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Background: An ultra‐high dose rate (UHDR) electron accelerator for FLASH radiotherapy (RT) produces very intense bremsstrahlung by the interaction of the electron beam with objects both inside and outside of the accelerator. The bremsstrahlung dose per pulse is typically 1–2 orders of magnitude larger than that of conventional RT x‐ray treatment of the same energy, and for electron energies above 10 MeV, the bremsstrahlung produces substantially more induced radioactivity outside the accelerator than for conventional RT. Therefore, a thorough radiation safety assessment is mandatory prior to the operation of a UHDR electron accelerator. Purpose: To evaluate the radiation safety of a prototype FLASH‐enabled Varian TrueBeam accelerator and to develop a general framework for assessment of all key radiation safety properties of a UHDR electron accelerator for FLASH RT. Methods: Production of bremsstrahlung and induced radioactivity by a UHDR electron accelerator is modeled by various analytical methods. The analytical modeling is compared with National Institute of Standards and Technology (NIST) bremsstrahlung yield data as well as measurements of primary bremsstrahlung outside the bunker and induced radioactivity of irradiated thick targets for a FLASH‐enabled 16 MeV Varian TrueBeam electron accelerator. In addition, the analytical modeling is complemented by measurements of secondary bremsstrahlung inside/outside the bunker and neutrons at the maze entrance. Results: Calculated bremsstrahlung yields deviate maximum 8.5% from NIST data, and all measurements of primary bremsstrahlung and induced radioactivity agree with calculations, validating the analytical tools. In addition, it is found that scattering foil bremsstrahlung dominates primary bremsstrahlung and the main source of secondary bremsstrahlung is the irradiated object outside the accelerator. It follows that primary and secondary bremsstrahlung outside the bunker can be calculated using the same simple formalism as that used for conventional RT. Measured primary bremsstrahlung tenth‐value layers for concrete of the simple formalism are in good agreement with NCRP and IAEA data, while measured secondary bremsstrahlung tenth‐value layers for concrete are considerably lower than NCRP and IAEA data. All calculations and measurements form a general framework for assessment of all key radiation safety properties of a UHDR electron accelerator. Conclusions: The FLASH‐enabled Varian TrueBeam accelerator is safe for normal operation (max. 99 pulses per irradiation) in a bunker designed for at least 15 MV conventional x‐ray treatment unless the UHDR workload is much larger than the x‐ray workload. A similar finding applies to other UHDR electron accelerators. However, during beam tuning, radiation survey, or other tests with extended irradiation time, the UHDR workload may become very large, necessitating the implementation of additional safety measures. [ABSTRACT FROM AUTHOR]

The optical radiation in a gaseous medium upon the irradiation of a lithium layer with a fast electron beam of a 5 ns duration has been studied. The irradiation chamber was filled with argon, krypton, or xenon at a pressure of 10 kPa up to 60 kPa. The lines of lithium atoms appear in the emission spectrum at a lithium layer temperature of 650–680 K, and the intensity of these lines sharply increases with the increasing temperature of the lithium layer. The optical radiation arises from both the transitions of noble gas atoms and the transition of the lithium atom in a time of about 20–30 ns. The duration of the radiation pulses at half maximum at temperatures above 800 K was 60–100 ns at a wavelength of 610.4 nm and 140–220 ns at 670.8 nm in krypton and argon. The various mechanisms for the population of lithium levels during the radiation pulse are discussed. [ABSTRACT FROM AUTHOR]

