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Nuclear Science, IEEE Transactions on

Issue 6 • Date Dec 1991

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Displaying Results 1 - 25 of 102
  • A double-peaked inner radiation belt: cause and effect as seen on CRRES

    Page(s): 1713 - 1718
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    Data from the Combined Release and Radiation Effects Satellite (CRRES) show the formation of a second peak in the inner proton radiation belt during the Sudden Storm Commencement (SSC) at 03:42 UT on 24 March 1991. The authors believe that the injection of high energy protons into an L-shell of 2.55 RF is directly related to the solar-initiated shock accompanying the SSC. Once injected, the greater than 20 MeV protons became stably trapped and produced the second peak in the proton belt that continues for months after the event. The secondary peak protons increased single event upset rates in microelectronic test devices on CRRES by over an order of magnitude in the region of the second peak, that is, for L-values of 1.8 RF to 2.6 RE. This second belt has far-reaching effects for radiation belt modelers and for determining radiation degradation and single event upset (SEU) levels that must operate in this region of near-Earth space View full abstract»

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  • Fluorescent computer tomography: a model for correction of X-ray absorption

    Page(s): 1721 - 1727
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    The distributions of individual trace elements within a sample can be found using fluorescent computed tomography (FCT). The absorption of incident and fluorescent X-rays results in degraded reconstructions of the distributions. The proposed method uses the absorption density, measured using conventional absorption tomography, to remove absorption effects. A model for FCT with absorption is developed and simulated. The resulting corrected reconstructions are compared to the reconstructions degraded by attenuation efforts. A comparison is made with other methods which utilize knowledge of the sample composition and a standard source to estimate the absorption coefficients used to correct for attenuation effects View full abstract»

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  • Comparison of experimental charge collection waveforms with PISCES calculations

    Page(s): 1540 - 1545
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    Calculations of the charge collection transient, performed using PISCES v5.0n (Aerospace modified) are compared with previous experimental measurements for energetic He, B, Si, and Fe ions incident on 1, 3, and 10 ohm-cm silicon diodes. Lumped circuit elements are used to represent resistances, capacitance, and inductance attached to the charge collection region. PISCES does not satisfactorily reproduce the changes in the charge collection waveform that occur when bias voltage, ion, or resistivity is changed View full abstract»

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  • Transient SEUs in a fiber optic system for space applications

    Page(s): 1546 - 1550
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    The results of an investigation on the SEU sensitivity for a fiber optic operating system are reported. Measurements were made on the upset cross sections for the system in static and dynamic modes of operation. The heavy ion SEU test facility at Brookhaven and the proton facility at Harvard University were used in this study. Cross sections were obtained for Honeywell transmitter and receiver devices operating in a system at a frequency of 100 kHz. Both devices were independently irradiated. The results show that the dynamic mode was the worst case, and the receiver was the most sensitive part type in the system. The threshold linear energy transfer (LET) for the receiver was determined to be 1.6 MeV.cm 2/mg for the three input signals used in the tests, which were: a continuous high state, a low state, and a 100 kHz square wave View full abstract»

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  • Hardness assurance for low-dose space applications [MOS devices]

    Page(s): 1552 - 1559
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    The authors present a method to conservatively estimate MOS hardness in space that shares the same technical basis as MIL-STD 883C, Test Method 1019.4, but permits greater latitude in part selection for low-dose space systems. Cobalt-60 irradiation at 50-300 rad(Si)/s followed by 25°C anneal is shown to provide an effective test of oxide-charge related failures at low dose rates that is considerably less conservative than Method 1019.4. For MOS devices with gate oxides thinner than 100 nm, it is shown that an elevated temperature rebound test generally is not required for systems with total dose requirements less than 5 krad(Si). For thicker gate oxides and/or higher-dose system requirements, rebound testing per Method 1019.4 generally is required to ensure that devices do not fail in space due to interface-trap effects View full abstract»

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  • Experimental verification of bremsstrahlung production and dosimetry predictions for 15.5 MeV electrons

