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Nuclear Science, IEEE Transactions on

Issue 6 • Date Dec. 1967

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Displaying Results 1 - 25 of 53
  • Table of contents

    Publication Year: 1967 , Page(s): c1
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    Freely Available from IEEE
  • IEEE Nuclear Science Group

    Publication Year: 1967 , Page(s): c2
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    Freely Available from IEEE
  • Table of contents

    Publication Year: 1967 , Page(s): 1 - 4
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    Freely Available from IEEE
  • The Nucleus

    Publication Year: 1967 , Page(s): 5
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    Freely Available from IEEE
  • 1967 Radiation Effects Conference

    Publication Year: 1967 , Page(s): 6 - 7
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    Freely Available from IEEE
  • Committee

    Publication Year: 1967 , Page(s): 8
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  • 1967 Conference Paper Award

    Publication Year: 1967 , Page(s): 9
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  • Germanium γ-ray spectrometers

    Publication Year: 1967 , Page(s): 10 - 26
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    Potential uses of the Ge(Li) diode detector as part of a spectrometer system for space experimentation would include identification of energy sources and determination of the composition of materials. In laboratory experiments its greatest application is in low-energy nuclear physics, mainly (n, γ) reaction studies. The primary advantage in its present use is energy resolving capability. In future applications, as energy resolution is maintained close to the observed limit for the detector, increased attention must be given to optimization in terms of geometry. Further improvements are needed in the mechanical design of such systems, especially for experiments in space. View full abstract»

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  • Some Plasma Effects in Semiconductors

    Publication Year: 1967 , Page(s): 27 - 39
    Cited by:  Papers (1)
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    This is a review of some selected plasma effects in semiconductors, principally InSb at 77° K. The production of nonequilibrium electronhole plasmas by electrical injection and impact ionization is described including some instabilities which attend the latter process. Some new results on the pinch effect obtained by diagnosis with a 10.6 ¿ CW laser are shown. Observations of the manifestation of another instability, namely gigahertz radiation, not requiring an applied magnetic field are presented. A magnetic field is required to produce some instabilities in plasmas, among these are the helical instability. A bistable element resulting from an inherent hysteresis in the threshold conditions of this instability is described. Discontinuous changes in the plasma conductance can be produced by a magnetic field and the relation of this effect to high intensity microwave emission is outlined. Finally, some preliminary results on plasma decay are presented. View full abstract»

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  • Effect of Low Temperature Electron-Irradiation on the Electrical Properties of Undoped GaSb

    Publication Year: 1967 , Page(s): 40 - 45
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    Undoped GaSb samples were irradiated at 15°K and 80°K with 0.5 MeV and 1.0 MeV electrons. The effects of the irradiation on the temperature dependence of the Hall coefficient RH and the Hall mobility ¿H were investigated and a study of the recovery of the radiation-produced changes of these properties was made. After irradiation the Hall coefficient curves in a log RH vs T-1 diagram exhibit a maximum at low temperatures which indicates impurity conduction resulting from radiation-produced defects. At higher temperatures where the normal conduction mechanism is predominant the sign and magnitude of the radiation-produced changes of the Hall coefficient depend in a complex manner on measurement temperature, irradiation dose and irradiation energy. The Hall coefficient data obtained after small irradiation doses provide evidence that both acceptors and donors are produced by the irradiation. Donor production appears to be more pronounced at 1.0 MeV than at 0.5 MeV. At low temperatures the reciprocal Hall mobility has a tendency to vary stronger than linear with increasing irradiation dose. The dependence of the change of the reciprocal Hall mobility on the measurement temperature indicates that a substantial fraction of the radiation-produced defects act as neutral scattering centers. Recovery between 15 and 390°K occurs in four major stages which are located near 124, 168, 210 and 360°K. Acceptors are removed in all four stages. Evidence for the removal of donors is found only for stage IV. View full abstract»

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  • Effect of Fast-Neutron Irradiation on Optical Attenuation in Compound Semiconductors

