Theoretical investigation of dielectric corona pre-ionization TEA nitrogen laser based on transmission line method

This paper models the dielectric corona pre-ionization, capacitor transfer type of flat-plane transmission line traveling wave transverse excited atmospheric pressure nitrogen laser by a non-linear lumped RLC electric circuit. The flat-plane transmission line and the pre-ionizer dielectric are modeled by a lumped linear RLC and time-dependent non-linear RC circuit, respectively. The main discharge region is considered as a time-dependent non-linear RLC circuit where its resistance value is also depends on the radiated pre-ionization ultra violet (UV) intensity. The UV radiation is radiated by the resistance due to the surface plasma on the pre-ionizer dielectric. The theoretical predictions are in a very good agreement with the experimental observations. The electric circuit equations (including the ionization rate equations), the equations of laser levels population densities and propagation equation of laser intensities, are solved numerically. As a result, the effects of pre-ionizer dielectric parameters on the electrical behavior and output laser intensity are obtained.     

百焦耳级KrF准分子激光实验

介绍闪光Ⅱ号加速器泵浦的百焦耳级氟化氢激光研制情况，给出了激光器的构造和主要性能。在二极管电压为８４０ｋＶ，电流为２００ＫＡ条件下，获得了１５７Ｊ的最大激光能量，峰值功率为２．０ＧＷ。研究了激光输出能量随Ｆ２和Ｋｆ气体浓度的变化规律．     

百焦耳级KrF准分子激光装置设计与调试

首先用解析方法分析了提高激光输出能量的途径。其次用分析和反应动力学模拟计算相结合方法给出激光腔设计参数。并给出二极管、电子束传输系统以及变阻抗线预脉冲开关等设计参数。根据这些参数对百焦耳准分子激光器进行了工程设计。在安装调试时,采用单元安装、逐级调试然后总调。在调试中解决了阴极边缘电子发射和沿径向有机玻璃绝缘板表面的沿面滑闪等问题。在Marx电压1.1MV,主膜为50μmTi箔,二极管电压为620kV,电子束流为160kA,束能8kJ条件下,当腔内总气压为0.25MPa、气体混合比为F_2Kr:Ar=0.4:10:89.6,谐振腔全反镜反射率为96％,输出镜透射率为75％时,获得稳定、重复100JKrF激光输出能量。     

0.73 J脉冲能量KrF准分子激光器的特性

研制了一台KrF大能量准分子激光器,激光器采用紧凑型Chang电极与紫外火花预电离的结合, 实现了激活区大面积的均匀辉光放电,利用LC反转倍压以及一级磁脉冲压缩技术在放电电容上实现了峰值电压40 kV、脉冲上升时间约为100 ns的高压快脉冲激励。研究了工作气体含量对激光器能量输出的影响,在总气压3.3105 Pa,F2/He, Kr, Ne体积分数比值为1.97∶3.18∶94.85,充电电压27 kV时,得到了738 mJ的单脉冲能量输出,激光近场光斑30 mm14 mm,在充电电压23 kV时,全电效率最高,达到2.0%。     

半导体激光光栅外腔光谱合束压窄光谱的理论研究

介绍了一种减少半导体激光器阵列光栅外腔光谱合束(SBC)整体光谱展宽的方法,通过加入一组变形棱镜对传统光谱合束结构进行了改善。变形棱镜的作用实现减小半导体激光线阵输出光斑宽度,减小入射到光栅上的入射角度进而减小整体的光谱线宽。采用发光单元宽度为100 m、周期为500 m、由19个发光单元组成的常规CM-Bar条进行光栅-外腔光谱合束技术的理论推导及软件模拟,得到了光谱线宽为3.2 nm。与通过增大柱透镜焦距来减小光谱线宽的方法相比,此方法的优势是保证了整体光谱合束的整体结构在500 mm以内,使得各个发光单元有足够反馈量,抑制光束间串扰,保证合束后的光束质量和效率。     

The Nike electron-beam-pumped KrF laser amplifiers

Nike is a recently completed multikilojoule krypton-fluoride (KrF) laser that has been built to study the physics of direct-drive inertial confinement fusion. The two final amplifiers of the Nike laser are both electron-beam-pumped systems. This paper describes these two amplifiers, with an emphasis on the pulsed power. The smaller of the two has a 20×20 cm aperture, and produces an output laser beam energy in excess of 100 J. This 20 cm Amplifier uses a single 12 kJ Marx generator to inject two 300 kV, 75 kA, 140 ns flat-top electron beams into opposite sides of the laser cell. The larger amplifier in Nike has a 60×60 cm aperture, and amplifies the laser beam up to 5 W. This 60 cm amplifier has two independent electron beam systems. Each system has a 170 kT Marx generator that produces a 670 kV, 540 kA, 240 ns Bat-top electron beam. Both amplifiers are complete, fully integrated into the laser, meet the Nike system requirements, and are used routinely for laser-target experiments     

