Entwicklung leistungsfähiger Stickstofflaser mit abgeschmolzenem Laserrohr

For an increase of the laser pulse energy from longitudinally excited multiple electrodes tubes, experiments and model calculations have been accomplished. A variation of the electrode spacing in the laser tube has shown, that a maximum pulse energy could be achieved with about 40 mm electrode spacing. If barium titanat capacitors with a dielectric constant of 10000 in the pulse forming unit were applied, a voltage pulse transform occured enabling an increase of the laser power up to 50%. With a sealed off operated laser tube of 100 cm active length, a laser peak power of 600 kW and a pulse duration of 10 ns could be achieved. A tube with 200 cm active length generated a pulse power of 1.2 MW. The decrease of laser pulse energy with increasing pulse repetition rate can be explained by the decrease of impulse breakdown voltage. For an increase of the lifetime of laser tubes, appropriate technologies for the production of the tube have been developed.     

多路Marx并联高压脉冲电源研究

脉冲功率技术在工业和生物医学领域有着广泛的应用,很多应用场合要求输出数百安培的高压脉冲。固态Marx发生器虽已研究多年,但是被广泛采用直插封装的IGBT和MOSFET功率半导体开关管的额定电流通常都低于100 A,无法满足低阻抗负载的应用需求。为提高输出脉冲电流幅值,提出两种多路Marx发生器并联的脉冲电源的拓扑结构,第一种方案采用多路Marx发生器直接并联,第二种是共用一组充电开关管的多路Marx发生器并联。由FPGA提供充放电控制信号,采用串芯磁环隔离驱动方案实现带负压偏置的同步驱动,主电路选用开通速度快、通流能力强的IGBT为主开关的半桥式固态方波Marx电路。实验结果表明,6路16级Marx直接并联的脉冲发生器能输出重频100 Hz高压方波脉冲幅值可达10 kV,在30Ω负载侧输出峰值电流可达300 A,上升时间230 ns。共用充电开关管的6路4级Marx并联发生器在5Ω电阻负载上的输出电流峰值可达300 A,最大输出电流可达460 A,上升时间272 ns。表明多路Marx发生器并联可以有效地减小系统内阻,提高系统带载能力;改进后的并联方案实现大电流脉冲输出的同时,所采用的开关管数量减小近一半,提高了系统的抗干扰能力的同时,降低了脉冲电源的成本;且增加级间并联导线可进一步改善均流效果。     

两节反谐振式网络输出方波脉冲的参数计算

研究了反谐振式脉冲形成网络的紧凑化、小型化问题。介绍了两节反谐振式网络的组成和特点,并建立了相应的电路模型,运用电路的拉普拉斯变换和方波的傅里叶级数展开,通过波形拟合和参数对比的方法,找到了一种解决此类型电路输出方波脉冲的参数计算方法。模拟仿真结果显示:此网络输出的方波脉冲平顶约占整个脉冲时间的1/4且基本无抖动,前沿约占整个脉冲时间的1/7,半高宽约占整个脉冲时间的5/7。利用此方法设计了一套实验装置,并进行了初步的实验探究,实验结果表明:利用两节反谐振式网络可获得输出波形质量较好的百ns级方波脉冲输出,与理论分析结果基本一致。     

变象管、双近贴象增强器及带微通道板光电倍增管的快门选通电路

本文主要简介我国变象管、双近贴象增强器毫微秒分幅相机的研制现状,并讨论这些相机的快门脉冲发生器电路。同时还介绍了用于带微通道板光电倍增管的选通电路。这些电路作适当修改后可用于微光硅靶摄象管的控制,高压电器特性试验,毫微秒脉冲源以及激光调制等场合中。     

中子管非中子产物性质

采用两只经过标定的ST401闪烁探测器,测量了脉冲中子管的中子产额,在其中一只探测器前端增加铅板屏蔽,1 cm的铅屏蔽使探测器输出减少了18.20%,在加速器中子源上进行的类似实验表明,0.5 cm的铅使探测器的输出减少了2.90%。对两个中子源上测量的情况进行了蒙特卡罗模拟,加速器实验与模拟符合较好,脉冲中子管实验差别较大。对实验和模拟的情况进行了分析,结果表明:中子管除产生中子外,还会产生数量较多的轫致辐射X射线,这些X射线对准确测量中子管中子产额将造成不良影响。     

