Characteristics of a high-frequency barrier discharge in mixtures of mercury diiodide vapor with gases

The spectral and electric characteristics of atmospheric-pressure high-frequency barrier discharge plasma based on mixtures of mercury diiodide with neon and admixtures of argon, xenon, and nitrogen are analyzed. A repetition rate of sinusoidal voltage pulses of about 100 kHz is used both to produce the gas discharge plasma and to excite the components of the working mixture. The radiation of the discharge in the range 200–900 nm is analyzed with a high resolution. It is found that, in the range 400–900 nm, the system of bands of excimer molecules HgI(B → X) emits 85% of the barrier discharge radiation. It is established that the radiation intensity of HgI(B → X) molecules is maximal in the mixture HgI₂/Xe/Ne = 0.6/10/90 kPa. In this mixture, UV radiation of molecules XeI(B → X) and XeI(B → A) is observed. The regular features of the spectral and electric characteristics of the gas discharge plasma are discussed. An atmospheric-pressure high-frequency barrier discharge in mixtures of mercury diiodide with gases is of interest for use in a selective (Δλ = 438–446 nm) excilamp with a cylindrical working aperture.     

Spectral characteristics of a broadband exciplex spontaneous emission source upon mixtures of the cadmium dibromide vapor with gases

The spectral characteristics of radiation from atmospheric-pressure gas-discharge plasma in mixtures of cadmium dibromide vapor with gases (Ne, Ar, Kr, Xe, and N₂), as well as the temporal characteristics of the voltage and current, have been investigated. A barrier discharge at the repetition frequency of sine voltage pulses up to 140 kHz has been used to create the gas-discharge plasma and excite the components of the working mixture. The discharge radiation has been analyzed in the spectral range 200–900 nm with a high resolution (0.05 nm). In the spectra, we have revealed radiation from exciplex molecules CdBr(B → X) and CdBr(C → X), atomic lines of cadmium and inert gases, and, in mixtures with xenon, radiation of exciplex molecules XeBr(B → X, B → A). The XeBr(B → X) radiation prevailed in the spectra at mixture temperatures up to 200°C. The further increase of the temperature resulted in the prevalence of the CdBr(B → X) radiation. The most intense CdBr(B → X) radiation was observed in mixtures of CdBr₂/Xe. When the temperature of the mixture was higher than 250°C, the discharge radiation had a silvery-white color. Regularities in the spectral characteristics of the radiation from the gas-discharge plasma are discussed. The high-frequency atmospheric-pressure barrier discharge in mixtures of cadmium dibromide with gases, excited by sine voltage pulses, can be used in multiwave and broadband excilamps, operating in the UV and visible regions.     

Emission characteristics of a glow discharge in a mixture of heavy inert gases with iodine vapor

The results of a systematic investigation of the emission characteristics of a low-pressure UV excimer-halogen lamp pumped by a longitudinal dc glow discharge are presented. The discharge was initiated in mixtures of heavy inert gases with iodine vapor at a total pressure of 100–2000 Pa and a power deposited into the plasma of 10–100 W. Current-voltage characteristics of the glow discharge and emission spectra of the plasma in the region of 190–360 nm are studied. The radiation intensity at the resonance line of the iodine atom (206.2 nm) and the intensity at the peaks of the XeI(B-X) (253 nm) and I₂(B-X) (342 nm) emission bands are analyzed as functions of the pressure and partial composition of the mixtures of Ar, Kr, and Xe with iodine vapor, as well as the electric power of the glow discharge. The most efficient gas mixtures are determined for an electric-discharge UV iodine vapor lamp with continuous-wave emission and a long service life before a change of the mixture is required.     

全固态高重频高压脉冲电源

设计了一款全固态高重频高压脉冲电源,主电路采用以IGBT为主开关的半桥式固态Marx电路,驱动电路采用磁芯隔离带负压偏置的同步驱动方案,并由FPGA提供充放电控制信号和故障诊断、保护。该方案既可实现对多级电容的低阻抗的快速并联充电控制,又可实现截尾功能以加快脉冲后沿获得方波脉冲,且可实现百μs以上的宽脉冲输出,可用来产生高压脉冲电场。此外,该电源还可在突发模式下输出脉冲个数和频率均可调的多个高频脉冲系列。实验表明,该输出电压幅值可高达40 kV,输出峰值电流可达100 A,重频可达30 kHz,上升沿和下降沿均低于100 ns,突发模式下重频可高达200 kHz。所设计的脉冲电源输出参数连续可调,且体积小巧。     

Small volume coaxial discharge as precision testbed for 0D-models of XeCl lasers

In order to check the predictions of 0D-models experimentally, a small coaxial discharge configuration for the generation of homogeneous high pressure glow discharges (diameter 11 mm, length 20 mm) in rare gas halogen excimer laser gas mixtures under accurately controlled conditions has been developed. It uses X-ray preionization and a special pulse-forming network (PFN) delivering fast rising (8 ns) single square pulses (U ₀=25 kV; I=300 A; =100 ns). Discharge current and voltage are measured precisely by a capacitive voltage divider and a shunt integrated into the discharge chamber. All circuit data needed for the model calculations have been evaluated. Interferometric and spectroscopic diagnostics of the bulk of the discharge and of the cathode sheath have been performed. First results for Ne/Xe/HCl mixtures are compared with model calculations.     

