混合式电极结构X-pinch的研究

X-pinch作为X射线源进行背光照相,具有较高的空间分辨率和时间分辨率,可用于拍摄快速变化的过程,如丝阵负载的内爆过程。为了得到同一组丝阵负载内爆过程的多幅背光成像图片,需多个X射线源对其进行背光成像,在天光Ⅱ-B(~250kA,50ns)脉冲功率装置的驱动下,通过实验选择了一种混合式电极结构X-pinch。实验结果表明:此种混合式电极结构X-pinch可箍缩产生X射线,所辐射出的X射线光子能量主要在2~4keV之间,因其固有的空间对称性及出光电流较小,可完成多路背光照相。     

Z-箍缩X射线辐射功率闪烁探测系统

研制的Z-箍缩X射线辐射功率探测系统，利用闪烁体与X射线作用产生的荧光，在X射线入射45°方向进行探测。系统具有平坦能量响应、大动态范围和抗干扰能力强的特点。在Z-箍缩“强光1号”装置上，对X射线辐射功率进行测量，获得了W丝阵负载最大X射线辐射产额为36-58kJ，辐射功率为0-84TW。     

An Experimental Study on Kr Gas-puff Z-pinch

Kr gas-puff Z-pinch experiment performed recently on Qiang-uang I pulsed power generator is reprted.The generator has a 1.5MA current with a pulse width of 100ns.The total X-ray energy as well as its spectrum has been obtained.and the average power of X-ray radiation in 50-700eV measured by XRDs is 2 TW.The generator configuration.gas-puff load assembly and diagnostic system for the experiments are described.     

基于X-pinch丝负载的背光照相研究

以天光Ⅱ-B装置（250 kA/50 ns）作为实验平台,在装置负载的阴阳极和回流盘上同时安装X-pinch丝负载,利用天光Ⅱ-B驱动X-pinch丝负载,通过背光照相实验获得箍缩发展不同时刻的序列图像。在序列图像中可观察到箍缩叉点处等离子体的内爆及外爆消散。实验结果有助于进一步理解丝负载箍缩等离子体发展的物理机制。     

Generation of Ultrafast Jets Through the Implosion of a Nested Conical Wire Array

It is shown that in contrast to the electric pulse power driven implosion of a single conical wire array, the implosion of a nested conical wire array with opposite alternate opening angles can lead to the generation of fast jets, with velocities of the order 10⁸ cm/s. This technique can be applied for the supersonic shear flow stabilization of a dense z-pinch, but possibly also for the fast ignition of a pre-compressed dense deuterium–tritium target.     

线缆瞬态辐照响应的数值研究

应用Holland细线模型和时域传输线模型,并结合实验结论,对裸线、带保护层导线以及同轴电缆3种线缆的瞬态响应进行了数值研究。结果表明：对于裸线,负载较小时,负载的变化对负载电压电流、负载功率和负载能量的影响不大,负载较大时,对响应的影响较大;负载增大时,负载电流响应脉宽增加、幅度减小,负载功率存在最大值,但负载吸收能量却一直增大;负载响应与导线半径成正比、与光子能量成反比。对于带保护层导线,变化保护层厚度时,负载响应存在峰值。相同光子能量和芯线半径条件下,带保护层导线比裸线的响应小,同轴电缆比带保护层导线的响应小,减小幅度与光子能量有关。     

百千安电流下的单丝Z箍缩实验研究

为更深层次理解Z箍缩基本物理过程,认识单丝早期演化对丝阵后续内爆过程产生的影响,基于百千安直线脉冲变压器（FLTD）平台开展了不同材料（钨丝、镀膜钨丝和铝丝）单丝Z箍缩实验研究,实验获得了单丝演化过程的双分幅激光阴影和干涉图像。实验发现：初始直径相同（15 μm）的条件下,铝丝核的膨胀速度比钨丝核的快,在电流开始一段时间内,铝丝核沿轴向呈均匀膨胀,而钨丝核因电极效应沿轴向膨胀不均;镀膜钨丝（15 μm W+2 μm Polyimide）核的膨胀速度远大于钨丝核的,甚至高于铝丝核的,同时镀膜还降低了消融等离子体不稳定性的发展速度。     