    Publication Year: 1967 , Page(s): 46 - 54
    Cited by:  Papers (4)
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    Recently a model was proposed to account for anomalous infrared attenuation noted experimentally for fast-neutron-irradiated, compound semiconductors. The model represents neutron damage by localized phase transitions to a high-pressure metallic-like state. It is shown that this model not only accounts for the anomalous, continuous optical attenuation at photon energies less than the band gap, but also can explain the absorption edge fuzziness noted for neutron-irradiated GaAs. The optical attenuation produced by embedded metallic zones at frequencies above the absorption edge is derived, and it is shown that the metallic resonance absorption band is altered from the usual Lorentzian shape. It is shown that in GaAs irradiated with fast neutrons at sufficiently high doses the resonant absorption by the metallic phase can dominate the host semiconductor absorption. View full abstract»

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  • Mechanisms of Radiation Effects on Lasers

    Publication Year: 1967 , Page(s): 55 - 61
    Cited by:  Papers (8)
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    Lasers offer many potential advantages for space communications and space instrumentation. Their performance is, however, affected by the high energy radiation found in the space environment, e.g., trapped proton and electrons, solar flare protons, and possibly gamma rays and neutrons from on-board nuclear power, auxiliary or propulsive. We report here on some studies of the effects observed on lasers and laser components exposed to irradiation, and in particular on the mechanisms of these effects. View full abstract»

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  • Transient radiation effects in optical materials

    Publication Year: 1967 , Page(s): 62 - 67
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    The use of the prototype Phermex electron accelerator to simulate high dose rate nuclearradiation environments is discussed. The free electron density produced in optical materials by the beam from this machine, and that expected from a typical incident prompt-gamma radiation flux are compared. An experimental setup to measure the effects on the transmission of selected optical materials is described, and data obtained on these materials are presented. Transient or permanent loss of transmission was observed in optical glasses and GE-101 fused quartz, but no effect was seen in purified fused silica. Reflectivity of front-surface aluminum and dielectric mirrors was also checked and no effects were seen. View full abstract»

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  • Injection-Level Studies in Neutron-Irradiated Silicon

    Publication Year: 1967 , Page(s): 68 - 77
    Cited by:  Papers (11)
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    The dependence of carrier lifetime on excess density was investigated for neutron-irradiated silicon. Five bulk specimens of n-type (1.0 to 55 ohm-cm) and five of p-type material (2.2 to 56 ohm-cm) were employed. In all cases the lifetime was constant at low excess densities, increased to a value several times larger at excess densities near the equilibrium carrier density, and then decreased. An analysis of the data was performed on the basis of recombination at disordered regions. The effective barrier heights associated with disordered regions were small, about 0.05 eV in n-type silicon and about 0.07 eV in p-type material. These values represent a weighted average for those regions participating in recombination and tend to favor low values. Capture probability ratios and other parameters were also obtained. View full abstract»

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  • Influence of Impurities on Carrier Removal and Annealing in Neutron-Irradiated Silicon

    Publication Year: 1967 , Page(s): 78 - 81
    Cited by:  Papers (11)
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    The influence of impurities on carrier removal and annealing has been investigated in neutron-irradiated silicon in the resistivity range from 0.5 to 50 ohm-cm. Carrier removal rates in n-type material are strongly dependent upon the crystal growth method and are lower in Czochralski-grown (oxygen containing) material than in material grown by the vacuum-float-zone or LOPEX techniques. A slight dependence of the removal rate on the dopant impurity is observed in vacuum-float-zone material but not in Czochralski-grown material. The annealing behavior of n-type material is also very crystal growth dependent. An annealing stage located between approximately 144°C and 170° C is observed in vacuum-float-zone and LOPEX-grown material but not in material grown by the Czochralski method. The location of the stage is dependent upon the dopant impurity. Carrier removal at room temperature in p-type material is not influenced by the growth method or the dopant impurity. However, dopant effects are observed upon annealing. View full abstract»

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  • Electron Damage Coefficients in P-Type Silicon

