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A commercial ultraviolet erasable programmable read-only memory (UVPROM) was used to demonstrate a dosimetry technique for both ground and space applications. An equivalent amount of UV to reproduce the same amount of erasure was used to calibrate dose. The new method of readout, unlike other methods, does not require the evidence of exposure to be destroyed in the course of a measurement. It requires power only during readout. Results from an experiment using this technique aboard the Microelectronics and Photonics Test Bed (MPTB) satellite are discussed. Application of Extreme Value Theory is used to analyze whether early failures in the device were statistically feasible or more likely due to large, rare energy depositions. A new dosimeter approach using a change injection method that will eliminate the need for UV as a metric is also presented as well new experiments for the devices under test aboard MPTB. Index Terms--Extreme value, extreme value analysis, extreme value theory, floating gate, microdose, MPTB, non-volatile, NVM, UVPROM, satellite, single event, stuck bit, transfer orbit.

The standard estimates of the GEO total ionizing dose are revised to account for enhancement of the bremsstrahlung dose by high-Z layers in IC packages, IC die, and spacecraft shields.

The spectrum of a Co-60 facility includes more than the two photopeaks of gamma ray emission. If there is a large low energy contribution from scattering, dose enhancement might be a problem. It is important to know the spectrum of a Co-60 facility and understand how experimental modifications can change that spectrum. The AFRL Co-60 cell spectrum is found to be a clean spectrum with small low energy contributions and dominant Co-60 photopeaks. Experimental modifications to reduce dose enhancement such as the use of a Pb/Al box and even better a Pb/Sn/Cu/Al box are found to decrease the low energy contributions. Experimental modifications to reduce dose rate such as using lead attenuators in front of the experiment and/or raising the source partially are found to significantly alter the spectrum, sometimes creating large low energy contributions.

The feasibility of a dose mapping system using Optically Stimulated Luminescent (OSL) Phosphors is demonstrated. The OSL technique is briefly reviewed as well as its interest for calculation codes calibration. The sensors and the reading apparatus are presented. An example of attenuation dose map obtained for a Dual In Line Plastic Package (DIL) is given and the results compared to calculations with the code EGS4 PRESTA. Results obtained by experiment and simulation are discussed as well as the potentialities of the method.

A new method is described for measuring ionizing radiation on spacecraft using an array of Floating gate Avalanche injected Metal Oxide Silicon (FAMOS) transistors. A commercial UltraViolet erasable Programmable Read Only Memory (UVPROM) is used to demonstrate the technique for both ground and space dosimetry applications. An indirect measurement of the charge remaining on the floating gate is used to determine the absorbed dose. This method of determining dose leaves the data and the detector intact and capable of further measurements. The device requires power only during readout. Measurements of different ionizing radiation types are presented. Results from an experiment using this technique aboard the Microelectronics and Photonics Test Bed (MPTB) satellite are discussed.

Total dose and dose rate performance of GaAs MESFET devices of various geometries and sidegating structures at various distances and orientations are presented. Parameters measured include low frequency noise, I-V curves and sidegating. The GaAs MESFET devices tested are shown to be useful to a total dose greater than 500 Mrad(GaAs). The observed reduction in drain current for a given bias point versus total dose is believed to e due to the sinking gate effect. The post irradiation degradation of 1/f noise performance shows a Lorentzian component which grows continuously with total dose to 1 Grad(GasAs). The during irradiation noise peformance exhibits a dose rate dependent Lorentzian component. This component has been named selfgating dose rate noise. The sidegating effect exhibits a dose rate dependent degradation which decreases with increasing distance at low dose rates and saturates at a dose rate of approximately 150 krad(GaAs)/hour. The dose rate dependent sidegating effect is reduced with accumulated total dose.

We have studied transient irradiation effects on the optical and electrical responses of a laser diode. The influence of dose rate, ranging from [10.sup.9] to [10.sup.12] rad(Si)/s, has been investigated through a complete experimental study. Dose rate vulnerability of the laser diode has been observed. Electrical and optical transient responses are determined by the dose rate, the diode structure, and its operating point.

Open air three electrode (point-grid-plane) corona streamer counter with a preamplification gap has been utilized for detecting weakly ionizing beta rays. This is based on the fact that when the primary electrons produced by beta rays are multiplied in the external preamplification gap, they form a trigger electron swarm before entering the counter, produce the same effect as the direct incidence of strongly ionizing particle in the corona counter, and allow the counter to operate efficiently. However, operation of this counter in open air as one of its most attractive features requires a complete analysis of the counter response to the changes of ambient conditions. The effect of temperature on the beta particle corona counter performance is studied. A theoretical model is suggested to calculate the counter operating voltage as well as the beta particles triggered corona pulse characteristics at different temperatures (20 [degrees] C-50 [degrees] C). The temperature effects on the counter-energy response is explained. A compensation for the errors due to temperature effects is suggested. All the theoretical findings are confirmed by experiments.

