电引发非链式脉冲DF激光器实验研究

为获取得高能脉冲中红外激光,对两种形式的电引发非链式脉冲DF化学激光器进行了研究。通过研究紫外预电离自持放电非链式脉冲DF化学激光器的输出特性,确定了最佳气压比,实现了350 mJ的DF激光脉冲输出,激光峰值功率为1.4 MW,激光能量比输出达35 J/l.101.3 kPa,电光转换效率约为1.6%;为突破预电离条件的限制,研究了非链式脉冲DF化学激光器的自引发体放电特性,通过采用针-盘电极对放电来模拟单通道放电的过程,利用非均匀场粗糙表面阴极,在注入能量密度高达200 J/l时实现了无预电离的稳定体放电。实验结果表明,采用自引发体放电技术有望实现更高能量的中红外激光输出。     

放电感应稳定的高效HF化学激光器

目前对大体积激活介质 HF( DF)化学激光器的兴趣很活跃。增大化学激光器激活体积的难度在于预电离 ,因为它要求提高抽运源的电压 ,从而导致电感增加 ,同样会增加放电的持续时间 ,使稳定性降低。为此迫切需要研制一种简单的电极组件结构 ,它可以形成均匀稳定的放电 ,而不需要专门的预电离装置。这一问题在用碳氢化合物 (碳化氘 )为基础的混合物中很快得到解决 ,取代了 H2 ( D2 )使体放电相当稳定。在不同的激活介质中 ,用半导体材料制成的电阻电极、平衡电阻及电感器来控制放电电流可以自持放电稳定 ,应用于各种气体激光器 [HF,Kr F( Xe…     

可调谐脉冲氟化氢(氘)化学激光器及其光谱性能

本文报导波长可调谐的脉冲横向放电 HF/DF 激光器的研制工作。采用了多级低电感平板电容作传输线的 LC 反转电路、Rogowski 型面的黄铜电极以及紫外预电离技术,可以有效地发射光束截面较宽的 HF/DF 化学激光。激光谱线分布中出现低 J 值 R 支,证明在所使用的条件下激光腔内存在 HF(或 DF)的全反转集居数分布,激光器的增益是较高的。调谐结果还出现文献中较少见的 HFP_2(1)单谱线。此外,还考察了气体组成、气体流动状态、放电参数和电极材料对激     

印刷电路板预电离TEA CO2激光器的阴极表面预电离研究

弧光放电不利于TEA CO2激光器输出高功率激光,通常采用预电离技术来获得主电极间的均匀辉光放电。印刷电路板预电离较其他紫外光预电离方式具有更好的预电离强度和预电离均匀性的结合,有利于产生高重复频率和高平均功率的脉冲激光。本文研究了印刷电路板预电离TEA CO2激光器中有、无紫外光体积光电离的两种不同预电离结构形式,主放电均匀性实验表明,在无紫外光体积光电离的情况下,也可以获得放电均匀性很好的大体积主放电。这说明在印刷电路板预电离中起主导作用的是阴极表面的预电离效应。本研究结果对探讨TEA CO2激光器的预电离放电机理具有参考价值。     

小型化轴流式非链式脉冲氟化氘激光器

采用轴流循环流动方式更新非链式脉冲氟化氘（DF）激光器工作介质，搭建了一台小型化自引发放电DF激光器实验装置，开展了轴流DF激光器输出性能实验研究。单脉冲工作时，在工作气体配比SF₆∶D₂=10∶1，总气压8 kPa时，实现单脉冲能量800 mJ激光输出，全波半高宽约120 ns，其性能与横流放电非链式脉冲DF激光器相似。重复频率放电时，实现了DF激光器重复频率20 Hz稳定运转，得到的最大输出功率为13.1 W，重频脉冲幅值差优于±5%，并展望了轴流式DF激光器高重频工作的前景。文中提出的轴流式非链式脉冲DF激光器为小型化、工程化中红外光源提供了新的技术途径。     

气动冷却电激励CO2激光器的研究

采用超音速喷管绝热膨胀冷却与放电激励相结合的办法,使激光器兼有电激励CO2激光器电光转换效率高和气动CO2激光器冷却效果好的双重优点,同时可避免放电激励CO2激光器采用风机和热交换器复杂的循环冷却结构,也无须使用昂贵的He气. 激光器系统由电源、前后级超音速列阵喷管、放电电极、谐振腔和排气系统组成.激光头基本尺寸为813 mm×40 mm×85 mm.放电阴极针材料选用钼,80根钼针排成一排,有效放电长度为800 mm.阴极阵列喷管由陶瓷板上均排列的陶瓷管和其中的阴极针之间形成的环形通道构成,阴极阵列喷管将储气腔和放电室隔离为两个独立空间,通过阴极列阵喷管的N2被绝热膨胀而冷却.由于阴极阵列喷管沿放电室空间均匀分布,放电室内气体流速、压力、温度、密度分布均匀,利于大体积辉光放电的稳定均匀性.阳极采用紫铜板制造,均匀排列列阵小孔,小孔中心非对应阴极针.阳极列阵小孔将放电室与光腔连通,使受激励N2进入混合激励室(光腔区),并使N2再次被阳极列阵小孔绝热膨胀冷却.光腔采用平-凹稳腔,全反镜反射率大于99%,曲率半径R=12 m,窗口透过率T=12%,腔长为0.86 m. 实验中,混合激励室气压为5.2×104 Pa,混和比为CO2∶N2=1∶2,获得输出功率195 W,光束直径为Φ15 mm的TEM00激光束,比注入功率达到413 W/gsec-1.实验表明采用气动冷却技术和电激励技术相结合是一种切实可行的优化方案.(OE38)     