一种调节Marx电源脉冲边沿的驱动电路北大核心CSCD

为了调节固态Marx发生器输出脉冲的边沿,提出了一种新型的的驱动电路,该方案通过调整充放电管的驱动电压,结合驱动电路的硬件结构,调节米勒平台时间,进而调整充放电管开通速度,实现了对于高压输出脉冲的边沿调节,其结构简单,不需要每级独立的控制信号。对于该电路中驱动电压和开关管开通速度的关系建立了模型进行了推导。结合理论分析结果设计了驱动电路的参数,仿真结果表明该驱动电路能够调节输出脉冲边沿。搭建带有设计参数下驱动电路的固态Marx发生器在容性负载下和阻性负载下进行了实验验证。利用该方案实现了对于6级Marx电路的3.6 kV输出脉冲在55~7.7μs的边沿调节,验证了该方案的可行性,并对比分析了不同阻性负载对于脉冲边沿造成的影响。实验结果表明:该电路在提高固态脉冲电源的边沿调节性能方面有独特的优势。     

The formation of an ion beam in a vacuum neutron tube

The formation of a deuteron beam in a diode with a plasma emitter that is integrated into the structure of a vacuum neutron tube is considered. Computations are carried out for plasma with given time dependences of parameters (density, relative concentration, and expansion velocity) at the inlet to an accelerating gap. It is shown that it is possible to increase the ion-beam current possible by sectioning the diode at the given external parameters.     

基于Blumlein 脉冲形成网络的直线变压器驱动源设计

 设计了基于Blumlein 脉冲形成网络的直线变压器驱动源单元模块。双路阻抗各为20 Ω的Blumlein 脉冲形成网络对称连接于直线变压器驱动源(LTD)的初级绕组上,此种接法降低了脉冲形成网络(PFN)的设计难度,有利于形成更好的脉冲。在LTD次级绕组所接的10 Ω匹配负载上输出高压脉冲,实验结果表明,单个LTD模块输出脉冲半高宽约200 ns,前沿约为55 ns,平顶约为100 ns。     

氘代乙烷团簇库仑爆炸产生高能氘核和中子的研究

采用简化库仑爆炸模型对强激光脉冲照射氘代乙烷团簇发生的库仑爆炸过程进行数值模拟,研究了氘代乙烷团簇爆炸产生的氘核动能、中子产额与团簇尺寸的关系,且与氘代甲烷团簇产生的氘核动能及中子产额进行了比较.研究表明,尺寸为5 nm的氘代乙烷团簇在发生库仑爆炸后氘核的最大动能为20.96 keV,获得的中子产额为6.31×105,比同尺寸氘代甲烷团簇产生的氘核最大动能及中子产额更大.因此相对于氘代甲烷团簇,大尺寸的氘代乙烷团簇更适合作为激光驱动团簇库仑爆炸获得高额中子的靶材,这与报道的实验推论相一致.     

Short-channel drain current model for asymmetric heavily / lightly doped DG MOSFETs

Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for repetitive operation. A magnetically coupled tangential blower is used for gas circulation inside the laser chamber for repetitive operation. The exciter consists of C–C energy transfer circuit and thyratron is used as a high-voltage main switch with single-stage magnetic pulse compression (MPC) between thyratron and the laser electrodes. Low inductance of the laser head and uniform and intense pre-ionization are the main features of the electric circuit used in the laser. A 250 ns rise time voltage pulse was compressed to 100 ns duration with a single-stage magnetic pulse compressor using Ni–Zn ferrite cores. The laser can generate about 150 mJ at ～100 Hz rep-rate reliably from a discharge volume of 100 cm ³. 2D spatial laser beam profile generated is presented here. The profile shows that the laser beam is completely filled with flat-top which is suitable for material processing applications. The SEM image of the microhole generated on copper target is presented here.     

Pulse shortening in high-peak-power Reltron tubes

Pulse shortening has been observed in nearly all high-power (>100 MW) microwave tubes that have attempted to extend the useful duration of the power pulse beyond shout 100 ns. Although Titan's high-peak-power Reltron tubes are notable in that they have produced 300 J/pulse in L-band, we have observed and eliminated several pulse-shortening phenomena to reach this level of performance. In this paper, we will present the results of several experiments related to pulse shortening that have examined the use of different materials and construction techniques; the importance of a good vacuum system, especially when operating under repetitive pulse conditions; and the effects of various conditioning processes. We believe that a major pulse-shortening problem has been the result of a mechanism involving rf electric-field-induced gas evolution and subsequent ionization. With our present construction techniques, using explosive emission cathodes and plastic insulators, we believe that it is possible to achieve 1 kJ/pulse at perhaps a few tens of Hertz pulse repetition rate. To exceed these levels will most likely require the use of conventional microwave tube construction techniques. Including thermionic cathodes, ceramic insulators, and brazed joining with high-temperature bakeout     

Neutron–Deuteron Scattering Observables at E lab = 14.1 MeV

Inelastic neutron–deuteron scattering is studied on the basis of configuration-space Faddeev equations. Calculated are neutron–deuteron breakup amplitudes using AV14 nucleon–nucleon potential at incident neutron energy of 14.1 MeV. The results of calculations are presented for the differential cross sections under quasi free scattering and space–star configurations, and compared with those of the previous calculations and experimental data. The choice of the cutoff radius R _cutoff for asymptotic conditions is discussed.     

