Design Features of a Start-Stop Time-to-Amplitude Converter

A time-to-amplitude converter of the start-stop type is described. Automatic suppression of readout in the absence of a timely stop signal and an analog memory, which permits delay of readout to allow independent evaluation of a conversion, are two of its several novel design features. With full scale ranges of 0.1 usec to 30 usec, the instrument provides good linearity, stability and resolution over a wide range of operational conditions.     

A Microprocessor - Controlled Extensometer for Fuel Cladding Strain Measurements

An instrument for measuring radial strain of nuclear fuel cladding has been developed for use during in-core characterization tests of candidate materials. Employing a microwave sensor of coaxial geometry, a strain as small as several microinches can be detected. At the opposite extreme, the large dynamic range of the instrument permits measuring strain equal to ten percent of the original specimen diameter. In all configurations tested, the sensor comprises a hollow metal cylinder enclosing a test specimen positioned coaxially within the cylinder. Microwave energy absorbed by the sensor/specimen unit at particular frequencies relates to diameter of the specimen. Consequently, determination of specimen size results from measurement of the resonant absorption frequencies of the sensor. Tests to determine operational characteristics of the sensor and associated instrumentation have been conducted in a gamma (2 × 107R/hr) irradiation facility, and in high temperature (1000°F) laboratory ovens. Most recently concluded tests concerned evaluation of a microprocessor-controlled instrument design. As indicated by the instrumentation, elastic strain of a pressurizable specimen of 0.23-in. OD fuel cladding occurred linearly with stress at a modulus of about 30 × 106 psi. The gamma radiation appeared not to cause any short or long term effects upon sensor performance. During several tests of the sensor/specimen at 1000°F, indicated elastic and inelastic strain of 316 SS test specimens were monitored. Completely satisfactory data resulted even though a light oxidation of the sensor occurred during the initial high temperature test.     

Integral Type Position-Sensitive Proportional Chamber with Multiplexer Readout System

A new position-sensitive detector with a multiplexer readout system for synchrotron radiation measurements is described. The detector consists of many proportional chamber cells with capacitors for charge accumulation. Charges delivered from a detector cell are accumulated in an associated capacitor during a measuring time. The accumulated charges are transferred to a charge-sensitive amplifier through a multiplexer channel which is addressed by binary coded signals. This process corresponds to the integral type radiation measurement which has no dead time in the pulse measurement. Each cell is regarded as a memory cell containing information about X-ray photons. Experiments carried out with a direct X-ray beam show that the detecting system is applicable to a wide range of photon rates from 103 cps to 108 cps per cell.     

热释光测量系统的质量控制及剂量刻度

热释不剂量计在读出器上的测量读数是一个相对值,要把仪器测读数值换算成剂量值,须对剂量计进行刻度。本文主要介绍热释光测量系统的质量控制以及剂量计的刻度方法,量值传递等有关标准规定。     

Pulse Height Analyzer with Internal Storage for Space Use

A pulse height analyzer has been designed for space use which is able to handle input count rates in excess of 5 X 104 counts per second with low power consumption and very small size. It can operate in the temperature range of -15 to + 70°C and survive storage temperature from -55 to + 125°C. A parallel-serial, coincident current, wide-temperature-range, ferrite core memory of 256 channels, 16 bits per channel is provided. A digitizing rate of 0. 5 microsecond per channel plus an average 25.5 microsecond storage time is used. An internal, nonoverloading linear amplifier is provided to handle up to 100 millivolt negative pulses for full scale storage. Control logic is provided for external commands for power, accumulate, nondestructive readout, and destructive readout functions. All input-output logic levels are compatible with conventional integrated circuits. All components are run at a fraction of their ratings in order to obtain maximum reliability.     

Measurements of the Average Energy Per Electron-Hole Pair Generation in Silicon between 5-320°K

The average energy expended to create an electron-hole pair in silicon ?Si(T) has been measured in the 5-320°K temperature range with thin totally depleted surface barrier and diffused junction radiation detectors. The data have been normalized to a value of ?Si (300°K) = 3.62 eV. A dependence of ?Si on T much weaker than previously published by other authors has been observed. In the examined temperature range (5-320°K) our data are well fitted by ?si(T) = 2.15 Eg(T) + 1.21 eV where Eg(T) (in eV) is the value of the forbidden bandgap.     

