Displacement of the electron cyclotron resonance heating region and time evolution of the characteristics of short-wavelength turbulence in the 3D magnetic configuration of the L-2M stellarator

Reflection of the heating extraordinary microwave incident obliquely onto the surface of the electron cyclotron resonance (ECR) at the second harmonic of the electron gyrofrequency in the 3D magnetic configuration of the L-2M stellarator was studied experimentally. The plasma was heated using two gyrotrons with a total power of 600–700 kW, the specific heating power being 2.4–2.8 MW/m³. The displacement of the ECR region in the course of heating was monitored by measuring the phase of the reflected extraordinary wave. It is found that the growth of the plasma density is accompanied by the displacement of the ECR heating region from the center of the plasma column toward its periphery. The coefficient of reflection of the heating microwave beam from the ECR region was measured. The spectra of short-wavelength (k _s ≈ 30 cm^?1) plasma density fluctuations were explored by analyzing backscattered microwave radiation. A tenfold increase in the energy of short-wavelength density fluctuations and the growth of the spectral density of fluctuations in the frequency range of 0.3–1.5 MHz were observed.     

Discharge in a Subthreshold Microwave Beam as an Effective Means for Mercaptan Decomposition

Plasma Physics Reports - A subthreshold microwave discharge in atmospheric-pressure air is used to process mixtures of mercaptans (thiols) with air and with air and methane. It is found that, at...     

Effect of microwave reflection from the region of electron cyclotron resonance heating in the L-2M stellarator

In experiments on electron cyclotron resonance (ECR) heating of plasma at the second harmonic of the electron gyrofrequency in the L-2M stellarator, the effect of partial reflection of high-power gyrotron radiation from the ECR heating region located in the center of the plasma column was revealed. The reflection coefficient is found to be on the order of 10^?3. The coefficient of reflection of an extraordinary wave from the second-harmonic ECR region is calculated in the one-dimensional full-wave model. The calculated and measured values of the reflection coefficient are found to coincide in order of magnitude.     

Microwave Discharge in Gas above Regolith Surface

Plasma Physics Reports - A layer of regolith with a 1.35% Al content was irradiated from the side of the reactor supporting plate with a microwave pulse with an intensity of 10–15 kW...     

Testing of the spectroscopic method for location of water microleakages in ITER at the L-2M stellarator

Results of testing of a possible method for location of water microleakages in the cooling system of the first wall and vacuum chamber of ITER are presented. The method consists in spectroscopic detection of the emission lines of atoms and ions of the Xe additive dissolved in water. These lines are excited when the water with dissolved Xe contacts the plasma. The high electron cyclotron resonance heating (ECRH) power deposited in a relatively small plasma volume in the L-2M stellarator (P = 0.5 MW, V = 0.24 m³, and the specific heating power ??2 MW/m³) makes it possible to achieve plasma parameters close to those in the edge plasma of ITER for different operating modes, including the H-mode with an edge transport barrier. In test experiments, several lines of Xe ions were revealed suitable for detection of xenon in plasma with parameters close to those in the edge plasma of ITER at leakage rates at a level of ??10^?6 Pa m³ s^?1 and spatial resolution of ??0.5 cm.     

Discharge in a Subthreshold Microwave Beam as an Unusual Type of Ionization Wave

Plasma Physics Reports - Ionization−overheating instability of a non-self-sustained discharge in air in a subthreshold microwave field creates a self-sustained discharge with a fine cellular...     

A new MIG-3 gyrotron complex for creation and heating of plasma in the L-2M stellarator and the first experimental results

The characteristics of a new MIG-3 gyrotron complex for creating and heating plasma in the L-2M stellarator are presented. The first experimental results using the complex are reported. The complex consists of two three-electrode GYCOM gyrotrons of the new generation with electron beam energy recuperation, a high-voltage modulator that enables both separate and simultaneous operation of the two gyrotrons, and a control/data-recording unit. The total specific power to be inserted into plasma reaches 5 MW/m³ when both gyrotrons in operation.     

Backscattering of gyrotron radiation and short-wavelength turbulence during electron cyclotron resonance plasma heating in the L-2M stellarator

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.     

Self-Action of a Gaussian Beam of Microwaves in the Subthreshold Field Generated by the Waves in Air

Plasma Physics Reports - A microwave beam (wavelength 4 mm, power 150–300 kW) generates an ionization wave in air in the subthreshold field in the shape of a conglomerate of thread-like...