High-power Electron Accelerators Research Articles

Optimization of irradiation conditions for photon activation analysis of biological and environmental samples using a high power electron accelerator.

Using the bremsstrahlung flux density data of Tanaka et al. (1983), the PHOTAC code has been developed to calculate the activity induced in a sample during photon activation as a function of the geometrical arrangement of the electron energy and the beam profile. Some results are given for sample volumes from 1 to 1000 cm3 and sample distances from 1 to 10 cm at 25 MeV. Examples for the application of the PHOTAC code to estimate the maximum activity output and to minimize the heating up of the sample during irradiation are discussed.

Sensitivity of self-powered detector probes to electron and gamma-ray fields

A self-powered detector (SPD) is a simple, passive device that consists of a coaxial probe with a metallic outer sleeve, a mineral oxide insulating layer, and a metallic inner core. SPDs are used in nuclear reactors to monitor neutron and gamma fields. Responses of SPDs to electrons and γ-rays of various energies were investigated with Monte Carlo simulations. Transmission filters were studied for the design of threshold SPD probes used for on-line monitoring of the energy spectrum of high-power industrial electron accelerator beams. Filters were also investigated for the enhancement of γ-ray sensitivity of an SPD placed in a mixed electron and γ-ray field.

Gas phase dosimetry connected with radiation processing of industrial flue gas

The concise review of dosimetric methods suitable for gas phase is presented. The spatial dose distribution from low energy high power electron accelerators, the ELV-3A type, inside the process vessel of industrial flue gases was measured. Complementary measurements using small power and the same energy Van de Graaff were also performed. The agreement between measured and theoretically predicted results is satisfactory.

Windowless output for high power-low energy electron accelerators

The purpose of this paper is to outline the electron beam window efficiency and its ability to operate at electron beam power levels approaching MW in geometries suitable for process stream. A windowless high power electron accelerator designed as a point source can offer: compact construction, high energy and high beam power operation, no window is required (primary or secondary), no losses in the output system and better performance in efficiency and cost when beam power level is above 500 kW. The following disadvantages are considered for windowless accelerators: the necessity of using a multistage vacuum pump system, non-homogeneity of dose distribution, additional processes caused by higher temperature levels and no experience in flue gas application.

Beam dosimetry in high-power electron accelerators

In order to evaluate beam utilization efficiency, measure the radiation yield, and determine the cost effectiveness of the new technologies, it is necessary to know the radiation power of the electron beam absorbed by the reacting medium. To measure the electron-beam power the authors designed, built, and tested a radiation detector combining a Faraday cylinder with a continuous-flow calorimeter. The construction of the detector is shown. The radiation detector was tested on a number of electron accelerators. The beam-power and mean-electron-energy measurement results for the LUE-8M accelerator with 8 MeV maximum electron energy are given.

Bremsstrahlung Beams from High-Power Electron Accelerators for Use in Radiation Processing

In this paper, the authors present the results of calculations of bremsstrahlung produced by a high power electron beam that is incident on a water cooled target. The calculation yields the efficiency of conversion of electron beam power to bremsstrahlung, the energy and angular distributions of the photons and the dose distribution of the resultant photon spectrum in a water phantom. The result is used to estimate radiation processing rates with bremsstrahlung photons and comparison is made with Co-60 radioisotope sources. In their analysis, 4 and 5 MeV electron beam sources are considered, since these machines are now available commercially at power levels up to 200 kW. Furthermore, while higher energy would provide higher conversion efficiency, 5 MeV is chosen as the maximum electron beam energy because it is likely that the U.S. Food and Drug Administration will place an upper limit of 5 MeV on bremsstrahlung sources for food irradiation. The bremsstrahlung converter is assumed to consist of a high-Z slab followed by a water filled copper channel, which provides the required cooling and reduces the transmission of electrons through the converter.

Examination of Product Throughput Obtained from High Power Bremsstrahlung Sources

The Bremsstrahlung from high power electron accelerators provides an intense source of penetrating radiation for industrial processing. Applications include the sterilization of disposable medical products and radiation preservation of food. This paper reports on theoretical and experimental investigation of the Bremsstrahlung radiation processing throughput that can be achieved using 3 to 6 MeV electron accelerators with up to 300 kilowatts of electron beam power. The theoretical calculation integrates experimentally determined angular distributions of unscanned electron beams to calculate the fields produced by scanned beams. Absorbed dose distributions for continuous processes are calculated and the maximum-to-minimum dose ratio and product throughput are obtained as a function of package dimensions. Data are presented for multipass conveyors that move the product on linear or circular trajectories through the radiation field. Results of experimental measuring using thin film dosimeters to check the results of the calculation are also discussed.

The prospects for very high-power electron accelerators for processing bulk materials

The recent growth in the industrial usage of ionizing radiation has been stimulated by the development of reliable, high-power, electron beam generators which operate in the beam power range of 10 to 100 kilowatts. This high output has reduced the costs of radiation processes to about $0.001 per megarad-pound of product material. At this rate electron beam treatment is now less expensive than conventional methods for curing plastic and rubber products and sterilizing medical disposables. Future applications of electron beam radiation to bulk chemicals and waste materials will require even larger generators operating in the power range of 100 to 1000 kilowatts to handle greater material thruputs. Unit processing costs must be further reduced because of the lower intrinsic values of these materials. Fortunately, lower unit costs will follow the development of more powerful equipment because most of the cost factors do not increase in proportion to the output power. This is demonstrated by analyzing the downward trends in radiation processing costs as the machine voltage and the beam current are increased. The Dynamitron accelerator technology is reviewed to show that this could be one method of achieving the projected power levels. Several large-scale radiation processes are discussed to show that applications can be found for electron beam systems operating in the projected range.

60 kW Electron Accelerator for a Paint-Curing Facility

Compared with radioactive isotopes, electron accelerators are very powerful sources of radiation. Due to the limited penetration depth of the electrons, these accelerators can only be applied for the radiation processing of surfaces or thin materials. Of special interest is the utilization of low-energy, high-power electron accelerators for the curing of paint coatings on wood, metal, and plastic surfaces. A paint-curing facility was built with a 600 keV electron accelerator with an output power of 60 kW. During the first year of continuous operation, important improvements were made in the entire process, particularly in developing suitable paint and maintaining a pure nitrogen atmosphere in the radiation chamber.