Emission characteristics of a discharge iodine vapor plasma in the spectral region of the main absorption maximum of DNA molecules

Radiation of glow and capacitive discharges in inert gas-iodine vapor mixtures is studied in the spectral range 150–210 nm, which coincides with the main absorption maximum of the DNA molecules. Iodine atomic spectral lines at 150.7, 161.8, 170.2, 183.0, and 206.2 nm are observed in the spectra. The emission intensity of the iodine spectral lines is optimized by varying the glow discharge current, capacitive discharge frequency, as well as pressure and composition of the gas mixtures. The glow and capacitive discharges are ignited in cylindrical quartz tubes with interelectrode gaps of 10 and 6 cm. Helium and neon are found to be the most effective buffer gases. The optimum partial pressures of the light inert gases and iodine vapor in the glow discharge are within 0.4–0.6 kPa and 100–150 Pa, respectively. In the capacitive discharge in He(Ne)-I₂ mixtures, the optimum partial helium, neon, and iodine vapor pressures are within 0.8–2.0 kPa, 0.5–1.0 kPa, and ≤ 60 Pa, respectively. It is demonstrated that pulsed bactericidal radiation sources with light pulse lengths of 400–500 ns and continuous radiation sources emitting within the spectral range 150–207 nm can be designed on the basis of low-density iodine vapor plasma.     

Characterization of the high—voltage pulsed discharge plasma of ammonia by emission spectroscopy

We have used optical emission spectroscopy to characterize the high-voltage pulsed discharge of ammonia.Ammonia was highly dissociated in the discharge at low pressures.More atomic nitrogen was generated as compared to the discharge of nitrogen gas at the same pressure of 0.8kPa.We discuss the elimination of the oxygen impurity in the ammonia discharge,and we estimate the time-dependent atomic excitation temperature and the electron density from the measured spectra.     

A time-resolved study of the u-v radiation produced in the initial time period of a pulsed argon discharge

The time development of the integral intensity of ultra-violet radiation from the positive column of a pulsed discharge was studied and the results compared with those for visible light. The measurements were made at various pressures in the range 0·3–4·8 torr. We found that at a pressure about 4 torr the maxima of intensity of the u-v and the visible light occurred at nearly the same time after the initiation of the discharge. On the other hand, at a pressures of about 0·5 torr the positions of the maxima were different.     

Origin of surface microwave discharges

The high-pressure gas discharge initiated at the focus of pulsed powerful microwave radiation is a branched network of thin plasma channels completely filling the volume of the focal zone. A detailed experimental investigation of such discharges is carried out with a setup operating at a wavelength of 8.9 cm and at pressures ranging from 0.05 to 1.00 atm. When the initiator is placed on a dielectric plate, the discharge channels are found to propagate solely over the surface of the dielectric. It is shown that electrodynamic interaction between the gas discharge and dielectric is the main reason for the surface propagation of the discharge.     

The characteristics of pulsed hollow cathode discharges used forpseudospark switch triggering

The complex interaction between the trigger discharge and the main switch discharge in high-power gas discharge switches influences both the switching characteristics, and the switch and trigger lifetime. Any attempts to improve either of these parameters has to take into account the pressure and geometry dependence of a particular trigger geometry. Yet, although not very intensely investigated in detail for this particular purpose, pulsed hollow cathode discharges are commonly used for low-pressure gas discharge triggering as in pseudospark switches. Measurements of the electron current flowing to the cathode backplane of a pseudospark switch from the pulsed hollow cathode trigger discharge show that maximum current densities are peaked around the symmetry axis of the trigger electrode, an effect which is more pronounced at low pressures. Delayed (and slowed-down) increase of the current density at larger radii leads to increasing delay and jitter, provided the trigger coupling holes in the cathode backplane are located off-axis. The electron current density increases with decreasing diameter of the trigger electrode, and with increasing pressure of the working gas. In addition, it is shown that a preionization (keep-alive) current in the trigger electrode region shows a distinct influence on the trigger current distribution, proving that there exists an optimum keep-alive current depending on the geometry and gas pressure     

