kW electron beam would thus process 180 kg of food or other materials, the 67,578-Ci 60Co would process 108 kg, and the 308,641-Ci 137Cs would process 72 kg, always with a dose of lOkGy in 1 h. If a 5-MeV electron beam were converted to x-rays with % efficiency and the x-ray beam were absorbed by the irradiated food with 50% efficiency, the electron beam power would have to be about 14.5 kW to process 180 kg with a dose of 10 kGy/h (12). If we recalculate this in each case for a throughput of 1.8t/h, the beam power or source load indicated in Table 2 is obtained. Many 60Co sources of this size exist all over the world, but not a single 137Cs source approaching 7 MCi exists anywhere. Electron accelerators of the capacity indicated in Table 2 are commer­ cially available. The possible throughput is only one of the parameters that influence the choice of a particular type of irradiator. Many other technical, economical, and, increas­ ingly, sociopolitical aspects must be taken into consideration. Technical considerations refer primarily to the different penetrating power of various types of radiation and to differences in dose rate. If large crates of potatoes are to be irradiated, it is obvious that a gamma source rather than an electron irradiator must be chosen. When the two types of gamma sources are compared, it must be considered that the use of Co, due to the higher penetrating

1995 ◽  
pp. 43-43
Keyword(s):  
Electron Beam ◽  
Dose Rate ◽  
Beam Power ◽  
X Rays ◽  
137Cs Source ◽  
Gamma Source ◽  
Electron Accelerators ◽  
The World ◽  
Gamma Sources ◽  
Technical Considerations

Some of these could also be operated in the energy range above lOMeV for experiments designed to determine at which energy level radioactivity can be induced in the irradiated medium. A linac with a maximum energy of 25 MeV was commissioned for the U.S. Army Natick Research and Development Labora­ tories in 1963. Its beam power was 6.5 kW at an electron energy of 10 MeV, 18 kW at 24 MeV. Assuming 100% efficiency, a 1-kW beam can irradiate 360 kg of product with a dose of 10 kGy/h. The efficiency of electron accelerators is higher than that of gamma sources because the electron beam can be directed at the product, whereas the gamma sources emit radiation in all directions. An efficiency of 50% is a realistic assumption for accelerator facilities. With that and 6.5 kW beam power an accelerator of the type built for the Natick laboratories can process about 1.2t/h at 10 kGy. In Odessa in the former Soviet Union, now in the Ukraine, two 20-kW accelerators with an energy of 1.4 MeV installed next to a grain elevator went into operation in 1983. Each accelerator has the capacity to irradiate 200 t of wheat per hour with a dose of 200 Gy for insect disinfestation. This corresponds to a beam utilization of 56% (9). In France, a facility for electron irradiation of frozen deboned chicken meat commenced operation at Berric near Vannes (Brittany) in late 1986. The purpose of irradiation is to improve the hygienic quality of the meat by destroying salmonella and other disease-causing (pathogenic) microorganisms. The electron beam accelerator is a 7 MeV/10 kW Cassitron built by CGR-MeV (10). An irradiation facility of this type is shown in Figure . Because of their relatively low depth of penetration electron beams cannot be used for the irradiation of animal carcasses, large packages, or other thick materials. However, this difficulty can be overcome by converting the electrons to x-rays. As indicated in Figure 9, this can be done by fitting a water-cooled metal plate to the scanner. Whereas in conventional x-ray tubes the conversion of electron energy to x-ray energy occurs only with an efficiency of about %, much higher efficiencies can be achieved in electron accelerators. The conversion efficiency depends on the material of the converter plate (target) and on the electron energy. Copper converts 5-MeV electrons with about 7% efficiency, 10-MeV electrons with 12% efficiency. A tungsten target can convert 5-MeV electrons with about 20%, 10-MeV electrons with 30% efficiency. (Exact values depend on target thickness.) In contrast to the distinct gamma radiation energy emitted from radionuclides and to the monoenergetic electrons produced by accelerators, the energy spectrum of x-rays is continuous from the value equivalent to the energy of the bombarding electrons to zero. The intensity of this spectrum peaks at about one-tenth of the maximum energy value. The exact location of the intensity peak depends on the thickness of the converter plate and on some other factors. As indicated in Figure

