Ion charge-state distribution in a high-power pulsed electron cyclotron resonance discharge sustained by millimeter-wavelength radiation

Measurements have been made of the ion charge-state distribution in a high-power, pulsed, electron-cyclotron discharge in argon sustained by millimeter radiation. It has been observed that the maximum of the distribution is shifted toward higher charge states compared with the distributions in conventional cw sources of multiply charged ions pumped by centimeter radiation. This shift of the distribution maximum evidently occurs because a so-called quasigasdynamic plasma confinement regime can be established in a magnetic trap when higher-power, shorter-wavelength gyrotron radiation is used, and in this regime, an increase in plasma density is accompanied by an increase in the confinement parameter Nτ, which determines the ion charge distribution. Pis’ma Zh. Tekh. Fiz. 23, 60–64 (April 26, 1997)     

Unipolar semiconductor laser for the terahertz frequency range

In this paper a new design is proposed for a unipolar semiconductor laser with longitudinal transport of electrons and a stepped variation in the thickness of quantum wells, in which population inversion is obtained, and as a result the electrons of the first subband in the narrow part of the well, with injection into the wide part, preferentially populate its second subband. Deceased Pis’ma Zh. Tekh. Fiz. 23, 90–94 (February 26, 1997)     

Initial stage of gas discharge in an inhomogeneous electric field

A model of the initial stage of gas discharge has been developed within the framework of the particle in cell (PIC) method, with allowance for the space charge and particle collisions described using the Monte Carlo (MC) numerical simulation technique. The PIC/MC simulations of the initial stage of discharge under conditions of the electric field strength to gas pressure ratio E/P > 1 kV/(cm Torr) showed that a beam of runaway electrons is formed within ∼10 ps near the cathode, which consists of both emitted electrons and those generated as a result of the gas ionization. The duration of the beam pulse is determined primarily by plasma screening of the external electric field near the cathode and amounts to 10–20 ps.     

Soft X-rays generated by the electron-cyclotron resonance discharge in heavy gases sustained by a high-power microwave beam in a magnetic trap

The soft X-ray line emission from a pulsed electron-cyclotron resonance discharge in argon, maintained by a high-power millimeter-wavelength beam in a magnetic mirror trap, was studied using a multilayer mirror X-ray monochromator. The X-ray spectrum was measured, and the absolute spectral intensity of emission was determined in a 6–17 nm wavelength range. The discharge can be used as an effective source of soft X-rays with an efficiency of the microwave to X-ray power conversion on a level of 10% and a maximum spectral power density of 7.3 kW/nm at a wavelength of 9 nm.     

Shadow method for measuring the average electron density in an ionized gas flow induced by a high-frequency barrier discharge

The electron density distribution in an ionized gas flow induced by a high-frequency barrier discharge has been investigated by an optical method. It has been shown that ion acceleration occurs mainly near the minima of the electron density, and the extremes in the temperature distribution are in antiphase with the corresponding extremes of the electron density. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 364–370, March–April, 2009.     

Method for identifying diffraction satellites of surface plasmons in terahertz frequency range

A new method for the identification of diffraction satellites accompanying surface plasmons (SPs) in the terahertz frequency range is proposed and verified. Reliable detection of these satellites allows the accuracy of plasmon spectrometers for the terahertz range to be significantly increased. The idea of the proposed method is based on the fact that a local thin-film coating element applied onto the SP-guiding surface in the absence of diffraction satellites must reduce the SP intensity by the same amount irrespective of the site of application. Experiments performed on the Novosibirsk free-electron laser facility confirmed the efficiency of the proposed method.     

Investigation of the parameters of laser radiation emitted by a single-frequency high-power gas laser

Studies to determine whether it is possible to obtain a stable single-frequency mode of generation in large He–Ne lasers were undertaken. Selection of the frequencies in the particular lasers was performed by means of a Fabry–Perot interferometer situated at a low angle to the axis of the cavity resonator. It is shown that a laser that has been converted to function in a single-frequency mode of emission assures a coherence length of at least 10 m even when subjected to technical vibratory and acoustic effects. Translated from Izmeritel’naya Tekhnika, No. 3, pp. 24–26, March, 2009.     

Plasma aerodynamics in a supersonic gas flow

We perform an experimental study and numerical simulation of the process of periodic initiation of spark extended discharge in air flow with a Mach number M = 2. Critical parameters of the discharge are measured in a high velocity air flow, and visualization of the gas flow in the presence of the discharge is performed. The influence of the discharge on the flow near the body surface streamlined by the supersonic flow is studied.     