感应叠加型固态冲击磁铁脉冲发生器设计与实验

文章介绍了用于冲击磁铁的感应叠加型脉冲发生器的实验装置. 电路中采用3.3kV/800A IGBT开关, 大尺寸纳米晶磁环, 2.5kV/50uF储能电容. 设计了基于CPLD的多路延时可调、光耦输入触发驱动电路. 探讨了IGBT短路时的失效原因及保护措施. 利用现有的组元电路, 进行了多个单元叠加的样机实验, 给出了实验波形. 结果表明输出脉冲上升下降时间较快, 脉宽可调, 最大脉冲电流可达2kA, 可以满足束流注入技术的进一步提高的要求.     

对受激布里渊散射激光进行组束的数值模拟及方案设计

 提出了时间上串行的多路激光脉冲通过受激布里渊散射(SBS)池进行组束的方法,并对其进行了数值模拟研究。利用6束每束能量为45J的KrF激光进行组束, 可获得能量为141.89J,脉宽为670ps的Stokes输出光。根据模拟结果设计出了时间上串行的SBS激光组束的两个方案, 对其进行了讨论。数值模拟还发现在介质的增益系数更大、声子寿命更短的情况下,输出激光脉冲的脉宽可以压缩得更窄。     

Propagation of supercontinuum laser sources in a slant path through the atmosphere

Taking the atmospheric refraction, extinction and turbulence into account, the propagation characteristic of supercontinuum laser sources in a slant path through the turbulent atmosphere is investigated. The effect of spectral width, initial spot size and zenith angle in a slant path on the beam width and propagation efficiency are studied in details. Numerical examples reveal that the beam width and propagation efficiency are different values while the spectral width varies. With the zenith angle in a slant atmospheric path increasing, the beam width of supercontinuum laser sources will increase and propagation efficiency will decrease. The initial spot size has an optimal value when spectral width and zenith angle are fixed.     

放电泵浦KrF激光放大器的高电压脉冲发生器

描述了一台用于泵浦KrF激光放大器的可重复频率运行的高电压脉冲发生器。该脉冲发生器由恒流充电机、储能电容器、传能开关、低阻抗布鲁姆林脉冲形成线、多通道轨条型输出开关组成。介绍了布鲁姆林线和轨条开关的结构,对充电回路和放电回路特性进行了分析,完成了各部分的调试并给出了实验结果。在储能电容器直流充电电压30kV,布鲁姆林线输出电压脉冲在激光器负载上峰值可达到60kV,脉宽80ns,脉冲上升时间30ns。     

高功率LD阵列泵浦激光器小型化研究

为满足一些武器装备对激光系统小型化及输出激光光斑均匀性较高的要求,通过设计LD侧面对称半环状泵浦的泵浦方式,使得输出的激光光斑形状基本为圆形,激光光斑的均匀性有了较大提高.采用凹面全反射镜补偿热效应以及设计紧凑激光谐振腔型,在注入电流60 A、频率为20 Hz时,得到平均单脉冲能量为96 mJ (脉冲能量波动小于6%)、脉宽为10 ns、发散角为3 mrad的近似圆形激光输出,激光系统在高温50℃时工作稳定.     

Optimization of coupled confocal cavities for an injection-seeded,discharge-excited KrF laser system

The output energy and beam divergence of an injection-seeded KrF laser system, operating at 248 nm, were measured for twelve different coupled confocal unstable cavity arrangements, as a function of the relative timing between the slave and master oscillator lasers as well as of the cavity magnification. The output energy was found to be strongly dependent on both the cavity magnification and the time delay, although the beam divergence shows a less sensitive dependence. An optimized output of 2.2 J in 23 ns with a divergence of 38 μrad was achieved, representing a brightness several times larger than any previously reported for a system of this type. PACS 42.55.Lt; 42.60.Da; 42.60.Jf     

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.     

