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。     

Laser dye stability,part 12. The pyridinium salts

Improved laser output is demonstrated in KrF and XeCl lasers with x-ray preionization. The influence of gas composition, preionization geometry, x-ray dose,E/p value and temporal delay between x-ray pulse and laser discharge is discussed. In XeCl lasing has been achieved with an x-ray dose of 0.2 mR whereas approx. 3 mR are required for KrF. For both systems, the highest output energy and the lowest possibleE/p ratio were observed with Ne buffered gas mixtures. Dissociative attachment to halogen molecules on a ns time scale supported by a relatively slow laser voltage rise is recognized as the main electron loss channel preventing a long lifetime of the preionization electrons. High preionization intensity is thus desirable at the moment of voltage breakdown.     

印刷电路板预电离3.6 kW TEA CO2激光器

在TEA CO₂激光器中采用印刷电路板预电离结构,在单节放电体积为5cm×4cm×90cm 的两节串连的激光器中获得了20.4 J单脉冲能量输出,电光转换效率达12.8％.激光器重复频率工作时,气体清洗系数大于3,在最高重复频率180 Hz下获得了3.6 kW平均输出功率.     

Compact,simple, high-energy,discharge-pumped rare gas halide laser

A simple, lumped capacitor, avalanche discharge excimer laser has been developed which uses a single spark array preionization rod located under a grid electrode to preionize the discharge region. A surface corona discharge is found to play an important role in achieving a more uniform transverse preionization. On KrF, energy in excess of 0.5 J is obtained (?2.4 J/1) with a wide (16 × 25 mm) uniform beam of good divergence (1.8 × 5 mrad) and electrical efficiency above 1%.     

用于薄膜沉积的XeCl激基激光器研制

以镀制半导体薄膜、巨磁薄膜、金刚石及其它薄膜,外延生长及后续的光刻,激光与物质的相互作用、等离子体研究为目的,设计、研制了脉冲放电激励的XeCl激基激光器.试验结果表明:激光脉宽18ns,单脉冲能量150mJ,矩形光斑大小2cm×1cm,束散角3mrad,最高重复频率5HZ.与同类激光器相比,具有结构简单、造价低廉、性能稳定等特点.     

Synchronization of ultraviolet-preionization in a Marx-driven TEA CO2 laser

In a TEA CO₂ laser a two-stage spark gap was used to control the predischarge, which produced the ultraviolet-preionization, and to generate a trigger pulse for the Marx bank, which excited the main discharge. The time-sequence of the predischarge and the trigger pulse could be reversed so that the main discharge could commence before the preionization process. This set-up has enabled temporal synchronization on the laser performance, or basically the time delay between the pre- and the main discharges, to be investigated from about − 150 ns to 600 ns.     

Performance studies of a pulsed HF laser with a sliding discharge plasma cathode

The plasma electrode design concept is applied for the first time to an HF laser. The discharge along the surface of a dielectric (sliding discharge) is used as a plasma cathode for the main laser discharge. The laser operates at atmospheric pressure with a gas mixture of He/SF₆/C₃H₈. Details are presented on the efficiency of energy transfer, the dependence of laser performance on circuit parameters, gas mixture, relative energy loading and time delay between the plasma electrode and main discharges. The F atom production rate is estimated from the linear dependence of the output energy on the electric charge passed through the discharge. Output energies of 600 mJ were obtained at 1.6% efficiency from a small active discharge of 108 cm₃ volume and 38 cm length, while the maximum specific input and output energies were 370 J/1 and 5.7 J/1, respectively. These values compare favourably with those reported in the literature for non-chain-reaction-type gas mixtures at 1 atm pressure and demonstrate that the plasma electrode design is a powerful scheme for developing gas-discharge lasers.     

A 10 cm aperture,high quality TEA CO2 laser

Experiments have been performed on a corona preionization type 10 cm aperture TEA CO₂ laser. For a CO₂:N₂:He=1: 1: 7: mixture an output energy of 34 joule per liter and for a 1 : 1 : 10 mixture 40 joule per liter could be obtained. The overall efficiency is about 18%. The time behaviour of the current and voltage of the system shows a delay of several hundreds of nanoseconds after the preionization peak, which indicates a relatively low initial electron-density level. Neverthe less, it proved to be high enough to obtain a very homogeneous discharge and reproducible output energy.     

Preionization and discharge stability study of long optical pulse duration UV-preionized XeCl lasers

This paper presents a complete study of the temporal and spatial characteristics of the preionization of a XeCl rare-gas halide laser. The detailed study was made possible using the technique of laser-induced preionization which utilizes the uv radiation from a KrF laser to preionize a second rare-gas halide laser. In addition to the preionization study, high spatial and temporal resolution framing camera photographs have been used to investigate the growth of discharge instabilities which can lead to the premature termination of the XeCl optical pulse. The roles played by HCl, Xe, the buffer gas as well as the discharge energy loading in the development of discharge instabilities have been determined experimentally.     