重复频率放电引发的脉冲HF(DF)激光器

研制了一台重复频率放电引发的脉冲HF(DF)激光器,采用了横向放电、横向流动和侧面滑闪预电离结构,该激光器的有效增益体积为80cm×2.5 cm×2cm,最大输出激光脉冲能量1.6(1.2)J,重复频率1～3 Hz,采用特种碱性分子筛吸附剂对化学反应生成物进行吸收,激光器在准封离状态下以重复频率2 Hz运转,103个脉冲后激光脉冲能量仅有20%的下降.     

放电引发非链式脉冲HF/ DF 激光器的研究进展

文中介绍了放电引发的非链式脉冲HF／DF激光器三十年来的研究进展，分析讨论了此类激光器的发展趋势。     

大功率射频板条CO_2激光器电极波导介质膜研究

针对高功率射频板条CO2激光器铜电极表面放电氧化、受射频放电的电子溅射,致使电极表面不光滑,辉光放电不均匀,光波导损耗严重等问题。利用Al2O3波导介质膜具有的反常色散效应、耐高温能力强的特点,采用磁控溅射镀膜技术对激光器电极表面先镀Al,而后阳极氧化获得Al2O3波导介质膜。分析了磁控溅射工艺对膜层结构的影响,测量了镀膜电极对CO2激光的反射率,并进行了放电实验检测。结果表明,溅射功率为250 W时可得到致密的镀膜层结构;厚度6μm的Al2O3薄膜,对波长10.6μm的CO2激光波导反射率最高达75%;电极镀膜后激光器输出功率在占空比为30%时为700 W,占空比为60%时达到了1300 W。     

100 J侧面滑闪预电离TE CO2激光器

提出了一种新型侧面滑闪放电技术,为TE CO2激光器均匀放电提供高效、均匀的紫外预电离。采用这种技术,成功实现5.5 cm电极间距的高气压CO2均匀放电,放电截面达27.5 cm2。放电体积为5.5 cm×5 cm×90 cm的单元模块采用V(CO2)∶V(N2)∶V(He)=1∶1∶4的混合气体在60 kPa的气压下,获得了53 J的激光脉冲输出,激光比输出能量达3.46×10-4J/(L.Pa)。采用简单的谐振腔,利用两个相同的单元模块串联实现了103 J的激光输出。实验表明双模块器件存在很强的激光脉冲能量增强效应,双模块串联输出的激光能量比单模块激光能量的两倍还大15%。     

Diffuse volume-discharges without pre-ionization formed in SF6 and C2H6 mixtures

It has been shown that a volume discharge is forming in non-uniform electric-field rough cathode and even anode without pre-ionization in SF6 and C2H6 mixtures. The discharge is presented with many diffuse channels attached to bright circular cathode spots that diverge towards the anode, with the channels overlapping, form a spatially uniform glow discharge. Self-Initiated Volume Discharge （SIVD） has been performed at a total mixture pressure up to 8 kPa and energy deposition up to 200 J/L. The experimental results indicate that Self-Sustained Volume Discharge （SSVD） in SF6 and C2H6 mixtures develops in the form of SIVD, which is promising for creation of high energy and pulse-pe- riodic HF laser.     

Radio-frequency preionization in a supersonic transverse electrical discharge laser

Preionization produced by a radio-frequency (RF) discharge near the cathode of a transverse flow electrical-discharge laser is used to initiate spatially diffuse discharge pulses in a Mach 3 flow of CO2-N2-He gas at pressures up to 160 torr. Main discharge uniformity and laser output performance have been determined as a function of pressure and RF discharge characteristics.     