Dynamics of pulsed magnetron discharge in high-current electron guns

High-speed video filming is applied to investigate low-pressure (argon 0.053–0.133 Pa) pulsed gas discharge dynamics in a planar magnetron built-in the explosive emission cathode of a high-current electron gun. It has been found that, in the beginning, the discharge starts at the side surface of the cathode and then spreads to its face. The stability of the discharge ignition instant at the cathode face as a function of the working pressure of the gas and the cathode design has been studied. It has been found that the pulsed longitudinal magnetic field results in the discharge switching over in the axial direction onto the electron gun collector. A qualitative explanation of the observed discharge behavior has been given.     

Plasma supported combustion

Oxidation of molecular hydrogen and different hydrocarbons in stoichiometric mixtures with air and oxygen in the pulsed nanosecond discharges was studied at room temperature, and the detailed kinetics of the process has been numerically investigated. In the discharge afterglow, the reactions including electron-excited particles play a dominant role for the time up to 100 ns, ion–molecular reactions—for the time of microsecond range, and reactions including radicals mostly contribute for the time interval of several milliseconds. The principal role of processes with formation of excited components that support the development of the chain mechanism of oxidation has been shown. The spatial uniformity of the gas-mixture combustion initiated by a high-voltage nanosecond volume discharge is investigated at gas pressures of 0.3–2.4 atm and temperatures of 1000–2250 K. The self-ignition time and the time of discharge-induced ignition are determined. It is found that the discharge significantly (by 600 K) decreases the ignition temperature with very low energy in the discharge (10⁻² J/cm³). The influence of gas excitation by a pulsed nanosecond discharge with a high-voltage pulse amplitude up to 25 kV on the properties of a premixed propane–air flame has been investigated over a wide range of the equivalence ratios (0.4–5). It was experimentally found that the flame’s blow-off velocity increased more than twice at a discharge energy input less than 1% of the burner power. Efficient production of active radicals under the action of a barrier discharge has been observed. The increase in the flame’s propagation velocity is explained by the production of atomic oxygen in a discharge by the quenching of electronically excited molecular nitrogen N₂ and the dissociation of molecular oxygen on electron-impact. A numerical model has been developed, which describes the influence of pulsed electric discharges on the ignition, combustion, and flame propagation.     

水中脉冲放电金属电极烧蚀机理

采用板-板电极, 在放电间隙距离为2 mm、放电电流峰值为22 kA条件下, 对黄铜、钨铜电极的烧蚀特性进行了对比研究。利用高精度天平测量放电过程中的电极质量损失, 分别获取了阴极、阳极及总的平均烧蚀速率。通过放电后电极表面微观形貌、微观元素组成的分析及液体中金属离子的含量分析, 对水中脉冲放电金属电极的烧蚀机理进行了探讨。结果表明, 水中脉冲放电时, 钨铜电极的抗烧蚀性能明显高于黄铜电极。黄铜电极的主要烧蚀是以中心的大量孔洞及其边缘的波纹结构为表现形式的液体金属的溅射;钨铜电极的突出物及较平整的表面暗示了气相侵蚀的作用。以电弧的焦耳热效应为催化剂, 钨铜与水的电化学反应更为强烈, 因此电化学腐蚀是水中放电电极烧蚀的形式之一。     

Characteristics of an “orbitron” ion source with a two-wire anode

An orbitron-type ion source is considered, with a cylindrical cathode and two wire anodes, operating at hydrogen pressures of 0.07–0.5 Pa with a firing voltage of 1–5 kV and mean discharge current of several mA. In pulsed high-current operation, a peak current of 25 A can be achieved with 2–3-sec pulses. The ion current is extracted through two longitudinal slits in the cathode and reaches 30% of the discharge current. The source performance is analyzed as a function of the gas pressure and geometrical parameters.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 35–39, November, 1991.     