    Publication Year: 1967 , Page(s): 82 - 87
    Cited by:  Papers (1)
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    Crucible grown p-type silicon, as used for the base of many commercial solar cells, exhibits a damage coefficient under electron bombardment that appears to involve a double defect in each recombination center. The damage coefficient has been fitted to an empirical formula that accounts for silicon resistivity and for energy of the bombarding particles. To apply this formulation to a practical evaluation of solar cell damage in orbit, two complications were considered. The first is the angular distribution of the space radiation incident on the cell. An experiment showed that electron flux, and not current, determines the extent of the damage. The second is the presence of a transparent coverslide over the cell. By the application of Monte Carlo data for the transmission loss and energy degradation of the electrons, modifications to the damage coefficient can be made to account for coverslide shielding. An exponential attenuation appears adequate to describe these shielding effects. The end product of this study is an analytic formula for the damage coefficient that allows a simple calculation of the damage caused by energetic electrons to n/p silicon solar cells with coverslides. View full abstract»

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  • A Two Level Model for Lifetime Reduction Processes in Neutron Irradiated Silicon and Germanium

    Publication Year: 1967 , Page(s): 88 - 102
    Cited by:  Papers (15)
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    A two level mnodel for recombination processes in neutron irradiated silicon and germanium is proposed. This model successfully explains published experimental data for lifetime and. life-time damage constant as a function of resistivity, injection level and, temperature. View full abstract»

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  • Role of Lithium in Damage and Recovery of Irradiated Silicon Solar Cells

    Publication Year: 1967 , Page(s): 103 - 109
    Cited by:  Papers (3)
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    Lithium plays a role in the degradation and recovery of diffusion length in lithium-doped silicon p/n solar cells irradiated with 1 MeV electrons. Salient experimental results are that (1) the diffusion length degrades when these cells are irradiated at a fast rate; (2) the time constant for recovery of diffusion length decreases with lithium concentration, and increases with fluence, as ¿2/3; and (3) recovery is a temperature-sensitive process with an activation energy of (0.61 ± 0.10) eV. These results suggest the following model for the damage and recovery process. Degradation of diffusion length occurs when radiation-induced vacancies pair with lithium and other available impurities to form immobile, negatively-charged recombination sites. These sites are formed at a rate governed by the irradiation rate and the high vacancy mobility. Unpaired lithium ions diffuse to, and pair with, these recombination sites, reducing their cross sections to very low values. Thus, recovery of diffusion length occurs. Recovery follows diffusion-limited kinetics in which the reacting species are of unequal concentrations. The capture radius of the recombination site for a lithium ion is proposed to decrease with fluence as ¿-2/3 to achieve better accord between theory and experiment. View full abstract»

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  • Radiation Damage in Lithium Doped Silicon

    Publication Year: 1967 , Page(s): 110 - 115
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    Majority carrier removal rates for electron irradiation were studied in lithium doped float zone silicon. The removal appears to be due to reaction of lithium donors with displacement products to form uncharged complexes. A time dependent removal was observed after termination of the radiation. An exponential removal of carriers with electron fluence was also observed. View full abstract»

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  • Injection Dependence of Transient Annealing in Neutron-Irradiated Silicon Devices

    Publication Year: 1967 , Page(s): 116 - 126
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2448 KB)  

    Studies have been performed to explore accurately the injection level and temperature dependence of transient annealing in neutron-irradiated P- and N-type silicon. In P-type material, the annealing factor in the 0 to 0.1 second time interval is very sensitive to the minority carrier injection level. For example, by varying the injection level from 10-5 to 10-1 the annealing factor at 0.001 second can be reduced from 10 to approximately 2. In contrast to the P-type results, the injection dependence observed in N-type silicon is very small and, furthermore, is in the opposite sense; i.e., an increase in the injection level causes an increase in the annealing factor. However, this study shows that this seemingly different behavior can be correlated on the basis of the hole-to-electron ratios of the different material types and resistivities. Annealing measurements performed in the temperature range from 180°to 300°K reaffirm the 0.3 eV activation energy previously found in P-type silicon and establish a value of 0.17 eV for N-type silicon. View full abstract»

