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Poly(vinyl alcohol) (PVA) films containing methyl viologen (MV2+) that colours blue upon exposure to ionizing radiation were investigated as possible dosimeters for use in radiation processing applications. In order to find the most suitable composition of the PVA-MV2+ film, different concentrations of the dye have been studied. The absorbance values at selected wavelengths, obtained from irradiation of the PVA film containing the most suitable MV2+ concentration, can be satisfactorily related to the absorbed dose over a wide range, from 50 Gy up to 40 kGy. The effects of dose, dose rate, humidity and temperature on the response of the PVA-MV2+ dosimeter film have been studied under laboratory conditions. We conclude that the PVA film containing MV2+ is a promising tool for the absorbed dose measurements in several industrial applications of ionizing radiations.

The electron beam energy monitoring device, previously developed and tested under standard laboratory conditions using electron beams in the energy range 4-12 MeV, has now been tested under industrial irradiation conditions in high-energy, high-power electron beam facilities. The measuring instrument was improved in order to measure high peak current delivered at low pulse repetition rate as well. Tests, with good results, were carried out at two different EB plants: one equipped with a LUE-8 linear electron accelerator of 7 MeV maximum energy used for cross-linking of cables and for medical device sterilization, and the other with a 10 MeV Rhodotron type TT 100 used for in-house sterilization. © 2009 Elsevier Ltd. All rights reserved.

Two different types of window glasses have been investigated as possible routine dosimeters in the range of 1-50 kGy. Glass samples were irradiated with 3.4 MeV and 8.4 MeV electron beams, and the results compared With those obtained by (60)Co gamma irradiation. Due to the strong optical absorption at wavelengths < 3 10 run, even at low closes, Optical measurements were limited to the range 320-700 nm. In both types of glasses, irradiation induced two absorption hands around 410 and 600 run the intensities of which are proportional to close: the 600 nm hand being less sensitive to radiation. These hands have been attributed to non bridging oxygen hole centres existing in two different configurations. Because of the rapid fading of the optical absorbance observed at room temperature immediately after irradiation (> 15% in two days), the samples underwent it post-irradiation thermal treatment (150 degrees C For 20 min) to improve the stability of absorbance. The fading characteristics of the irradiated and thermally treated glasses, kept in the dark at room temperature, were studied for several weeks. A fast decay, whose intensity depends oil the type and energy of the ionizing radiation, wits observed for few clays after irradiation and thermal treatment, followed by a much slower decay. The results Show that this kind of material could be used as routine dosimeters within it certain dose range, its long its proper calibrations are made for each batch of glass and the appropriate precautions are taken when doing calibration and performing routine dosimetr

Results of the characterization studies on a power bipolar transistor investigated as a possible radiation dosimeter under laboratory condition using electron beams of energies from 2.2 to 8.6 MeV and gamma rays from a Co-60 source and tested in industrial irradiation plants having high-activity Co-60 gamma-source and high-energy, high-power electron beam have previously been reported. The present paper describes recent studies performed on this type of bipolar transistor irradiated with 1.9 and 2.2 MeV electron beams in the dose range 5-50 kGy. Dose response, post-irradiation heat treatment and stability, effects of temperature during irradiation in the range from -104 to +22 degrees C, dependence on temperature during reading in the range 20-50 degrees C, and the difference in response of the transistors irradiated from the plastic side and the copper side are reported. DLTS measurements performed on the irradiated devices to identify the recombination centres introduced by radiation and their dependence on dose and energy of the electron beam are also reported.

Atmospheric neutrons are a known source of Soft Errors (SE), in static and dynamic CMOS memories. This paper shows for the first time that atmospheric neutrons are able to induce SE in Flash memories as well. Detailed experimental results provide an explanation linking the Floating Gate (FG) cell SE rate to the physics of the neutron-matter interaction. The neutron sensitivity is expected to increase with the number of bits per cell and the reduction of the feature size, but the SE issue is within the limit of current ECC capabilities and will remain so in the foreseeable future.

Summary Reliability of the photo-stimulated luminescence (PSL) technique, both as screening and identification methods, has been tested with several kinds of irradiated herbs and spices over a long period of storage. To check the influence of storage modality on the PSL response, the samples were divided into groups kept in environments with different light exposure. The results clearly indicate a marked light-induced bleaching of the PSL signal, which may lead to a false negative classification, in a significant percentage, for spices stored in typical market conditions. To limit the occurrence of wrong classifications, the suggestion reported in the European Committee of Normalization Standard 13751 to draw the necessary amount of product from a light-protected position becomes mandatory. Thermoluminescence measurements, performed for comparison purposes, gave correct results for all the samples tested.

A bipolar transistor, previously investigated as a possible radiation dosimeter, has been tested under industrial irradiation conditions in high-activity gamma and high energy, high-power electron beam facilities. In-plant calibrations have been performed against transfer standard alanine and reference standard ethanol-monochlorobenzene (ECB) dosimeters over an absorbed dose range of 5-45 kGy. Routine irradiations have been done by placing the transistors, side-by-side with the routine dosimeters used in the plants, on product boxes during production runs. The results of the studies have shown that the agreement between the absorbed dose measured by the transistors and other well established routine dosimeters is within +/-3% (1sigma). This indicates that this type of transistors could be used as routine radiation dosimeters in the dose range investigated. (C) 2004 Elsevier Ltd. All rights reserved.

