Experimental validation of universal plasma blob formation mechanism

Bisai, Nirmal; Banerjee, Santanu; Zweben, Stewart J.; Sen, Abhijit

doi:10.1088/1741-4326/ac3f1a

Title: Experimental validation of universal plasma blob formation mechanism

Journal Article · 03 January 2022 · Nuclear Fusion

DOI: https://doi.org/10.1088/1741-4326/ac3f1a · OSTI ID:1856189

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Institute for Plasma Research, Gandhinagar (India); Homi Bhabha National Institute, Mumbai (India)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Anomalous plasma transport in the boundary region of a tokamak plasma is commonly associated with the formation and evolution of coherent density structures known as blobs. Recently, a theory for a universal mechanism of plasma blob formation has been put forward. It is based on a breaking process of a radially elongated streamer due to poloidal and radial velocity shears. The theory is well supported by two-dimensional and three-dimensional numerical simulation results but lacks experimental validation. Here, we report the first ever experimental validation of this universal criterion by testing it against NSTX data on blobs obtained using the gas-puff imaging diagnostic. It is found that the criterion is widely satisfied in most L-mode discharges and may explain the significantly larger number of blob events. We also validate the theoretical criterion against ADITYA Langmuir probe data taken in the scrape-off layer region.

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Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1856189

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 2 Vol. 62; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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