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  • Factors Influencing Prediction of Transistor Current Gain in Neutron Radiation

    Publication Year: 1967 , Page(s): 127 - 133
    Cited by:  Papers (7)
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    Prediction of transistor performance in neutron radiation is subject to many variables. Several of these were investigated in order to improve prediction accuracy. Experimental data are discussed for the base transit time parameter, variation in damage with different bias conditions during irradiation, changes in damage observed after room-temperature storage and repeated high current measurements, and junction capacitance as a function of measurement frequency before and after irradiation. View full abstract»

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  • Annealing Characteristics of Neutron Irradiated Silicon Transistors

    Publication Year: 1967 , Page(s): 134 - 146
    Cited by:  Papers (4)
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    When a transistor is subjected to neutron irradiation, a component of base current proportional to neutron fluence is induced. From the effects of annealing on the base and collector currents, the conclusion was drawn that there is an apparent difference in the annealing characteristics between the neutral and the space-charge regions of the semiconductor device. This study of the anomalous annealing indicates that the neutron-induced component of base current is a result of one, or a combination, of the following mechanisms: a quasi-tunneling recombination phenomena in the emitter-base space-charge region, or an influence of the p-n junction electric field on the formation, annealing, and electronic behavior of the neutron-induced defect centers. A field dependence of the formation and annealing of the neutron-induced defects appears to be present both during the introduction and annealing of the neutron-induced defect centers. It could not be finally determined whether or not the quasitunneling phenomena occurred although it can be shown on theoretical grounds that it is possible for such phenomena to occur. The annealing characteristics of the defects, as represented by changes in the collector and base currents, have been obtained. Three sets of devices were irradiated and then annealed, with one set having a forward bias during annealing, one set having no bias, and one set having a reverse bias. The dependence of the field on annealing is present but appears quite complex. View full abstract»

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  • Application of Silicon Damage to Neutron Exposure Measurement

    Publication Year: 1967 , Page(s): 147 - 152
    Cited by:  Papers (1)
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    A technique is described for using the damage in silicon to measure neutron exposure in Radiation Damage Units (RDUs) with transistors called Radiation Damage Monitors (RDMs). The technique is useful in measuring the damage gradients across experiments and in determining the relative damage effect of a neutron environment. Two calibration procedures are described, as are the operating characteristics and use procedures for five transistor RDMs to cover the exposure range from 1011 to 1015 n/cm2. View full abstract»

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  • The Analysis of Radiation Effects in Semiconductor Junction Devices

    Publication Year: 1967 , Page(s): 153 - 169
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2809 KB)  

    A computer program has been written for the prediction of transient and permanent radiation damage in junction devices. This program calculates the transient solutions of Poisson's equation and the continuity equations throughout a one-dimensional structure. Mobility, lifetime, and carrier generation are described by nonlinear functions of carrier density and current so that scatter-limiting velocity, Shockley-Read-Hall recombination, and avalanche ionization phenomena are described. Three examples are presented which illustrate the utility of such programs in predicting both ionization and displacement damage effects in a PIN diode and a bipolar transistor. View full abstract»

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  • Computerized Model for Response of Transistors to a Pulse of Ionizing Radiation

    Publication Year: 1967 , Page(s): 170 - 178
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1199 KB)  

    A computer program has been formulated to solve the time-dependent differential equations describing electron and hole concentrations and the electric field in one-dimensional planar semiconductor-device geometry. The usual assumptions of small minority-carrier concentration and requirements for separating devices into neutral and space-charge regions are not required since the depletion layer is a natural result of the computer solution. Problems which have been studied include the relaxation of P-N junction diodes and transistors from an intense short pulse of ionizing radiation. The phenomena observed include an apparent long recovery time of diodes in high-impedance circuits, ambipolar diffusion of electron-hole pairs toward the junction of alloy diodes, and electric-field peaking in the depletion layer of reverse-biased alloy junctions. View full abstract»

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IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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