Positive column of glow discharge in longitudinal gas flow

A system of nonlinear equations describing a positive discharge column in a cylindrical channel with a gas flow is solved.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 818–823, May, 1988.     

A calculation of the temperature of contact surfaces in a high-power discharge of electric current of commercial frequency

Thermal processes occuring at the surface of disconnected electric contacts subjected to a high-power electric arc are considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 5, pp. 878–882, May, 1970.     

A resonant-tunneling transit-time diode for the terahertz frequency range employing transitions between quantum states in a double-barrier injector

The possibility of considerably reducing the start-up current of a coherent resonant-tunneling transit-time diode operating in the terahertz range is demonstrated. The proposed scheme relies on resonance electron transitions in a double-barrier injector.     

Generation of terahertz radiation by hot electrons in carbon nanotubes

We demonstrate theoretically that quasi-metallic carbon nanotubes emit terahertz radiation induced by an applied voltage. It is shown that in the ballistic transport regime their spontaneous emission spectra have a universal frequency and bias voltage dependence, which raises the possibility of utilizing this effect for high-frequency nanoelectronic devices.     

A cell for studying discharge in gas flow with rotating electrodes

A cell with rotating electrodes for studying discharge in gas flow is described. It is demonstrated that, using a reasonable combination of the values of external longitudinal magnetic field, flow velocity, and electrode rotation rate, it is possible under certain conditions to control the delay of gas breakdown and the duration of a short volume discharge preceding the discharge contraction stage.     

Glow discharge in a transverse supersonic gas flow at low pressures

A low-pressure glow discharge in a transverse supersonic gas flow was experimentally studied for the case where the flow only partially fills the interelectrode gap. It is shown that the space region with supersonic gas flow has a higher concentration of gas particles and, therefore, works as a charged particle generator. The near-electrode regions of glow discharge are concentrated specifically in this region. This structure of glow discharge is promising for plasma deposition of coatings under ultralow pressures.     

Glow discharge in external magnetic field in hypersonic flow of rarefied gas

A two-dimensional computational model is used to investigate the gasdynamic structure of a rarefied (pressure of several torr) hypersonic flow of molecular nitrogen in a plane channel, with a glow discharge maintained between two surfaces of this channel. An asymmetric configuration of electrodes is considered, namely, the cathode is a narrow strip located on the lower surface of the channel, and the upper surface of the channel is a continuous anode. The fundamental possibility is studied of using an external magnetic field transverse to the flow for modifying the shock-wave structure of flow in the channel.A two-dimensional conjugate electrogasdynamic model is given, which includes equations of continuity, Navier-Stokes equations, equations of conservation of energy, and equations of continuity of charged particles in ambipolar approximation. The real thermophysical and transport properties of molecular nitrogen are included.It is demonstrated that the use of a surface glow discharge in a rarefied hypersonic flow enables one to effectively modify the shock-wave structure of flow and, thereby, consider discharges of this type as additional means of control over rarefied gas flows.     

Discharge current and ultrashort avalanche electron beam current in a volume nanosecond gas discharge in inhomogeneous electric field

The moment of generation of an ultrashort avalanche electron beam (UAEB) relative to the discharge current pulse front has been determined in a volume discharge formed upon nanosecond breakdown of an air gap at atmospheric pressure in an inhomogeneous electric field. The UAEB current reaches maximum on the front of the discharge current pulse, ～100 ps before the peak of this current. Bias currents with amplitude above 1 kA have been observed. The amplitude of this current increases due to the charging of a capacitor formed by the flat metal anode and a dense discharge plasma expanding from the cathode.     

Control of the glow discharge parameters at low pressures by means of a transverse supersonic gas flow

According to the results of a numerical experiment, we show the possibility of control of the glow discharge parameters and structure by means of creating a supersonic gas flow in the selected section of the interelectrode spacing.     

Increasing the operating frequency in high-power distributed microgate bipolar switches

The dynamic turn-off losses can be decreased, and the operating frequency increased in high-power distributed microgate bipolar switches (MGBSs) by optimizing the device design so as to ensure that the charge extracted from the high-ohmic base and the built-in impurity charge would have opposite signs. In particular, in MGBS with a hole-extracting cathode gate and an anode buffer layer, this is achieved by using p type doping of the base instead of the n type. A special analytical model has been constructed that describes the MGBS turn-off process. It is established that, at a voltage of ∼5 kV, the losses per turn-off operation can be reduced from 200 to 100 mJ/cm² and the frequency increased from 0.5 to 1.0 kHz.