Changes in Statistical Characteristics of Turbulent Plasma Density Fluctuations During a Transport Transition in the L-2M Stellarator

• Published in: Plasma physics reports Vol. 48; no. 7; pp. 740 - 753
• Main Authors: Batanov, G. M., Borzosekov, V. D., Gorshenin, A. K., Sarksyan, K. A., Stepakhin, V. D., Kharchev, N. K.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.07.2022; Springer Nature B.V
• Subjects: Atomic; Cyclotron resonance; Deviation; Distribution functions; Electron cyclotron resonance; Electron energy; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Plasma; Plasma density; Plasma turbulence; Probability distribution functions; Statistical analysis; Stellarators; Stochastic processes; method of moving separation of mixtures; density fluctuations; scattering; stellarator; electron cyclotron resonance heating; gyrotron; statistical analysis; EM algorithm; high-temperature plasma
• ISSN: 1063-780X; 1562-6938
• DOI: 10.1134/S1063780X2270026X

At the specific power of electron cyclotron resonance (ECR) heating of 3.2 MW m –3 (plasma density of 2 × 10 19 m –3 , electron temperature of 0.6 keV), an increase in the plasma energy lifetime by not less than 30% is accompanied by a two-time-decrease in the level of short-wave turbulent density fluctuations. In such a shot, before the beginning of the quasi-stationary confinement stage, the turbulent state of density fluctuations is characterized by the stronger deviation from zero of the coefficient of excess of fluctuation increments than it is in shots without transport transitions. This indicates the stronger deviation of the probability distribution function of density fluctuation increments from the normal law in shots with transport transitions. Based on the analysis of increments of short-wave fluctuations using the special method for separating the continuous components in stochastic processes, a qualitative difference was established between the behaviors of the structural components forming the plasma turbulence in shots with and without transport transitions. In addition, for shots with transport transitions, a change in the shape of the approximating finite mixture of normal distributions and parameters of its component densities is demonstrated.