    Page(s): 1160 - 1170
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    The radiation produced by a 15.5-MeV monoenergetic electron beam incident on optimized and nonoptimized bremsstrahlung targets is characterized using the ITS Monte Carlo code and measurements with equilibrated and nonequilibrated TLD dosimetry. Comparisons between calculations and measurements verify the calculations and demonstrate that the code can be used to predict both bremsstrahlung production and TLD response for radiation fields that are characteristic of those produced by pulsed simulators of gamma rays. The comparisons provide independent confirmation of the validity of the TLD calibration for photon fields characteristic of gamma-ray simulators. The empirical Martin equation, which is often used to calculate radiation dose from optimized bremsstrahlung targets, is examined, and its range of validity is established View full abstract»

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  • Neutron damage equivalence in GaAs

    Page(s): 1216 - 1224
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    A 1-MeV neutron damage equivalence methodology and damage function have been developed for GaAs based on a recoil-energy dependent damage efficiency and the displacement kerma. This method, developed using lifetime degradationIn GaAs LEDs in a variety of neutron spectra, is also shown to be applicable to carrier removal. A validated methodology, such as this, is required to ensure and evaluate simulation fidelity in the neutron testing of GaAs semiconductors View full abstract»

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  • Measurements of SEU and total dose in geostationary orbit under normal and solar flare conditions

    Page(s): 1686 - 1692
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    The Meteosat-3 radiation effects experiment includes two 256-kb SRAMs configured for SEU detection and a RADFET array for dose measurement. SEU rates and doses are enhanced during solar flares. Two years of orbital data are compared with ground tests and prediction. The measured background dose is found to be lower than prediction. The measured solar flare dose agrees well with prediction. The view angle of the RADFETs was insufficient to allow the relative efficiency of low-Z/high-Z shielding to be verified View full abstract»

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  • Energy dependence of electron damage and displacement threshold energy in 6H silicon carbide

    Page(s): 1111 - 1115
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    The frequency response of silicon carbide (SiC) light-emitting diodes has been used to measure the energy dependence of displacement damage produced in 6H SiC by energetic electrons. The minimum electron energy required to produce displacement damage was determined to be 108±7 keV, corresponding to an atomic displacement of silicon atoms. For electrons of energies greater than 0.5 MeV, the damage constant for lifetime degradation in SiC is lower than that for GaAs by more than three orders of magnitude, indicating a greatly superior resistance of SiC to displacement damage in most radiation environments View full abstract»

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  • TDRS-1 single event upsets and the effect of the space environment

    Page(s): 1708 - 1712
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    The systematic recording of single event upsets on TDRS-1 from 1984 to 1990 allows correlations to be drawn between those upsets and the space environment. Ground based neutron monitor data are used to illustrate the long-term relationship between galactic cosmic rays and TDRS-1 upsets. The short-term effects of energetic solar particles are illustrated with space environment data from GOES-7 View full abstract»

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  • Gate-charge measurements for irradiated n-channel DMOS power transistors

    Page(s): 1352 - 1358
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Gate-charge measurements provide information on power-MOSFET capacitances, drive requirements, and power dissipation. A gate-charge curve is a plot of gate-top-source voltage vs. charge supplied to the gate by a current source, and it consists of three distinct regions. Ionizing radiation affects primarily the second, or plateau, region. The change in the plateau voltage is related to the radiation-induced threshold-voltage shift, while the length of the plateau increases with the density of radiation-induced interface traps. Radiation-induced changes in the gate-charge curve provide useful information to circuit designers, as well as information on charge densities in the device View full abstract»

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  • Comparison of experimental measurements of power MOSFET SEBs in dynamic and static modes

    Page(s): 1310 - 1314
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    A study to determine the single-event burnouts (SEBs) sensitivity for burnout of IRF-150 power MOSFETS in both static and dynamic modes in terms of LET threshold and cross section is described. The dynamic tests were conducted with a power converter which was designed for actual space application. The results were compared with static measurements which were made during the exposure to the heavy ions. The data showed that the dynamic mode was less sensitive than the static by two orders of magnitude in cross section. It was also observed that ions with a range less than 30 microns did not produce destructive burnout in the dynamic mode even when their LET exceeded the threshold value. The extent of physical MOSFET damage in the destructive, dynamic tests appeared to correlate with the ion LET and source-drain voltage View full abstract»

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  • Radiation-hardened phototransistor

