Effect of Ionizing Radiation on Gunn Diode Amplifiers

X-band Gunn diode amplifiers have been tested while exposed to pulsed ionizing radiation. Peak photo currents induced vary as the .65 power of the dose rate, as had been found for oscillator diodes. The principal effect is a transient loss of gain, with the recovery time less than 400 ns for dose rates up to 5×1010 rad (Si)/s. The dependence of gain on dose rate agrees very well with a calculation based on the change in electric field distribution caused by radiation-induced excess carriers. A permanent failure mode was also observed at the maximum operating voltage and dose rate.     

Study of X-ray Emission from a Compact Diode Operated by a High-Inductance Capacitor Discharge

A compact diode comprising a flat plate anode and a sharp-edged cathode (a piece of razor blade) energized by 0.5 F capacitor charged to 30 kV is investigated for optimization of X-rays emission vis-à-vis separation between electrodes and width of the cathode, which is responsible for electron emission by impact of electric field. It is a high-inductance system, the parasitic inductance is found to be 353 ± 5 nH, and the recorded peak discharge current is just 35 ± 02 kA. The maximum X-ray emission is observed for a 2-mm-wide cathode with an interelectrode separation of 3 mm. The X-ray yield in 4-geometry is found to be 34 ± 3 mJ with a wall-plug efficiency of 0.015 ± 0.001%. The X-ray emission occurs about 200 ns after the application of high voltage, synchronized with the dip in current wave form. The low efficiency of the system for X-ray generation is attributed to high parasitic inductance.     

中子辐照对隧道二极管性能的影响

本文介绍了中子辐照环境中,隧道二极管性能的退化,即谷电流增加,峰谷比下降、摆幅电压减少。用二次隧道效应理论解释了这种退化过程。     

碳化硅结势垒肖特基二极管的质子辐射效应

碳化硅结势垒肖特基二极管(SiC JBS)是新一代航天器电推进系统的关键部件,但高能粒子辐射严重威胁其可靠性与稳定性。为揭示其辐射损伤机理,为其抗辐射加固设计与考核评估储备数据,本研究基于加速器开展了先进商用SiC JBS 10~20 MeV中能质子地面辐照实验,并提取器件辐照前后的正向伏安特性、反向伏安特性、电容电压等电学参数及缺陷特性。系统分析器件关键特性随辐照条件的改变规律。结果显示,质子辐照引起了器件肖特基势垒升高、载流子浓度降低,且10 MeV较低能质子导致的位移损伤退化更严重。分析认为,PN结界面缺陷导致高性能商用SiC JBS反向电学性能对中能质子的辐照更加敏感,正向特性相对稳定,辐照生碳缺陷造成载流子去除效应是引起SiC JBS性能退化的主要机制。     

变容二极管中子辐照损伤

在中子辐照环境下,变容二极管C—V特性发生变化,在给定偏置下,结电容随中子注量的增加而下降。它是因外延层中引入深俘获能级所致,在高中子注量下,漏电流和正向压降均变大,优值Q也发生变化。     

Effect of Gamma Radiation on Silica Gel, (II)

Radiolysis of N₂O adsorbed on silica gel degassed at 200, 450 and 600°C has been studied to investigate the behavior of electrons on the gel surface. The G-value of nitrogen as the major radiolytic product increases with an increase of N₂O concentration adsorbed approaching a plateau value which depends on degassing temperature of the gel prior to irradiation. By the competitive electron scavenging of N₂O with several electron scavengers, such as CCl₄, SF₆ and nitrobenzene, initial yield of electrons G (e ^?), and relative rate constant for reaction of electrons with scavenger to that with N₂O, k _s /k _N2O, have been obtained. The G (e ^?) is 3.8 and 2.0 for the gel degassed at 200 and 600°C respectively. In the former gel, the value of k _s /k _N2O is comparable with that in aqueous system, while in the latter, with that in non-polar hydrocarbon such as neopentane. The observed difference may be attributed to the presence of silanol groups and residual water which facilitate some form of hydration of electrons on the gel degassed at low temperature. Despite of the complexity of the heterogeneous system, Hammett's relationship is observed among the reactions of electrons with monosubstituted derivatives of benzene, providing the reaction constant ρ as 2.8.     

Buried Channel Charge Transfer Device (CTD) Transient Radiation Hardening Using N-P-N Structures

Buried channel CTD's must be designed to isolate their depleted channels from charge generated in the substrate by penetrating radiation to obtain optimum transient radiation hardness or radiation detector time response. This can be achieved by employing an NPN structure so that the electrons generated in the N substrate are confined by the reverse biased P-N junction from diffusing across the P layer to the N channel. Unfortunately, moderate doped P layers often do not have the necessary conductivity required experimentally to pin the junction bias during intense transient radiation. However, the use of P+ layers is shown to accomplish this purpose. Although buried channel CTD's are used as experimental examples, the principles are applicable to a wide range of MOS charge storage devices. One potential application is in the reduction of alpha particle induced soft errors associated with conventional packaging. This soft error problem is a significant issue in future small cell VLSI development.     

