Development of a 100-kV multimegawatt repetition rate gas switch

A 100-kV gas switch has been developed and tested which is capable of controlling 5-MW average power when operated up to 250- pps repetition rate. Recovery of the switch voltage holdoff capability after each discharge was accomplished by providing both a 1-ms grace period during which no voltage is reapplied, and by continuously purging the switch with 40-psig pressurized air at flow rates up to 60 SCFM. The switch was tested using a simulation technique in which the switch was subjected to the same repetitive peak voltage and current as it would in controlling several megawatts of average power. Limits of switch performance as a function of air flow rate and peak voltage have been established.     

大功率XeCl准分子激光器放电开关的实验研究

本文报道了一台输出功率大于100W、重复频率达300Hz的XeCl准分子激光器的放电开关系统进行实验结果，比较了激励电路放电开关系统中带磁开关和无磁开关两种情况下闸流管的动态放电参数，证明了带磁开关的开关系统有利于激光器高重复频率工作和大功率输出。     

Configuration Q-switching in a diode-pumped multirodvariable-configuration resonator

We report on a novel technique for Q-switching at high repetition rates, where the change in the Q of the cavity is due to the capability of a variable-configuration multirod resonator (VCR) to switch between an unstable Fabry-Perot configuration and a stable ring configuration. The switching between the configurations is accomplished simply by the means of a Pockels cell. Using the new Q-switching technique, 35-ns-long pulses with a peak power of 17 kW at a repetition rate of 4 kHz, giving an average power of 2.4 W, were obtained     

准分子激光电源磁脉冲压缩开关的磁芯复位研究

为了解决高重复率下准分子激光电源磁脉冲压缩开关的磁芯复位问题,以理论分析为指导,结合磁开关工作特性,设计了一种磁芯精确复位电路,该电路可快速精确复位饱和后的磁开关。将此复位系统应用于准分子激光器脉冲电源测试其性能,复位电流在磁开关饱和后200μs内平息振荡。结果表明,这一磁芯复位系统可满足4kHz重复率下脉冲电源的复位要求。此研究对今后高重复率准分子激光电源的设计是有帮助的。     

LD单端泵浦Nd:GdVO4声光调Ｑ高重频窄脉宽激光器

激光二极管（LD）泵浦的Q调制高频率、窄脉宽、高峰值功率的固体激光器在激光雷达、激光加工等领域日益得到广泛的应用，而更高调制频率的固体激光器在将来会更受青睐。分析了泵浦功率和输出透过率两个因素在10~100 kHz调制频率下对脉宽的影响程度。研制了LD单端泵浦Nd:GdVO4声光调Q 激光器，实现了重频100 kHz下窄脉宽激光输出。在重频为80 kHz时，获得脉宽17.7 ns，平均输出功率3.49 W，峰值功率2.46 kW和在重复频率为100 kHz时，获得脉宽19.6 ns，平均输出功率3.52 W，峰值功率1.79 kW的效果。     

高效高峰值功率全固态355nm紫外激光器

为了获得结构紧凑的瓦级实用化高峰值全固态355nm紫外激光器,采用简单紧凑的平平直腔结构,使用声光Q开关进行调制,通过LD端面抽运Nd:YAG激光晶体,在重复频率1kHz～50kHz的情况下,产生平均功率1.03W～6.1W的1064nm红外光;采用LBO晶体进行2倍频和3倍频,在重复频率10kHz时得到紫外的最高输出功率1.08W,峰值12kW;在重复频率5kHz时得到紫外的最高峰值功率为17kW。结果表明,该方案满足了实际的应用需求。     

高重频可调小型高功率半导体激光电源研究

为了获得高功率、高重频半导体激光脉冲,设计了一种体积小、重量轻、造价低的纳米级大功率半导体激光器驱动电源。采用改进的单稳态触发器产生窄脉冲,经放大后驱动快速开关MOSFET获得大电流窄脉冲;电源脉冲电流驱动能力0A～80A,脉冲上升时间2.8ns,下降时间3.8ns,脉冲宽度5ns～500ns范围内可调,最小5.2ns,重复频率可达200kHz。用该电源实验测试了激光波长为905nm的半导体激光器,在重复频率为10kHz时,激光脉冲峰值功率达到70W以上。结果表明,采用窄脉冲驱动MOSFET可以得到高重复频率10ns以内的大电流窄脉冲,可以驱动大功率半导体激光器,若驱动100A以上的激光器需进一步研究。     

高功率涡流稳弧闪光灯

我们研制成了用高速涡流气体产生的压力梯度场来稳定脉冲放电电弧的高功率涡流闪光灯。当工作氩气的流量为5升/秒时,已经实现了工作频率为110次/秒的万瓦放电。放电的峰值电流最大达20千安,放电闪光上升时间为1～1.5微秒,脉宽为3～4微秒,发光效率达30％。本文报告了这种灯的结构,灯的放电电路、灯内压力梯度场的分布、灯的电光特性和灯的功率平衡分析等结果。     

Pulse nitrogen laser at high repetition rate

An output of 1.5 W of average power at 3371 Å is obtained from a pulsed nitrogen laser operating at a repetition rate of 1200 Hz. Pulse powers up to 300 kW are observed, with 10-ns pulse duration. The high repetition rate is made possible through the use of a closed-cycle transverse gas flow system to supply fresh ion-free gas to the laser for each pulse.     