1995 ◽  
pp. 40-40
Keyword(s):  
Electron Beam ◽  
Electron Energy ◽  
Maximum Energy ◽  
Metal Plate ◽  
Beam Power ◽  
X Rays ◽  
X Ray ◽  
Emit Radiation ◽  
Electron Accelerators ◽  
Gamma Sources

scholarly journals Economical evaluation of radiation processing with high-intensity X-rays

Nukleonika ◽  
2020 ◽  
Vol 65 (3) ◽  
pp. 167-172
Author(s):  
Zbigniew Zimek
Keyword(s):  
Electron Beam ◽  
Electron Energy ◽  
High Power ◽  
High Intensity ◽  
Power Level ◽  
Unit Cost ◽  
Utilization Efficiency ◽  
Beam Power ◽  
X Rays ◽  
Radiation Processing

AbstractX-rays application for radiation processing was introduced to the industrial practice, and in some circumstances is found to be more economically competitive, and offer more flexibility than gamma sources. Recent progress in high-power accelerators development gives opportunity to construct and apply reliable high-power electron beam to X-rays converters for the industrial application. The efficiency of the conversion process depends mainly on electron energy and atomic number of the target material, as it was determined in theoretical predictions and confirmed experimentally. However, the lower price of low-energy direct accelerators and their higher electrical efficiency may also have certain influence on process economy. There are number of auxiliary parameters that can effectively change the economical results of the process. The most important ones are as follows: average beam power level, spare part cost, and optimal shape of electron beam and electron beam utilization efficiency. All these parameters and related expenses may affect the unit cost of radiation facility operation and have a significant influence on X-ray process economy. The optimization of X-rays converter construction is also important, but it does not depend on the type of accelerator. The article discusses the economy of radiation processing with high-intensity of X-rays stream emitted by conversion of electron beams accelerated in direct accelerator (electron energy 2.5 MeV) and resonant accelerators (electron energy 5 MeV and 7.5 MeV). The evaluation and comparison of the costs of alternative technical solutions were included to estimate the unit cost of X-rays facility operation for average beam power 100 kW.

frequency of 100-200 Hz the beam is moved to and fro like a pendulum. The reason for this is that the material to be irradiated must, as nearly as possible, receive the same radiation dose in all its parts. The electron beam has a diameter of only a few millimeters or centimeters. Without scanning, the electron beam would concentrate the whole beam power on a very small area of the irradiated goods. By scanning the electron beam and simultaneously moving the material to be irradiated perpendicularly to the scanning line of the electron beam, an even distribution of radiation energy to the irradiated material can be achieved. It is very difficult to handle accelerating potentials higher than 5 MeV in DC accelerators, whereas linacs can produce electron energies even higher than the 10 MeV allowed for food irradiation. In a linac (Fig. 7), pulses or bunches of electrons produced at the thermionic cathode are accelerated in an evacuated tube by driving RF electromagnetic fields along the tube. The electrons ride on a traveling electromagnetic wave, comparable with a piece of wood or a surfer riding the crest of a water wave. The RF generator is designated high-power klystron tube in Figure 7. The electron beam leaving the accelerator tube can be scanned in the same way as for DC accelerators. Linac electrons are also monoenergetic, but the beam is pulsed rather than continuous. An electron pulse of a few micro-seconds duration may be followed by a dead time of a few milliseconds, with different manufacturers using different timings. When the dose rate provided by a pulsed electron beam is described, it is important to indicate whether this is the pulse dose rate or the overall dose rate of pulse plus dead time. Linac designs other than the traveling wave type described here are available (7). A number of linacs have been built specifically for food irradiation studies.

