Possibility of quasicontinuous measurement of the evolution of the electron temperature of a plasma by the Thomson scattering method

A method is proposed for increasing the frequency of Thomson scattering measurements of the electron temperature of a plasma to 100 kHz. The approach makes it possible to raise the diagnostic sensitivity under stationary discharge conditions by three orders of magnitude. The possibilities of the method are confirmed experimentally. Pis’ma Zh. Tekh. Fiz. 23, 34–40 (September 12, 1997)     

Reconstruction of the X-ray emission spectrum of a nanosecond creeping discharge

A method is proposed for determining the soft x-ray emission spectrum of a nanosecond creeping discharge. The method includes a determination of the photoelectron density from photocurrent measurements and a calculation of the spectral flux density. The results are compared with experimental data on the wavelength interval of maximum radiation intensity. Pis’ma Zh. Tekh. Fiz. 24, 39–44 (April 12, 1998)     

Formation of dense electron beams in a gun with a plasma anode based on a reflecting discharge

A method of obtaining low-energy, high-current electron beams in a gun with a plasma anode based on a reflecting discharge is proposed and implemented for the first time. Pis’ma Zh. Tekh. Fiz. 23, 42–46 (May 26, 1997)     

Rearrangement of the shock wave structure in a decaying discharge plasma

A study has been made of the change in the structure of a shock wave in a decaying discharge plasma with Mach numbers between 1.2 and 2. A novel method is proposed to investigate the rearrangement of the shock wave structure under transient conditions. The times of the main processes responsible for this effect are determined. Pis’ma Zh. Tekh. Fiz. 23, 18–22 (April 12, 1997)     

Investigation of a glow discharge in a mixture of Ar and OH

A glow discharge in a mixture of argon and hydroxyl (OH) is investigated experimentally. It is shown that under certain discharge conditions a considerable portion of the electrical energy imparted to the discharge is used to generate resonant emission of OH molecules. The results obtained point to a realistic possibility of creating a new, ecologically friendly source of optical radiation, which can replace mercury lamps in the near future. “Applied Chemistry” State Scientific Center Pis’ma Zh. Tekh. Fiz. 25, 62–66 (April 26, 1999)     

Localization of an rf capacitive discharge in a long strip line

The self-consistent problem of a an intermediate-pressure rf capacitive discharge in a long strip line is analyzed with allowance for heating of the gas. Steady-state distributions of the discharge parameters along the line are derived. It is shown that the discharge burns in certain regions, whose lengths and locations depend on the amplitude of the applied voltage. Pis’ma Zh. Tekh. Fiz. 23, 64–70 (January 26, 1997)     

Characteristics of a submicrosecond transverse discharge in mixtures of helium with N2 and CO molecules and xenon atoms

An investigation is made of the electrical and optical characteristics of a moderate-pressure transverse discharge in typical active media of infrared CO lasers. The discharge was ignited in a system of unprofiled “ grid-plane” electrodes with automatic ultraviolet preionization by a corona discharge and had a 2×3 cm aperture. The pulse repetition frequency was 1–10 Hz, the current pulse length was ≤0.5 μs, and the pressure of the working mixtures was 10–100 kPa. Studies were made of the transverse discharge current voltage pulses, and also the spectral and temporal characteristics of the plasma radiation in N₂:CO, He:N₂:CO, and He: N₂:CO:Xe mixtures in the ultraviolet and visible ranges. Pis’ma Zh. Tekh. Fiz. 23, 71–76 (October 12, 1997)     

“Ecological” transformer-type plasmatron

A mathematical model of a transformer-type induction toroidal discharge is used to determine the gas flow pattern in the cross section of a circular torus. A method of pumping and heating the injected cold gas transverse to the circular axis is proposed. It is concluded that an “ecological” transformer-type plasmatron may be produced. Pis’ma Zh. Tekh. Fiz. 24, 20–24 (April 26, 1998)     

