Relevance of E × B drifts for particle and heat transport in divertors

Tsui, C. K.; Boedo, J. A.; Février, O.; Reimerdes, H.; Colandrea, C.; Gorno, S.

doi:10.1088/1361-6587/ac6890

Title: Relevance of E × B drifts for particle and heat transport in divertors

Journal Article · Fri May 13 00:00:00 EDT 2022 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/ac6890· OSTI ID:1979306

^[1]; Boedo, J. A. ^[1];

^[2];

^[2]; Colandrea, C. ^[2];

^[2]

University of California San Diego (UCSD), La Jolla, CA (United States)
Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland)

Radial electric fields up to ~4 kV m^–1 are observed in the boundary between the private flux region (PFR) and the scrape-off layer (SOL) driving E × B drifts between the inner and outer targets at speeds up to 2.8 km s^–1 in the Tokamak à configuration variable divertor. The resulting E × B fluxes, located in a narrow region ($$\Delta {\rho _\Psi } < 0.012$$ in normalized radius or $$\Delta $$^R – R_sep <4 mm mapped to the outer midplane) are equivalent to around 20% of the total heat and particle flux to the divertor targets (inner + outer). At the peak E_r, the E × B poloidal transport is equivalent to parallel flows with M_∥ ~ 3. In the snowflake divertor with a second X-point in the outer SOL, the drifts in the PFR-SOL boundary were equivalent to around 30% of the total heat and particle flux to the divertor targets and cover a region ~50% wider than in the single null ($$\Delta {\rho _\Psi }$$ ~ 0.018, $$\Delta $$R – R_sep ~ 6 mm). Furthermore, the location of the PFR-SOL boundary drift shifts radially in the E_∥ × B direction when reversing the toroidal field direction. Peaks in density and electron pressure have been identified near the primary X-point along with large gradients in density, temperature, and potential, the latter resulting in a local electric field ~2.7 kV m^–1 which drives a drift (1.9 km s^–1) upwards towards the closed flux surfaces. Floating potential (V_f) magnitudes up to 75 V (~2 kT_e) were measured, indicating that V_f and parallel currents should not be neglected when estimating plasma potential.

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Research Organization:: Univ. of California, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Contributing Organization:: The TCV Team

Grant/Contract Number:: SC0010529

OSTI ID:: 1979306

Journal Information:: Plasma Physics and Controlled Fusion, Vol. 64, Issue 6; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Title: Relevance of E × B drifts for particle and heat transport in divertors

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