Optimization of a Dielectric Barrier Discharge for Pulsed UV Emission of XeCl at 308 nm

A pulsed dielectric barrier discharge (DBD) has been investigated in a wide range of experimental conditions with the purpose of optimization for XeCl excimer radiation. For that the following operation parameters had been considered: four different lamps of coaxial geometry with gas gaps in the range of 1.3 ‐ 6.5 mm; gas mixtures of xenon and chlorine containing admixtures of 1%, 2% and 4% Cl₂ at total filling pressures between 5 mbar and 600 mbar; voltage rise times of 20 ‐ 50 ns and voltage amplitudes of up to 12 kV. A maximum radiation pulse energy of 1.8 µ J has been detected at 310 ± 10 nm with an estimated radiation decay by three orders of magnitude within about 5 µ s. It was shown that the minimization of the voltage rise time is essential for enhancing the radiation pulse energy. Furthermore a correlation between the discharge geometry and the optimum pressure for maximum radiation output was observed. The decay characteristics of the excimer emission provides evidence of the harpoon reaction being the main channel of XeCl formation under our operation conditions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

One- and two-barrier excilamps on xenon dimers operating in the VUV range

Spontaneous emission sources in the VUV range based on one- and two-barrier pulsed-periodic gas (Xe) discharges are experimentally investigated. Volt-coulomb figures, as well as typical waveforms of current pulses and discharge voltage are presented. The time dependences of the voltage drop across the gas-discharge plasma, excitation power, and excitation energy are calculated. The radiation power versus xenon pressure, exciting pulse repetition rate, and average excitation power is determined. The radiation power average densities for one- and two-barrier excilamps are found to be 20–30 and ～40 mW/cm², respectively.     

Emission characteristics and parameters of gas-discharge plasma in mixtures of heavy inert gases with chlorine

The ultraviolet (UV) radiation from longitudinal glow-discharge plasma in three- and four-component mixtures of argon, krypton, and xenon with chlorine has been investigated. The total radiation of Ar, Kr, and Xe monochlorides and chlorine molecules in the spectral range 170–310 nm has been optimized with respect to the composition and the pressure of gas mixtures, as well as the discharge current. The mean output power, the electric power of discharge, and the efficiency of a broadband low-pressure exciplex halogen lamp have been determined. Parameters of the glow discharge in Ar-Kr-Cl₂ and Kr-Xe-Cl₂ mixtures have been simulated numerically. The electron energy distribution functions have been determined through the solution of the Boltzmann kinetic equation. These functions have been used to calculate the plasma parameters, namely, electron transfer characteristics, specific losses of discharge power for electronic processes, and ionization and attachment coefficients.     

Electric-discharge He/Xe/I<Subscript>2</Subscript> excimer-halogen UV lamp

The characteristics of a low-size low-pressure UV lamp operating on the atomic iodine resonant line (λ=206 nm) and xenon iodide (λ=253 nm) and dimer iodine (λ=342 nm) bands are investigated. A lamp with an interelectrode distance of 19 cm was pumped by a longitudinal dc glow discharge. The working gas mixtures were He/I₂ and He/Xe/I₂ mixtures with a total pressure of 50–1500 Pa. The output parameters of the electric-discharge excimer-halogen lamp were optimized in terms of the gas mixture pressure and composition and the power deposited in the discharge. It is shown that the total UV power emitted from the entire aperture of the lamp in the spectral range 200–350 nm attains 5–7 W with an efficiency of ≤5%.     

