
Keywords
Plasma diagnostics - charged-particle spectroscopy; Plasma diagnostics - interferometry; spectroscopy and imaging
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Funding
- Russian Science Foundation [18-72-10084]
- Russian Science Foundation [18-72-10084] Funding Source: Russian Science Foundation
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This study describes the use of visible range optical diagnostic technique to measure the ambipolar electrostatic potential variation in a linear gas dynamic trap, employing Doppler shift of plasma emission lines for observation. By utilizing room temperature hydrogen jet for charge exchange, potential and ion temperature in both central and mirror areas can be measured simultaneously.
The ambipolar electrostatic potential rising along the magnetic field line from the grounded wall to the centre in the linear gas dynamic trap, rules the available suppression of axial heat and particle losses. In this paper, the visible range optical diagnostic is described using the Doppler shift of plasma emission lines for measurements of this accelerating potential drop. We used the room temperature hydrogen jet puffed directly on the line of sight as the charge exchange target for plasma ions moving in the expanding flux from the mirror towards the wall. Both bulk plasma protons and He2+ ions velocity distribution functions can be spectroscopically studied; the latter population is produced via the neutral He tracer puff into the central cell plasma. This way, potential in the centre and in the mirror area can be measured simultaneously along with the ion temperature. A reasonable accuracy of 4 divided by 8% was achieved in observations with the frame rate of approximate to 1 kHz. Active acquisitions on the gas jet also provide the spatial resolution better than 5 mm in the middle plane radial coordinate because of the strong compression of the object size when projected to the centre along the magnetic flux surface. The charge exchange radiation diagnostic operates with three emission lines: H-alpha 656.3 nm, He-I 667.8 nm and He-I 587.6 nm. Recorded spectra are shown in the paper and examples for physical dependences are presented. The considered experimental technique can be scaled to the upgraded multi-point diagnostic for the next generation linear traps and other magnetic confinement systems.
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