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Radiation treatment of food products carried out to increase their shelf life can result in chemical transformations initiated by free radicals. Volatile compounds (alcohols, aldehydes, ketones, etc.) formed, in particular, as a result of lipid oxidation, impair the organoleptic properties of products. Method of gas chromatography-mass spectrometry (GC-MS) makes it possible to identify the fact of food processing by detection of volatile marker compounds: in the case of meat products, the existing standard brings under regulation detection of 2-alkylcyclobutanones, however, the products with a reduced fat content, such as turkey and chicken, require an alternative marker. The results of GC-MS study revealed the dependence of microbiological parameters and the content of various volatile organic substances in chilled turkey meat on the dose of electron radiation. It is shown that the total amount of alcohols, ketones and aldehydes (11 compounds) decreases exponentially with an increase in the absorbed dose. An increase in the radiation dose leads to a higher content of carbonyl compounds (aldehydes and acetone), which results in a specific taste and smell of the irradiated products. At the same time, the acetone concentration increases linearly with the absorbed dose, which makes it possible to use acetone as a potential marker of the degree of irradiation of low-fat meat products. Irradiation in the "working" doses (0.5–1 kGy) significantly suppresses the pathogenic microflora and keeps the organoleptic properties of the product. [ABSTRACT FROM AUTHOR]

Abstract: Radiation-induced demagnetization of permanent magnets is one of the most important issues of synchrotron radiation facilities, especially the next-generation light sources. In this paper, the radiation damage of the permanent magnet is investigated. The relative reduction of the magnetic field intensity of Nd2Fe14B magnet and its spatial distribution is derived with the radiation damage experiments carried out at a 2.5GeV electron beam. The radiation field as well as the radiation quantities related to the radiation damage, mainly including the absorbed dose and 1MeV equivalent neutron fluence are studied with Monte Carlo simulation. The radiation-induced demagnetization is analyzed based on the above results and fitted formulas are proposed to estimate the relative reduction of magnetic field intensity. Good agreement is found between the experiment data and fitted data. The variation of hysteresis loops before and after irradiation show that the remanence could not be restored to its original value by the remagnetization. [Copyright &y& Elsevier]

Abstract: The electron beam technology for flue gas treatment (EBFGT) has been developed in Japan in the early 1980s. Later on, this process was investigated in pilot scale in the USA, Germany, Japan, Poland, Bulgaria and China. The new engineering and process solutions have been developed during the past two decades. Finally industrial plants have been constructed in Poland and China. The high efficiency of SO x and NO x removal was achieved (up to 95% for SO x and up to 70% for NO x ) and by-product is a high quality fertilizer. Since the power of accelerators applied in industrial installation is over 1MW and requested operational availability of the plant is equal to 8500h in year, it is a new challenge for radiation processing applications. [Copyright &y& Elsevier]

Abstract: When a pulsed radiation is incident on an air-filled ionization chamber wherein the primary electrons are rapidly absorbed to become negative ions, it is known that the reciprocal of the ionizing current is linearly proportional to the reciprocal of the polarization voltage in the near saturation region. However, the relationship between the reciprocal of the ionizing current and the reciprocal of the polarization voltage will deviate from a simple linearity when the ion transit time in the ionization chamber is longer than the interval between the radiation pulses. Two thimble-type ionization chambers, one of which was designed and fabricated by us, were employed to measure the saturation curves of the ionization chambers in a pulsed Bremsstrahlung X-ray, which was generated with an electron accelerator. A model was developed to explain the shape of the measured saturation curves in the overlapping pulsed radiation, and the results of it were compared with the measured ones. The dependency of the shape of the saturation curve on the geometrical design of the ionization chambers in the pulsed radiation was discussed. [Copyright &y& Elsevier]

A novel technique is proposed for studying the effect of radiation treatment on sensitivity of energetic materials, based on irradiation of specimens by a series of pulses on an electron accelerator. Data obtained in experiments with silver azide crystals are reported. The explosion probability in irradiated specimens is shown to be a nonmonotonic function of the radiation dose, exhibiting a rise for low doses and a fall for high doses. The experimental data obtained agree with the divacancy model for heavy metal azide initiation. [ABSTRACT FROM AUTHOR]