高气压预电离短脉冲XeCl准分子激光产生研究

研究了在高气压、大体积、泵浦功率1.395 9 MW·cm-3抽运下,产生的XeCl*准分子激光光谱,波段307.7～308.5 nm,结果显示有两个谱线峰值307.98和308.19 nm,谱线最强的跃迁是B—X跃迁,脉冲宽度11.13 ns。在气体配比HCl∶Xe∶He=0.1%∶1%∶98.9%下,采用预电离初始电子,产生稳定辉光放电过程,获得了0.5～5 Hz,单脉冲能量450 mJ,束散角3 mrad, 短脉冲的准分子激光。     

A broadband excimer source of visible radiation with barrier discharge pumping

We investigate the characteristics of a broadband cylindrical excimer source of visible radiation with a surface area of 230 cm² excited by a pulse-periodic barrier discharge based on multicomponent mixtures (mercury diiodide and dibromide with helium and admixtures of molecular nitrogen and xenon). The working mixture components were excited by a pulse-periodic (pulse repetition rate 500–5000 Hz, pulse duration ～150 ns) barrier discharge. We detected radiation from excimer HgI* and HgBr* molecules, the second positive system of molecular nitrogen, and mercury and xenon atoms. The amplitude, duration, and trailing edge of the radiation pulses in the HgI₂:HgBr₂:Xe:He and HgI₂: HgBr₂:N₂:He mixtures with admixtures of xenon and molecular nitrogen were found to change compared to the HgI₂:HgBr₂:He mixture. The optimal partial pressure of helium lies within the range 162–195 kPa. The most intense radiation from HgI* and HgBr* molecules (in a ratio of more than 3: 1) is observed in the HgI₂:HgBr₂: Xe:He mixture. The mean and pulse radiation powers are 45 W and 93 kW, respectively, at a pumping pulse repetition rate of 5000 Hz and an efficiency of 30%. We discuss the spectral and temporal characteristics of the radiation source and the dependence of the radiation intensity of excimer molecules of mercury monoiodide and monobromide on the partial pressures of xenon and nitrogen. We point out that the radiation source is of considerable interest for applications in biotechnology and medicine.     

Spectroscopic diagnostics of barrier discharge plasmas in mixtures of zinc diiodide with inert gases

The spectral characteristics of the emission of gas discharge atmospheric pressure plasmas in mixtures of zinc diiodide vapor with inert gases (He, Ne, Ar, Kr, and Xe) are investigated. The formation of a gas discharge plasma and the excitation of the components of a working mixture were performed in a high-frequency (with a repetition frequency of sinusoidal voltage pulses of 100 kHz) barrier discharge. The gas discharge emission was analyzed in the spectral range 200–900 nm with a resolution of 0.05 nm. Emission bands of ZnI(B-X) exciplex molecules and I₂* excimer molecules, lines of inert gases, and emission bands of XeI* exciplex molecules (in Xe-containing mixtures) were revealed. It is ascertained that the strongest emission of ZnI* molecules is observed in ZnI₂/He(Ne) mixtures. The regularities in the spectral characteristics of the gas discharge plasma emission are considered.     

Acoustic characteristics of a barrier-discharge XeCl excilamp

The generation of an acoustic signal by means of voltage pulses (f = 15 kHz) applied to the electrodes of a barrier-discharge excilamp based on a Xe/Cl₂ = (50?C500)/1 mixture kept at a pressure of 5?C500 Torr is studied. It is shown that, from the time variation of the acoustic signal intensity, one can judge the time instant the excilamp starts operating in a steady mode. Optimal (in power and efficiency) operating conditions of the excilamp are found (Xe/Cl² = 240/1, p = 98 Torr, ?? ?? 9.5%). It is experimentally demonstrated that the discharge energy at a low pressure is spent largely on heating the gas. This is indicative of the volume heat release and volume glow discharge (as the pressure grows, the efficiency of this source of energy consumption drops and more and more energy is spent on acoustic vibration excitation). Under higher pressures, the Fourier spectrum of the acoustic signal becomes richer, the intensity of the spectrum rises, and the dispersion of the signal grows. At very high pressures, the intensity of the acoustic signal drops to a level corresponding to the natural vibrations of the excilamp envelope without the discharge (when the discharge is quenched, the Fourier spectrum of the signal becomes depleted and contains only harmonics corresponding to the carrier frequency of voltage pulses from the power source).     

喷射等离子体触发气体开关导通特性

利用内嵌微孔火花放电产生喷射等离子体、作用于两电极开关,研究了间隙距离、气压、气体种类、开关工作系数和电压极性配合等因素对等离子体喷射控制开关导通特性的影响。实验结果表明,等离子体喷射触发开关可在工作系数为10%的条件下可靠快速导通,当开关采用0.5 MPa_N₂作为绝缘介质、间隙距离5 mm时,触发导通时延为11.7 μs,抖动为1.42 μs;当间隙距离增大到18 mm时,触发导通时延增大至19.7 μs,触发可靠性降低;当工作系数由10%增大到60%时,触发导通时延由11.7 μs降低至1.1 μs。在确保开关自击穿电压一致的前提下,短间隙、高气压、负触发脉冲电压、正工作电压更有利于减小开关触发导通时延。     

Simulation of the discharge process in a barrier discharge cell based on a three-parameter model

Electric parameters of a barrier discharge cell with flat tips are studied experimentally and numerically for Xe/NF₃ (50 : 1) and Xe/SF₆ (50 : 1) gas mixtures. The discharge process is simulated using a three-parameter model. The dependences of the computational model parameters on the pressure of the Xe/SF₆ (50 : 1) gas mixture and on the electrode spacing are presented. Comparison of experimental and theoretical results shows that the error of simulation of the main discharge parameters (current, voltage drop, and transferred charge) does not exceed 10%.     

