Power system for a high-power burst mode pulsed load

A novel power system, recently completed and commissioned, is described. Operating directly from an ll-kV, 50-Hz public supply, it provides the electrical energy for a burst mode, pulsed load. In each burst, the minimum energy delivered by the power system is 100 kJ at a rate of 330 kW. The pulse modulator operates at a peak charge of 105 kV and is capable of switching 200 MW over a range of pulse lengths and repetition rates. The high-voltage, high-current thyratrons used as the charge, discharge, and PFN energy dump switches were specially developed, four-gap, double-ended CX 1199B thyratrons. Supply voltage stepup transformers were designed to operate over bursts of variable pulse number, length, and rate, with the rectified unfiltered transformer output directly feeding the modulator charging circuit at up to 65 kV. Polarizing effects in the transformer core caused by the use of repetition rates equal to, or harmonically related to, the supply frequency were analyzed and effectively eliminated. Special winding techniques were developed to provide the strength and insulation for withstanding fault transients. While the power supply is capable of limiting fault currents occurring in the modulator and load, normal full system protection is provided by PFN energy dumping and, in the ac supply, by fast-acting vacuum contactors. Comprehensive control, monitoring, and mode selection are based on micrologic elements. By using direct, high-voltage modulation considerable flexibility is possible. The various alternative arrangements which derive from this design concept are explained. In addition, factors which determined the major features of the equipment are reviewed. The construction, layout, and performance are illustrated.     

Generation of closely spaced, doublet, CFA cathode pulses with aline-type modulator

Dual-channel, line-type modulators that have advantages in size, weight, redundancy, duty cycle, and independent pulse energy adjustment are described. The dual-channel, line-type modulators are used to generate doublet cross-field amplifier (CFA) cathode pulses in a 1.25-MW peak RF power output master oscillator power amplifier (MOPA) transmitter chain. The amplifier chain consists of a 20-kW peak power traveling-wave tube, a 150-kW peak power intermediate CFA, and a final 1.25-MW CFA stage. The intermediate CFA stage modulator (22 kV and 14 A peak) and the final CFA stage modulator (35 kV and 77 A peak) are described with equipment photographs, test data, and results. The performance requirements for each CFA stage are presented. The advantages of the doublet line-type modulator in comparison to other high-power pulse modulators are presented     

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.     

The MAPS-40 burst-mode 40-kV megawatt average power hydrogen thyratron

A hydrogen thyratron capable of switching 40 kV and 40 kA in repetitive bursts at the 1-MW average power level is described. Major design problems were obtaining the necessary forward and inverse holdoff capability and controlling the thermal and mechanical effects of the several kilowatts of operating dissipation encountered at this power level. A conventional external anode, planar-electrode, ceramic-metal tube design was chosen to meet the design requirements, which include reliable, kickout-free operation following long periods of standby. Emission was provided by a large cathode specifically designed to handle ohmic heating due to the 1500 A of rms-equivalent pulse current, as well as the heat developed in the surrounding plasma. Massive auxiliary, control, and gradient grids were incorporated into a tightly baffled box-type grid structure of sufficient total aperture area to prevent quenching below 70-80 kA. Molybdenum wall shielding was employed to improve holdoff capability and prevent arc damage. Design and operating considerations are discussed and representative test results for the first 16 tubes are given, together with the results of special tests for high peak current, high average current, and high-voltage holdoff.     

Compact megawatt average power burst pulse generator

A compact, lightweight, burst mode pulse generator has been designed and evaluated at a megawatt of average power. The modulator occupies a volume of 0.81 m³and weighs 225 kg. The recently developed MAPS-40 thyratron [1] and two high-energy density pulse-forming networks [2] (PFN) are used as the switch and energy store. A solid-state end-of-line clipper circuit is included and was found to be essential at high average power loadings. The modulator has been evaluated using a copper sulphate load at 40-kV peak voltage, 40-kA peak current, 10-µs pulsewidth, 40-kA/µs rise time,and 50 A of average current at a repetition rate of 125 Hz. Repeated burst on times of 5 s in a 35-s time period have been demonstrated.     

铜蒸汽激光器双闸流管触发系统的研究

研制成用于钢蒸汽激光器的双间流管触发系统。用两个闸流管并联进行交替触发，总输入电功率达7．8kW。低功率运行时，激光器的效率为0．6％与单间流管激光器的效率一致。     

L-band high power silicon p-i-n diode switch

An extremely high power silicon p-i-n diode switch was developed for operation over the 1255- to 1385-MHz frequency range. It was successfully tested at 4-MW peak power with 100-µs pulsewidth. and 2.5-MW peak and 100-kW average power with 200-µs pulsewidth in a balanced duplexer configuration.     

