Experimental Study of the Recovery Times of Spark Gap Switch with Different Gases

A two-pulse method is used to determine the insulation recovery time of the gas spark gap switch with different types of gas applied in a high power accelerator with a water dielectric pulse forming line. At the breakdown voltage of 450 kV, with the vacuum diode voltage of about 200 kV, and a current of 30 kA, recovery characteristics of H2, N2, SF6 were studied. The recovery percentages of the gas breakdown voltage and vacuum diode voltage were determined. The results show that hydrogen has the best recovery characteristics. At a pulse interval of 8.8 ms, the recovery percentages of both the gas breakdown voltage and vacuum diode voltage for hydrogen exceed 95%. For SF6 and N2 with an interval of 25 ms and 50 ms respectively, a 90% voltage recovery was obtained. The experiments also proved that the repetitive rate of the high power accelerator with a pulse forming line is mainly restricted by the gas switch repetitive rate; the recovery percentages of the vacuum diode voltage are limited by the recovery percentages of the gas switch breakdown voltage. The hydrogen switch can be employed for a high repetitive rate-high power accelerator with a pulse forming line.     

Study on a Planar Multi-Gap Multi-Channel Gas Switch

To reduce the inductance and prolong the life of the switch in linear transformer driver, diving the current into multiple discharge channels is effective. Thus, a planar multi-gap multi-channel gas switch with trigger plate was developed in this paper. The switch has five channels in parallel and is triggered by the coupling capacitance between the electrodes and the trigger plate. The results from experiments show that the switch can be triggered reliably and the framing camera images provide the evidence of multiple discharge channels. We calculated the circuit’s and switch’s inductance and observed the erosion spots of the electrodes, which indicates that multiple discharge channels indeed help to reduce the inductance and prolong the life of the switch. The factors that influence the number of discharge channels were also studied, mainly including the working voltage and crosswise resistor. These work and results can give some guiding principles and advices to design a multi-channel switch in the future.     

Electrode Erosion of a High Energy Impulse Spark Gap Switch

Based on the principle of thermal conduction, three metal alloys (stainless steel,copper-tungsten and graphite) were chosen as the material of the high impulse current discharging switch. Experimental results indicate that the mass loss and surface erosion morphology of the electrode are related with the electrode material (conductivity σ, melting point Tm, density ρ and thermal capacity c) and the impulse transferred charge (or energy) per impulse for the same total impulse transferred charge. The experimental results indicate that the mass loss of stainless steel,copper-tungsten and graphite are 380.10 μg/C, 118.10 μg/C and 81.90 μg/C respectively under the condition of a total impulse transferred charge of 525 C and a transferred charge per impulse of 10.5 C. Under the same impulse transferred charge, the mass loss of copper-tungsten(118.10 μg/C)with the transferred charge per impulse at 10.5 C is far larger than the mass loss (38.61μg/C)at a 1.48 C transferred charge per impulse. The electrode erosion mechanism under high energy impulse arcs is analyzed briefly and it is suggested that by selecting high conductive metal or metal alloy as the electrode material of a high energy impulse spark gap switch and setting high erosion resistance material at the top of the electrode, the mass loss of the electrode can be reduced and the life of the switch prolonged.     

Simultaneity of Spark Gap Switch Firing in the Dense Plasma Focus Device

To gain insight into the synchronization, simultaneity, and switching behavior of the individual switch, two TIA-525 Optical/Electrical converters have been recently introduced to DPF experiments at Lawrenceville Plasma Physics (LPP). These electronic devices, attached to two spark gap switches through optical fibers, detect light sampled from the switch firing and convert it to amplified voltage signals. We observed that in terms of simultaneity and synchronization, the firing behavior and quality of the pair of switches monitored are not the same. Some switches, among the twelve that are being used, fired at the trigger voltage within few tens of ns while the others fired much later (after ~1–2 μs) and are triggered at or after the pinch voltage rise. The results from the present work show evidence of pinch voltage triggering the switches. Since the pinch voltage is over three times the voltage of the capacitors, this voltage triggers those capacitors that do not fire during the regular high voltage trigger pulse. This, we suggest, could affect the efficiency of the device as it simply drains the reserved energy in the system. We present results of an empirical study of spark gap switch firing as well as the total current that is followed using the Rogowski coil.     

