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TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics: Difference between revisions
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TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics (view source)
Revision as of 17:40, 21 January 2022
, 21 January 2022→Name and affiliation of proponent
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== Name and affiliation of proponent == | == Name and affiliation of proponent == | ||
L. Eliseev and the HIBP Kurchatov team, Russia | |||
A. Kozachek and the HIBP Kharkov team, Ukraine | |||
M. Koepke UWV, USA | |||
T. Estrada, E. de la Cal, I. Voldiner, M.A. Ochando, CIEMAT | |||
== Details of contact person at LNF == | == Details of contact person at LNF == | ||
Teresa Estrada | |||
https://orcid.org/0000-0001-6205-2656 | |||
== Description of the activity == | == Description of the activity == | ||
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] | At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4]. | ||
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition. | Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition. | ||
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition. | The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition. | ||
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* Number of plasma discharges or days of operation: | * Number of plasma discharges or days of operation: | ||
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements. | Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements. | ||
Experiments in May 2022 focussed on HIBP & DR & Probes | Experiments in May 2022 focussed on HIBP & DR & Probes | ||
Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics | Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics | ||