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High energy radiation treatment of foodstuff for microbial control and shelf-life extension is being used in many countries. However, for consumer protection and information, the European Union has adopted the Directives 1999/2/EC and 1999/3/EC to harmonize the rules concerning the treatment and trade of irradiated foods in EU countries. Among the validated methods to detect irradiated foods the EU directives also include Electron Paramagnetic Resonance (EPR/ESR) spectroscopy. We describe herein the use of EPR for identification of four species of bivalve mollusks, i.e. brown Venus shells (Callista chione), clams (Tapes semidecussatus), mussels (Mytilus galloprovincialis) and oysters (Ostrea edulis) irradiated with 60Co γ-rays. EPR could definitely identify irradiated seashells due to the presence of long-lived free radicals, primarily CO2−, CO33−, SO2− and SO3− radical anions. The presence of other organic free radicals, believed to originate from conchiolin, a scleroprotein present in the shells, was also ascertained. The use of one of these radicals as a marker for irradiation of brown Venus shells and clams can be envisaged. We also propose a dosimetric protocol for the reconstruction of the administered dose in irradiated oysters.

Treatment of food with ionising radiations in order to increase its shelf-life is largely employed in many countries. Because of restrictions issued by different governments on the use of this technique, in addition to the identification of irradiated foodstuffs, it may be important to determine the radiation dose administered to the foodstuffs. An EPR based protocol to reconstruct the administered dose from samples of irradiated meats (rabbit, pork and duck) within an uncertainty of ±25% is reported. © 2010 Elsevier Ltd.

An easy-to-use and robust energy monitoring device has been developed for reliable detection of day-to-day small variations in the electron beam energy, a critical parameter for quality control and quality assurance in industrial radiation processing. It has potential for using on-line, thus providing real-time information. Its working principle is based on the measurement of currents, or charges, collected by two aluminium absorbers of specific thicknesses (dependent on the beam energy), insulated from each other and positioned within a faraday cup-style aluminium cage connected to the ground. The device has been extensively tested in the energy range of 4–12 MeV under standard laboratory conditions at Institute of Isotopes and CNR-ISOF using different types of electron accelerators; namely, a TESLA LPR-4 LINAC (3–6 MeV) and a L-band Vickers LINAC (7–12 MeV), respectively. This device has been also tested in high power electron beam radiation processing facilities, one equipped with a 7-MeV LUE-8 linear accelerator used for crosslinking of cables and medical device sterilization, and the other equipped with a 10 MeV Rhodotron TT100 recirculating accelerator used for in-house sterilization of medical devices. In the present work, we have extended the application of this method to still lower energy region, i.e. from 1.5 to 2.4 MeV. Also, we show that such a device is capable of detecting deviation in the beam energy as small as 40 keV.

Commercial silicate glass has been investigated as a possible high dose dosimeter using an UV–vis spectrophotometer. Glass samples were irradiated by 60Co γ rays and the results compared with those obtained with 3.4 and 8.4 MeV electron beams. The irradiated samples showed rapid fading at room temperature immediately after irradiation. In order to improve the stability of absorbance, glass samples were submitted to post-irradiation thermal treatments (150 °C for 20 min). The influences of the dose, type and energy of the ionizing radiation on the fading characteristics and on the response of the irradiated and thermally treated glasses were studied. Dependence of the glass response on the temperature during gamma irradiation in the range −3 to 80 °C is reported. The reproducibility to reuse glass dosimeter by thermal bleaching the radiation induced colour centres at 300 °C for 30 min was also investigated. Calibration curves in the range 0.1–17 kGy were obtained by using in-plant calibration techniques against transfer standard alanine dosimeters in the Tunisian semi-industrial gamma irradiation facility.

A bipolar transistor, previously investigated as a possible radiation dosimeter and tested under industrial irradiation conditions in high-activity gamma and high-energy, high-power electron beam facilities has been subjected to stability test in order to understand its behaviour and help to improve its performances. Charge carrier lifetime was measured for several sets of transistors which were then irradiated with various doses (3–60 kGy): seven sets with 60 Co gamma rays and eight with a 10 MeV electron beam. After irradiation all the transistors were measured and each set was divided into three groups: one group was left untreated, the second group was heated at 100 °C for 30 minutes and the third group was heated at 150 °C for 30 minutes, for testing the stability of the lifetime. Our data showed that heat treatment quite successfully eliminates post-irradiation changes in the response. Response measurements of the irradiated transistors, heat-treated and untreated, were carried out at room temperature over several weeks after irradiation to establish post-irradiation stability and assess if these transistors could be used for recording dose history. Calibration curves in the range 3–60 kGy for the thermally treated and untreated devices are presented. Dependence of the response of the transistors on the temperature of the measurements in the range 20–50 °C is reported.

We investigate Total Ionizing Dose effects on 4 Mbit Phase Change Memories (PCM) arrays. We demonstrate a high robustness of PCM against ionizing radiation. We irradiated PCM with 8-MeV electrons. Only small variations are measured in the cell distributions after irradiation. The primary cause of these variations is the degradation of the Bit-Line and the Word-Line selector MOSFETs. Finally, radiation does not compromise the functionality of the SET and the RESET operations.

Gamma-irradiated NaCl samples of different origin were studied with the aim to find a reliable, easy-to-use, low-cost standard for the PSL technique, an increasingly used screening method for irradiated food identification. Five different natural salt types (rock and sea salts) purchased in the local markets were studied along with a laboratory-grade NaCl. High sensitivity and reproducibility of the PSL response are good properties of salt, but the pronounced fading of the signal may be a severe limitation of its use as a reference material. The high sensitivity along with the linear dose dependence of the PSL response opens up the interesting possibility of salt as suitable material for retrospective and environmental dosimetry, especially in the case of accidental irradiation or malevolent use of ionizing radiation. Again, the extreme sensitivity of the PSL signal to light and the pronounced fading must be considered limiting factors, and further basic research is required before practical applications of salt be feasible.

Reliability of the photo-stimulated luminescence (PSL) technique, as screening method for irradiated food identification, has been tested with three kinds of herbs and spices (oregano, red pepper and fennel), prepared in two different ways (granular: i.e. seeds and flakes, or powdered), over a long period of storage with different light exposures. The irradiated samples kept in the dark gave always a positive response (the sample is correctly classified as “irradiated”) for the overall examination period. The samples kept under ambient light conditions, in typical commercial glass containers, exhibited a reduction of the PSL signal, more or less pronounced depending on the type of food and packaging. The different PSL response of the irradiated samples is to be related to the quantity and quality of the mineral debris present in the individual food. It was also found that, for the same type of food, the light-induced fading was much stronger for the flaked and seed samples than for the corresponding powder samples, the penetrating capability of light being much more inhibited in powdered than in whole seeds or flaked form samples. The observed light bleaching of the PSL signal in irradiated herbs and spices is of practical relevance since it may lead to false negative classifications.

The electron beam energy is one of the critical parameters for electron processing, since it can affect the dose distribution in the product. We have developed a robust device for monitoring small variations in the electron beam energy that is easy-to-use during an irradiation run. It involves measurement of currents intercepted by two aluminium plates located in the beam. The ratio of these two currents is quite sensitive to the beam energy; sensitivity is optimised by selecting the appropriate thickness of the front plate depending on the beam energy. We had reported on this energy device earlier for the energy range of 7–12 MeV. In the present paper, we have investigated the feasibility of using this energy device at lower energies, from 4 to 6 MeV.

Deep level transient spectroscopy(DLTS) and capacitance-voltage (C-V) characteristics were used to investigate the effects induced by electron irradiation on the majority carrier traps in Schottky diodes prepared on 4H silicon Carbide (SiC) epilayers grown by chemical vapour deposition (CVD). Electron beam induced current (EBIC) method was applied to measure the change in minority carrier diffusion length L related to the generation of traps by electron irradiation. Several energy levels were detected and their concentration monitored as a function of the irradiation dose. The correlation with the diode charge collection efficiency is also reported.

Plasma treatments are widely used in microelectronic industry, but they may leave some residual passivated damage in the gate oxides at the end of the processing. The plasma-induced damage can be amplified by metal interconnects (antenna) attached to the gate during the plasma treatments. Ionising radiation reactivates this latent damage, which produces enhanced oxide charge and Si/SiO2 interface state density. Two CMOS technologies have been investigated, with 5 and 7 nm gate oxides. Threshold voltage shifts, transconductance decrease, and interface traps build-up are always larger for plasma damaged devices than for reference devices.

Films of polymethylmethacrylate (PMMA) and polystyrene (PS) containing alpha-terthiophene (3T) undergo a radiochromic effect when exposed to electrons and gamma rays. The films turn either red-green or red, due to the formation of oligomeric radical cations. In both matrixes, absorbance at 465 nm grows linearly with dose when alpha-terthiophene concentration reaches 12%. Explored range goes up to ~ 2 x 10^6 Gy, with dose rates spanning over three orders of magnitude. Concerning their application as dosimeters, a higher sensitivity characterises the 3T-PMMA moiety, suggesting its suitability from the kGy range up to 1 MGy. Above this value films become fragile. 3T-Polystyrene films are less sensitive, but more radiation resistant. Therefore they better suit the medium-to-high dose dosimetry range. Dose rate influences the response sensitivity in a complex way, however above 80 and up to 3.6 x 10^4 Gy/min an approximate linearity exists between log(dose rate) and sensitivity, as in the analogous cellulose triacetate system.

When a non-conducting plastic block is irradiated with high-energy electrons, the thermalised electrons are trapped in the block if the range of the incident electrons is less than its thickness. These stored charges set up an electrostatic field in the block that can affect the trajectories of the incident electrons. The strength and the shape of the field depend on the intrinsic properties of the material as well as on the irradiation geometry. For this study, we selected various commercial electrical insulators such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene (PE), Teflon (PTFE), polyvinylchloride (PVC) and nylon. We measured the influence of the electrostatic field on depth-dose distribution in these materials using GafChromic® film dosimeters, and the subsequent leakage of the stored charge. This is an extension of our previous work on PMMA. The effect on the depth-dose distribution was most pronounced in PMMA, while in PTFE and PE it was minimal. On the other hand, PC showed an intermediate behaviour. Nylon and PVC electrically broke down at low doses. We have attempted an explanation of this behaviour of the various plastics based on radiation-induced conductivity, the measured leakage charge and also on their intrinsic electrical properties such as dielectric constant and dielectric strength.

PMMA-rubber blends are formed through electron beam induced in situ polymerisation. The influence of rubber nature and irradiation dose has been investigated through mechanical tensile tests, solubility analysis and the results were related to material structure investigated through atomic force microscopy. Some blend formulations present a significant increase of ductility with respect to pure PMMA, without a dramatic decrease of modulus, yield stress and stress at break values. The results are interpreted on the basis of the criterion of the critical inter-particle thickness.

The radiation-induced UV-vis spectrum of α -terthiophene radical cation in solid is reported. The radical cation initiates an oligomerization in the CTA matrix producing permanently coloured conjugated polarons. The specific net absorbance at 465 nm is linearly related with dose up to 2×10 6 Gy, for electrons and gamma irradiation. The decrease of the UV typical absorption (355 nm) and of four IR bands of α -terthiophene is linear with dose, as well. Although sensitivity is influenced by dose rate, it turned out that a linear relationship holds between sensitivity and log dose rate, in the range from 2 to 10 5 Gy/min. These findings suggest a potential application of the system for dosimetric purposes over a wide range of dose and dose rate.

