TJ-II:Imaging of pelet cloud dynamics in TJ-II using Halpha and bremsstraahlung filters and a fast-frame camera: Difference between revisions
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[https://orcid.org/0000-0000-0000-0000 Gabor Kocsis], CRC-Budapest and | [https://orcid.org/0000-0000-0000-0000 Gabor Kocsis], CRC-Budapest and | ||
[https://orcid.org/0000- | [https://orcid.org/0000-0002-8305-3858 Tamás Szepesi], CRC-Budapest | ||
== Details of contact person at LNF == | == Details of contact person at LNF == | ||
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== International or National funding project or entity == | == International or National funding project or entity == | ||
Include funding here | Include funding here: Hungarian and EUROfusion grants plus Spanish PN: PID2020-116599RB-I00. | ||
== Description of required resources == | == Description of required resources == | ||
Latest revision as of 09:47, 21 January 2022
Experimental campaign
Spring 2022
Proposal title
Imaging of pellet cloud dynamics in TJ-II using Halpha and bremsstrahlung filters and a fast-frame camera
Name and affiliation of proponent
Gabor Kocsis, CRC-Budapest and Tamás Szepesi, CRC-Budapest
Details of contact person at LNF
Kieran J McCarthy
Description of the activity
This aim of this proposal is to investigate the interaction of cryogenic hydrogen and impurity pellets (TESPEL) with stellarator plasma by evaluating fast framing video data. In early 2020, LFS TESPEL and hydrogen pellet injection experiments were conducted on TJ-II but these were cut short by the pandemic. Movies (frame-rates up to 700 kHz) with TOP and TANGENTAL views were recorded using different filters (C I, C III, Hα, Li II). It was seen that the drifting pellet clouds extend broadly along the magnetic field lines. In the case of the impurity pellet, which travels inwardly into the plasma at a constant speed, the C+2 cloud surrounding a TESPEL is small and spherical. In was determined that plasmoids (partialy ionized clouds) are launched frequently (every 5-10µs) - as expected - and drift outwards from the plasma at a speed of approximately 5 km/s. In the case of cryogenic pellets, it was difficult to recognize the individual drifting clouds, despite the 700 kHz frame rate, so perhaps the time resolution was not high enough. Nonetheless, it was concluded that the cloud is hollow around the pellet and drifts outwards. Further experiments are needed in this area to achieve a better understanding of the cloud dynamics. Such information will be compared with cloud dynamics for similar pellets on the stellarator W7-X in order to achieve a more comprehensive understanding. It is proposed to continue these studies in TJ-II with the W7-X fast camera during 2022 with higher frame rates and with Hα and bremmstrahlung filters. Again, TOP and TANGENTIAL views will be needed and pellets will be injected into both ECRH and NBI plasmas. The proponents have significant experience in using fast-frame cameras on tokamaks and stellarators. Recently, they studied pellet cloud drifting (cryogenic and TESPEL) on the stellarator W7-X [1]. Also, the local team have significant experience with pellet injectiona nd fast frame image analysis [2].
International or National funding project or entity
Include funding here: Hungarian and EUROfusion grants plus Spanish PN: PID2020-116599RB-I00.
Description of required resources
Required resources:
- Number of plasma discharges or days of operation: 4 (2 in March and 2 in May or June)
- Essential diagnostic systems:Pellet Injector and Fast frame imaging camera with fibre bundle connected to A8:TANGENTIAL and B2:TOP
- Type of plasmas (heating configuration): ECH and NBI (standard configuration is best)
- Specific requirements on wall conditioning if any: Recent lithium and boron coatings
- External users: No
- Any external equipment to be integrated? Fast-frame camera as in spring 2020
Preferred dates and degree of flexibility
Preferred dates: March 2022 and May or June 2022