High Purity Germanium Radiation Detectors

The fabrication and characterization of high purity germanium radiation detectors are described. These detectors are n-i-p diodes with a shallow (1.5?) diffused junction and a noninjecting metal-semiconductor contact. The germanium has a net acceptor concentration of approximately 7 × 1011 cm-3 and contamination during processing was prevented by using clean procedures and a KCN treatment. Electrical measurements show that with 500 volts of bias these detectors are fully depleted and have a capacitance of approximately 4.5 pf. Detection characteristics are determined from measurements of ?-rays and x-rays over the energy range of 6 keV to 136 keV. A deviation from linearity of less than ± 0.2 percent was measured. The resolution of the detectors is characterized by an effective Fano factor of 0.12. The average energy expended per created pair was determined to be 2.95 ±0.02 eV at 90°K.     

全帧CCD探测器CT扫描数据读出与拖影校正研究

以光纤耦合全帧CCD方式制作的X射线探测器在实验室高精度X射线CT扫描中广泛应用。由于X射线的强穿透特性,全帧CCD探测器通常工作在无快门模式,图像拖影是该模式下必定存在的伪影。本文针对全帧CCD探测器CT扫描图像拖影校正进行研究,提出了非曝光行校正法校正投影图像拖影,避免了利用暗像元校正法校正投影图像拖影时可能会带来的条形伪影;针对动态曝光CT扫描,设计了基于辐射屏蔽的投影图像感兴趣区域快速读出模式,通过降低电荷转移时间有效抑制投影图像拖影的产生,提高探测器有效信号动态范围。实验结果表明：应用非曝光行校正法能有效校正投影图像拖影、提高投影图像质量;采用投影图像感兴趣区域快速读出模式可有效解决动态曝光CT扫描图像拖影校正难题。     

Versatile Logic System for Use in Nuclear Experiments on Scientific Satellites

An improved fast low-power-drain logic system has been developed for use in nuclear experiments on scientific satellites. The basic unit of the system is an AND-NAND gate which has a response in the 10 nanosecond range, a power drain of 2.0 milliwatts and operates over the temperature range of -40°C to +80°C. In addition to providing the AND-NAND logic functions, one or more of the basic units may be connected to yield the following: a. monostable pulse generator, b. pulse generator yielding an output pulse at the leading edge of the input pulse, c. Delay, d. Threshold Detector, and e. Bistable Circuit. The system requires relatively simple circuitry for interfacing at its outputs and inputs.     

A Computer-Based Multiparameter Analyzer

A system has been constructed and used for on-line acquisition of data at the Iowa State Synchrotron Laboratory. The principal components include eight Victoreen analog to digital converters (ADC) and a fast general purpose digital computer (SDS 910) along with the necessary interface circuitry to couple to the digitized outputs of scalers, clocks, etc. Although quite flexible in application, the ADC-to-computer interface was designed especially for efficient use (minimum deadtime and bias) both with an accelerator having a beam burst of about 100 microseconds duration and for continuous operation. To minimize ADC deadtime ineither circumstance, each 8Mc/sec ADC, equipped with an analog buffer, is connected through a plugboard to a digital buffer register synchronized to the ADC. This permits readout of the digitized pulse heights in less than one microsecond. In experiments where the ADC's operate completely independently of one another, a hardware option is provided to interpret the buffer register contents as addresses in the computer memory. This option eliminates the necessity for software programming of data input: the contents of the associated word in memory may be either incremented or decremented automatically in a minimum of two computer cycles. Some biasing in efficiency normally occurs in multiple ADC systems at high counting rates when two or more registers are waiting for readout. To reduce such bias to a negligible amount, logic governing data transfer to the computer sequences through a hierarchy of register preferences with a periodicity of 128 microseconds.     