Optical characteristics of barrier discharge plasma based on mixtures of cadmium diiodide vapors with gases

The spectral, integrated, and working life characteristics of the radiation from atmospheric pressure gas discharge plasma based on multicomponent mixtures (cadmium diiodide with helium and small admixtures of molecular nitrogen and xenon) are analyzed. A pulsed barrier discharge (pulse repetition rates 5000, 5500, and 6000 Hz; pulse duration ～150 ns) is used both to produce the gas discharge plasma and to excite the components of the working mixture. Visible radiation is detected from excimer molecules of cadmium monoiodide and cadmium, xenon, and krypton atoms. Regular features are found in the variations of optical plasma characteristics with pumping pulse repetition rate and with component and quantitative mixture composition.     

全固态双极性纳秒脉冲电源研制及应用

研制了一种双极性交替的纳秒高压脉冲电源,进行了双极性纳秒脉冲放电产生等离子体研究。该电源先通过固态开关IGBT将直流电压截断成电压脉冲,通过可饱和脉冲变压器拓扑,实现升压并缩短脉冲上升沿。该电源可在一个周期内输出极性相反的2个脉冲,且时序可以灵活控制。通过优化调整器件参数,研制了两种不同输出性能参数的双极性纳秒脉冲电源:①峰值电压10 kV、爆发模式脉冲重复频率500 kHz（正负脉冲间隔2 μs）、连续重复频率1 kHz;②峰值电压25 kV、爆发重频200 kHz、连续重频600 Hz。测试电源的运行性能,发现电源存在温度升高的情况,但长时间（＞0.5 h）运行温度趋于稳定。10 kV电源连续运行在1 kHz时最高温度点50.5 ℃;25 kV电源连续运行在600 Hz时最高温度点60 ℃。利用该电源驱动线板电极阵列和表面介质阻挡放电结构,证实了该电源可以用于常压空气条件下产生大面积等离子体。     

Electric-discharge UV radiation source based on a Xe-CsCl vapor-gas mixture

A source of spontaneous UV radiation (excilamp) with a maximum radiation intensity at a wavelength of 308 nm is created. The active medium of the excilamp consists of a mixture of Xe with a CsCl vapor, and this mixture is excited in a longitudinal pulsed-periodic discharge. The B → X transition in the XeCl* exciplex molecule most strongly contributes to the total UV radiation power of the excilamp. The spectral composition of the UV radiation, the time characteristics of the source, and the formation of exciplex molecules as a function of the main discharge excitation parameters are studied.     

UV Radiation of Low Pressure XeCl* and KrCl* Glow Discharges

The positive column of low pressure DC glow discharges in Xe/Cl₂ and Kr/Cl₂ gas mixtures has been investigated with respect to its UV radiation power and radiative efficiency for a wide range of parameters (total gas pressure: 1–30 mbar, current 10–30 mA, partial pressure of Cl₂: 1–33%). Also the radial distribution of the particle number densities of XeCl* (B) and KrCl* (B) has been determined by absolutely calibrated emission spectroscopy. Optimum UV (190–350 nm) output and efficiency has been found in gas mixtures with a relative Cl₂ partial pressure of 2–3% and total gas pressure of 12–18 mbar. At these parameters, the UV radiation power per column length is greater than 40 Watt/m with a radiative efficiency of 15–18%. These discharges could be used for UV induced photochemical processes.     

猝发双脉冲直线感应加速器组元研究

 在原单脉冲直线感应加速器（LIA）组元的基础上，利用电缆延时和电缆反射两种方式获得了间隔500～1 000 ns的猝发双脉冲输出。在感应加速腔上进行了双脉冲实验，获得了幅度大于200 kV、前沿小于35 ns、平顶大于60 ns的双脉冲加速电压波形。两种方式中第一个脉冲的前沿和幅度都达到了原单脉冲组元的水平，表明加速腔负载的变化对波形没有明显影响，但由于电缆对波形的损耗，第二个脉冲的幅度和前沿比第一个脉冲略差。可以利用水介质传输线来代替长电缆，减小传输线的长度及其对波形的损耗。两个脉冲间的幅度差异可以通过改变长电缆的阻抗来调节。实验表明，通过这两种猝发双脉冲的产生方式并结合加速腔磁芯的改进，可简单高效地完成原单脉冲LIA的双脉冲改造。