Ultraviolet laser emission at 337 and 358 nm by collisional energy transfer in fast electron-beampumped,high-pressure Ar-N2 mixtures

Successive laser emission at 337.1 nm and 357.7 nm in the second positive band of N₂ have been observed in high-pressure Ar-N₂ gas mixtures excited by a high current (15 kA) and fast rise time (8 ns) relativistic electron beam. Laser action at 357.7 nm was confirmed in the pressure range 450–6000 torr where output intensity was approximately independent of pressure, while strong pressure dependence of the emission at 337.1 nm was observed in a rather limited pressure range of 760–3000 torr. From the results of spectrally resolved pressure dependences of the laser lines, the processes of successive laser oscillation at these two wavelengths are discussed.     

Low energy ion beams by laser interaction

We developed an ion accelerator with a double accelerating gap system supplied by two power generators of different polarity. The ions were generated by laser ion source technique. The laser plasma induced by an excimer KrF laser, freely expanded before the action of accelerating fields. After the first gap action, the ions were again accelerated by a second gap. The total acceleration can imprint a maximum ion energy up to 160 keV per charge state. We analysed the extracted charge from a Cu target as a function of the accelerating voltage at laser energy of 9, 11 and 17 mJ deposited on a spot of 0.005 cm². The peak of current density was 3.9 and 5.3 mA for the lower and medium laser energy at 60 kV. At the highest laser energy, the maximum output current was 11.7 mA with an accelerating voltage of 50 kV. The maximum ion dose was estimated to be 10¹² ions/cm². Under the condition of 60 kV accelerating voltage and 5.3 mA output current the normalized emittance of the beam measured by pepper pot method was 0.22 π mm mrad.     

放电泵浦的多波长激光器

采用高气压紫外预电离放电装置和更换激射气体的方法,在一台器件上获得10个体系:F原子,Ne原子,N₂分子,N₂⁺离子,XeF,XCl,XeBr,KrF,KrCl,ArF相干辐射,并给出了激光器件的有关参数和输出特性等。 关键词：     

Theoretical application of z-dependent gain coefficient to describe amplified spontaneous emission

Based on the geometrical modeling of the unified gain coefficient and the reported amplified spontaneous emission (ASE) output energy measurement ε(ASE) versus amplifying excitation length, l(AMP) in a KrF laser oscillator, we managed, as an example, to explain the ASE output energy behavior both numerically and analytically. In this approach, introducing the ASE gain-coefficient profile for the KrF laser, g(0,KrF)(ASE), was not avoidable. It was found that while the g(0,KrF)(ASE) profile follows the introduced gain-modeling formulation, it is, however, slightly lower than the KrF laser gain profile, g(0,KrF)(exp), deduced from the measurements reported by different researchers. The present approach, up to the present time, is able to explain all of the existing ambiguities on understanding the ASE behavior.     

用于泵浦非链式HF/DF化学激光器的重复频率电子束发生器研究

 正在研究的1Hz重复频率电子束泵浦HF/DF化学激光器，预期产生的电子束能量为0.5MeV、束流强度为100kA、束流脉冲宽度为100ns。在该系统设计中，使用了一个脉冲变压器来对脉冲成形水线进行双共振充电。脉冲变压器的初级、次级电感与互感分别为331nH，26.5μH与1.9μH。脉冲成形线的电容、电感与阻抗分别为8.15nF，300nH与6.2Ω。脉冲成形线在1MV的峰值充电电压下的击穿因子为0.3。在3.3%的能量转换效率条件下，预期可以产生的HF/DF激光脉冲能量为２50J以上。     

大功率能源模块中的石墨电极气体开关系统

探讨了大功率脉冲电源模块中主放电开关和预电离开关整体系统的设计、制造和试验过程。在主放电回路中选择石墨型两电极气体开关作为主开关,因为其在高峰值和快上升沿时间电流的作用下具有很长的工作寿命,并由此构建了基于脉冲变压器的主开关触发器,其中气路控制装置是该系统的辅助设备。在预电离回路中选择石墨型三电极气体开关作为放电开关,并给出了能够同时输出高电压和大电流的预电离开关触发器的设计原理。最后,电气特性测试实验表明两电极主开关峰值电流超过700kA,总转移电荷量超过200kC,此外通过更换电极,开关的寿命可以延长。预电离开关在充气230kPa绝对气压、充电电压23kV下,击穿时延平均值为7.5μs,时延抖动为0.656μs;预电离开关寿命试验的结果显示开关工作4000发次后石墨电极无需更换,开关的总转移电荷量超过10kC。