快速光电倍增管的新进展

本文主要评论了三类亚纳秒时间分辨的光电倍增管。微通道板管脉冲响应快、线性电流大,其响应半宽度已达187ps。     

ICI探测器的时间响应特性研究

基于集电型探测器的等效电路模型得到了ICI探测器的输入-输出等效电路,应用实际测量的分布电容和电感计算得到ICI探测器的时间响应.采用快脉冲X射线源实验获得ICI探测器时间响应为(0.677±0.144)ns.实验结果与理论计算结果的一致验证了理论模型的正确性.研究结果表明,ICI探测器具有亚纳秒时间特性,可以用于快脉冲γ射线强度的测量.     

PIN探测器贯穿辐射与非贯穿辐射线性特性

采用脉冲X射线源和脉冲氙灯光源实验研究了PIN探测器对贯穿辐射和非贯穿辐射响应的最大线性电流输出特性,并与理论计算结果进行了比较。PIN探测器输出的最大线性电流随外加反向偏置电压线性变化,对贯穿辐射响应的最大线性电流输出比对非贯穿辐射响应的最大线性电流输出约大20%,理论计算的最大线性电流值比实验值小。在脉冲辐射探测中,采用可见脉冲光源获得的PIN探测器最大线性电流不会超出探测器对贯穿辐射的线性响应。     

用于X射线探测的CVD金刚石薄膜探测器

研制了用于X射线测量的化学气相沉积(CVD)金刚石薄膜探测器.该探测器灵敏区直径为15 mm、厚度300 μm,其暗电流在800 V偏压下小于50 pA,且暗电流-电压曲线线性较好.就CVD金刚石探测器对不同能量X射线的响应及脉冲X射线时间响应进行了理论和实验研究.结果表明:该探测器对6～22 keV X射线具有10-4～10-2A·W-1的灵敏度,假设电荷收集效率为39%时,灵敏度的理论值与实验测量值符合较好,探测器的RC时间常数约为1.5 ns;对亚纳秒脉冲X射线的响应上升时间为2～3 ns.     

GaAs化合物半导体光电导型探测器

本课题研发的GaAs化合物半导体光电导型探测器可用于脉冲辐射束的探测。化合物半导体GaAs、InP光电导探测器加上恒定电压，在脉冲X、γ射线束的照射下，光电导探测器的电阻下降，而在电极输出端输出正比于电阻变化的电流脉冲信号。本实验采用面垒工艺技术制备GaAs光电导探测器。     

GaAs光电导辐射探测器响应实验研究

实验研究了具有极快响应的SI-LECGaAs光电导辐射探测器的响应,测量它对皮秒级脉冲激光的时间响应及对532nm直流激光的灵敏度。实验结果表明：SI-LECGaAs光电导辐射探测器时间响应约为100ps,与探测器偏压无关,但受测试系统的影响较大;用中子辐照改性和改进工艺的方法可提高探测器的时间响应;探测器的直流激光响应与偏压则呈线性关系。     

大电流快响应的特殊结构型GaAs：Cr探测器

本文介绍了一种国产ＧａＡｓ：Ｃｒ材料基片和同轴电缆构成的特殊结构型ＧａＡｓ：Ｃｒ探测器，这种器件具有耐高电压，大电流输出，高灵敏快响应等特点，它更适合于强流脉冲辐射宽量程测量。     

平面工艺Si电流型X射线探测器研制

该项目主要研究X射线能谱及时间谱测量、强流脉冲X射线束测量所需的平面工艺硅电流型探测器。主要工作在于模拟核爆中高功率Z-pinch等离子体辐射研究中测量等离子体产生的X射线能谱及时间谱和用于X光束诊断和高功率Z-pinch等离子体辐射研究。该型探测器用于探测极低能量     

一种半透明多碱阴极快速光电倍增管

1、特点与用途 一种半透明多碱阴极快速光电倍增管——CDB-55型光电倍增管,具有较宽的光谱响应范围和较高的量子效率,适合于可见与近红外光信号的探测,特别是红光和近红外光信号的探测;时间响应快、线性电流大、阴极电阻率低和较低的增益,适合于10~(-9)秒持续时间的光脉冲波形的观测;时间分辨率高,适合于10~(-10)秒范围的事件出现时刻的精确测量,给出被测事件之间时间关联的信息;宽的通频带,适合于高频调制光信号的测量。在激光探测以及其它科学技术领域中有着广泛的应用。     

