Plasma parameters at nanosecond breakdown and capillary discharge in a solid insulator

The subject of investigation is the energy-mass composition of a plasma resulting from the breakdown of KCl single crystals and from discharges in capillaries produced by the breakdown of KCl and high-pressure polyethylene samples. The plasma flux formed by the head of the discharge channel in KCl is found to be much less intense than the plasma flux due to the capillary and surface discharges. Also, the first breakdown of KCl does not produced multiply charged ions of the related material. It is revealed that the energies and charge numbers for the capillary and surface discharges are close to each other.     

磁开关作为脉冲驱动源主开关的实验研究

使用矩形截面磁芯研制了一台磁开关作为脉冲驱动源的主开关,并利用电容器放电法对磁芯不同位置处的磁滞回线进行了测量。结果表明,短边和长边测量得到的磁滞回线均能够适应磁开关需求,不同的励磁位置对磁滞回线形状的影响有限。设计了基于该磁芯的磁开关,使用PSpice软件进行了数值模拟,结果与理论分析相一致。结合卷绕型带状脉冲形成线,对磁开关作为脉冲驱动源主开关进行了实验研究。结果表明研制的磁开关实现了主开关功能,在1.1 的低阻抗负载上获得了峰值电压9 V、上升沿80 ns、脉冲半高宽230 ns的准方波脉冲输出。     

磁开关作为脉冲驱动源主开关的实验研究

使用矩形截面磁芯研制了一台磁开关作为脉冲驱动源的主开关,并利用电容器放电法对磁芯不同位置处的磁滞回线进行了测量。结果表明,短边和长边测量得到的磁滞回线均能够适应磁开关需求,不同的励磁位置对磁滞回线形状的影响有限。设计了基于该磁芯的磁开关,使用PSpice软件进行了数值模拟,结果与理论分析相一致。结合卷绕型带状脉冲形成线,对磁开关作为脉冲驱动源主开关进行了实验研究。结果表明研制的磁开关实现了主开关功能,在1.1 的低阻抗负载上获得了峰值电压9 V、上升沿80 ns、脉冲半高宽230 ns的准方波脉冲输出。     

High current density spotless vacuum arc as a glow discharge

Vacuum discharge burning between a broad cathode and a point anode made of Mo, Cu, and Cd has been studied. This discharge operates in anode vapors and shows major arc characteristics, although no craters were examined on the cathode. The secondary electron emission is involved to explain current transport within the cathode region. This discharge is interpreted as a high density low voltage glow discharge. Having discussed the present and previous findings, the conclusion has been drawn that the secondary electron emission and “hump of potential” are dominant in the vacuum arc cathode spot     

Plasma opening switch research for DECADE

Plasma opening switch (POS) research for the DECADE radiation effects test facility is reviewed. This research was first performed on a half-scale generator, DECADE Prototype Module 1, and indicated the importance of the POS electrode geometry to obtain the required impedance at appropriate conduction times. It also was demonstrated that the conduction time jitter was suitable for a multimodule system. Preliminary experiments at full energy were then conducted on DECADE Module 1 that indicated significant current loss when using a bremsstrahlung load, limiting the output radiation to about half of the DECADE requirement. These results initiated an effort to thoroughly diagnose the power-flow region downstream of the switch, an effort that ultimately provided improved understanding of POS operation and improved coupling to bremsstrahlung loads. At the conclusion of this effort, it had been demonstrated that it is possible for the POS-driven system to meet the DECADE requirements     

等离子体喷射触发气体开关多通道放电特性

为了能够形成稳定的多通道放电,研制了一种等离子体喷射触发气体开关。在触发电极的内部嵌入多个微型激励腔以形成多通道等离子体喷射,从而在主间隙中诱导多通道放电。研究了触发电路连接方式、触发能量和极性对多通道等离子体喷射的影响,比较了开关在两种工作模式下各间隙放电通道数量随工作系数的变化规律。实验结果表明：采用触发电路II连接方式,触发电极的多通道放电效果更好;高触发能量、负极性和低气压条件有利于形成多通道等离子体喷射;当开关运行在工作模式Ⅱ,且在较高工作系数时,具有更好的多通道放电特性。     

Transverse interferometry of a hydrogen-filled capillary discharge waveguide

Transverse interferometric measurements are presented of the plasma channel formed in a hydrogen-filled capillary discharge waveguide recently used to generate 1 GeV electrons in a laser-driven plasma accelerator for the first time. The measurements were found to be in good agreement with nonlocal thermal equilibrium simulations, but showed significant differences with the results of a quasistatic model developed by Bobrova et al. [Phys. Rev. E. 65, 016407 (2001)]. The measurements are used to determine scaling laws for the axial electron density and matched spot size of the plasma channel, enabling optimization of the channel to specific applications.     

A new concept for a current switch based on a high-temperature superconductor

A new concept for a device for protecting an alternating-current network is offered. It is based on a combination of a superconducting limiter of a short-circuit current and a circuit breaker. A high-temperature superconductor in the form of a pile of plane rings is used as the active element of the limiter. The test results of a model of such a limiter are obtained in the steady-state short-circuit regime. The characteristics of composite silverless materials used for design of the breaker are given.     