    Page(s): 1323 - 1328
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    A radiation-hardened, monolithic, silicon bipolar phototransistor has been developed and produced. Common emitter current gain at 2 mA collector current is 225 and remains above 140 after irradiation of 1 E13 n/sq cm or 1 Mrad(Si). Device photoresponse to 820 nm light decreases about 30% after 1 Mrad(Si) exposure and 55% after 1 E13 n/sq cm irradiation for typical input light levels. This phototransistor is ideal for applications requiring a radiation-hardened optocoupler View full abstract»

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  • 28th IEEE Annual International Nuclear and Space Radiation Effects Conference (NSREC '91)

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    The following topics are dealt with: basic mechanisms of radiation effects; dosimetry and energy-dependent effects; isolation technologies; device radiation response and hardening; microcircuit radiation response and hardening; single-event phenomena; hardness assurance and testing techniques; spacecraft charging and space environments and effects View full abstract»

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  • Dose variation during solar minimum

    Page(s): 1671 - 1677
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    The authors use direct measurement of dose to show the variation in inner and outer radiation belt populations at low altitude from 1984 to 1987. This period includes the recent solar minimum that occurred in September 1986. The dose is measured behind four thicknesses of aluminum shielding and for two thresholds of energy deposition, designated HILET and LOLET. An average dose per day is calculated for each month of satellite operation. It is found that the average proton (HILET) dose per day (obtained primarily in the inner belt) increased systematically from 1984 to 1987, and has a high anticorrelation with sunspot number when offset by 13 months. The average LOLET dose per day behind the thinnest shielding is produced almost entirely by outer zone electrons and varies greatly over the period of interest. If any trend can be discerned over the four year period it is a decreasing one. For shielding of 1.5 gm/cm2 (227 mil) Al or more, the LOLET dose is complicated by contributions from >100 MeV protons and bremsstrahlung View full abstract»

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  • Test of SEU algorithms against preliminary CRRES satellite data

    Page(s): 1642 - 1646
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    The CRRES satellite's highly elliptical orbit exposes the SEU-sensitive devices within the microelectronics package to both the trapped protons of the inner radiation belts and the cosmic rays of deep space. Preliminary data from sensitive devices show more upsets due to protons than due to cosmic rays on this type orbit. This is consistent with pulse-height spectra measured from a photodiode within the package. Preliminary data obtained with the ratemeter experiment in the inner radiation belts are in reasonable agreement with predictions based on the trapped proton spectra given by the NASA AP8 model for solar maximum combined with CUPID simulations of the spallation reactions near the sensitive volumes of the memory elements. The more limited data from deep space are in agreement with the CREME calculations for cosmic ray traversals. CUPID is also in relatively good agreement with the pulse-height spectra measured in the inner belts as part of the PHA experiment View full abstract»

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  • Effects of switched gate bias on radiation-induced interface trap formation [MOS transistors]

    Page(s): 1130 - 1139
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    Switched gate bias experiments were used to test the hydrogen model for the time-dependent buildup of interface traps nit after a radiation pulse. In the hydrogen model, slow transport of radiation-induced H+ ions through the oxide to the Si/SiO2 interface is the rate-limiting step in the nit formation process. A model based on dispersive transport theory was used to numerically simulate the time-dependent H+ drift through the oxide toward the gate under negative bias, then back toward the Si/SiO2 interface under positive bias. Good agreement between the simulations and experiment is obtained for the final magnitude of ΔNit, both for positive and negative bias during irradiation. The procedure used for the numerical simulations provides only a lower bound on the transport time when the direction of the gate bias is switched during the Nit buildup. This behavior is due to a memory effect in the dispersive H+ transport View full abstract»

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  • A spacecraft charging study on the SCEX 3 rocket

    Page(s): 1622 - 1628
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    Instruments on the SCEX 3 rocket payload were used to study charging during electron beam emissions. The data show that electrostatic analyzers can be used to measure vehicle charging and direct beam return currents in dense plasma conditions. The data also show return current dependencies on pitch angle, beam current and beam energy. It is found that if the proper care is taken. ESAs can be used to detect charging on vehicles in low altitude (<400 km) orbits which are contaminated with high levels of outgassing and in dense plasma regimes. These results are particularly important for the TSS-1 electrodynamic tether program where ESAs are being used to determine Shuttle charging levels during tether employment and to look for high fluxes of directly returning electrons during electron generator operations to balance the Shuttle charging View full abstract»