15 MeV～3 GeV电子加速器90°方向光子源项研究

韧致辐射光子是电子加速器屏蔽设计中的重要源项。为研究90°方向光子源项特征以及靶体半径和厚度对90°方向光子源项的影响,采用蒙特卡罗程序MCNPX27对15 MeV～3 GeV电子束轰击铁靶后的辐射源项进行计算。分析了90°方向光子辐射剂量、光子能谱等源项随靶厚度和半径的变化。通过与0°方向光子源项以及靶体内级联电子沉积能量进行对比,进一步分析了90°方向的光子源项特点。结果表明,90°方向光子能量主要集中在10 MeV以内,光子能谱形状与入射电子能量关系较小。受级联电子在靶内能量沉积程度及靶体对光子自吸收的共同影响,靶体半径和厚度是影响90°方向光子源项的重要因素。在电子加速器的屏蔽设计中应考虑靶体尺寸差异所带来的影响,同时建议针对束流90°方向和0°方向光子源项的差异,对加速器辐射屏蔽和防护进行优化设计。     

Continuum Radiation from Arc Heated Plasmas

Measurements of the spectral continuum of arc heated nitrogen plasma have been made using high dispersion spectroscopic equipment. These measurements cover a wavelength range of 2700 ? to 44t,000 ? and a temperature range of 9500°K to 12,000°K. The measurements have been compared with a number of theoretical studies of both the spectral and total emissivity. An estimate of the contribution to the continuum of the negative nitrogen ion has been included, and a new value of the effective nuclear charge for Kramers free-free radiation has been measured.     

Data acquisition for the Combined Ion and Neutron Spectrometer (CINS)

The CINS (Combined Ion and Neutron Spectrometer) consists of three detector systems: a boron-loaded plastic scintillator for medium energy neutrons, a silicon detector system for high-energy neutrons, and a charged particle stack containing both silicon detectors and scintillators. A readout system built for the charged particle stack is described here. The stack must be able to detect particles over a wide range of charge and energy. It contains 7 detectors, including 4 silicon detectors that each have two output paths. The readout must have a large usable dynamic range and must be able to handle the relatively high event rates that occur when the stack is placed in an accelerator beam. The data acquisition system detects events (that is, compares incoming signals to user-supplied trigger definitions), proceeds to capture waveform data from the preamplifiers, and saves the data to a hard drive. Although only used with the charged particle stack to date, the system can also be used with the other elements of CINS.     

A Dewpoint Device for HTGR Coolant

High-temperature gas-cooled reactors (HTGRs) use a gaseous coolant for heat transfer between the nuclear core and two or more steam generators. Leakage of steam or water from the steam generators to the coolant would expose the nuclear core to water vapor. A moisture measuring system is required to determine the moisture content of the coolant gas in the range of 0.1 to 3000 volume parts per million (ppm). Another requirement is the rapid detection of large leaks resulting in 2000 ppm or more and the identification of the leaking steam generator, thus permitting isolation of the faulty coolant loop. An optical dewpoint detector has been developed that can be used either as a dewpoint monitor or as a dewpoint trip device. The response time of the device as a trip instrument is typically 1 sec in the dewpoint range of 27°F to 128°F (100 to 3000 ppm). As a dewpoint monitor, the mirror temperature can be changed at a rate of 1°F/sec, in the range of -87°F to +128°F (0.1 to 3000 ppm). The moisture detector head is designed to operate at the full coolant pressure of 700 psia. In the HTGR application, access to the device is difficult during reactor operation, and will be cumbersome at all times because of gamma radiation environment. Therefore, exhaustive testing of all detector head components, subassemblies, and materials selection from inorganic substances has been performed to reduce maintenance to a minimum.     