轴线起爆式螺线管型爆磁压缩发生器理论模型

 对轴线起爆式螺线管型爆磁压缩发生器进行了理论模型研究，建立了爆炸管的一维爆轰驱动模型、螺线管内空间磁场强度分布模型、爆炸管外表面磁压力模型和发生器系统的等效电路模型等，对此类发生器的物理过程进行系统描述。在此基础上，编制了相应的零维数值模拟程序CEMG 1.0，利用该程序分别对四种不同模型参数的发生器进行了理论计算和参数优化，并对其中一模型发生器爆炸管外表面的磁压力及其引起的剩余电感进行了计算，给出了剩余电感与初始输入条件及负载电感的关系，从而得到该模型的输出性能极限。对理论模型的正确性进行了实例验算证明。     

200 kV闪光照相测试系统

介绍了一种基于Marx发生器原理设计的200 kV闪光照相测试系统,该系统具有延时功能,可按照实验要求,在预定时刻产生脉冲X射线进行闪光照相测试。设计了一台10级同轴结构的Marx发生器,采用了正负极充电,极间电容耦合为Z形回路的Marx发生器线路,利用开关与屏蔽外筒间的结构电容来锐化高压脉冲的输出,同时采用紧凑性、低电感设计获得窄脉冲的输出。在充电电压为25 kV的情况下,75 的负载上获得了脉宽小于100 ns、幅度大于200 kV的高压脉冲,通过高压电缆驱动闪光X射线二极管, 在距光源25 cm处获得了剂量大于910-6 C/kg、脉冲宽度约为70 ns的闪光X射线。     

Investigation of the reaction D(γ, <Emphasis Type="Italic">n</Emphasis>)H near the threshold by means of powerful femtosecond laser radiation

The possibility of studying photonuclear reactions near the threshold by means of powerful femtosecond lasers is explored by considering the example of deuteron photodisintegration. The respective experiment was performed by employing the terawatt femtosecond laser facility of the International Laser Center at Moscow State University. The radiation from this facility is characterized by a pulse energy of up to 50 mJ, a duration of 50 fs, a repetition rate of 10 Hz, and a wavelength of 805 nm. This provides a power above 10¹⁸ W/cm². Intense relativistic-electron and photon beams of energy up to 10 MeV were obtained after the optimization of relevant experimental parameters, including the focus of the laser beam, its time structure, and the choice of target. The use of these beams made it possible to study neutron generation in heavy water, to measure the time of neutron moderation, and to determine the detection efficiency. The experimental data obtained in this way are in qualitative agreement with the results of simulations based on the GEANT-4 and LOENТ code packages and indicate that it is possible to create a neutron source on the basis of the aforementioned laser. The cross section measured for deuteron photodisintegration complies with theoretical estimates available in the literature.     

基于光斑跟踪器的脉冲峰值保持电路的实现

针对激光光斑跟踪器接收信号处理系统中常规A/D采样电路对脉冲电压峰值采集的技术要求,设计了一种脉冲峰值保持电路。通过对该峰值保持电路的各项指标进行理论分析,采用宽带宽跨导放大器MAX436设计该峰值保持电路,并对该电路进行了仿真分析与实验研究,得到满足参数指标设计要求的实验结果:对于脉宽50 ns的激光脉冲信号,在输入信号幅度大于100 mV时,峰值保持电路的响应速度2 ns,下垂速率6.0 mV/s,保持精度1.1%。     

Studies on a Laser Driven Photoemissive High-Brightness Electron Source and Novel Photocathodes

A laser driven photoemissive high-brightness electron source at Peking University is reported.Through a DC accelerating gap of 100kV voltage,the device is capable of delivering high-brightness electron beam of 35—100ps pulse duration when irradiated with a mode-locked YAG laser.The geometry of the gun is optimized with the aid of simulation codes EGUN and POISSON.The results of experimental studies on ion implanted photocathode and cesium telluride photocathode are given.The proposed laser driven superconducting RF gun is also discussed.     

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。     

多管PDE爆轰噪声传播过程物理特性实验研究

为研究多管脉冲爆轰发动机爆轰噪声传播过程及声波物理特性,对单管至四管脉冲爆轰发动机爆轰噪声物理特性开展实验研究,获得了多管脉冲爆轰发动机爆轰噪声的波形、声压衰减规律、辐射特性、持续时间和频谱特性等物理参数.结果表明,在管口区域,爆轰噪声峰值衰减较快,在远离管口区域,衰减速率逐渐放缓.随着爆轰管数量的增加,爆轰峰值噪声在...