The OSL (optically stimulated luminescence) based Sunna film containing a microcrystalline dispersion of LiF in a polymer matrix has been recently introduced for high-dose dosimetry. Our previous investigations revealed the applicability of the system in the dose range of 0.01–100 kGy, but irradiation temperature and dose rate effects above 5 kGy reduced its usefulness. The recent discovery of the use of spectrophotometric analysis in the UV range for measuring doses above 5 kGy is a suitable option, while the OSL analysis can be applied for measuring lower doses due to the lack of temperature effect on the response of the film below 1 kGy. The film can be applied both in gamma and electron fields, although its response to the two types of radiation is somewhat different. No significant effects of UV light and humidity have been found, and effects of irradiation temperature are only significant in the case of OSL analysis for doses above 5 kGy. The applicability of two types of Sunna films in electron and gamma radiation processing is discussed in the paper.

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.

MOS capacitors with 8 nm thick oxides have been irradiated by an 8 MeV LINAC electron beam. C-V and I-V measurements have shown a positive trapped charge, higher for irradiation performed under negative gate bias, as a consequence of preferential charge recombination at the cathodic interface. No saturation of the positive trapped charge is measured up to 20 Mrad(Si). Neutral defects induced by irradiation have been studied, by performing positive and negative Fowler-Nordheim injection. The distribution of neutral defects is similar to that of trapped holes, indicating a correlation between trapped holes and neutral defects. Electrical stresses performed after irradiation have shown that the accumulation kinetics of oxide defects is similar in both unirradiated and irradiated devices.

Irradiated CaSO 4 :Dy, a well known thermoluminescent material widely employed for personal and environmental dosimetry, was studied by electron paramagnetic resonance spectroscopy in the 10 3 − 10 7 Gy dose range. A reliable dose assessment can be performed in that range by measuring the concentration of the radiation induced paramagnetic centers (SO 3 ) − and (VCa) 2− . (VCa) 2− center was very stable over time while (SO 3 ) − center showed a dose dependent fading. Dose dependent sensitization effects in the yield of both centers were also observed up to about 10 6 Gy.

This paper reports on the influence that temperature during irradiation and dose-rate have on the radiation-induced free-radical yield and time stability in non de-proteinized bone. Bone from chicken legs was irradiated in the 253-293 K temperature range and with two different sources (60Co, 0.6 Gy/s and 12 MeV electrons, 6 x 10(6) Gy/s). Temperature influences type and number of radicals, while radical concentration seems to slightly decrease with dose rate.

Transistors used as switches in horizontal deflection circuits for high definition TV and Video Display Terminals were subjected to electron irradiation using a 12 MeV linear accelerator. The use of electron irradiation has made possible a fine control of the charge carrier lifetime thus improving the switching time and greatly reducing the power losses at turn-on and turn-off. Devices able to work at horizontal deflection frequency from 32 kHz up to 64 kHz, 1.2–1.5 kV and to handle current between 2 and 10A have been obtained. The effects of the thermal processes, that the irradiated devices undergo during assembly and packaging operations, have been investigated.

Starting from 1982, research in the field of electron irradiation of power semiconductor devices has been conducted in Italy on experimental basis. The use of high energy electrons for carrier lifetime control in these devices has been widely investigated. In collaboration with the three major Italian power semiconductor firms, Ansaldo, IRCI and SGS-Thomson Microeletronics, series of irradiation tests have been performed on fast diodes and thyristors, GTO thyristors, power MOS transistors and insulated gate bipolar transistors in order to achieve modelling of the electrical parameters and specific adjustment of carrier lifetime. The radiation-induced defects in silicon have been studied and characterized by the DLTS technique. The optimum conditions for radiation processing of different types of fast switching power devices with medium and high blocking capabilities have been determined. Diodes and thyristors, in all power categories, which did not have the required switching and release times after diffusion, were properly adjusted by irradiation thus saving them from rejection. The results obtained have led the above mentioned firms to use this technology for series production in place of the conventional high-temperature heavy metal diffusion for lifetime control. Equipment and methods for series production have been developed, tested and put into operation.