Study of n- and p-Type Silicon Exposed to Highly Energetic Radiation

For an understanding of displacement effects in semiconductors, it is important to establish a correlation of the magnitude of these effects with various types of radiation. A study has been made of the effect of highly energetic radiation on n-type silicon using two techniques. First, with electron-spin resonance studies, the energy dependence of formation of the Si-Bl center at 80° and 300°K by 1.5, 2.5, 5, and 30 MeV electrons and by reactor neutrons has been determined. In addition, the energy dependence of the production of the divacancy by electrons with energies between 2.5 and 30 MeV in n-type silicon have been obtained. Second, using galvanomagnetic techniques, information has been obtained on the irradiation response and subsequent recovery during annealing of the conductivity, Hall coefficient, and Hall mobility of n-and p-type silicon. The samples were bombarded at 80°K with 5 to 30 MeV electrons and isochronally annealed to 400°K. A considerable amount of annealing was observed in all cases, but the recovery was never complete.     

High-dose neutron induced radiation swelling simulated by heavy ion irradiation and its microscopic study with positron annihilation technique

1IntroductionStainlesssteel(SS)isanimportantreactorstructuralmaterial.SSusedinreactorsexperiencesneutronirradiationandtheaccumulateddosemayreach1022-23n'cm--2alleryearsofreactoroperation.Consequently,severeradiationeffectsoccurinSSandwouldleadtoareactorbreakdownorevenaccident.RadiationsWellingisamajorradiationeffectinSSwhichshouldbetakenintoaccountinreactordesignandoperation.Severeswellinggenerallyoccursatneutrondosesof2102on'cm--2.Thelackofneutronproducingson-rsesofsuchhighdoseshampersits…     

辐照温度对双极线性稳压器的辐射效应影响

为研究辐照温度对线性稳压器的电离辐射效应的影响,选取三个公司生产的同一型号线性稳压器7805在不同温度条件下进行60Co?电离辐射效应试验。结果表明:辐照温度的增加使三款线性稳压器输出电压的辐射损伤增大;使国家半导体公司和安森美半导体公司稳压器的线性调整率及国家半导体公司的输入电流敏感参数的辐射损伤减小。结合双极晶体管的空间辐照效应模型,对双极线性稳压器不同温度条件下的辐射损伤效应进行了分析和讨论,表明辐照温度对线性稳压器的辐射敏感参数的影响主要取决于陷阱电荷。     

Event Priority Instrumentation System for Nuclear Experiments on Scientific Satellites

The number of information bits per unit time, or data rate, which can be telemetered back to earth from a scientific satellite is limited by restrictions on weight, volume and power. Thus, each experimenter (generally one of many) is allotted a very limited data rate capability. In nuclear experiments, where a wide variety of events may occur per unit time, use of this rate capability may be optimized by selection of events on a priority basis. Described here is an event priority instrumentation system developed for use in scientific satellites. The system allows for the selection of the highest priority event occurring during a telemetry sequence. Also, provision is made for periodically changing the order of priority. All circuitry was designed and developed to minimize weight, volume and power drain and to maintain stable characteristics while unattended for periods as long as one year. The operating temperature range is -20°C to 60°C.     

Gain vs Temperature Effects in Nal(Tl) Photomultiplier Scintillation Detectors Using 10 and 14 Stage Tubes

The manner in which the gain of a radiation transducer comprised of a 2" × 2" NaI(Tl) crystal, and either a 5-inch 10-stage or 2-inch 14-stage photomultiplier tube viewing a Cs137 source, varies with ambient temperature changes over the range of 0° C to 50° C has been investigated. Gain vs temperature response curves are presented and operating temperatures which minimize gain variations are delineated. A method is given for evaluating the magnitude of gain variations encountered from the curves.     

AN Improved Solid-State Logarithmic Amplifier

A logarithmic amplifier is described which is composed entirely of solid state components. Logarithmic characteristics can be improved by the compensation of low saturation current Si-diodes with an appropriate Ge-diode. By the use of reverse-biased Si-diode dielectric modulator as the input stage of the amplifier, an input resistance of 5 × 1010 ohms and a signal threshold of 10-11 amp. are obtained at room temperature. A range of 7 decades is covered, that is, from 5 × 10-11 to 5 × 10-4 amp., with the accuracy less than ±2% of a decade and the temperature drift less than ±0.005 dec./°C over a temperature range from 0°C to 50°C.