高重复率铜蒸汽激光的充氢机制

通过数值求解时空自洽的铜蒸汽激光动力学方程，详细研究了铜激光的充氢机制．少量充氢提高激光功率的原因是：1）氢具有的大热导率使管壁温度升高，铜粒子数密度增加；2）充氢增加了电子与氢的动量输运碰撞，使放电电流减小．当电源功率一定时，闸流管的功率损耗减小，输入激光管的功率增大．此外，充氢过多（大于（1—2）%氖），通过电子碰撞激发氢分子振动能级，使电子温度和电子密度下降较大，电子没有足够的能量密度激励激光能级，导致激光功率下降 关键词：     

Method of Measuring Electron Density in Pulse Metal Vapor Lasers Using Microwave Technique

A method of measuring the electron density kinetics in the plasma of pulse-periodic metal vapor and metal compound vapor lasers using microwave technique within the wavelength region of 78–142 GHz is realized. The method is based on the dependence of the absorption efficiency of a probe microwave radiation on the frequency of electron collisions and also on the dependence of the cut-off or the critical density on the frequency of the probe radiation. In a quasioptical translucence scheme the plasma of a copper bromide vapor laser is studied within an interpulse time interval in a gas-discharge tube of 20 mm in inner diameter and with a 300 mm long active heated region excited by a capacitor discharge with a pulse repetition rate of 10 kHz. It is shown that under operational conditions typical for metal vapor lasers the absorption of the probe radiation within the interpulse intervals is totally determined by Coulomb electron–ion collisions. This allows one to measure both the density kinetics and the electron temperature. Probable measurement errors are analyzed and it is shown that they result in a systematic error for the absolute value of the electron density but have a slight influence on the density kinetics.     

CuBr激光充氢机理研究

详细研究了ＣｕＢｒ激光充氢后的激光动力学过程,解释了实验中观测到的两个现象：１）充氢后功率增大,其主要原因是：充氢使中心气体温度和ＣｕＢｒ分子蒸汽密度降低,从而减少了电子碰撞离解ＣｕＢｒ的有量损耗,导致电子温度上升。同时,脉冲期间的电子密度增加,电子密度的趋肤效应减弱,激光的“黑心”现象被改善。２）存在一个最佳充氢范围,其原因是：充氢后,随着气体温度的进一步降低,电子温度和铜原子度也将下降,它们与     

Effect of gas convection induced by cross-field discharge in a copper vapor laser

Magnetic field has been applied to a copper vapor laser with an intention of improving the laser characteristics by inner gas convection. The convection induced by the J×B cross-field discharge (the Lorentz force) is used for partially replacing or mixing the laser medium in a highly heated discharged region with relatively cold gas surrounding the region. It is observed that the output power increases with the increase of the magnetic field. A 23% increase in the output power is obtained with a magnetic field of 150 gauss. The cross-field discharge causes an increase in the peak discharge voltage and a reduction in the initial part of discharge current (Phantom current). Based on the results observed, the possible mechanisms for increasing the power are discussed.     

Pulsed barium vapor laser with hydrogen additive and interactive circuit

A small-size discharge heated barium vapor laser with an axial temperature controller was designed and made. The operational characteristics of the laser with different hydrogen additives and two excitation circuits were experimentally investigated and compared. The results indicate that the addition of a small ratio (1.5%) of hydrogen to neon and the interactive circuit (IC) can greatly increase the laser output power. The maximum average laser power of 3.5 watts and a record specific power of 117.3 mW/cm³ at a 1.5 μm wavelength were obtained under optimal discharge conditions. Some possible mechanisms were suggested to explain the enhanced effect of the hydrogen additive and IC to the laser output performances. PACS 42.55.Lt; 42.60.Lh; 52.80.Tn     

低气压直流放电金属铜等离子体

在原子蒸气激光同位素分离技术中用直流电源实现原子化和激发电离过程,低气压下使用焊锡短路阴、阳极得到了金属铜等离子体稳定射流。在气压10^-3Pa、功率0.9kW下,测得稳定放电的伏安特性曲线和光谱强度图。通过计算得到电子密度在10⁹cm^-3左右、电子温度在0.69eV左右。     

Ar/H2O大气压等离子体射流放电特性

为了研究水蒸气体积分数对大气压等离子体射流放电机理及放电效率的影响,进而产生高活性低温等离子体并优化其效率。通过对大气压氩水等离子体射流的电压电流波形和Lissajous图形等电气特性的测量及发射光谱和发光图像等光学特性诊断,研究了不同水蒸气体积分数时,等离子体射流的放电特性。通过计算放电功率、传输电荷量、电子激发温度、分子振动温度和分子转动温度等主要放电参量,研究了它们随水蒸气体积分数的变化趋势,并结合放电机理对所得实验结果进行分析。结果表明,Ar/H2O等离子体射流除了产生N2和Ar,还有OH和O,气体温度在525~720 K之间变化,为典型的低温等离子体;随着水蒸气体积分数的增加,等离子体羽喷出管口的长度减小,放电功率减小,发光强度减弱,转动温度和振动温度增加;相同功率下,水蒸气体积分数为0.5%时,产生的OH达到最大。     