兆安级电流下Al丝阵的芯晕结构抑制研究

为了抑制丝阵Z箍缩中金属丝在电流早期电爆炸形成的芯晕结构,基于强光一号加速器,利用二级丝阵负载开展了Al丝阵早期物理状态的调控研究。通过陡化预脉冲和调整二级丝阵的参数,实现了负载Al丝的全部汽化,抑制了芯晕结构的产生,气态Al丝芯的平均直径约为1.80 mm,且沿轴向均匀分布,降低了丝阵消融引起的初始不稳定性。若丝长度和直径保持不变,反转型丝阵的关断时间主要取决于Al丝的丝数;反转型丝阵关断后,气态丝芯在主电流脉冲作用下迅速电离并开始内爆,磁瑞丽泰勒不稳定性迅速发展,内爆等离子体流沿轴向呈周期性调制分布,调制波长约为650 μm。Al丝阵初始状态的改变,有效抑制了丝的消融过程,消除了先驱等离子体,在内爆后期降低了拖尾质量,提高了箍缩品质。     

Neutron generator for the array borehole logging

The performance mechanism of the array neutron generator to be used to porosity logging is presented.The neutron generator utilizes a drive-in target ceramic neutron tube,which cursts nerutron with fast-slow period selectively pressure.Regulation of the neutron tube is accomplished by pulse width modulation.The high voltage power supply is poerated at optimum frequency.     

工业脉冲X射线发生装置放射防护检测与评价方法研究

目的探讨利用热释光剂量计对工业脉冲X射线发生装置进行放射防护检测与评价的可行性。方法分别用热释光剂量计和AT1123型X/γ辐射剂量率仪测量脉冲X射线发生装置的辐射剂量,通过对测量结果的分析和比较验证热释光剂量计测量脉冲X射线的有效性,通过对周围环境中年累积剂量的估算来评价试验人员和公众的受照剂量是否满足辐射防护要求。结果1号脉冲X射线发生装置曝光4次,2号脉冲X射线发生装置曝光10次,热释光法测得不同距离处的累积剂量符合距离平方反比衰减规律,实际检测结果与理论推算值较为吻合。两个X射线发生装置现有的工作负荷下,工作人员和公众的年累积剂量均在辐射防护控制目标值内。结论热释光法得出检测结果与理论推算值较为吻合,能够满足工业脉冲X射线发生装置放射防护检测需求。     

A novel multicell silicon drift detector module for X-rayspectroscopy and imaging applications

A novel 61-cell silicon drift detector module is proposed for high-counting rates and high-resolution X-ray spectroscopy and imaging applications at energies up to about 30 keV. Its hexagonal geometry with sloped sidewalls allows a buckyball arrangement. Up to 1860 cells of an active area of 5 mm² each can he reached at an average distance to the specimen of only 4.3 cm. An optimized electrical connection concept offers a vertical integration of a sensor array and signal processing electronics. Worst-case crosstalk of 0.3% (-50 dB) and signal loss of 7% (-24 dB) were derived from electrical field analysis. A sandwich of metal foils between the X-ray sensor and electronics reduces the dose of radiation at the electronics by more than eight orders of magnitude. Module-induced background fluorescence reaches its maximum at an incident energy of 13 keV, but remains below 10^-4 of the incoming photon flux at all energies. Three-dimensional (3-D) simulations on thermal module behavior show that the use of graphite as housing material allows an operation with spatial inhomogeneities of <1°C on the sensor's active area. Empirically, we found that the difference between the temperatures of the sensor and the heat sink depends linearly on the power dissipated by the electronics and sensor chip. The corresponding thermal resistances are 4.3 and 0.8 K/W     

Comparison of pulse-modulated and continuous operation modes of a radio-frequency inductive ion source

The paper describes an experimental study of the characteristics of a pulse-modulated radiofrequency(RF) discharge sustained at low pressures, typical of the operating modes of RF gridded ion sources. The motivation for the study is the question of whether the RF pulsemodulated mode can increase the efficiency of the ion source. The ion current values extracted from an RF inductive ion source operating in continuous and pulse-modulated modes were compared. The experimental data were also compare...     