Light-driven molecular current switch

A scheme of a light-driven current switch based on properties of a conducting polymer containing photochromic moieties chemically attached to the main chain is put forward. The idea is supported with results of 3D calculations of local states for charge carriers formed in the vicinity of dipolar species in molecular materials, and with quantum chemical calculations.     

用于等离子体焦点装置的强流装置

研制了用于稠密等离子体焦点的强流装置,该装置采用八台低电感低内阻脉冲电容器和八个低感大电流、可控触发高压开关并联组成初级储能模块,高压开关同步击穿后产生μs级强电流经平行板传输线加载到负载。脉冲电容器和高压开关采用一体化设计,结构紧凑,使脉冲电容器与高压开关间的连接电感尽可能小;平板传输线为扇形结构,一个扇形平板传输线连接一个高压开关,平行板传输线可以将电感做得较小,有利于大电流回路的传输。在脉冲电容器充电20 kV时,假负载上可以得到500 kA的电流,电流上升时间约为3.7 μs。     

电晕均压多间隙串联气体开关特性实验

研制了一种电晕放电均压的小型多间隙串联气体开关,分析了电晕放电在开关工作过程中的作用,开展了开关自击穿特性、电晕放电伏安特性、针尖烧蚀以及开关寿命测试等特性实验。结果表明：老练后开关自击穿电压标准偏差小于3.5%,电晕均压效果明显;随着放电次数增加,电晕针尖逐渐钝化,触发性能变化不大;开关电晕放电电流随耐受电压升高增大,增长趋势逐渐变快;开关充400 kPa干燥空气,100 kV工作电压下开关放电50 000次以上,触发性能稳定,触发击穿时延抖动约4.3 ns,自放电概率低于110-4。     

电晕均压多间隙串联气体开关特性实验

研制了一种电晕放电均压的小型多间隙串联气体开关,分析了电晕放电在开关工作过程中的作用,开展了开关自击穿特性、电晕放电伏安特性、针尖烧蚀以及开关寿命测试等特性实验。结果表明:老练后开关自击穿电压标准偏差小于3.5%,电晕均压效果明显;随着放电次数增加,电晕针尖逐渐钝化,触发性能变化不大;开关电晕放电电流随耐受电压升高增大,增长趋势逐渐变快;开关充400 kPa干燥空气,100 kV工作电压下开关放电50 000次以上,触发性能稳定,触发击穿时延抖动约4.3 ns,自放电概率低于110-4。     

Limit current of a multipoint corona discharge

A corona discharge in a system with a multipoint electrode is studied. The conditions for maximizing the limit current manifesting the corona-spark transition are found.     

High-order harmonic generation from ions in a capillary discharge

We demonstrate a significant extension of the high-order harmonic cutoff by using a fully-ionized capillary discharge plasma as the generation medium. The preionized plasma dramatically reduces ionization-induced defocusing and energy loss of the driving laser due to ionization. This allows for significantly higher photon energies, up to 150 eV, to be generated from xenon ions, compared with the 70 eV observed previously. We also demonstrate enhancement of the harmonic flux of nearly 2 orders of magnitude at photon energies around 90 eV when the capillary discharge is used to ionize xenon, compared with harmonic generation in a hollow waveguide. The use of a plasma as a medium for high-order harmonic generation shows great promise for extending efficient harmonic generation to much shorter wavelengths using ions.     

大电流两电极气体开关研究

由于引燃管难以满足现在能源系统对放电开关承受大电流的要求,因此研制了大电荷转移量两电极气体开关。这种新型气体开关电极间距可调,无触发极,采用同轴结构,并将主电极置于金属腔体内,减少了放电对绝缘支撑的污染。主电极为铜钨合金材料,设计为平顶圆柱状,以提高烧蚀均匀度和热传导效率,减少电极材料喷溅,延长其寿命。绝缘支撑采用碗状结构,提高了机械强度,增加了沿面击穿距离。该开关工作电压达25 kV,放电电流超过100 kA（脉冲宽度600 μs）,单次脉冲电荷转移量达50 C。实验结果显示该气体开关触发性能稳定,电极表面烧蚀均匀,多次大电流实验后电极表面保持完好,可应用于强激光能源系统。     

大电流两电极气体开关研究

 由于引燃管难以满足现在能源系统对放电开关承受大电流的要求,因此研制了大电荷转移量两电极气体开关。这种新型气体开关电极间距可调,无触发极,采用同轴结构,并将主电极置于金属腔体内,减少了放电对绝缘支撑的污染。主电极为铜钨合金材料,设计为平顶圆柱状,以提高烧蚀均匀度和热传导效率,减少电极材料喷溅,延长其寿命。绝缘支撑采用碗状结构,提高了机械强度,增加了沿面击穿距离。该开关工作电压达25 kV,放电电流超过100 kA（脉冲宽度600 μs）,单次脉冲电荷转移量达50 C。实验结果显示该气体开关触发性能稳定,电极表面烧蚀均匀,多次大电流实验后电极表面保持完好,可应用于强激光能源系统。