微秒级宽脉冲信号下能输出大于1.5 A线性电流的光电倍增管

测量了CHφT3型光电倍增管配上ST401塑料闪烁体,在波形半宽度约2400ns脉冲光源照射下的电流输出情况,还提供了该光电倍增管与对中子相对不灵敏的晶体CeF3组成探测器应用于宽脉冲γ辐射源测量得到的电流输出情况。结果表明,CHφT3型光电倍增管其饱和电流输出大于3．5A,最大线性电流大于1．5A,暗流小于10nA,是一种在微秒级宽脉冲信号下都可以输出大于1．5A线性电流的大电流光电倍增管,是在大动态范围脉冲测量中,使用多探测器量程衔接时降低不确定度的一种可选方法。     

Heavy Metal Detection in Soils by Laser Induced Breakdown Spectroscopy Using Hemispherical Spatial Confinement

Spatial confinement has great potential for Laser Induced Breakdown Spectroscopy(LIBS) instruments after it has been proven that it has the ability to enhance the LIBS signal strength and repeatability.In order to achieve in-situ measurement of heavy metals in farmland soils by LIBS,a hemispherical spatial confinement device is designed and used to collect plasma spectra,in which the optical fibers directly collect the breakdown spectroscopy of the soil samples.This device could effectively increase the stability of the spectrum intensity of soil.It also has other advantages,such as ease of installation,and its small and compact size.The relationship between the spectrum intensity and the laser pulse energy is studied for this device.It is found that the breakdown threshold is 160 cm~(-2),and when the laser fluence increases to 250 J/cm~2,the spectrum intensity reaches its maximum.Four different kinds of laser pulse energy were set up and in each case the limits of detection of Cd,Cu,Ni,Pb and Zn were calculated.The results show that when the laser pulse fluence was 2.12 GW/cm~2,we obtained the smallest limits of detection of these heavy metals,which are all under 10 mg/kg.This device can satisfy the needs of heavy metal in-situ detection,and in the next step it will be integrated into a portable LIBS instrument.     

脉冲离子束流聚焦装置的研制

用小型化的质量分析系统进行脉冲离子束流实验研究时,从真空弧离子源中引出的束流脉冲幅度大、能量低,由于空间电荷效应使脉冲束流发散度很大,使得离子束流成分分析的不确定度增大。为克服在有限的空间范围内脉冲离子束流聚焦的困难,研制了一种新的双限束光阑三膜片透镜离子束流聚焦装置。双限束光阑着重减少束流发射度,三膜片透镜则适合小尺度空间的脉冲束流聚焦。计算机模拟的结果符合这种大脉冲离子束流聚焦的设计思想。磁质谱仪应用该聚焦装置后,发散到质量分析器分析盒上的脉冲离子束流幅值从未加聚焦前的115 mA减少至0.06 mA,脉冲离子束流质量分析的不确定度降低。     

Online plasma diagnostics of a laser-produced plasma

In this study,we report a laser interferometry experiment for the online-diagnosing of a laserproduced plasma.The laser pulses generating the plasma are ultra-fast(30 femtoseconds),ultraintense(tens of Terawatt) and are focused on a helium gas jet to generate relativistic electron beams via the laser wakefield acceleration(LWFA) mechanism.A probe laser beam(λ?=?800 nm) which is split-off the main beam is used to cross the plasma at the time of arrival of the main pulse,allowing online plasma density diagnostics.The interferometer setup is based on the No Marski method in which we used a Fresnel bi-prism where the probe beam interferes with itself after crossing the plasma medium.A high-dynamic range CCD camera is used to record the interference patterns.Based upon the Abel inversion technique,we obtained a 3D density distribution of the plasma density.     

查找表方式的粒子辐射脉高分析器

介绍了一个用于空间高能粒子探测的多道脉高分析器电路的设计。该分析器通过模数转换器把输入信号数字化,再利用查找表来完成能段甄别工作。能档计数和数据传输由80C31单片机控制。该电路能精确地对辐射脉冲进行幅度甄别,并给出入射粒子的能档,而且系统可靠性高,易于校准和标定。     

一个用于加速器时间分辨分析系统的纳秒高压脉冲装置

设计了一个纳秒高压脉冲装置，脉冲电压可达16kV，前沿上升时间为10ns，此装置已用于加速器时间分析系统，系统的物理分辨时间小于0．8％，时间半高宽为25ns。     

Research of a fractional-turn ratio saturable pulse transformer and its application in a microsecond-range pulse modulator