Influence of the Electron Emission on the Properties of the Cathode Sheath

There are many cathode electron emission mechanisms which have been discussed [1]. But in arc discharge ) the thermionic and the field emission playan important role. The electron emission has influence on the properties of cathode fall region, whichcan be divided into two subzonesf space charge zoneand ionization zone [21. In this paper, the spacecharge zone is called cathode sheath (CS). The cathode sheath, being nearest to the cathode surface, isaffected by the electron emission first. Th…     

Experiment Method of Effect for Radiation Caused by High Energy Electron Device

正In recent years,with the rapid development of space industry,the stability of the space equipment caught the attention of people.The semiconductor industry continues to scale CMOS technologies to smaller feature sizes with reduced operating voltages in pursuit of performance and density goals.Continuing decreases in device dimension     

电荷耦合器件质子辐照效应研究

利用2×6 MV串列静电加速器提供的1~10 MeV质子,开展了线阵电荷耦合器件辐射损伤效应的模拟试验和测量,研制了加速器质子扩束扫描装置及电荷耦合器件辐射敏感参数测量系统,建立了电荷耦合器件质子辐射效应的模拟试验方法,分析了质子注量、质子能量、器件偏置等对器件电荷转移效率和暗电流的影响。模拟试验结果表明,电荷转移效率随辐照质子注量的增加而下降,暗电流随辐照质子注量的增加而增大,在1~10 MeV质子能量范围内,质子能量越低,电荷转移效率的降低与暗电流的增加越显著。     

Simulation of Filament Heater for Uniform Emission from Dispenser Cathode

This paper presents the design study of toroid shape filament heater for dispenser cathode.The filament heater will be used in cathode assembly of 200 kW 42 GHz gyrotron. A 3 D model of cathode assembly is designed using electromagnetic and thermal simulation software, ANSYS. The simulations are performed for optimizing the input filament heater power with respect to cathode surface temperature. The parametric study shows that the input power and cathode surface temperature depends strongly on the potting material, diameter of filament, number of turns, position and height of the filament heater with respect to cathode pellet. The design analyses are also carried out for two different filament heater materials i.e. tungsten and molybdenum. Further, the thermal, structural and transient analyses are also carried out to study the mechanical strength of the filament heater. It is concluded that the input heater power should be greater than 200 W to achieve cathode surface temperature greater than 1,000°C.     

大束流场发射阴极X射线管的阳极设计

采用蒙特卡罗软件和有限元分析软件分析了固定阳极X射线管中电子轰击阳极靶的能量沉积和热量传输过程,固定阳极由铜棒和钨片组成。研究了在不同形状、尺寸和占空比的电子束脉冲轰击下,阳极靶面不同厚度的钨片和相邻铜棒的温度上升过程。结果表明,钨片厚度存在最优值,但最优值与具体使用条件相关;在脉冲成像方式下,固定阳极靶能承受更强束流强度的轰击。因此,采用固定阳极靶方案,研制140 kV高压、10 mA以上电流、直径1 mm以下有效焦点的场发射阴极X射线管是可行的。     

(20-300)kV X射线参考辐射装置的建立

为了推进X射线空气比释动能基准量值传递工作的开展,建立了(20-300)kV X射线参考辐射装置。距离X光管焦点1 m的均匀野处,建立了CCRI会议推荐的两组低能X射线参考辐射质50kV(a)和50 kV(b),采用拟合方法测量得到的半值层、同质系数与推荐值相差2%以内。通过蒙卡模拟软件EGSnrc研究两组参考辐射质的能谱分布情况,并计算了其平均能量,分别为33.3和28.1 keV。     

Compact ignition test reactor (CITR)

Design considerations have been developed for a compact ignition test reactor (CITR). The objectives of this tokamak device are to achieve ignition, to study the characteristics of plasmas that are self-heated by alpha particles, and to investigate burn control. To achieve a compact design, the toroidal field magnet consists of copper-stainless steel plates to accommodate relatively high stresses; it is inertially cooled by liquid nitrogen. No neutron shielding is provided between the plasma and the toroidal field magnet. The flat-top of the toroidal field magnet is 10 s. Strong auxiliary heating is employed. In one design option, adiabatic compression in major radius is employed to reduce the neutral beam energy required for adequate penetration; thiscompression boosted design option has a horizontally elongated vacuum chamber; illustrative parameters are a compressed plasma witha=0.50 m, R=1.35 m,B _T =9.1 T, and a neutral beam power of 15 MW of 160 keVD ⁰ beams. A design option has also been developed for alarge bore device, which utilizes a circular vacuum chamber. Thelarge bore design provides increased margin and flexibility; both direct heating with RF or neutral beam injection and compression boosted startup are possible. The large bore design also facilitates the investigation of high-Q driven operation. Illustrative plasma parameters for full use of the large bore area=0.85 m,R=1.90 m, andB _T =7.5 T.     