铜蒸气激光脉冲终止机理的数值研究

建立了一个反映纵向脉冲放电激励铜蒸气激光动力学过程的自洽物理模型并进行了数值求解. 根据模拟结果深入分析了铜蒸气激光脉冲的终止机理，表明受激辐射跃迁、激光下能级的电子碰撞激发和激光上能级的铜原子经电子碰撞被抽运到更高激发能级这三个过程，是导致激光脉冲终止的重要因素. 关键词： 铜蒸气激光 激光脉冲终止机制 电子碰撞 更高激发能级     

Designing of a lead ion model source for plasma separation of spent nuclear fuel

Plasma sources of model substances are required for solving problems associated with the development of a plasma separation method for spent nuclear fuel (SNF). Lead is chosen as the substance simulating the kinetics and dynamics of the heavy SNF component. We report on the results of analysis of the discharge in lead vapor with a concentration of 10¹²–10¹³ cm^–3. Ionization is produced by an electron beam (with electron energy up to 500 eV) in the centimeter gap between planar electrodes. The discharge is simulated using the hydrodynamic and one-particle approximations. The current–voltage characteristics and efficiencies of single ionization depending on the vapor concentrations and thermoelectron current are obtained. The experimentally determined ion currents on the order of 100 μA for an ionization efficiency on the order of 0.1% are in conformity with the result of simulation.     

基于连续谱的氩气纳秒脉冲放电中电子温度的研究

采用了一种针对针的放电结构,将其放置在一个高纯氩气的密闭腔室中,通过施加正极性的过电压产生可重复的大气压纳秒脉冲放电,并提出建立大气压放电的连续辐射模型来诊断氩气纳秒脉冲放电中的电子温度。实验利用电压和电流探头分别获取放电过程中的电压和电流波形图,其放电脉宽约为20 ns。通过消色差透镜、单色仪和ICCD等光学系统的组合来测量放电正柱区在不同时刻（0<t<20 ns）的时间分辨发射光谱。结果表明,放电中连续谱的强度随时间先增加（0<t<10 ns）后减小（10 ns<t<20 ns）,但是氩原子的谱线强度则随时间的增加而一直增大。研究表明连续谱强度与电子密度成正相关,因而电子密度随着时间也是先增加而后减小,这与放电电流的变化规律是完全一致的。根据连续谱模型拟合得到放电过程中（0<t<10 ns）的电子温度为(1.4±0.2) eV。随着驱动电压的下降（10 ns<t<20 ns）,电子温度逐步减小至0.9 eV。在0<t<10 ns中,激发态氩原子主要是由电子碰撞激发产生的,因而谱线强度随着电子密度的增加而增大。然后,随着电子温度的减小,Ar+₂复合反应速率激增,导致电子与离子的复合过程主导产生激发态氩原子,即谱线强度继续增大。通过加入0.5%的水蒸气以获取OH的振转光谱。实验发现,OH(A)的产生机制使其偏离玻尔兹曼平衡分布,本文采用了双温的OH(A-X)光谱模型来考察气体温度。在放电过程中,气体温度保持不变,大约为400 K。此外,水蒸气的加入使得短波长的连续谱发生显著增强。光谱分析认为H₂O在放电中能够解离产生H₂,继而与氩原子的亚稳态发生能量转移生成激发态H₂(a3Σ+_g)。H₂(a3Σ+_g)将会自发辐射跃迁到排除态H₂(b3Σ+_u),同时发射短波长的连续谱。由于短波长的连续谱对电子温度（T_e>1 eV）的响应较为灵敏,所以载气中少量的水蒸气将会对连续谱诊断电子温度带来较大的影响。     

Effect of hydrogen additives on characteristics of the CuBr laser

Kinetic processes in the active medium of the copper bromide vapor laser with hydrogen additives are described in detail. Mechanisms for improvement of its lasing characteristics by hydrogen additives are analyzed.     

Development of copper bromide laser master oscillator power amplifier system

Development of master oscillator power amplifier (MOPA) system of copper bromide laser (CBL) operating at 110 W average power is reported. The spectral distribution of power at green (510.6 nm) and yellow (578.2 nm) components in the output of a copper bromide laser is studied as a function of operating parameters. The electrical input power was varied from 2.6 to 4.3 kW, the pulse repetition frequency (PRF) was changed from 16 to 19 kHz, and the pressure of the buffer gas (neon) was kept fixed at 20 mbar. When the electrical input power was increased to 4.3 kW from 2.6 kW, the tube-wall temperature also increased to 488°C from 426°C but the ratio of the green to yellow power decreased to 1.53 from 3.73. The ratio of green to yellow power decreased to 1.53 from 1.63 when the PRF of the laser was increased to 19 kHz from 16 kHz. These observations are explained in terms of electron temperature, energy levels of transitions, and voltage and current waveforms across the laser head.     