Triggering of radial multichannel pseudospark switches by a pulsedhollow cathode discharge

We report on a special trigger discharge for pulsed high-power pseudospark switches. The switch used is a radial three-channel pseudospark switch. For triggering, a cylindrical trigger electrode is inserted into the hollow cathode of the main gap. This electrode acts as a hollow cathode for the dc preionization, while the hollow cathode of the main gap is the anode. A negative high-voltage pulse supplied to the trigger electrode ignites the main discharge. We report the temporal evolution of the trigger discharge observed with a fast camera. This trigger method gives an excellent current distribution among the discharge channels, as can be proven by fast photography. The switch has a delay of 220 ns and a jitter of 15 ns     

Discharge instability induced by external laser preionization of a XeF discharge laser

External-laser-induced preionization of excimer lasers was investigated. A discharge XeF laser was preionized by two different UV lasers [a KrF laser (λ=249 nm) and an ArF laser (λ=193 nm)], and the improvements in performance of the XeF laser were compared. The XeF laser beam profiles were measured by an intensified CCD (ICCD) camera with temporal resolution of 10 ns. Striated XeF laser profiles were obtained with 249 nm laser preionization, whereas there was no striation in the profiles for 193 nm laser preionization. These striations originated from discharge in the XeF laser induced by laser preionization. The influence of excited rare-gas atoms on the discharge instability was examined.     

Gas spark switches with increased operating life for Marx generator of lightning test complex

A new design of gas spark switches with an increased operating life and stable dynamic characteristics for the Marx generator of the lightning test complex has been developed. The switches are characterized by the following parameters in the mode of operation: voltage up to 80 kV, discharge current up to 50 kA, flowing charge up to 3.5 C/pulse. An increased operating life is achieved by using torus-shaped electrodes with increased working surface area and a trigger electrode in the form of a thick disk with a hole located between them. Low breakdown delay time and high stability of breakdown voltage under dynamic conditions are provided by gas preionization in the spark gap using UV radiation of an additional corona discharge in the axial region.     

Study of self-preionized XeCl* electron-avalanched discharges

Summary Some performances of an excimer discharge at the formative stage are calculated and compared to the experimental results obtained in a XeCl^* laser device with a pin cathode without external preionization. We present a simplified discharge model for exploring the process of the preionization generated by the coronas in the cathode pin region.     

Rapid discharge-pumped wide aperture X-ray preionized KrF laser

A wide aperture X-ray preionized discharge-pumped KrF excimer laser has been constructed. A flat plate pulse-forming line (36 nF, 340 kV) charges a peaking capacitor (6 nF) through a rail-gap to facilitate a rapid discharge in the laser head. Collimated X-ray preionization is employed to obtain a wide and uniform discharge. The laser is intended to be used as a short pulse amplifier and results are presented when characterized as an oscillator. The active cross-section of the laser beam is 10×8 cm² with 50 cm effective electrode length. The laser pulse energy exceeds 4.7 J in a 28 ns pulse (FWHM).     

高功率横流CO2激光器大体积放电研究

详细讨论了脉冲预电离高功横流ＣＯ２激光器的工作特性，研究了一套新型的电极结构，对其放电，注入功率，输出功率等待进行了讨论。实验结果表明，脉冲预电离可以提高高功率横率流ＣＯ２激光器的注入和输出功率，并有效地改善了放电的稳定性和均匀性。     

新型脉冲CO2激光器预电离测量参量研究

对5 kW横流CO₂激光器脉冲预电离过程进行理论分析和实验研究.表明了预电离过程中电子密度的重要作用,它能为下一步的主放电提供良好的条件.结果表明理论分析与实验结果相符合.     

强激光能源系统预电离实验研究

 新型能源系统预电离实验研究证实：采用预电离技术可以减少闪光灯的导通延时,使电流脉冲前沿变陡,这对提高泵浦效率和闪光寿命无疑是十分有益的。     

TEA CO2激光器不同放电电路放电过程的比较

 利用像增强CCD相机对脉冲CO₂激光器的放电区进行观测,获得了放电辉光的发展过程,由此研究了长脉冲放电电路和短脉冲放电电路对放电过程的影响。发现普通电容放电电路（长脉冲放电电路）存在与自持放电阶段相对应的二次辉光;采用磁压缩开关的短脉冲放电电路,预电离出现较晚,但预电离辉光峰值和主放电辉光峰值之间间距较短,不存在自持放电阶段,只观测到一次强辉光。长脉冲放电电路与短脉冲放电电路在放电的后期均存在一个阴极位降区形成的过程。短脉冲放电电路有利于产生更窄的脉宽和更高的峰值功率。     

Performance of a ten-liter electron avalanche-discharge XeCl laser device

This paper describes the laser performance of an X-ray preionized ten-liter volume, electron-avalanche discharge XeCl system, operated at dc charging voltages of up to 70 kV both with and without X-ray preionization. An output energy of more than 11J uniformly distributed over a (7×10) cm² spot size was achieved using a multichannel spark-gap as the main discharge switch. The discharge was also successfully operated in the switchless mode, yielding a 4.8 J output energy and a 0.9% efficiency. The time-resolved gain measurements provided information on the laser discharge evolution.ENEA GuestENEA Guest on leave from the Shanghai Institute of Optics and Fine Mechanics, the Chinese Academy of Sciences, Shanghai, China     

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