Role of ion-ion recombination in population of triplet resonance levels of cadmium and mercury

In this paper, we present the results of the experimental study of the spectral line emission of cadmium and mercury atoms in the pulsed discharge afterglow in gas mixtures containing vapors of bromides of these metals, hydrogen, and helium buffer gas. It was shown that the population of triplet resonance levels is controlled by recombination of positive metal ions and negative bromine ions.     

Measurement of Excited States Density and the VUV-Radiation in the Pulsed Xenon Medium Pressure Discharge

Time resolved absolute density measurements of the 1s5 (metastable) and 1s4 (resonance) level in the positive column of a pulsed xenon gas discharge for gas pressures between 1 and 40 Torr and currents between 100 and 300 mA are presented. The densities ranged from 1 × 10¹¹ to 5 × 10¹² cm^?3 and were found to be ten times larger in the afterglow than in the active part of the discharge. The enhanced radiation obtained in the afterglow in the near infrared regions as well as in the VUV region is caused by a dissociative recombination and formation of excimer states.     

Thermal conductivity of refrigerant R-415A in the vapor phase

Thermal conductivity of refrigerant R-415A in the vapor phase has been studied by the steady-state method of coaxial cylinders in the range of temperatures 308–415 K and pressures 0.12–1.68 MPa. The approximation dependence of thermal conductivity on pressure and temperature was determined. Thermal conductivity on the dew line and in the ideal gas state was calculated.     

Two-dimensional model of the Penning discharge in a cylindrical chamber with the axial magnetic field

The drift–diffusion model of a Penning discharge in molecular hydrogen under pressures of about 1 Torr with regard to the external electric circuit has been proposed. A two-dimensional axially symmetric discharge geometry with a cylindrical anode and flat cathodes perpendicular to the symmetry axis has been investigated. An external magnetic field of about 0.1 T is applied in the axial direction. Using the developed drift–diffusion model, the electrodynamic structure of a Penning discharge in the pressure range of 0.5–5 Torr at a current source voltage of 200–500 V is numerically simulated. The evolution of the discharge electrodynamic structure upon pressure variations in zero magnetic field (the classical glow discharge mode) and in the axial magnetic field (Penning discharge) has been studied using numerical experiments. The theoretical predictions of the existence of an averaged electron and ion motion in a Penning discharge both in the axial and radial directions and in the azimuthal direction have been confirmed by the calculations.     

Application of a new equation of state to energy carriers

A new equation of state (IR EOS) recently reported for liquids and gases has been utilized to predict the densities of some energy carriers at different temperatures, pressures. The ability of IR EOS is examined by comparing its results with experimental data for some energy carriers in homogeneous gas, homogeneous liquid and gas–liquid transition region from low to very high pressures. The IR EOS gives excellent results in homogenous gas and homogeneous liquid region while its predictions in gas–liquid transition have more deviations. The average absolute deviation between calculated and experimental densities for 968 data points of 12 energy carriers is 0.33% over the entire range of data with a maximum pressure of 1000 MPa.     

Generation of a pulsed high-current low-energy beam in a plasma electron source with a self-heated cathode

The transition of a low-current discharge with a self-heated hollow cathode to a high-current discharge is studied, and stability conditions for the latter in the pulsed–periodic mode with a current of 0.1–1.0 kA, pulse width of 0.1–1.0 ms, and a pulse repetition rate of 0.1–1.0 kHz are determined. The thermal conditions of the hollow cathode are analyzed, and the conclusion is drawn that the emission current high density is due to pulsed self-heating of the cathode’s surface layer. Conditions for stable emission from a plasma cathode with a grid acting as a plasma boundary using such a discharge are found at low accelerating voltage (100–200 eV) and a gas pressure of 0.1–0.4 Pa. The density of the ion current from a plasma generated by a pulsed beam with a current of 100 A is found to reach 0.1 A/cm². Probe diagnostics data for the emitting and beam plasmas in the electron source are presented, and a mechanism behind the instability of electron emission from the plasma is suggested on their basis.     