Subnanosecond multi-gigawatt CO2 laser

A semiconductor switching technique has been utilized to produce 30-300 ps variable duration CO₂ laser pulses of 0.5-MW peak power. Eight passes through a 1.2-m long, UV-preionized, 3-atm TE CO₂ amplifier raise the output laser peak power to the 10¹⁰ W level. Sampling the amplifier gain in linear and saturated regimes using CO₂ laser radiation ranging from CW to 30 ps pulse length permits comparison with computer modeling of picosecond CO₂ pulse amplification. The potential for further peak power scaling of picosecond molecular lasers is discussed     

A high-voltage modulator for high-power RF source research

The design, construction, and operating results of a high-voltage modulator system capable of generating 700-kV, 2.5-μs pulses at 5 p.p.s. into a load of 900 Ω are presented. The modular is used to energize a variety of high power microwave devices requiring voltage stability and reproducibility. Voltage ripple is less than 0.2% during the 1.0-μs flat top, with a shot-to-shot voltage variation of less than 0.1%. The primary circuit consists of two seven-stage tunable Rayleigh-type pulse-forming networks (PFNs) connected in parallel with a total impedance of 2.25 Ω, a total capacitance of 0.56 μF, and a total inductance of 2.8 μH. The PFN is charged by a highly stable 80-kV capacitor charging power supply (0.1% RMS voltage ripple) at a rate of 10 KJ/s. The total energy stored (1.5 kJ) is released through an ITT F-187 thyratron into a 20:1 pulse transformer, which generates 700-kV, 2.5-μs pulses. By changing the transformer, it was possible to obtain 250-kV, 1.70-kA pulses for driving low-impedance relativistic magnetron diodes. The flat-top voltage generated by the modulator is highly desirable for driving RF sources requiring high-quality electron beams, such as free-electron lasers (FELs) and cyclotron autoresonance masers (CARMs). The modulator performance in the relativistic magnetron and CARM experiments is described     

2.5 GHz and 5 GHz harmonic mode-locking of a diode-pumped bulkerbium-ytterbium glass laser at 1.5 microns

Third-order harmonic mode locking of a diode-laser pumped bulk Er:Yb:glass laser by frequency modulation with a lithium niobate modulator is reported. Stable pulses at a repetition rate of 2.5 and 5 GHz with a pulse duration down to 9.6 ps are obtained. The average output power is 3 mW, the pulse peak power is 120 mW at 2.5 GHz repetition rate, and the pulses are approximately 1.4 times transform limited. The pulse duration can be increased up to 30 ps by decreasing the mode-locker drive power     

小型化高压固态脉冲调制器

针对高峰值功率发射机调制器的技术要求,介绍了常用的线型调制器和固态刚管调制器电路拓扑,讨论了不同调制器的特点和适用场合。介绍了小型化高压固态脉冲调制器的电路拓扑,分析了影响调制器性能的主要因素。该调制器基于单个大功率绝缘栅双极型晶体管模块和初级采用多组导线并联绕制的脉冲变压器,并采用能量回馈电路来箝位脉冲变压器的反峰电压。文中给出了调制器的输出脉冲波形,并指出了该调制器的适用场合。     

受激布里渊散射主被动混合调Q光纤激光器

基于瑞利散射和受激布里渊散射(RS-SBS)的被动调Q掺铒光纤(EDF)激光器的输出脉冲序列具有重复频率低、脉宽窄、功率高的特点,适合光时域反射(OTDR)系统对脉冲光源的基本要求,但是输出的脉冲序列不够稳定。提出在被动调Q激光腔中插入声光调制器(AOM)构成主被动混合调Q激光器。实验结果证明,这种混合调Q的方法既保持了声光调制器主动调Q激光器输出脉冲序列重复频率低而且稳定的特点,又发挥了瑞利散射和受激布里渊散射被动调Q机制动态速度快、输出脉冲宽度窄的优势。在120~200 mW的抽运功率条件下,得到的脉冲序列重复频率从30 Hz~90 kHz连续可调,脉冲宽度最小可达20 ns,峰值功率最高可达200 W,脉冲重复频率稳定度优于5%,脉冲幅度起伏不大于10%。脉冲峰值功率和脉冲宽度受抽运功率的影响不大,但随着调制频率增加,脉冲峰值功率降低而脉冲宽度加宽。     

Analysis and optimization of Q-switched operation of a Tm/sup 3+/-doped silica fiber laser operating at 2 /spl mu/m

Analysis and operation of a Q-switched Tm/sup 3+/-doped silica fiber laser in the wavelength region of 2 /spl mu/m is described when pumped with a Nd:YAG laser operating at 1.319 /spl mu/m. A large core of 17-/spl mu/m diameter was used to increase the laser gain volume, allowing high pump-power absorption and an output of high pulse energy and peak power. An acoustooptic modulator was used as Q-switching element and operated at repetition rates up to 30 kHz. A maximum peak output power of greater than 4 kW and a pulse duration at full-width at half-maximum of 150 ns has been obtained. This is the first report of high peak-power operation of the thulium-doped silica fiber laser.     