Sättigungsverhalten und Verlauf der Elektronentemperatur beim Argon-Ionenlaser

Recently saturation of laser power ofCW ion lasers has been observed with large bored laser tubes made of metal segments. The saturation was observed in Argon, Krypton and Xenon in high current regions. In this case it was necessary to calculate the correlation between the electron temperature, electron- and ion-density and on the other hand the discharge quantities as current density and voltage drop. By measuring the discharge quantities at optimum laser power it is possible to determine the optimum electron temperature for any current density. The comparison of the run of these quantities leads to the assumption that the saturation mechanism causes a decrease of the optimum electron temperature.     

A computer model of a transverse discharge cw CO laser

A kinetic model has been developed for the investigation of the novel performance of a CO laser, on which efficient extraction of laser power was obtained by exciting a subsonic gas mixture of CO/N₂/He/O₂ through transverse dc discharge. Kinetic equations for direct excitation by electron impact, V-V and V-R/T energy transfer, and stimulated emission are coupled with a semi-one-dimensional flow model. Careful consideration is devoted especially to the V-V transfer process of CO–N₂ and N₂–N₂. The laser power was calculated by a constant gain method. The laser output performance, examined as a function of gas mixture ratio, temperature, flow velocity, and discharge current, was in good agreement with the experiment.     

Ablation of molybdenum and niobium with a HyBrID copper laser

A hydrogen bromide in discharge (HyBrID) copper laser with 12 W of maximum average power, 16 kHz repetition rate and 35 ns pulse duration, emitting simultaneously in 512 and 578 nm, was used to study molybdenum and niobium ablation. A modified Balzer QMG-311 mass spectrometer was used for monitoring presence of metal vapor and a pair of polarized flat electrodes placed parallel to the metal vapor stream was used in order to observe electric charges formation. Thin films on BK-7 optical-quality flats allowed the estimation of deposition rate. The measured ablation thresholds of 6.9 and 5.4 J/cm² for Mo and Nb, respectively, agreed well with theoretical estimations. Charge formation was observed for laser fluencies below the vapor formation thresholds and this was attributed to thermoionic emission. The maximum film growth rate in our experimental facility was measured to be about 16 Å/min for Mo and 11 Å/min for Nb.     

百瓦级铜蒸汽激光器最大功率的全局优化设计

将全局优化的遗传算法应用于百瓦级铜蒸汽激光器（CVL）,以最大输出激光功率为目标函数,整体优化设计和确定了铜蒸汽激光器同轴结构的激光和放电电源的电路参数等。提高激光功率的一条途径是：在采用相对较小的储能电容的同时,提高输入功率（主要是峰值电压）和管壁温度,且使激光头与供电电源相匹配。     

Analysis of the spectral structure of CuBr laser lines

The spectral structure of spontaneous emission of copper atom at 510.6 nm and 578.2 nm was calculated considering the hyperfine structure of energy levels and the isotope shift. The spectral structure of the 510.6 nm and 578.2 nm laser lines was measured in a sealed-off CuBr laser tube with periodic refreshment of the neon buffer gas under different work temperature and excited voltage. The spectral structure of the spontaneous emission of copper atom was found to have similar outline with its laser lines. The spectrum of the 510.6 nm laser line maintains similar outline with three peaks at various discharging parameters while the spectrum of the 578.2 nm laser line is strongly dependent on the reservoir temperature and the discharge voltage.     

Fourier-transform sensitivity analysis

Fourier-transform sensitivity analysis has been applied to a simplified model of a XeCl self-sustained discharge laser. Sensitivity coefficients have been calculated for chemical, electron and photon densities and for the discharge current and voltage. The role of preionization instability on model sensitivity has also been investigated. The sensitivity analysis has been coupled to a statistical analysis of the output data (mean, maximum and minimum values), which can help to better understand the behaviour of the tested model.     

Prospects for Further Development of Self-Heated Lasers on the Self-Contained Transitions of a Copper Atom

An analysis of the causes restricting the frequency–energy characteristics of a copper vapor laser is carried out. The principal cause of the restriction is shown to be the high deexcitation rate of the higher laser levels into the ionized state. This involves a strong increase in the expenditures of energy for the population inversion with a rise in the electron density before the pulse and a high $Q$ factor of the discharge circuit at the end of the exciting pulse. The high Q factor of the discharge circuit is responsible for the oscillatory process of energy dissipation within the time spacing between pulses. This energy is stored in the reactive component of impedance of the discharge tube during the excitation pulse. The oscillatory dissipation defines a slow relaxation of the lower laser levels within the time spacing between the pulses. Analysis of the conditions of population inversion formation in a copper vapor laser shows that the active medium should be pumped in a two-pulse excitation mode to realize the energy potential of the laser of 1–2 kW/liter. The advantages of such an excitation mode over the traditional single-pulse excitation are confirmed.     

铜蒸气激光器等离子体阻抗动态特性研究

 给出了铜蒸气激光器放电电路各参数的表达式及取值。与铜蒸气激光器动力学模型相结合,讨论了铜蒸气激光器动力学过程中由于放电管内等离子体参数的变化引起等离子体阻抗动态演变过程,并与采用固定等离子体参数的等离子体阻抗进行了比较。