Одномерное квазилинейное уравнение для описания генерации токов увлечения в плазме токамака геликонами

A quasi-linear equation which allows describing evolution of electron distribution function and generation of non-inductive currents by helicons is obtained. It is shown that in the analysed case the Fokker-Planck equation can be approximated by a one-dimensional equation in the longitudinal electron velocity space with a diffusion coefficient proportional to the helicon power absorbed by electrons due to Landau damping.

Effect of Electric Field On Electron Mobility in Sub-100 nm InAlN/GaN High Electron Mobility Transistors

Electron mobility is important for electron velocity, transport current, output power, and frequency characteristics. In conventional mobility extraction methods, electron mobility is usually extracted directly from the measured gate capacitance (CG) and current-voltage characteristics. When device gate length (LG) scales to sub-100 nm, the determination of CG becomes more difficult not only for the measure equipment but also the enhanced effect from parasitic capacitance. Here in this paper, the CG extracted from high-frequency small-signal equipment circuit is used for the InAlN/GaN high electron mobility transistors (HEMTs). Electron mobility of the device with LG of 60-nm under VDS of 0.1 V and 10 V is extracted using two-dimensional scattering theory, respectively. The obtained results show that under a high electric field, the electron temperature (Te) and addition polarization charges (∆σ) increase, resulting in the enhanced polar optical phonon (POP) as well as polarization Coulomb field (PCF) scatterings and degradation of the electron mobility. This study makes it possible to improve the electron mobility by reducing Te and ∆σ for the InAlN/GaN HEMTs application.AlGaN/GaN heterostructure field-effect transistors with different gate lengths were fabricated. Based on the chosen of the Hamiltonian of the system and the additional polarization charges, two methods to calculate PCF scattering by the scattering theory were presented. By comparing the measured and calculated source-drain resistances, the influence of the different gate lengths on the PCF scattering potential was confirmed.

Kinetic theory of instability in the interaction of an electron beam and plasma with an arbitrary anisotropic electron velocity distribution function

Based on the kinetic approach, this work investigates the stability of the system consisting of a fast electron beam and a dense plasma at an arbitrary (anisotropic) electron velocity distribution function. It is shown that during the interaction of a fast electron beam with a cold plasma, both the conditions for losing stability and the increment do not depend on the form of the electron distribution function (EDF) of a plasma and are determined only by the ratio of the electron beam energy to the mean energy in a plasma. With an increase in the mean electron energy in the plasma, it becomes necessary to take into account the moments of the EDF following for energy moment. It was found that the plasma anisotropy has a significant effect on both the stability loss conditions and the increment. The physical reason for this effect is the shift in the plasma frequency due to the Doppler effect caused by the plasma anisotropy in the coordinate system moving along with the beam. Other findings include a region of anomalous dispersion of the electron beam - plasma system and regions of negative group velocity of perturbations in such system. Physical interpretations are proposed for all the observed effects.

Beam-Plasma Stabilizer for the New Type of Nuclear Power Energy Systems

In this paper the electrokinetic characteristics of helium low-voltage beam discharge plasma in operating conditions of a three-electrode device with a hot cathode are studied. A method and a device are proposed to ensure effective voltage stabilization in a range up to 110 V by controlling the electron velocity distribution function using the plasma channel external boundaries.

Skew-kappa Distribution Functions and Whistler Heat Flux Instability in the Solar Wind: The Core-strahlo Model

Electron velocity distributions in the solar wind are known to have field-aligned skewness, which has been characterized by the presence of secondary populations such as the halo and strahl. Skewness may provide energy for the excitation of electromagnetic instabilities, such as the whistler heat flux instability (WHFI), which may play an important role in regulating the electron heat flux in the solar wind. Here we use kinetic theory to analyze the stability of the WHFI in a solar-wind-like plasma where solar wind core, halo, and strahl electrons are described as a superposition of two distributions: a Maxwellian core, and another population modeled by a Kappa distribution to which an asymmetry term has been added, representing the halo and also the strahl. Considering distributions with small skewness, we solve the dispersion relation for the parallel-propagating whistler mode and study its linear stability for different plasma parameters. Our results show that the WHFI can develop in this system and provide stability thresholds for this instability, as a function of the electron beta and the parallel electron heat flux, to be compared with observational data. However, since different plasma states, with different stability level to the WHFI, can have the same moment heat flux value, it is the skewness (i.e., the asymmetry of the distribution along the magnetic field), and not the heat flux, that is the best indicator of instabilities. Thus, systems with high heat flux can be stable enough to WHFI, so that it is not clear whether the instability can effectively regulate the heat flux values through wave–particle interactions.

Magnetic sensitivity modeling of dual gate MOS transistor

In this paper, the magnetic field effect on the carrier transport phenomenon in the double gate metal-oxide-semiconductor field-effect transistor (MOSFET) has been investigated. This is done by exploring the Lorentz force and the behavior of a semiconductor subjected to a constant magnetic field. The magnetic field modulates the electrons position and density as well as the potential distribution in the case of silicon tunnel tunneling field-effects (FETs). This modulation impacts the device electrical characteristics such as ON current (I_ON), subthreshold leakage current (IOF), threshold voltage (V_T), magneto-transconductance (g_mm) and output magneto-conductance (gm_DS). In addition, a hall voltage (V_H) is induced and modulated by the magnetic field. It has been observed that this voltage influences the effective applied gate voltage. It has been observed that the threshold voltage variations induced by the magnetic field is of paramount importance and affects the device switching properties both speed and power dissipation, noted that the threshold voltage VT and (Ion/Iof) ratio are reduced by 10^-3V and 10² for a magnetic field of ±6 and ±5.5 Tesla, respectively. We have simulated the different behavior in the channel, mainly doping concentration, potential distribution, conduction and valence bands, total current density, total charge density, electric field, electron mobility, and electron velocity.

Study on Electric Field Modulation and Avalanche Enhancement of SiC/GaN IMPATT Diode

This paper proposes a 6H-materials silicon carbide (SiC)/gallium nitride (GaN) heterogeneous p-n structure to replace the GaN homogenous p-n junction to manufacture an impact-ionization-avalanche-transit-time (IMPATT) diode, and the performance of this 6H-SiC/GaN heterojunction single-drift-region (SDR) IMPATT diode is simulated at frequencies above 100 GHz. The performance parameters of the studied device were simulated and compared with the conventional GaN p-n IMPATT diode. The results show that the p-SiC/n-GaN IMPATT performance is significantly improved, and this is reflected in the enhanced characteristics in terms of operating frequency, rf power, and dc-rf conversion efficiency by the two mechanisms. One such characteristic that the new structure has an excessive avalanche injection of electrons in the p-type SiC region owing to the ionization characteristics of the SiC material, while another is a lower electric field distribution in the drift region, which can induce a higher electron velocity and larger current in the structure. The work provides a reference to obtain a deeper understanding of the mechanism and design of IMPATT devices based on wide-bandgap semiconductor materials.