掺Yb3+全光纤环形腔主动调Q光纤激光器

报道了用976 nm激光二极管(LD)抽运掺Yb~(3 )增益光纤,用光纤耦合的声光调制器(AOM)实现全光纤环形腔主动调Q激光输出的实验研究。激光器的调制频率在200 Hz～60.9 kHz之间调节时获得稳定的调Q脉冲输出。当抽运光功率为183 mW,调制频率为500.2 Hz时,获得输出峰值功率为2.7 W,脉冲宽度为53.2 ns,单脉冲能量为145.5 nJ的激光脉冲,激光器的输出波长为1030 nm。当Q开关关闭时间较短时,从实验中观察到高低脉冲间隔输出的情况,利用调Q原理给出了相应解释。从实验和理论上分析了调制频率和抽运功率对激光器输出脉冲的影响,并进行了相应的计算,计算值和实验结果符合得较好。     

An all solid-state modulator for the ARSR-3 transmitter

This paper describes an all solid-state, high-power pulse modulator used in the ARSR-3 system (an FAA air route surveillance radar system). The modulator, the culmination of a number of years of both device and circuit development, uses fast switching Reverse Blocking Diode Thyristors (RBDT's) to directly switch 14-MW, 3-µs video pulses at high current without the use of magnetic switching aids. The modulator consists of five identical PFN modules, a trigger amplifier, and a pulse transformer which matches the modulator output to the beam characteristics of a klystron. Each module contains its own PFN, discharge RBDT switch assembly, and associated circuitry. This modulator is the first production equipment to use the new Westinghouse T62R RBDT devices. The devices switch 2200-A pulses with a turn-on rate of rise of up to 3000 A/µs.     

Voltage Balancing Control for a Three-Level Diode-Clamped Converter in a Medium-Voltage Transformerless Hybrid Active Filter

This paper discusses a transformerless hybrid active filter integrated into the 6.6-kV, 1-MW adjustable-speed motor drive having a three-phase diode rectifier at the front end. The hybrid filter consists of an active filter using a three-level diode-clamped pulsewidth modulator converter rated at 60 kVA, and a 250-kVA passive filter tuned to the seventh harmonic frequency. They are directly connected in series without a transformer. This circuit configuration enables one to use 1.2-kV insulated gate bipolar transistors because the dc voltage of the three-level converter is 1.32 kV (20% of 6.6 kV). Voltage balancing control characterized by superimposing a sixth harmonic zero-sequence voltage on the active filter voltage reference in each phase is introduced to the three-level converter with triangle carrier modulation. Experimental waveforms obtained from a 400-V, 15-kW downscaled system verify the viability and effectiveness of the proposed hybrid filter, keeping the two dc capacitor voltages well-balanced.     

142 W高峰值功率窄线宽线偏振脉冲光纤激光器

报道了一种基于主振荡功率放大(MOPA)结构工作的全光纤窄线宽线偏振纳秒脉冲光纤激光器。脉冲种子源是由一个分布反馈直腔型(DFB)单频光纤激光器被光电调制器进行强度调制后产生的。为了抑制受激布里渊散射(SBS)效应,脉宽被调节为3 ns,并且种子源线宽被相位调制器展宽为2.9 GHz。经两级保偏掺Yb3+光纤放大器放大后,获得了平均功率142 W,重复频率1 MHz,脉冲宽度2.88 ns,峰值功率49.3 kW的脉冲激光输出。在最大输出功率时,激光光束质量因子M2约为1.15,偏振消光比(PER)大于15.4 dB。     

CuBr Laser Excited by a Capacitively Coupled Longitudinal Discharge

The paper presents the study of the CuBr laser energy characteristics using capacitively coupled discharge excitation. We have studied the effect of the addition of HBr on laser performance for gas discharge tubes of different bore diameter at various input power conditions. When adding HBr pulse and average output power as well as laser efficiency more than double increase due to the shortening of the current pulse rising time and its duration. The total maximum average lasing power of 3.7 W was obtained at 0.27% efficiency. In the paper, we also notice that when adding admixtures capacitively coupled discharge pumping is superior to traditional glow discharge pumping.     

X波段固态功率放大器的研制

介绍一种新型X波段固态功率合成放大器,其为脉冲工作方式,采用4个30 W末级功率放大模块,通过混合方式进行功率合成,得到80 W以上的峰值输出功率。最大脉冲宽度200μs,最大占空比40%。实测结果表明,无论是输出功率、体积尺寸大小,还是散热、可靠性等方面都有较大的提升。     

天气雷达回扫充电调制器的应用分析

为了提高发射机输出脉冲幅度的稳定度,研制了平均功率约30kW的脉冲电源,采用回扫充电技术给线型调制器的脉冲形成网络充电。该电源充电、放电分时进行,可控制调制器连通以减小电源纹波影响调制器指标;采用IGBT作为充电开关。研究了临沂新一代天气雷达回扫充电调制器的工作原理和电路组成,最后还阐述了回扫充电电源中重要参数指标。