A linear array of 980 nm VCSEL and its high temperature operation characteristics

A 980 nm bottom-emitting vertical-cavity surface-emitting laser linear array with high power density and a good beam property of Gaussian far-field distribution is reported. This array is composed of five linearly arranged elements with a 200 μm diameter one at the center, the other two 150 μm and 100 μm diameter ones at both sidesof the center with center to center spacing of 300/zm and 250 μm, respectively. A power of 880 mW at a current of 4 A and a corresponding power density of up to 1 kW/cm~2 is obtained. The temperature dependent characteristics of the linear array axe investigated. The thermal interaction between the individual elements of the VCSEL linear array is smaller due to its optimized element size and device spacing, which make it more suitable for high power applications. A peak power of over 20 W has been achieved in pulsed operation with a 60 ns pulse length and a repetition frequency of 1 kHz.     

A pulse repetition frequency scaling law for the high repetition rate neutral barium laser

The variations in the output energy per pulse and in the average power output of the neutral Ba cyclic metal vapor laser as a function of the pulse repetition rate have been analyzed. At constant input power, the output energy per pulse is found to vary inversely as the two-thirds power of the pulse repetition frequency and so the average output power varies as the pulse repetition frequency to the one-third power up to the point where the Ba metastables do not have sufficient time to relax between pulses. Since the experiments which have been analyzed were conducted with a constant value for the laser discharge capacitance, these results imply that the output energy per pulse of this laser varies as the four-thirds power of the input voltage.     

高功率Er/Yb共掺光纤脉冲放大器中ASE的影响分析

为了研究自发辐射对高功率铒镱共掺脉冲光纤放大器性能的影响,在速率方程理论的基础上,采用有限差分法对理论模型进行了数值求解。对不同抽运、信号和光纤参量配置情况下,自发辐射对放大器性能的影响进行了模拟分析。结果表明,由于自发辐射自饱和的限制,在其它条件相同的情况下,为了得到最高的单脉冲能量和峰值功率,放大器输入信号存在一个最佳的重复频率,且该最佳重复频率与抽运功率成正比与脉冲宽度成反比。研究结果对高功率铒镱共掺光纤脉冲放大器的设计和实验研究有重要指导意义。     

自调Q掺铒光纤激光器动态特性研究

为了研究自调Q掺铒光纤激光器输出动态特性,采用搭建全光纤结构的线形腔和环形腔自调Q掺铒光纤激光器进行了理论分析和实验验证。实验中,当抽运功率达到起振阈值后,随着抽运功率的增加,用示波器观察输出激光,线形腔输出激光依次经历了连续波、自调Q两种运行状态,由于抽运功率的限制,未能再次出现连续波运行状态,而环形腔输出激光则先经历了自调Q运行状态,然后是连续波运行状态;线形腔在抽运功率21mW~190mW的范围内,可获得脉冲宽度8s ~100s范围内可调、重复频率2.5kHz~54kHz范围内可调的自调Q脉冲;环形腔在抽运功率为16.2mW~110mW时,可获得的脉冲宽度在165s左右。结果表明,自调Q掺铒光纤激光器因腔结构的不同,输出激光动态特性也不同;线形腔和环形腔均有自调Q脉冲输出,但线形腔自调Q范围更大。     

激光二极管双端抽运声光调Q高重复频率Nd:GdVO4激光器

激光二极管(LD)抽运的固体激光器(DPSSL)的调Q器件是获得高重复频率、高峰值功率的有效手段之一,随着激光雷达、激光加工业的发展,要求调Q器件向着更高重复频率的方向发展。Nd∶GdVO4以其优异的物理和激光特性,使得它在激光二极管端面抽运固体激光器的声-光(A-O)调Q器件中,即使在很高的调制重复频率下,仍可获得窄脉宽、高峰值功率的脉冲激光输出。理论分析了影响脉冲激光的输出能量和脉宽大小的决定因素,研究了脉宽、平均输出功率及峰值功率随调Q重复频率的变化关系。利用双激光二极管双端抽运Nd∶GdVO4晶体棒,实现了声-光调Q高重复频率窄脉宽1063 nm激光输出。在晶体入射端面总抽运功率约43 W条件下,当重复频率f=10 kHz时,获得脉宽Δt=10.2 ns,单脉冲能量E=0.95 mJ,峰值功率PM=93.1 kW的输出;在重复频率f=100 kHz时,获得Δt=28.1 ns,E=0.10 mJ,PM=3.6 kW的结果。     