Preparation of ultrafine tungsten wire via electrochemical method in an ionic liquid

Ultrafine tungsten wire less than 10 μm in diameter is often used as wire array load applied in Inertial Confinement Fusion (ICF) physical experiments. In order to obtain a higher yield of X-ray, both initial radius and line quality of metal wire were required to be of high quality simultaneously. This paper has studied the electrochemical method to corrode tungsten wires uniformly in an ionic liquid electrolyte containing 1 wt% sodium hydroxide. A three electrode system composed of a tungsten anode electrode, a stainless steel cathode and a saturated calomel electrode as a reference electrode, was used in the electrochemical experiments. Liner sweep voltammetry (LSV) and Tafel experiments were used to investigate the electrochemical behaviors of tungsten wires in ionic liquid and aqueous solution. Based on scanning electron microscope (SEM) observation, the morphologies of tungsten wire surface with uniform corrosion under different applied voltages have been demonstrated. X-ray diffraction (XRD) methods were employed to track the evolution of the crystal structure before and after corrosions, and there is an obvious difference in peak intensities. The ultrafine tungsten wire with a uniform diameter of 8.5 μm was obtained under the optimized electric potential (2.5 V) applied for decreasing diameter at 30 °C.     

Discharge and post-explosion behaviors of electrical explosion of conductors from a single wire to planar wire array

This work deals with an experimental study of a Cu planar wire array (PWA) in air and water under the stored energy 300–1200 J. A single Cu wire is adopted as a controlled trial. Four configurations of PWA and a wire with the same mass (cross-section area) but the different specific surface areas (15–223 cm² g⁻¹) are exploded. The transient process is analyzed using high-speed photography in combination with the results of optical emission and discharge. Discharge characteristics revealed that PWA always has a higher electric power peak, early but higher voltage peak, as well as faster vaporization and ionization process than the single-wire case. Two to three times stronger optical emission could be obtained when replacing the single-wire with PWA, indicating a higher energy-density state is reached. Phenomenologically, in both air and water, single-wire load tends to develop a transverse stratified structure, while PWA is dominated by the uneven energy deposition among wires. Finally, the synchronism and uniformity of the PWA explosion are discussed.     

Thermal-hydraulic analysis for wire-wrapped PWR cores

This work focuses on the steady-state and transient thermal-hydraulic analyses for PWR cores using wire wraps in a hexagonal array with either U (45% w/o)-ZrH_1.6 (referred to as U-ZrH_1.6) or UO₂ fuels. Equivalences (thermal-hydraulic and neutronic) were created between grid spacer and wire wrap designs, and were used to apply results calculated for grid spacers to wire wrap designs. Design limits were placed on the pressure drop, critical heat flux (CHF), fuel and cladding temperature and vibrations. The vibrations limits were imposed for flow-induced vibrations (FIV) and thermal-hydraulic vibrations (THV). The transient analysis examined an overpower accident, loss of coolant accident (LOCA) and loss of flow accident (LOFA).The thermal-hydraulic performance of U-ZrH_1.6 and UO₂ were found very similar. Relative to grid spacer designs, wire wrap designs were found to have smaller fretting wear, substantially lower pressure drop and higher CHF. As a result, wire wrap cores were found to offer substantially higher maximum powers than grid spacer cores, allowing for a 25% power increase relative to the grid spacer uprate [Shuffler, C.A., Malen, J.A., Trant, J.M., Todreas, N.E., 2009a. Thermal-hydraulic analysis for grid supported and inverted fueled PWR cores. Nuclear Technology (this special issue devoted to hydride fuel in LWRs)] and a 58% power increase relative to the reference core.     

