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The energy of directed plasma flows accelerated in a current sheet is studied experimentally as a function of the current flowing through the sheet. It is found that the plasma flow energy rapidly increases with increasing current amplitude, nearly according to a power law with an exponent of 1.8–1.9. Using relations for the neutral current sheet and the concept of plasma acceleration under action of the Ampere forces, the energy of directed plasma flows is estimated as a function of the total current flowing through the sheet. It is shown that, as the current rises, the ion energy grows due to an increase in both the Ampere forces and the width of the current sheet within which plasma is accelerated.

The distributions of the ion temperature, ion pressure, and electron density over the width (the major transverse dimension) of the current sheet have been studied for the first time. The current sheets were formed in discharges in argon and helium in 2D and 3D magnetic configurations. It is found that the temperature of argon ions in both 2D and 3D magnetic configurations is almost uniform over the sheet width and that argon ions are accelerated by the Ampere force. In contrast, the distributions of the electron density and the temperature of helium ions are found to be substantially nonuniform. As a result, in the 2D magnetic configuration, the ion pressure gradient across the sheet width makes a significant contribution (comparable with the Ampere force) to the acceleration of helium ions, whereas in the 3D magnetic configuration, the Ampere force is counterbalanced by the pressure gradient.

Results are presented from L-2M stellarator experiments on testing a possible method for detection of water microleakages in the cooling system of the first wall and vacuum chamber of ITER. The method consists in the spectroscopic detection of spectral lines of the OH hydroxyl, which forms via the dissociation of water molecules in plasma. Emission in the spectral band of 305–310 nm can be detected even at water leakage rates less than 10−4 Pa m3/s. Chemical reactions between water and boron compounds on the vacuum chamber wall delay the detection of leakages up to ∼2000 s. A similar phenomenon can be expected when a leakage will occur in ITER, where the materials suggested for the first wall (Be, Li) can also chemically react with water.

A mathematical model of data transmission from the site of self-warming in a dispersed system with distributed parameters is suggested which allows one to perform systematic calculations of the parameters of the process of heat propagation in a silo tower. The inverse heat conduction problem is solved allowing one, by using information signals on the current temperature of a granular bed, to promptly guard against the occurrence of local sites of self-warming under conditions of grain storage.

Results are presented from experimental studies of variations in the plasma parameters during the excitation of a multiaxis magnetic configuration by the induction current (up to 17 kA) in the basic magnetic configuration of the L-2M stellarator in the regime of ECR heating at a microwave power of ∼200 kW (∼1 MW m−3) and an average plasma density of (1–2) × 1019 m−3. The current direction was chosen to reduce the net rotational transform (the so-called “negative“ current). The current was high enough for the rotational transform to change its sign inside the plasma column. Computer simulations of the L-2M magnetic structure showed that the surface with a zero rotational transform is topologically unstable and gives rise to magnetic islands, i.e., to a multiaxis magnetic configuration. Magnetic measurements showed that, at negative currents above 10 kA, intense bursts of MHD oscillations with a clearly defined toroidal mode number n = 0 were observed in the frequency range of several kilohertz. Unfortunately, the experimental data are insufficient to draw the final conclusion on the transverse structure of these oscillations. The radial temperature profiles along the stellarator major radius in the equatorial plane were studied. It is found that the electron temperature decreases by a factor of 1.3 in the plasma core (r/a ≤ 0.6) and that the temperature jump is retained near the boundary. A change in turbulent fluctuations of the plasma density during the excitation of a negative current was studied using wave scattering diagnostics. It is found that the probability density function of the increments of fluctuations in the plasma core differs from a Gaussian distribution. The measured distribution is heavy-tailed and broadens in the presence of the current. It is found that the spectrum of turbulent fluctuations and their Doppler shift near the plasma boundary are nonuniform in the radial direction. This may be attributed to the shear of the poloidal velocity. The experimental results indicate that the formation of regions with a zero rotational transform in the plasma core somewhat intensifies plasma transport.

Results are presented from studies of the effect of the discharge parameters (in particular, plasma density and heating power) and the characteristics of the magnetic configuration (e.g., rotational transform) on the confinement of a low-pressure plasma during electron-cyclotron resonance heating in the L-2M stellarator. An analysis shows that the plasma energy in the steady-state phase of a discharge is fairly well described by the product of power functions of the plasma density, heating power, and rotational transform: $$W = W_0 n_e^{\alpha _n } P^{\alpha _p } \iota ^{\alpha _\iota } $$ . The energy scalings constructed in terms of the parameters in the initial stage of free plasma decay and those in the steady-state phase are close to one another. The dynamic analysis of the plasma energy decay is now under way.

Boronization of the vacuum chamber of the L-2M stellarator has resulted in modification of the electron temperature profile. In particular, a well-defined jump in the electron temperature to Te ~ 100 eV in a narrow region Δr/r ~ 0.05 is observed in the temperature profile at the plasma edge. In the present paper, the value and shape of the jump in Te are studied at different values of plasma parameters and ECR heating power. A jump in Te is absent at a power of P ~ 100 kW, whereas at P ~ 200 kW the electron temperature drops from 150 eV to zero within Δr ~ 0.5 cm. The value of threshold power for the formation of a jump in Te at ne ~ 1.7 × 1019 m−3 lies within the range P ~ 100–160 kW. In terms of power per particle this power threshold is P/V/Ne ~ 0.2–0.3 Mw/m3/1019m−3, the value of which coincides with threshold power for ETB formation found recently in the CHS stellarator. When the helical-field strength is 25% or 50% below its standard value, a jump in Te at the plasma edge in L-2M is absent.