Investigations of two-stage-pseudospark switches for high-currentapplications

To avoid the lowering of the holdoff voltage due to the electrode erosion in one stage high current pseudospark switches (PSS), a two stage PSS with no axial aperture in the intermediate electrode was tested. For investigations a pulse generator was used generating peak currents up to 120 kA at a maximum voltage of 30 kV with a period length of 5 μs of a weakly damped sine wave with 90% current reversal. In comparison with a one stage PSS the breakdown characteristic was shifted to higher pressure. With a free floating intermediate electrode, the device could not be triggered, however, with additional capacities of a few nF between the three electrodes the discharge was ignited. The discharge in the second gap is triggered by the pseudospark discharge in the cathode gap, discharging the auxiliary capacities. Simultaneously, observation of both gaps with fast shutter photography showed an independent movement of the discharges in the two gaps. In the cathode gap as current increases, the discharge moves away from the center to the plane electrode surface as has been observed in the one stage PSS. However, in the anode gap the discharge moves away from the center after a contraction to the center. The two discharges are transmitted to metal vapor arc type discharges as the erosion patterns prove. With this kind of a two stage PSS holdoff voltages exceeding 35 kV would be possible. The characteristic switch data, i.e., delay and jitter, are nearly equal to a one stage PSS     

The Growth of Pre-breakdown Current in Helium†

The growth of pre-breakdown current across a uniform electric field discharge gap of finite dimensions has been calculated for helium. The current has been assumed to be amplified by electron ionization and by the production of secondary electrons at the cathode by positive ions, metastables and non-resonance radiation, with allowance made for the loss of secondary currant out of the discharge gap.

It has been shown that experimental measurements of the pre-breakdown current obtained for the range 3 ?1 torr^?1 cannot be analysed to give the electron ionization coefficient (α) without the help of subsidiary experiments to measure the relative abundance and secondary coefficients for the processes producing the secondary electrons. The analysis of these currents by the currents by the Townsend equations (1915) has been shown to give incorrect values of α, especially at the low E/p values where αT may be several times larger than α.     

Experimental Study with LaB6 Cathode on DCN Laser

A new LaB₆ cathode has been developed on DCN laser in this experiment. The LaB₆ cathode is expected with long-life time at high current discharge. Optimization of various parameters for maximum output power with the LaB₆ cathode at the DCN laser were performed and reported in this paper.     

等离子体平板背光源单元放电特性的研究

采用粒子网格-蒙特卡罗碰撞(PIC-MCC)方法对等离子体平板背光源单元的放电过程进行了数值模拟,获得了放电过程中各带电粒子在空间区域的分布以及各区域的形成和性质,并结合模拟结果,详细分析了等离子体平板背光源单元的放电特性.结果表明,放电单元采用大电极间距可获得正柱区放电,正柱区的形成是正离子在阴极鞘层区不断积累将电位抬高所致.通过增加电极间距以增加正柱区的长度,可以有效地改善放电特性,从而提高背光源的发光效率.     

A self-consistent model for negative glow discharge lasers: thehollow cathode helium mercury laser

A model for negative glow metal-vapor ion lasers that self-consistently describes the dynamics of the negative glow and the cathode sheath regions of the discharge has been developed. The model computes the electron energy distribution and the population of relevant excited states in the negative glow self-consistently with the charged particles fluxes and electric field distribution in the cathode sheath. Its application to the study of the helium-mercury charge transfer ion laser is reported. The model accurately depicts the operation of a hollow cathode in the laboratory, where for a defined cathode geometry and material, the discharge characteristics are determined by the selected discharge voltage and the gas pressure. The laser output power calculated as a function of the discharge parameters is in good agreement with experimental measurements reported in the literature. The model can be modified to simulate other negative glow discharge lasers, such as electron-beam pumped CW ion lasers     

Fabrication of carbon nanomaterials by atmospheric pressure microplasma

Atmospheric pressure microplasma was produced in a scanning electron microscope (SEM) chamber for synthesising carbon nanomaterials. The SEM observation is convenient for both adjusting the gap length and observing the electrode surface before and after experiments. After adjusting the gap length, the electrodes were housed in a small removable gas cell equipped in the SEM chamber and CH₄ discharge gas was introduced into the gas cell. It was found that the discharge was pulsated automatically because of slow discharge through a large ballast resistor and fast discharge through gas breakdown, even though a DC voltage was applied. The peak pulse current density was almost 60 kA/cm², the peak power density in the microplasma volume was approximately 555 MW/cm³ and the pulse width was 10 ns typically. Spherical and nanotube-like carbon nanomaterials were found on the cathode surface after microplasma discharge for 1? 5 s.With the discharge time increasing, the spherical substance changes into nanotube-like carbon nanomaterials.     

An ac-primed quartz—chlorine stage for X-band receiver protectors

A gas discharge waveguide limiter in X-band with relatively fast recovery characteristics is discussed. The problem of supplying priming electrons at a sufficiently high rate to the microwave gap (to ensure first pulse breakdown at the beginning of the pulse) in a halogen-gas quartz system is overcome by using an ac ignitor. The ac ignitor voltage is coupled through the gas reservoir wall to maintain a weak discharge whose free electrons diffuse toward the microwave gap.     

Stable discharges in an HF laser with large electrode seperation

The characteristics of a fast discharge HF chemical laser are described. A Blumlein pulse forming line is used with a resistive cathode (50 Ω . cm resistivity germanium). Uniform arc-free discharges have been obtained in gas mixtures of SF6/H2/Ar, SF6/C2H6/Ar, and SF6/C3H8/Ar with electrode separations up to 5.2 cm.