Multiple-gap back-lighted thyratrons for high power applications

Switching of high voltage and high current simultaneously with a fast current rate of rise by an optically triggered back-lighted thyratron is reported at very high pulsed power levels, including 100-kV stand-off voltage and >70-kA switched peak current. This switch is triggered by an unfocused ultraviolet light incident on the back of the cathode and is referred to as a back-of-the-cathode, light-activated thyratron (BLT). It has a simple structure that can be electrically isolated from the trigger circuit. The switch closure is a glow discharge rather than an arc; this dramatically reduces electrode degradation. The holdoff capability of one gap is limited by surface flashover and field emission. Experiments for improved holdoff voltage were conducted by scaling the BLT into multiple-gap switch configurations. The voltage of a multiple-gap chamber is divided among gaps, reducing the voltage across one gap. Hence the holdoff voltage is enhanced by additional stacks of intermediate electrode and insulator. Simultaneous optical triggering of each gap for precision timing, and plasma triggering, are also discussed. The results suggest that fairly simple multiple-gap configurations of the device are useful for applications such as multiple high-power modulator systems for accelerators     

Design and characteristics of high pulse repetition rate and highaverage power excimer laser systems

The authors describe the design and the performance characteristics of an X-ray preionized discharge pumped XeCl laser system operated at very high repetition rate frequency and high average power (200 W). The laser system is mainly composed of a fast flow subsonic closed cycle wind tunnel, a laser head, a high average power electrical excitation system, and an X-ray preionization source. The laser head design and the damping of acoustic waves induced by fast electrical energy deposition of 50 J/L bar allows this device to be operated at repetition rate frequencies of up to ≈1700 Hz     

Photo-injection p-i-n diode switch for high-power RF switching

The high RF power-switching properties of the photo-injection p-i-n switch (PIPINS), an optically controlled RF switch, are investigated. Proper functioning of a PIPINS as a low insertion-loss RF switch requires that it operates as a photoconductor, where the photo-injected charge is much greater than the RF sweep out charge. Insertion loss using 650-mW optical power was <0.4 dB at RF (VHF-UHF) power in excess of 200 W, and devices successfully standoff 200-W incident RF power with the series isolation being determined by the device capacitance (e.g., 225 fF). PIPINS hot-switching measurements are reported for the first time, with output RF power up to 180 W at low duty cycle, rise times of 1 ps, and fall times for a series shunt switch of ≈2.5 μs. The RF power for hot switching a PIPINS is limited by a latch-on effect, which is dependent on a variety of parameters, including duty cycle and repetition period, consistent with thermally generated carriers contributing to the latch-on effect. The switching properties of PIPINS make them a candidate for high RF power applications such as reconfigurable antennas, where electromagnetic isolation of the switch and control lines are critical     

Compact, megavolt, rep-rated Marx generators

A concept for compact, megavolt Marx generators has been developed, resulting in several designs which are approximately half the diameter and half the height of conventional units. The customized Marx capacitor assemblies utilize multiple windings incorporated into a single common capacitor case. Spark gap switch electrodes extend directly from the external capacitor terminals, eliminating the need for additional buswork. In order to construct the Marx generator, two capacitor assemblies are positioned opposite each other so that the electrodes line up in a vertical column between the two assemblies. Because the entire assembly is housed inside a pressurized (207 kPa of SF₆) gas vessel, the need for individual switch housings is eliminated. A four-stage, 400-kV-output Marx generator has been tested, operating at a repetition rate of 2-3 pps (power supply limited) continuously for over 5000 discharge cycles at 85-kV stage charging voltage. A second design has been fabricated and tested, utilizing 16 Marx stages to develop a 1.5-MV (open circuit) output voltage, and is contained in a cylindrical gas vessel 76.2 cm in diameter and 55.9 cm in height, weighing approximately 72.6 kg. Experimental measurements indicate a stage inductance of approximately 45 nH per 100-kV Marx stage     

MOS-gated thyristors (MCTs) for repetitive high power switching

Certain applications for pulse power require narrow, high current pulses for their implementation. This work was performed to determine if MOS controlled thyristors (MCTs) could be used for these applications. The MCTs were tested as discharge switches in a low inductance circuit delivering 1 μs pulses at currents between roughly 3 kA and 11 kA, single shot and repetitively at 1, 10, and 50 Hz. Although up to 9000 switching events could be obtained, all the devices failed at some combination of current and repetition rate. Failure was attributed to temperature increases caused by average power dissipated in the thyristor during the switching sequence. A simulation was performed to confirm that the temperature rise was sufficient to account for failure. Considerable heat sinking, and perhaps a better thermal package, would be required before the MCT could be considered for pulse power applications     

Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2laser

The envelope and frequency characteristics of the output pulse of a high repetition rate hybrid TEA-CO2laser are presented. Both the intrapulse and interpulse laser frequency stabilities are experimentally determined at repetition rates up to 300 Hz. The recovery of the CW laser signal following the generation of the TEA laser pulse is analyzed theoretically and experimentally. Short term reproducibilities of ±2 MHz are observed at a pulse repetition rate of 300 Hz with initial chirp rates of about 1.5 MHz/μs. Improvements and limits on power and repetition rate are discussed.