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  • Radiation characteristics of SIPOS and polysilicon resistors

    Page(s): 1365 - 1369
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    The radiation characteristics of polysilicon and SIPOS resistors are compared. SIPOS is being considered as a replacement material for polysilicon in feedback resistors in rad-hard ICs. Both materials show little change in resistivity to gamma radiation and are much more neutron-radiation resistant than bulk silicon View full abstract»

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  • The effect of temperature on single-particle latchup

    Page(s): 1435 - 1441
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    Special test structures fabricated with three different CMOS processes were used to investigate the effect of elevated temperature on single-particle latchup. The latchup threshold was strongly affected by contact geometry, and its temperature dependence is consistent with a model based on triggering of the vertical parasitic transistor. Threshold LET values decreased by about a factor of 2.5 at 125°C relative to room temperature values for all three processes. Saturation cross sections exceeded the isolation well area for the two bulk processes because of diffused charge. Laser studies showed that latchup could be triggered by strikes outside the isolation well, consistent with the diffused charge mechanism. These same mechanisms were consistent with measurements of the latchup cross section of a static CMOS RAM View full abstract»

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  • Post irradiation effects (PIE) in integrated circuits [CMOS]

    Page(s): 1584 - 1589
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    Post-irradiation effects (PIE) ranging from normal recovery to catastrophic failure have been observed in integrated circuits during the PIE period. Data presented show failure due to rebound after a 10 krad(Si) dose. In particular, five device types are investigated with varying PIE response. Special attention has been given to the HI 1-507A analog multiplexer because its PIE response is extreme. X-ray diffraction has been uniquely employed to measure physical stress in the HI 1-507A metallization. An attempt has been made to show a relationship between stress relaxation and radiation effects. All data presented support the current MIL-STD Method 1019.4 but demonstrate the importance of performing PIE measurements, even when mission doses are as low as 10 krad(Si) View full abstract»

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  • Charge collection mechanisms in MOS/SOI transistors irradiated by energetic heavy ions

    Page(s): 1226 - 1233
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    The authors have investigated with both experimental and numerical methods (Monte Carlo and drift-diffusion model) various charge collection mechanisms in NMOS/SOI transistors irradiated by single energetic heavy ions. Physical interpretations of data emphasize the influence of various parasitic structures of the device. Two charge collection mechanisms are detailed: substrate funneling in the buried MOS capacitor and latching of the parasitic bipolar transistor View full abstract»

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  • Radiation damage assessment of Nb tunnel junction devices

    Page(s): 1359 - 1364
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    The radiation hardness of a new technology using Josephson junctions was explored by an irradiation using a fluence of 7.6×10 14 protons/cm2 at an energy of 63 MeV from the U.C. Davis cyclotron. In what may be the first radiation assessment of Nb/Al2O3/Nb devices, the permanent damage in these devices was investigated. No permanent changes in the I-V characteristics of the junctions were observed, indicating no significant level of material defects have occurred at this level of irradiation View full abstract»

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  • Dosimetry considerations for the high-energy photon/electron environment of HERMES III: implications for experiments and modeling

    Page(s): 1736 - 1745
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    Measurements of energy deposition as a function of equilibrator thickness and position in the HERMES III radiation field are compared to ITS code predictions. These measurements demonstrate the combined photon/electron nature of the radiation field and the importance of the electron field in both measurements and calculations View full abstract»

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  • Correlation between channel hot-electron degradation and radiation-induced interface trapping in N-channel LDD devices

    Page(s): 1336 - 1341
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    It is shown that the correlation model developed in previous work to determine hot-carrier device lifetime from radiation-induced interface state data can be extended to lightly-doped drain (LDD) devices by selecting different, but equivalent, failure criteria. Excellent agreement between the model and experimental data is shown for LDD devices from several different manufacturers. These results indicate that a radiation test can be used as a quick alternative to a voltage stress test for predicting hot-carrier-induced device lifetime. Charge pumping measurement results are presented that demonstrate the basis for such a correlation 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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