热电子发射同轴二极管几何结构对空间电荷限制流的影响

本文基于同轴二极管一维空间电荷限制流经典理论公式,利用CST粒子工作室研究了热电子向外发射同轴二极管二维空间电荷限制流随二极管几何结构参数变化的规律和几何结构对虚阴极产生临界条件的影响。结果表明,二极管修正系数是纵横比的单调递减函数;随阳极半径与阴极半径比值的增大,修正系数逐渐降低;二极管的电压、阳极和阴极半径及阴极长度均会影响虚阴极的产生。本文研究结果将为射频四极管结构设计及优化提供参考和理论依据。     

Oxide Coated Cathode Plasma Source of Linear Magnetized Plasma Device

Plasma source is the most important part of the laboratory plasma platform for fundamental plasma experimental research. Barium oxide coated cathode plasma source is well recognized as an effective technique due to its high electron emission current. An indirectly heated oxide coated cathode plasma source has been constructed on a linear magnetized plasma device. The electron emission current density can reach 2 A/cm 2 to 6 A/cm ² in pulsed mode within pulse length 5–20 ms. A 10 cm diameter, 2 m long plasma column with density 10 ¹⁸ m ⁻³ to 10 ¹⁹ m ³ and electron temperature T_e ≈ 3–7 eV is produced. The spatial uniformity of the emission ability is less than 4% and the discharge reproducibility is better than 97%. With a wide range of the plasma parameters, this kind of plasma source provides great flexibility for many basic plasma investigations. The detail of construction and initial characterization of oxide coated cathode are described in this paper.     

聚乙烯醇膜材料氚衰变辐照效应研究

利用FTIR、XRD、AFM等方法,分析了聚乙烯醇（PVA）膜材料在不同氚气氛下的氚衰变辐照效应,表征了氚衰变β射线对PVA中氢与氚同位素置换的诱导激化作用,明确了PVA中的氚取代主要发生在C-H基团,而醇羟基O-H基团因强烈的氢键作用而未发生氚取代;材料的表面形貌、结晶度等均发生了变化。通过PVA膜拉伸力学性能实验,测定了不同氚衰变辐照下PVA膜材料的拉伸强度和伸长率。结果显示,与其微观结构变化趋势一致。     

Radiation Response of Several Memory Device Types

Radiation testing was performed on a number of specific memory devices representative of the major LSI process technologies to address the problem of selection of suitable memories for hardened mircroprocessor based systems. Responses to dose-rate and total-dose irradiation were obtained using the Boeing Linac and Gammacell cobalt facilities. The devices chosen for testing were the Intel 2147 4K and 2125H 1K HMOS RAMs, the American Micro Systems 4017 4K VMOS RAM, the Fairchild 93471 4K TTL/ECL RAM, the Harris 6508 1K hard oxide CMOS RAM, the Harris 6611 256×4 CMOS PROM, the Intersil 6604 512×8 CMOS EPROM, and the Fairchild 93481 4K TTL/I2L dynamic RAM. Test methods are described and results are summarized for each.     

241Am-Be中子源紧凑型屏蔽装置及辐照器设计

²⁴¹Am-Be中子源被广泛用于实验研究,为保护实验人员免受中子及γ射线照射,需要设计适当的屏蔽。利用蒙特卡罗方法计算中子透射不同材料后的能谱分布与剂量,优选各层屏蔽材料种类与厚度,设计一套²⁴¹Am-Be中子源紧凑型屏蔽装置。装置由内而外采用钨+聚乙烯+含硼聚乙烯+不锈钢进行防护,外表面周围剂量当量率H^*(10)低于10μSv/h,满足辐射防护要求。同时对装置内部热中子、超热中子和快中子注量分布进行研究,确定装置快中子和热中子输出通道最佳位置。在辐照装置同时开放快中子和热中子通道进行实验测试时,需要设置距离大于130 cm的控制区,以保障操作人员安全。     

参考中子辐射与辐射防护中子测量装置校准

国际标准化组织核能标准化委员会辐射防护分委员会(ISO／TC 85／SC2)最近编制了几个有关辐射防护中子测量装置校准的标准，其中ISO8529规定了参考中子辐射的特性和产生方法、辐射场校准以及场所和个人中子剂量仪(计)校准和响应的确定；此外，ISO12789—2002规定了利用模拟中子辐射场对辐射防护中子测量装置的校准。本文介绍ISO8529系列标准的主要内容及一些相关问题。