气体开关触发间隙与过压间隙击穿特性研究

为研究快脉冲直线变压器驱动源（FLTD）多间隙气体开关的触发击穿特性,针对一种环形电极两间隙等效实验开关,开展不同触发电压、工作系数和电极材料下的击穿特性实验,对比两个间隙的击穿延时和抖动,分析间隙击穿特性的主要影响因素和作用机制。实验结果表明：触发间隙击穿延时主要受触发电压影响,而工作系数是过压间隙击穿延时的主要影响因素;开关抖动主要来自于触发间隙,触发间隙抖动随触发电压的增大明显减小,过压间隙抖动基本不随触发电压和工作系数变化且维持在较低值;石墨电极开关的击穿延时和抖动明显小于不锈钢、黄铜和钨铜电极开关,具有良好的触发击穿性能。通过分析指出,是否有预电离可能是两个间隙击穿特性差异的主要原因。     

Experimental Study on Triggering Characteristics of a Surface Flashover Triggered Vacuum Switch

Triggering characteristics of triggered vacuum switch （TVS）, including the discharge delay time, delay jitter, range of operational voltage and peak of pulsed current, are investigated. Both structure and experimental circuit of TVS are presented. The results indicate that TVS, as a surface flashover triggering device with high dielectric permittivity material, is with excellent triggering characteristics. When the hold-off voltage reaches 120 kV, the minimum operational voltage is 1.3 kV, and the minimum discharge delay time and jitter are 100 ns and ?10 ns, respectively. The peak current is up to 240 kA when the operational voltage reaches 100 kV. TVS can well satisfy the main demands of high voltage and current applications, and can also be used under a multi-crowbar circuit.     

Experimental Study for Gas Entrainment in Fast Reactor

正Some facilities were designed across the free surface and the argon space.If the phenomenon of gas entrainment was neglect,more severe flow will be on the free surface,such as the violence wave,surface circulation,vortex,gaseous core     

离心法生产氙同位素

采用离心法进行了氙同位素离心分离。利用4台级联，经过三次分离，将129Xe同位素的丰度浓缩到65％以上；应用多个分离装置，通过多次分离，得到了丰度达99％的124Xe。     

气体扩散法分离二氧化碳实验研究

随着碳13呼气检测实验的推广和普及,碳13同位素产品的市场需求呈上升趋势.为探索碳13同位素的工业化分离方法,开展以二氧化碳为介质分离碳同位素的气体扩散分离实验研究.根据二氧化碳的平均自由程,使用平均孔径55～65 nm的有机高分子多孔膜作为分离膜,并开发了单级分离装置.通过单级扩散分离实验,探究分离膜层数和膜前压强对...     

离心法分离锇同位素的试验研究

对天然锇同位素进行了离心分离。选择()sO4作为工作介质，以单机分离实验结果证实了γij=γ0^△Aij关系式，拟合出实际的γ0。在此基础上通过四台级联分离实验得到了^192Os丰度大于99％的OsO4。     

钨同位素离心分离的实验研究

本工作对离心法分离钨的同位素进行了研究.从工作气体的选择,离心机参数的调整,到具体分离过程的设计和试验,解决了一系列技术问题,得到了186W丰度大于98%的WF6.此外,通过单机分离试验还得到了离心机分离钨同位素的单位质量数的全分离系数,有助于今后进行其它稳定同位素的分离工作.     

强X光辐射场加门光电倍增管实验研究

我们在神光装置打靶现场对加门光电倍增管进行了调试和研究。实验结果表明，光电倍增管的恢复时间是随基饱和深度的增加而增加的。ＸＰ２０４０光电倍增管配上２μｓ的高压脉冲开关可用于偿烁探测器在神光装置辐射驱动聚变靶时进行强Ｘ射线辐射场的低产额中子测量。     

火花氢离子源的等离子体特性研究

提出了氢离子源等离子体的一维动态CRAM（collisional radiative atomic and molecular）模型，计算了非平衡态（NTE）下等离子体中分子、电子、离子、基态原子、激发态原子共9种粒子浓度以及电场强度、气体温度和电子温度在一个脉冲内随时间和轴向空间的分布。计算表明：氢离子源中粒子分布在轴向极不均匀，阳极附近有很高的粒子浓度；氢原子离子占总离子数的93．9％，与文献值相符；巴耳末系谱线强度与文献值符合较好。     

