Probable reasons are discussed why the absorbed energy determined from diamagnetic measurements in experiments on electron cyclotron resonance plasma heating is less than the input microwave energy.

The experiments on ECR plasma heating were carried out at the L-2M stellarator at very high volume power density (up to 3.0 MW/m3). Under these conditions, non-monotonous hollow density profiles were measured. At the maximum heating power of P = 0.75 MW, the concavity in the axial region becomes drastic ne(0)/nemax = 0.5. In these experiments, plasma temperature profiles measured in the axial plasma region r/ap < 0.4 occur to be rather flat. We have also measured two-slope SXR spectra in the range from 2 to 12 keV. The possible reasons for these observed phenomena were discussed. However, with growing ECRH power up to PECRH = 0.75 MW, we have not observed dramatic deterioration of plasma confinement at the L-2M stellarator. The measured energy lifetime is generally consistent with that determined from the international LHD scaling.

Дан обзор наиболее интересных результатов, представленных на ежегодной XLII Международной (Звенигородской) конференции по физике плазмы и управляемому термоядерному синтезу. Проведен анализ главных направлений исследований в области физики плазмы в России.

Various methods of determining the ambipolar electric field in toroidal magnetic systems (predominantly, in stellarators) and the evolution of views on this problem are discussed. Paradoxes encountered in solving this problem are analyzed, and ways of resolving them are proposed.

In order to model transport processes in magnetic confinement systems, it is necessary to have information on the charged particle source. This in turn requires calculation of the inward flux of neutral particles. In this paper, a method for solving this problem in the hydrodynamic approach for the neutral gas is proposed. The average velocity of neutral particles and the spatial distribution of their density are determined. The obtained expression for the neutral density almost completely coincides with that calculated previously by solving the kinetic equation. However, the computational time required to solve the problem in the proposed hydrodynamic approach is much shorter than that in the kinetic approach.

Дан обзор наиболее интересных результатов, представленных на XL Международной Звенигородской конференции по физике плазмы и управляемому термоядерному синтезу. Проведен анализ главных направлений исследований в области физики плазмы в России.

Дан обзор наиболее интересных результатов, представленных на ежегодной XLI Международной (Звенигородской) конференции по физике плазмы и управляемому термоядерному синтезу. Проведен анализ главных направлений исследований в области физики плазмы в России.

Backscattering of gyrotron radiation (θ = π) by short-wavelength density fluctuations (k ⊥ = 30 cm−1) in the plasma of the L-2M stellarator was studied under conditions of electron cyclotron resonance (ECR) plasma heating at the second harmonic of the electron gyrofrequency (75 GHz). The scattering of the O-wave emerging due to the splitting of the linearly polarized gyrotron radiation into the X- and O-waves was analyzed. The signal obtained after homodyne detection of scattered radiation is a result of interference of the reference signal, the quasi-steady component, and the fast oscillating component. The coefficients of reflection of the quasi-steady component, R = 2 (Y), and fast oscillating component, R ∼ 2 (Y), of scattered radiation are estimated. The growth of the R ∼ 2 (Y) coefficient from 3.7 × 10−4 to 5.2 × 10−4 with increasing ECR heating power from 190 to 430 kW is found to correlate with the decrease in the energy lifetime from 1.9 to 1.46 ms. The relative density of short-wavelength fluctuations is estimated to be 〈n ∼ 2 〉/〈n e 2 〉 = 3 × 10−7. It is shown that the frequencies of short-wavelength fluctuations are in the range 10–150 kHz. The recorded short-wavelength fluctuations can be interpreted as structural turbulence, the energy of which comprises ∼10% of the total fluctuations energy. Simulations of transport processes show that neoclassical heat fluxes are much smaller than anomalous ones. It is suggested that short-wavelength turbulence plays a decisive role in the anomalous heat transport.

Дан обзор наиболее интересных результатов, представленных на XXXIX Международной (Звенигородской) конференции по физике плазмы и управляемому термоядерному синтезу.