Use of a transverse nanosecond discharge at the prebreakdown electron ionization multiplication stage for selective excitation of neon atoms

An investigation is made of the characteristics of a transverse nanosecond discharge in Ne/SF₆ and He/Ne/SF₆ mixtures at the prebreakdown electron ionization multiplication stage. The conditions needed to obtain a stable transverse discharge with ultraviolet spark preionization are studied as well as the spectral and temporal characteristics of the plasma radiation. It is shown that this transverse discharge burning regime may be promising for the selective excitation of neon atoms which may be used to develop an electric-discharge, λ=585.3 nm, Ne(3s–3p) plasma laser. Pis’ma Zh. Tekh. Fiz. 24, 85–90 (January 12, 1998)     

Photolytic properties of a pulsed discharge in water

Results are presented of an experimental investigation of the photolytic properties of a pulsed discharge in water. A model is proposed for this process which satisfactorily describes the dependence of the hydrogen peroxide concentration on the specific discharge energy. Pis’ma Zh. Tekh. Fiz. 24, 91–95 (February 12, 1998)     

On the conditions for contraction of a multielectrode corona discharge in He/Ar, Kr, Xe mixtures

The results of an investigation of the contraction of a corona discharge in “needle-grid” and “needle-plane” electrode systems maintained by a constant negative voltage are presented. The discharge was ignited in working media of infrared lasers on p-d transitions of atoms of heavy inert gases (He/Ar, Kr, Xe mixtures). Investigation of the current-voltage characteristics showed that in the mixtures He/Ar/Kr there is no hysteresis on the rising section of the current-voltage characteristic, while hysteresis does appear for a corona discharge in the mixture He/Xe. For voltages ≥5.5 kV on the needles and ballast resistance R_b≥0.5 MΩ dynamical contraction of a corona discharge together with current pulses with f=3–5 kHz and hysteresis loops were found on the descending section of the curve I=f(U), where I and U are the average current and voltage on the discharge gap. The maximum content of atoms of heavy inert gases for [He]=200–300 kPa is [Ar]≤12, [Kr]≤8, and [Xe]≤4 kPa. Pis’ma Zh. Tekh. Fiz. 25, 90–94 (September 12, 1999)     

Investigation of the decay of Freon-12(14) molecules in a transverse nanosecond discharge

Results are presented of an investigation of the characteristics of a transverse nanosecond discharge in Freon-12 and Freon-14 (CF₂Cl₂ and CCl₄ molecules) at pressures of 1–3 kPa. The plasma radiation spectra in the range 200–600 nm and the lifetime and temporal characteristics of the Freon decay product radiation were studied. The energy cost of the decay of a CF₂Cl₂ molecule does not exceed 10–20 eV/mol which is consistent with corresponding data for a microwave discharge. This discharge is of interest for applications in systems to purify air from Freon impurities, which are the main factor responsible for the formation of the ozone holes. Pis’ma Zh. Tekh. Fiz. 24, 30–34 (December 12, 1998)     

New efficient low-pressure gas-discharge source of optical radiation using hydroxyl OH

An experimental investigation was made of the possibility of developing a new efficient gas-discharge source of optical radiation based on an OH hydroxyl molecular additive. It is shown that under certain discharge conditions, the luminous efficiency of a positive discharge column in a rare gas-hydroxyl mixture is similar to that of a mercury discharge. The results suggest that it may be possible to develop a new ecologically innocuous source of optical radiation which may in future replace mercury luminescence light sources. Pis’ma Zh. Tekh. Fiz. 25, 10–16 (January 12, 1999)     

Determination of the electron density in a discharge with nonmetallic liquid electrodes in atmospheric-pressure air from the absorption of microwave probe radiation