Compact 500-kV RF Accelerating-Voltage Generator

A cascade accelerating-voltage generator with inductive coupling and parallel power supply to the cascades is examined. The basic parameters and dimensions of a generator for a voltage of 500 kW and power 10 kW are presented.     

阵列式低功耗Si-PIN个人剂量仪设计

采用瑞士TEVISO的阵列式Si-PIN探测器探测X、γ射线;以低功耗PIC单片机为核心,设计了低功耗电源转换电路、一键开关机电路、按键与LCD显示、蜂鸣器等,并采用多种单片机软件设计方法降低功耗。该个人剂量仪具有脉冲计数、剂量当量率实时显示及存储,可查看测量时间与历史数据,报警阈值设置与报警等功能。     

Development of a new X-ray source using backscattered X-ray with the use of a cold cathode

The development of an intense X-ray source using backscattered X-ray produced using an advanced electrode configuration is described. The electrodes were composed of field emitters deposited on a wire mounted on a perforated plate as the cathode and a copper plate as the anode. Electrons from these emitters collided with the copper plate and X-ray was generated at collision points. The backscattered X-ray in the direction normal to the electron trajectory through a hole in the anode escaped from the vacuum chamber through a beryllium window. Continuous and characteristic X-rays were detected at an applied voltage lower than that of a conventional X-ray source from 3.0 to 9.4 kV, respectively. Moreover, the X-ray dosage measured with a survey meter reached 0.95 mSv/h at 5.0 kV of applied voltage. The transmission images of three types of material used as an X-ray source for the X-ray imaging system indicate three advantages; low power consumption, focal point controllable by adjusting applied voltage, and photographable motion picture of X-ray transmission.     

Acoustic detection of boiling in LMFBRs: An estimate of sensitivity derived from experiments during the commissioning of PFR

This paper describes a programme of experiments undertaken during the commissioning of the 600-MW PFR at Dounreay. The objective of the programme was to obtain data on reactor background acoustic noise levels and to estimate the sensitivity of the installed acoustic boiling detection system.

The boiling-noise detection system installed in PFR consists of seven waveguides. The waveguides are solid metal rods which extend from the reactor top to just above the core top level. Five are arranged on a 0.75m radius circle with two at the edge of the core. The sensing elements are standard accelerometers.

For the commissioning experiment three rigs were installed in the core locations below three of the waveguides. Each rig was over 12m long and carried three sodium-proof microphones at levels corresponding to core top, mid-core and core bottom. Each rig also carried an electrically-powered vapour generator which could inject a stream of sodium vapour into the surrounding 250°C sodium, so producing a boiling type noise. In addition to these nine microphones in the core, microphones were also installed at the inlet and outlet of each of the three pumps. To handle the data for this experiment a system of amplifiers and three fourteen-track tape recorders was used. To check amplifier gains a calibration signal was automatically injected at the end of each record. On line one-third octave and narrow-band analysis was also available, but the bulk of the analysis was done from the tape records.

The commissioning programme was in two parts: a measurement of background noise and an investigation of the detection sensitivity at the waveguides of the noise from the vapour generator (this implicitly included the transmission loss). In the background measurement programme the noise level at each microphone was recorded at pump speeds from 200 to 960 rev/min, full speed, in approximately 10% steps. To determine the sensitivity, the signal at each transducer was recorded with each vapour generator operating in turn. The power input to the vapour generators was 1100W, of which some 800W required to balance the heat losses. The power available for boiling consequently was only 300W; nevertheless the signal was detectable at pump speeds up to 750 rev/min on waveguides radially 0.75m from the source.

Since the noise output of the vapour generator was measured by a microphone close to the source, this result could be used, with data obtained on background noise and measurements of sodium boiling noise obtained on force convection rig experiments, to deduce that a highly sub-cooled boiling source involving 40kW of thermal energy would be detectable in PFR with a margin of 10dB. The conclusion rests on the assumption that there is no major adverse change in the transmission losses at the time detection is required, such as might be caused by a large quantity of free gas in the sodium.