电晕均压多间隙串联气体开关特性实验

研制了一种电晕放电均压的小型多间隙串联气体开关,分析了电晕放电在开关工作过程中的作用,开展了开关自击穿特性、电晕放电伏安特性、针尖烧蚀以及开关寿命测试等特性实验。结果表明:老练后开关自击穿电压标准偏差小于3.5%,电晕均压效果明显;随着放电次数增加,电晕针尖逐渐钝化,触发性能变化不大;开关电晕放电电流随耐受电压升高增大,增长趋势逐渐变快;开关充400 kPa干燥空气,100 kV工作电压下开关放电50 000次以上,触发性能稳定,触发击穿时延抖动约4.3 ns,自放电概率低于110-4。     

Model of pulsed electric discharge expansion in dense gas taking into account electron and radiative thermal conductivities. I. Expansion mechanism

Using an ionization sensor, it was found that weakly ionized plasma with an ionization degree larger than 10^?6 is formed under exposure to UV radiation of a high-current pulsed electric discharge in gas (air, nitrogen, xenon, and krypton) at atmospheric pressure at a distance of ～1.2–2.5 cm from the discharge boundary. It was shown that the structure of such discharge includes, in addition to the discharge channel, a dense shell and a shock wave, also a region of weakly ionized and excited gas before the shock wave front. The mechanism of discharge expansion in dense gas is ionization and heating of gas involved in the discharge due to absorption of the UV energy flux from the discharge channel and the flux of the thermal energy transferred from the discharge channel to the discharge shell due to electron thermal conductivity.     

Analysis of the behavior of a discharge in a coaxial plasma jet accelerator

We analyze the behavior of the discharge in a coaxial plasma jet accelerator with a pulsed supply of the working gas released by an electric discharge from titanium hydride powder. Radiation (varying with time) from the discharge in the accelerator was detected using an optical method through a narrow slit cut along the outer electrode by a Bifo Company K008 streak camera. Stable operation of the source with the highest kinetic energy of a pure hydrogen plasma jet was attained for a relatively uniform glow of the discharge along the accelerator during the entire current pulse. Conversely, local glow of the discharge at the outlet or inlet of the accelerator considerably contaminated the discharge with impurities, and the kinetic energy of the plasma jet decreased by an order of magnitude. The highest energy of the plasma jet was attained when the polarity of the electrodes was the same as at the plasma focus.     

Organic dye removal from aqueous solution by pulsed discharge on the pinhole

Various active chemical species such as hydroxyl radicals, oxygen radical, hydrogen peroxide and ozone etc. can be produced by pulsed discharge. These active species can remove organic pollutants from the aqueous phase effectively. In present work pulsed discharge was formed on the pinhole of an insulating plate which was inserted between two plate electrodes. The characteristic of methyl orange decoloration by the discharge was investigated. The results of experimentation showed that peak voltage, pulsed frequency, initial solution conductivity and gas species impact the decoloration rate of the methyl orange (MO) significantly. The decoloration rate of MO solution is increased with increasing of the peak voltage, pulsed frequency, and decreasing initial solution conductivity. When the MO solution was treated with different gases bubbling, different decoloration rate was obtained and the order of decoloration rate is: oxygen > air > nitrogen.     

The influence of hydrogen bonds upon diffusion of simple amines and binary mixtures of ammonia

Abstract

Self diffusion coefficients of monomethylamine and trimethylamine and intradiffusion coefficients of some model mixtures containing ammonia have been measured up to pressures of 200 MPa at temperatures between the melting pressure curve and 423 K by pulsed field gradient Spin Echo NMR. Compared to water and the lower alcohols the self diffusion coefficients of pure fluid ammonia shows no clear influence from hydrogen bonds in contrast to other thermodynamic properties. Therefore the methylated substance monomethylamine has been studied to see weather a more structured charge distribution on the molecular surface compared to ammonia is needed to hinder fast rearrangements of the hydrogen bonds. For comparison also trimethylamine has been studied where no hydrogen bonds can be formed. Additionally binary mixtures of ammonia with methanol, benzene, trimethylamine and acetonitrile have been studied to see effects of intermolecular interactions.