As a combination device for a step-up pulse transformer and a magnetic switch,the saturable pulse transformer is widely used in pulsed-power and plasma technology.A fractional-turn ratio saturable pulse transformer is constructed and analyzed in this paper.Preliminary experimental results show that if the primary energy storage capacitors are charged to 300 V,an output voltage of about 19 kV can be obtained across the capacitor connected to the secondary windings of a fractional-tum ratio saturable pulse transformer.Theoretical and experimental results reveal that this kind of pulse transformer is not only able to integrate a step-up transformer and a magnetic switch into one device,but can also lower the saturable inductance of its secondary windings,thus leading to the relatively high step-up ratio of the pulse transformer.Meanwhile,the application of the fractional-turn ratio saturable pulse transformer in a μs range pulse modulator as a voltage step-up device and main switch is also included in this paper.The demonstrated experiments display that an output voltage with an amplitude of about 29 kV,and a 1.6 μs pulse width can be obtained across a 3500 Ω resistive load,based on a pulse modulator,if the primary energy storage capacitors are charged to 300 V.This compact fractional-turn ratio saturable pulse transformer can be applied in many other fields such as surface treatment,corona plasma generation and dielectric barrier discharge.     

大功率脉冲磁场电源系统

描述了中国环流器2号A(HL-2A)装置磁场电源系统,介绍了电源的控制系统和实验结果。磁场电源总脉冲容量近250 MVA,一次放电脉冲释能1 300 MJ,其中单套电源的最高直流电压为3510 V,最大电流为45 kA,均以脉冲方式运行,脉冲时间5 s,重复周期10 min。电源主回路主要由飞轮脉冲发电机、晶闸管变流设备、硅整流器等组成。采用了硅整流器直接并联、电流平衡、恒角移相控制、整流器全关断检测、先进的监控和脉冲高压强流检测等技术措施。实验表明,磁场电源的性能指标能够满足装置实验的要求。     

Stoichiometric cerium compounds as scintillators. I.CeF3

The authors present a study of the scintillation cerium trifluoride, CeF₃. They have investigated spectroscopy of CeF ₃ using optical and ionizing radiation excitations. It was shown that rapid quenching of Ce emission in this material was responsible for the loss of about 50% of the light output and generated the so-called ultra-fast component. This ultra-fast component provided evidence of nonradiative quenching, and therefore limited the efficiency. Additional competition came from unidentified centers, probably due to perturbed Ce ions. Although the light output of CeF₃ was only about 50% of BGO, the potential for large improvement was demonstrated     

The Damage Susceptibility of Integrated Circuits to a Simulated IEMP Transient

Recent investigations have been directed toward gaining insight into the effect of electrical pulse overstressing in integrated circuits, especially simple gates and bipolar LSI arrays. In order to determine the effect of ionizing radiation on the pulse-power failure susceptibility levels of small scale, monolithic, junction-isolated integrated circuits (simple gates), an experimental study was undertaken such that device failures could be induced in a simulated EMP or IEMP environment. The device types investigated included low- and high-power, quadruple, dual-input, positive NAND TTL gates. Permanent damage levels for these devices were determined for both positive and negative-polarity sub-microsecond pulses, introduced into the input, output and bias terminals of active devices, some of which were simultaneously irradiated by gamma radiation. The radiation dose rates ranged from 1 × 1010 to 5 × 1010 rads(Si)/sec. The failure susceptibility level of a device was found to depend uniquely upon the ionizing radiation, the device terminal subjected to the electrical stress pulse, and the polarity of the pulse. The data for device failures in the simulated EMP environment agree with the existing thermal-failure models characterized by P = Atm, where P is the power required to induce failure and t is the time to failure. In a radiation environment it was observed that initial ionization tends to reduce the magnitude of the constant A and shifts the time to failure t from the constant-energy regime (m = -1) to another.     

Ab initio approach to the effect of Fe on the diffusion in hcp Zr II: The energy barriers

Using density functional theory calculations together with the Monomer method for the search of saddle points (combined for the first time with an ab initio algorithm), we obtain the vacancy formation energies and the migration barriers for α-Zr self-diffusion and for the diffusion of interstitial impurities, including the ultra-fast diffuser Fe. Good agreement with measured diffusion coefficients is obtained, as a much lower energy barrier for the ultra-fast diffuser is found. We also suggest a possible mechanism for the increase in self-diffusion due to the Fe impurity, always present in the experimental samples.