The key results presented at the XXXVIII International Zvenigorod Conference on Plasma Physics and Controlled Fusion, held February 14–18, 2011 are reviewed, and the main research directions are analyzed.

Papers presented at the XXXVII International Zvenigorod Conference on Plasma Physics and Controlled Fusion in Russia are reviewed, and the main research directions are analyzed.

It was shown earlier that, in the range of rare collisions, transport equations for stellarators allow steady discontinuous solutions for the ambipolar electric field and for the plasma density and temperature gradients. Moreover, such solutions are non-single-valued; that is, their explicit form depends on the initial values of the ambipolar electric field. The time-independent transport equations are derived under the conventional quasineutrality condition; i.e., it is assumed that the electron and ion densities, N e and N i , are related by the relationship N e = ZN i (where Z is the ion charge number). In other words, the plasma charge density is assumed to be much less than the product e i N i . Under typical conditions, the corresponding inequality is satisfied by a large margin. However, if the electric field E has discontinuities, then it can be seen from the equation ▿·E = 4πρ that, at the discontinuity points, the charge density becomes infinite and the relationship N e = ZN i fails to hold, so it is necessary to replace it with N e = ZN i + ρ/ e e . In the transport equations, this latter replacement produces additional terms, proportional to the second radial derivative of the field E . With these additional terms, the steady solutions are modified substantially. First, the ambipolar field and the derivatives of the density and temperatures all become continuous functions of the coordinates, a result that seems to be quite obvious. The second, not-so-obvious result is that the steady solutions become single-valued, i.e., independent of the initial values of the ambipolar electric field. It turns out that, in this case, two regimes are possible, depending on the values of the plasma parameters. In the first regime, the solution is unique and is independent of the initial conditions. In the second regime, two steady solutions can exist, depending on the initial conditions. One of the solution is similar to that obtained in the first regime, and the other differs from the first one both in the ambipolar field profile and in the dependence of the density and temperatures on the minor plasma radius. It cannot be excluded that different plasma confinement modes revealed in experiments are associated with the existence of such solutions.

This paper reports on studies of short-wave turbulence in the plasma of the L-2M stellarator under markedly different conditions: with doubling the ECR heating power (100 and 200 kW) and with restricting the plasma radius by a sector limiter. The role of such short-wave turbulence in anomalous transport can appear important for conditions of a thermonuclear reactor. Experiments were carried out in a basic magnetic configuration of the L-2M stellarator during ECRH at the second harmonic of the electron gyrofrequency (75.3 GHz) at average electron densities of (1.5–1.7) × 1013 cm−3. The energy confinement time was ∼3.5 ms at P0 = 100 kW and was reduced to ∼2 ms at P0 = 200 kW. When the limiter was introduced inside the plasma to a depth of 2 cm from the last closed flux surface, τE decreased by a factor of 1.3–1.4. Plasma density fluctuations were measured from the scattering of gyrotron radiation at the second harmonic of operating frequency (∼150 GHz). A quasioptical receiving system allowed measurements of scattered radiation from plasma regions r/a ⩽ 0.6 at scattering angles π/4 ⩽ Θ ⩽ π/2 (24 cm−1 ⩽ k⊥ ⩽ 44 cm−1). The short-wave turbulence was studied for two radial positions of the scattering region: r/a = 0.3–0.4 and r/a = 0.5–0.6. Short-wave turbulence exhibits features of strong plasma turbulence. It is experimentally established that a change in the energy confinement time in the L-2M stellarator correlates with the level of short-wave turbulence.

К 80-летию со дня рождения академика Б.Б. Кадомцева. Научная сессия Отделения физических наук Российской академии наук, 10 декабря 2008 г., Смирнов В.П., Мирнов С.В., Коврижных Л.М., Гуревич А.В., Караштин А.Н., Рябов В.А., Чубенко А.П., Щепетов А.Л., Ильгисонис В.И.