The crosslinking of polyethylene by irradiation is a well known technology in the sanitary and heating pipe market. For more than 20 years, crosslinked polyethylene (PE-Xc) pipes have been used successfully in this market in dimensions up to 40 mm and wall thicknesses up to 4 mm. With the development of new crosslinking technology using irradiation in combination with higher energy (10 MeV) electron accelerators, together with an improved pipe conveying system, the crosslinking of polyethylene pipes has been extended up to 450 mm dia., 40 mm wall thickness and 12 m lengths. A general overview of the properties of large diameter PE-Xc pipe is presented, which include excellent resistance to crack growth. This new technology will extend the range of PE-X pipes for gas and water, as well as industrial applications. [ABSTRACT FROM AUTHOR]

Recently, electron-beam accelerators and gamma-ray sources, usually 60-Co, are the mostly used devices for radiation processing (Gamma and Electron Beam Irradiation Facilities, 2008). The electron-beam accelerators with conversion of electrons to X-rays merge the main advantages of both types of facilities, the high penetration ability of the photons from the gamma sources and the high power of the electron-beam devices. The University Centre of Electron Accelerators in Trencin is a research-oriented facility equipped by such a type of accelerator. The accelerated electrons can be converted to X-rays with continuous spectrum of energies up to 6.2 MeV via a tungsten target. The application possibilities of the device are wide thanks to this dual mode of operation (electron beam or X-ray beam) and wide range of applicable doses and also dose-rates. This paper deals with specification of material characteristics of irradiated targets in order to determine the suitable type of radiation to be used. The Monte Carlo based simulation codes were employed to calculate the behaviour of electrons and X-rays in matter according to its density and chemical composition. The wooden cultural heritage artefacts are presented as an example of utilizing both types of radiation (electron beam and X-rays) for processing depending on the artefacts' dimensions. • First report on disinfection of wooden artefact from woodworms by electron beam. • The maximal thicknesses of materials for electron-beam treatment simulated. • The dose depth distribution of 5 MeV electrons in artefact wood verified. • Electron-beam to X-ray conversion efficiency determined. • X-ray and electron-beam mode of electron accelerator utilized for disinfection. [ABSTRACT FROM AUTHOR]

The paper presents the principle of operation and the results of tests of an electron accelerator designed to obtain bremsstrahlung X-ray radiation. The accelerator was assembled according to the Blumlein scheme with a gas spark gap and a matching pulsed autotransformer forward of a vacuum electron diode with an explosive emission cathode. The main parameters of the accelerator were as follows: accelerating voltage 300–450 kV; half-amplitude pulse duration 80 ns; current in a vacuum diode 6–10 kA; pulse repetition rate 2 pps (can be increased up to 10 pps in a pulse burst mode of ∼ 1000 pulses). The voltage and current are given for the matched mode of the Blumlein and diode operation. Pulse-to-pulse fluctuations of the diode voltage were less than 10% for 10-pps operation mode. The variation of the accelerating voltage was provided by changing the pressure in a gap and by the magnitude of the initial voltage in the power supply. The absorbed dose of over 5 mGy per pulse was obtained when constructing a metred polar converter of bremsstrahlung X-ray radiation. [ABSTRACT FROM AUTHOR]

There is extensive, published research on the use of high energy irradiation for the modification of textiles, hut no reports pertaining to the use of this technique for the direct fixation of dyes could be found. This study demonstrates that dyes containing activated vinyl groups can be fixed with good yields on cellulose by means of high energy irradiation. The majority of the experiments were performed using high energy electrons, but gamma rays from a cobalt-60 source were shown to give similar results. The mechanism is believed to be grafting by vinyl addition to polymer radicals formed on irradiation. The fixed dyes exhibit good fastness and cannot be extracted from the fiber with an azeotrope of pyridine/water, or boiling N,N-dimethylformamide. To estimate the potential for fixation of a particular dye by irradiation, a method was developed which is based on redox initiated copolymerization of acrylamide and dye and subsequent chromatography. Simultaneous fixation of dye and N-methylolacrylamide has also been achieved, and the coapplication of dye and finishing agent to attain dyeing and durable press in one operation has been successfully demonstrated by a plant scale trial using a 500 kv electron accelerator system. [ABSTRACT FROM AUTHOR]