Particles detectors were made using semiconductor epitaxial 4H-SiC as the detection medium. The investigated detectors are formed by Schottky contact (Au) on the epitaxial layer and an ohmic contact on the backside of 4H-SiC substrates with different micropipe densities from CREE. For radiation hardness studies, the detectors have been irradiated with electrons (8.2 MeV) and g-rays (60Co source) at fluences and doses ranging from 0 to 9.48×10exp14 e/cm2 and 40 Mrad, respectively. We present experimental data on the charge collection properties by using 4.14 MeV alpha-particles impinging on the Schottky contact. Hundred percent Charge Collection Efficiency, CCE, is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the alpha-particle projected range, even after the irradiation at the highest dose. By comparing measured CCE values with the outcomes of drift-diffusion simulations, values are inferred for the hole lifetime within the neutral region of the charge carrier generation layer. Hole lifetime was found to decrease with increasing radiation levels, ranging from 300 ns in non-irradiated detectors to 3 ns in the most irradiated ones. The diffusion contribution of the minority charge carriers to CCE is pointed out.

An α-terthiophene/cellulose triacetate film system exposed to γ-rays and electron beam shows two new bands in the visible region of the spectrum. The absorbance at 490 nm is almost stable for a long time and responds linearly to the dose applied up to 400 kGy. A second band developed at 700 nm depends on dose rate and may indicate a chain-growth. The main species responsible for the color change and EPR signal is likely to be an enlarged oligomer radical cation stabilized by a semiquinoid structure.

We have investigated the degradation of MOS structure due to high energy electron irradiation as a function of radiation dose and gate bias applied during the irradiation. Devices have been characterized by current–voltage measurements, in order to study charge accumulation also at the gate interface. Three types of oxide charge have been observed: the unstable positive charge, due to trapped holes induced by the electron irradiation; the negative charge in the oxide bulk, deriving from capture of electrons injected during electrical measurements in radiation generated traps; and border traps, at both oxide interfaces.

Many applications of silicon p/sup +/-n junctions as detectors require high voltage operation. In particular the LHC experiments, because of the radiation damage level, need very high bias working voltage to fully collect the ionising generated charge multi-guard structures can be used in order to improve the breakdown voltage of microstrip detectors, limiting the occurrence of critical fields in the proximities of a reverse biased p/sup +/-n junction. In this work we present results for different designs of multi-guard structures, before and after irradiation with ionising and non-ionising radiation sources (p,n,/spl gamma/), and for different doses. Various experimental techniques have been used, like DC and AC electrical characterizations, and light emission microscopy. Moreover, a simulation work is presented. Its purpose is to improve the design on the basis of the experimental results.

The effect of carnosine on irradiation inactivation kinetics of Aeromonas hydrophila was studied. In phosphate buffer, carnosine had no effect on survival of the pathogen, whereas in turkey meat supplemented with carnosine the adverse effect of irradiation on A. hydrophila was reduced. Peroxy radicals were toxic to A. hydrophila, and this effect was counteracted by carnosine. Accordingly, in a kinetic test carnosine was capable of scavenging peroxy radicals. These results indicate that a free radical scavenger antioxidant such as carnosine can increase the radiation resistance of A. hydrophila in meat due to the inhibition of lipid peroxidation

High-voltage operation can be a solution to obtain full charge collection in strongly irradiated silicon detectors. The maximum bias voltage which can be applied is limited by the breakdown point of the junction. We show how multiguard structures can enhance the breakdown voltage in p+–n silicon devices designed for applications in the LHC environment.

MOS capacitors with a 4.4 nm thick gate oxide have been exposed to /spl gamma/ radiation from a Co/sup 60/ source. As a result, we have measured a stable leakage current at fields lower than those required for Fowler-Nordheim tunneling. This Radiation Induced Leakage Current (RILC) is similar to the usual Stress Induced Leakage Currents (SILC) observed after electrical stresses of MOS devices. We have verified that these two currents share the same dependence on the oxide field, and the RILC contribution can be normalized to an equivalent injected charge for Constant Current Stresses. We have also considered the dependence of the RILC from the cumulative radiation dose, and from the applied bias during irradiation, suggesting a correlation between RILC and the distribution of trapped holes and neutral levels in the oxide layer.

We have studied the effects of ionizing and non-ionizing radiation on the breakdown properties of different types of MOS capacitors, with thick (200 nm) and thin (down to 8 nm) oxides. In general, no large variations of the average breakdown field, time-to-breakdown at constant voltage, or charge-to-breakdown values have been observed after high dose irradiation (20 Mrad(Si) 9 MeV electrons on thin and thick oxides, 17(Si) Mrad Co/sup 60/ gamma and 10/sup 14/ neutrons/cm/sup 2/ only on thick oxides). However, some modifications of the cumulative failure distributions have been observed in a few of the oxides tested.

pMOSFETs biased with V/sub gs/