Effect of sheared E × B flow on the blob dynamics in the scrape-off layer of HL-2A tokamak

Abstract

The effect of sheared E × B flow on the blob dynamics in the scrape-off layer (SOL) of HL-2A tokamak has been studied during the plasma current ramp-up in ohmically heated deuterium plasmas by the combination of poloidal and radial Langmuir probe arrays. The experimental results indicate that the SOL sheared E × B flow is substantially enhanced as the plasma current exceeds a certain value and the strong sheared E × B flow has the ability to slow the blob radial motion via stretching its poloidal correlation length. The locally accumulated blobs are suggested to be responsible for the increase of plasma density just outside the Last Closed Flux Surface (LCFS) observed in this experiment. The results presented here reveal the significant role played by the strong sheared E × B flow on the blob dynamics, which provides a potential method to control the SOL width by modifying the sheared E × B flow in future tokamak plasmas.

Transverse magnetic field effects on the high-voltage pulsed discharge plasma in helium

“…In our work, positive particles are the atomic ions He + and molecular ions He + 2 . For a special case describing the behaviour of a weakly ionized plasma under a not strong magnetic field (until the ions are magnetized), if the frequency of elastic collisions does not depend on the electron energy at a fixed gas pressure, then the ionization frequency in a magnetic field only depends on the effective electric field E ef (Tonks 1937;Golant, Zhilinsky & Sakharov 1980;Scholfield, Gahl & Shimomura 1999;White et al 1999;Starikovskiy et al 2021). Under these conditions, the magnetic and electric fields in the kinetic equation are only in combinations E 2 /(1 + ω 2 /ν 2 ea ) and the ionization frequency v i depends only on the effective electric field E ef , since it is determined by the symmetric part of the EEDF, i.e.…”

“…where ω = qB/m is the electron cyclotron frequency in the magnetic field and v ea is the electron transport collision frequency. Equation (2.5) is known as Tonks' theorem (Tonks 1937), and according to it, the application of a magnetic field to a discharge qualitatively corresponds to an increase of the neutral density (pressure), which leads to a decrease of the mean energy. At high values of E/N and low values of B/N, the agreement between the results of Tonks' theorem and exact Monte Carlo calculations is better (Dujko et al 2005).…”

“…The effect of the magnetic field on the gas-discharge plasma has been investigated since the middle of the last century (Spitzer 1958;Sakharov 1959). The confinement of high-temperature plasma by the magnetic field is still of great interest to scholars worldwide (Blewin and Haydon 1958;Harcombe, Palmer & Gozna 1963;Huxley and Crompton 1974;Ness 1994;White, Robson & Ness 1999;Ness and Makabe 2000;Raspopovic et al 2000;Shidoji, Makabe & Ness 2001;Dujko, Raspopovic & Petrovic 2005;Hettkamp and Lindemann 2007;Bobrov et al 2013;Dujko et al 2015;Omarov et al 2018;Limpens et al 2021;Starikovskiy, Aleksandrov & Shneider 2021;Gao and Fang 2022;Rodríguez, Paul & Bhattacharjee 2022;Wang et al 2022;Li et al 2023). The influence of the magnetic field on low-temperature plasma of various types of discharges, such as glow discharge (Blewin and Haydon 1958), arc discharge (Hettkamp and Lindemann 2007), corona discharge (Gao and Fang 2022), pulse discharge (Li et al 2023) and after glow discharge (Limpens et al 2021) is also extensively studied.…”

“…2021; Starikovskiy, Aleksandrov & Shneider 2021; Gao and Fang 2022; Rodríguez, Paul & Bhattacharjee 2022; Wang et al. 2022; Li et al. 2023).…”

Transport barrier and spinning blob dynamics in the tokamak edge

“…The creation of blob-filaments and their interaction with background flows and turbulence were also examined in the HL-2A tokamak [33]. Blobs can slow down in response to sheared flow during Ohmic heating in HL-2A tokamak [34].…”