An optical ionizing radiation detector, based on the attenuation of 850-nm light in 50/125-||micro~meter~ multimode fibers, is described. The detector is especially well suited for application on spacecraft because of its small design. The detection element consists of a section of coiled fibers that has been designed to strip higher-order optical modes. Cylindrical radiation shields with atomic numbers ranging from Z = 13 (aluminum) to Z = 82 (lead) were placed around the ionizing radiation detector so that the effectiveness of the detector could be measured. By exposing the shields and the detector to 1.25-MeV cobalt 60 radiation, the mass attenuation coefficients of the shields were measured. The detector is based on the phenomenon that radiation creates optical color centers in glass fibers. Electron spin resonance spectroscopy performed on the 50/125-||micro~meter~ fibers showed the presence of germanium oxide and phosphorus-based color centers. The intensity of these centers is directly related to the accumulated gamma radiation.

The use of coiled optical fibers as radiation detectors was evaluated. The sensitivity of the detector and shielding effectiveness of the materials were tested by placing the coiled fiber sensors in metallic and metal-matrix composite cylinders. Sensitivity range was measured at ten to 100 kRad with accurate prediction of mass-attenuation coefficients of shielding materials. However, there is limited access to the detector because space applications requires it to be remote.

Fibre optics, exposed to ionising radiation, exhibit enhanced transmission loss. Recovery processes can take place over a wide time scale and, for extended exposures, as in space, will limit the observed loss. Prediction of the survivability of a fibre optic link in such an environment requires knowledge of the form of the recovery over a time comparable with the mission duration. The use of an Optical Time Domain Reflectometer to make the appropriate measurements with the necessary accuracy and sensitivity is discussed, and results are presented for recovery curves, extending to time >1 year, for a number of fibre types.

An investigation of thin film polymer electrets formed by ionizing radiation in air and their charge distributions are presented. The latter were evaluated in terms of several applied voltages and the air gap widths of electret ionization chambers (EIC). A discussion on the effects of the charging and discharging process on the distribution pattern and the linear reaction of the EICs to exposure is also included.

The ionizing radiation response of pMOSFETs used as dosimeters (RADFETs) is compared for Co-60 gammas and high-energy protons. For comparable Co-60 and proton doses, RADFET response for high-energy protons (60-200 MeV) was found to be only 65-85% of their Co-60 response. This difference is not fully understood but is shown to be partially a result of increased columnar recombination in [SiO.sub.2] for high-energy proton irradiation. Index Terms--Cobalt, proton radiation effects, protons, radiation detectors, radiation effects.

We describe systematic measurements carried out with single and double GEM detectors with printed circuit read-out. The maximum safe operating gain has been measured at increasing radiation flux and under exposure to heavily ionizing tracks. Detection efficiency, localization accuracy and cluster size have been measured in a minimum ionizing particle beam. With a suitably configured readout electrode, fast, two-dimensional localization of radiation is demonstrated.

Comprehensive tables of the spectra of numerous highly ionized heavy atoms have been published as a new monograph associated with the Journal of Physical and Chemical Reference Data. The monograph […]

Corona and induction charging mechanisms are frequently associated in modern roll-type electrostatic separators. Various electrode configurations have been proposed and numerous attempts have been made in order to fully characterize them. This paper approaches this problem from a computational point of view. The boundary-element method is employed for analyzing the electrostatic field distribution generated by a typical arrangement, consisting of a wire-type corona electrode and an ellipse-profile nonionizing electrode. The computed results pointed out the effect of various parameters on the uniformity of the electric field near the ionizing element and at the surface of the grounded rotating roll electrode. These data can be used by the designer in order to improve the electrode configuration, produce a uniform field in the active zone of the separator, and reduce the corona inception voltage. At the same time, they validate two important premises for the mathematical modeling of the combined corona-electrostatic field of a roll-type separator: 1) Peek's law can be used for evaluating the electric field strength at the surface of the wire electrode at corona onset in any of the usual electrode configurations and 2) the distribution of the electric field in the active zone of the separator is affected only by the geometry of the high-voltage electrode system. Index Terms--Boundary-element method, computational electrostatics, corona, electric field, electrostatic separation, ionized fields.