Measurements were made of the absorption of microwave power in a discharge plasma generated using tapwater electrodes in atmospheric-pressure air in order to determine the electron density. The high-voltage discharge burned in a bulk (diffuse) form with a lower current density than an arc discharge. This type of discharge with nonmetallic liquid electrodes is extremely promising for various technical applications. Regimes with I=50–60 mA and voltages U=2.9–3.1 kV were studied. The measurements were made at probe radiation frequencies F=29.6 and 35.2 GHz. A two-conductor transmission line was used to localize the microwave power in the plasma. An estimate was obtained for the average electron density in the central part of the discharge (4×10¹¹)<n _e <,(7×10¹¹)cm⁻³. This result shows good agreement with the results of earlier probe measurements. Pis’ma Zh. Tekh. Fiz. 24, 52–57 (December 12, 1998)     

Generation of vibrationally excited H2 molecules in a hydrogen stream flowing through a cesium-hydrogen discharge

A theoretical analysis is made of the electronic-vibrational kinetics in a stream of molecular hydrogen flowing through a cesium-hydrogen discharge. An analysis is made of the vibrational pumping of hydrogen molecules in the discharge and vibrational relaxation is studied in the cold flow zone beyond the discharge. It is shown that a very substantial increase in the concentration of vibrationally excited H₂ molecules may be achieved in the old zone. Pis’ma Zh. Tekh. Fiz. 23, 26–32 (January 12, 1997)     

Sealed efficient excilamps excited by a capacitive discharge

The development of sealed XeCl (λ∼308 nm), KrCl (λ∼222 nm), and XeI (λ∼253 nm) excilamps excited by a capacitive rf discharge is reported. It is shown that highly efficient emission of exciplex molecules is achieved under capacitive discharge excitation and the emitter has a simple design. An average emission power of 3W was obtained with a ∼12% efficiency and the lifetime of the sealed excilamps was longer than 1000 h. Pis’ma Zh. Tekh. Fiz. 25, 27–32 (November 12, 1999)     

Application of resonant Raman scattering of light for plasma diagnostics

An application of a diagnostics method based on the scattering of laser radiation by atoms in plasma is discussed. The high sensitivity of the method is due to resonant enhancement of the Raman scattering cross section with a small offset from the exact optical resonance with an intermediate level. The measurements of the spatial distribution of the excited argon atoms were performed in the plasma of a high-frequency induction discharge in a wide range of offsets from exact resonance under the conditions of linearity and with saturation of the scattering intensity. The results of the experiments are used to analyze the sensitivity of the method and to formulate the requirements for diagnostics so as to optimize the experimental conditions. Pis’ma Zh. Tekh. Fiz. 25, 46–54 (September 26, 1999)     

Formation of macroparticle structures in an rf induction discharge plasma

It was demonstrated experimentally that macroparticles may undergo levitation and form ordered structures in an rf induction discharge plasma. The experiments were carried out using 1.87 μm melamine formaldehyde particles in neon at a pressure of 25–500 Pa. The generator frequency was 100 MHz. Pis’ma Zh. Tekh. Fiz. 24, 62–68 (October 12, 1998)     

Ion energy cost in a combined inductive-capacitive rf discharge

Experimental measurements were made of the ion energy cost η as a function of the parameters of a combined rf inductive-capacitive discharge at low pressures (p<10⁻² Torr). It was established that η does not depend on the power supplied, it has a minimum as a function of pressure, and also decreases when an rf potential is applied to the electrodes. The results can be used to find the optimum parameters in terms of energy efficiency of ion formation and may be useful for refining the theoretical models of a combined rf inductive-capacitive discharge. Pis’ma Zh. Tekh. Fiz. 24, 33–39 (November 26, 1998)     

Analytic relations between the parameters of a high-voltage discharge channel plasma in a liquid and a plasma jet in an evacuated chamber

Analytic relations are derived between the parameters of a high-voltage electric discharge plasma in a liquid and the parameters of a plasma jet in an evacuated chamber. These relations can be used to calculate the plasma temperature and pressure in the axial zone of the discharge channel by using the experimentally measured temperature of the plasma jet and its geometric characteristics. Pis’ma Zh. Tekh. Fiz. 23, 75–78 (May 12, 1997)