The radiation response of FOXFETs (field oxide FETs) has been studied for proton, gamma, and neutron exposures. It is shown that the punch-through (PT) conduction mechanism is much less sensitive to radiation damage than the usual surface conduction in FOXFETs. The threshold voltage is strongly affected by the huge buildup of positive charge in the thick gate oxide. This effect can be reduced by decreasing the oxide thickness, but this modification seems to be unnecessary for detector applications. In fact, variations of a few volts of the PT voltage after irradiations in the Mrad range will result in a corresponding similar increase of the strip self-bias in detectors. Such modifications are still acceptable, and can be properly compensated by a suitable increase of the detector backside bias in order to ensure full depletion operation. It is also shown that the radiation-induced variations of the PT voltage can be tailored by the proper choice of the gate bias. Computer simulations have shown that the main radiation effects affecting the PT mechanism are the charge accumulation in the oxide and substrate-type inversion. >

A 12 MeV linear accelerator is currently used for electron beam processing of power semiconductor devices for lifetime control and, on an experimental basis, for food irradiation, sludge treatment etc. In order to control the irradiation process a simple, quick and reliable method for a direct evaluation of dose and fluence in a broad electron beam has been developed. This paper presents the results obtained using a “charge collector” which measures the charge absorbed in a graphite target exposed in air. Calibration of the system with super-Fricke dosimeter and comparison of absorbed dose results obtained with plastic dosimeters and alanine pellets are discussed.

High-frequency operation of electronic lamp ballasts is made possible by the controlled reduction of carrier lifetime in the base-collector junction of the two power transistors present in the circuit. The electron irradiation allows excellent control of the lifetime and, as a consequence, of the power transistors storage time on which the main operation parameters, working frequency and lamp power, depend. The recovery of the radiation induced defects, caused by the thermal processes that the irradiated devices undergo during packaging operations, has been investigated.

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.

This report is a short review of the work done in Italy on the electron irradiation of power semiconductor devices. Electron irradiation for carrier lifetime control has been investigated using a 12 MeV linear accelerator. These studies includes: modeling of electrical semiconductor component parameters, specific adjustment of carrier lifetime, DLTS measurements to identify and characterize the radiation-induced defects. The optimum conditions for radiation processing of various types of power diodes and thyristors have been determined. Equipment and methods for series production have been developed and tested with pilot production quantities, then put into operation for mass production.

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.

The use of silicon devices as possible radiation monitors and/or dosimeters has been considered since many years because of the effect of ionizing radiation on the physical and electrical properties of these devices. A bipolar transistor investigated under standard laboratory conditions and in industrial irradiation plants having high-activity γ- source and high-energy, high-power electron beam was found to be suitable as routine radiation dosimeter. Tests carried out by irradiating the transistor with electron beams of energy ranging from 2.2 up to 8.6 MeV and 60 Co γ-rays have shown that the response of this transistor is energy dependent. DLTS measurements have been performed on the irradiated devices to identify the recombination centers introduced by the radiation treatment. The influence of radiation energy on the behavior of this device is discussed.

The Sunna dosimeter was introduced for dose determination in the dose range of 50–300 kGy by measuring optically stimulated luminescence. The usefulness of the dosimeter film has already been shown in food irradiation for routine process control. The aim of the present study was to check the performance of the Sunna dosimeter film for process control in radiation sterilization under industrial processing conditions, i.e. at high activity gamma irradiators and at high energy electron beam facilities. To ensure similar irradiation conditions during calibration and routine irradiation “in-plant calibration” was performed by irradiating the Sunna dosimeters together with ethanol–monochlorobenzene transfer standard and alanine reference standard dosimeters. The Sunna dosimeters were then irradiated together with the routine dosimeter of the actual plant during regular production runs and the absorbed doses measured by the different dosimeters agreed within ±2%(1 σ ).