气空间对自然循环两相流动系统稳定性影响实验研究

微沸腾工况运行是核供热堆实现热电联供的关键性问题之一，微沸腾运行工况下，两相流系统稳定性更加不利和复杂。通过实验研究，揭示了气空间对两相流系统稳定性的影响，研究提出通过气空间改性来抑制系统不稳定。实验结果表明，在气空间加装隔离孔板，对两相流系统不稳定振幅有明显的抑制作用，对两相流系统不稳定边界也有改善。      

脉冲液-气射流泵基本性能试验

在相同的液-气射流泵实验装置上,采用脉冲和恒定工作液体射流,对液气射流泵的基本性能进行了试验研究。结果表明,对于恒定液-气射流泵存在一种最优工作压力,而脉冲液-气射流泵在同一脉冲频率、不同工作压力下的性能曲线基本重合;采用脉冲工作射流可以产生水锤效应,正是这种水锤效应,使得脉冲液-气射流泵在低于试验系统提供的极限压力0.1～0.15 MPa的工作压力范围内,液-气射流泵的工作效率可以提高4%～15%。     

Experimental Study on Gas Carry-Under in Down Flow from Two-Phase Mixture

In this paper, simultaneous optimization is carried out for successive two cycles of pressurized water reactors. At first, a simplified problem of the simultaneous optimization was studied by assuming the batch-wise power sharing as independent variable, i.e., batch-wise power sharing was optimized without considering corresponding loading patterns. The optimization of the batch-wise power sharing was carried out for the conventional single cycle, the equilibrium cycle and the two successive (tandem) cycles. The analysis indicated that the tandem cycle optimization well reproduce that of the equilibrium cycle optimization, which is considered as a typical case of the true multicycle optimization. Next, simultaneous optimization of loading patterns for tandem cycles is carried out using the simulated annealing method. Since the design space of the tandem cycles optimization is much larger than that of the conventional single cycle optimization, the optimization condition (i.e., number of calculated patterns) are established through sensitivity study. The optimization results are compared with those obtained by the successive single cycle optimizations and it is clarified that the successive single cycle optimization well reproduces the optimization results obtained by the simultaneous optimization if objective functions are appropriately chosen. The above result will be encouraging for the current in-core optimization method since single cycle optimization is utilized due to limitation of computation time.     

Numerical Simulation of Voltage Applied to the Gaps of a Planar Multi-Gap Multi-Channel Gas Switch

In the linear transformer driver (LTD) technology, the low inductance energy storage components and switches are directly incorporated into the individual cavities (named stages) to generate a fast output voltage pulse, which is added along a vacuum coaxial line like in an inductive voltage adder. To provide the theoretical foundation for structure design and ensure the reliable operation of the planar multi-gap multi-channel gas switches, numerical simulation of voltage applied to the gaps is carried out, taken into account a variety of factors such as working coefficient, triggering voltage, resistance of crosswise resistors, and coupling capacitance. Based on the theoretical analysis of development and maintenance of parallel discharge channels, simulation of voltage applied to the gaps was performed in PSpice program. The results of simulation show that high working coefficient, high triggering voltage, high resistance of crosswise resistors and high coupling capacitance are all beneficial to the increase of the voltage applied to the gaps.     

Estimation of Surface Roughness due to Electrode Erosion in Field-Distortion Gas Switch

Field distortion gas switch is one of the crucial elements in a Marx generator, fast linear transformer driver and other pulsed power installations. The performance of the gas switch, which is dramatically affected by the surface roughness due to electrode erosion during the discharge process, directly influences the output parameters, stability and reliability of the pulsed power system. In this paper, an electrode surface roughness (ESR) calculation model has been established based on a great deal of experimental data under operating current. The discharge current waveform, the peak height of the burr, the radius and the depth of etch pits in the electrode erosion region were used to predict the ESR. Also, experimental results indicate that this calculation model can effectively estimate the ESR of the test gas switch.