1995 ◽  
pp. 39-39
Keyword(s):  
Electron Beam ◽  
Dose Rate ◽  
Dead Time ◽  
Radiation Energy ◽  
Food Irradiation ◽  
Beam Power ◽  
Pulsed Electron Beam ◽  
Pulse Dose ◽  
Accelerator Tube ◽  
Scanning Line

PHOTON FIELD OF ~100–200 KEV FOR ENVIRONMENTAL DOSEMETER CALIBRATION

2020 ◽  
Vol 188 (4) ◽  
pp. 486-492
Author(s):  
S M Tajudin ◽  
Y Namito ◽  
T Sanami ◽  
H Hirayama
Keyword(s):  
Dose Rate ◽  
Low Dose ◽  
Gamma Source ◽  
X Ray ◽  
Dose Rates ◽  
Photon Field ◽  
Gamma Sources ◽  
Energy Dependent

Abstract As a reference photon field, several radionuclides have been used frequently, such as 241Am,137Cs and60 Co for calibration. These nuclides provide mono-energy photons for dosemeters covering few tens of keV–MeV. The main energy around 200 keV is important for both environmental and medical fields since the former should consider scattering photons and the later should measure photons from X-ray generator. In our previous work, a backscattered layout can provide a uniform photon field spectra and dose rate with an energy of 190 keV by using an affordable intensity 137 Cs gamma source. Several other quasi-monoenergetic photon fields in the range of 100–200 keV could be obtained by using several available gamma sources. Two calibrated environmental CsI(Tl) survey meters, Horiba PA-1000 and Mr. Gamma A2700, had been measured with the developed backscattered photon field to understand energy-dependent features in order to confirm dosemeter readings. Consequently, both scintillator instruments are sensitive for measurements of the relatively low dose rates at 190 keV.

X-ray micro tomography in the scanning electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 106-107 ◽  
Author(s):  
W. Brünger
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Target Surface ◽  
The Body ◽  
X Rays ◽  
Cross Sectional ◽  
X Ray ◽  
Micro Tomography ◽  
Scanning Electron

Reconstructive tomography is a new technique in diagnostic radiology for imaging cross-sectional planes of the human body /1/. A collimated beam of X-rays is scanned through a thin slice of the body and the transmitted intensity is recorded by a detector giving a linear shadow graph or projection (see fig. 1). Many of these projections at different angles are used to reconstruct the body-layer, usually with the aid of a computer. The picture element size of present tomographic scanners is approximately 1.1 mm2.Micro tomography can be realized using the very fine X-ray source generated by the focused electron beam of a scanning electron microscope (see fig. 2). The translation of the X-ray source is done by a line scan of the electron beam on a polished target surface /2/. Projections at different angles are produced by rotating the object.During the registration of a single scan the electron beam is deflected in one direction only, while both deflections are operating in the display tube.

A Color Coded STEM/SEM Image Storage System

1981 ◽  
Vol 39 ◽  
pp. 272-273
Author(s):  
Y. Kokubo ◽  
W. H. Hardy ◽  
J. Dance ◽  
K. Jones
Keyword(s):  
Image Processing ◽  
Electron Beam ◽  
Storage System ◽  
Particle Analysis ◽  
Specific Information ◽  
X Rays ◽  
Sem Image ◽  
Backscattered Electrons ◽  
Wide Range ◽  
Scanning Electron

A color coded digital image processing is accomplished by using JEM100CX TEM SCAN and ORTEC’s LSI-11 computer based multi-channel analyzer (EEDS-II-System III) for image analysis and display. Color coding of the recorded image enables enhanced visualization of the image using mathematical techniques such as compression, gray scale expansion, gamma-processing, filtering, etc., without subjecting the sample to further electron beam irradiation once images have been stored in the memory.The powerful combination between a scanning electron microscope and computer is starting to be widely used 1) - 4) for the purpose of image processing and particle analysis. Especially, in scanning electron microscopy it is possible to get all information resulting from the interactions between the electron beam and specimen materials, by using different detectors for signals such as secondary electron, backscattered electrons, elastic scattered electrons, inelastic scattered electrons, un-scattered electrons, X-rays, etc., each of which contains specific information arising from their physical origin, study of a wide range of effects becomes possible.

Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating

1990 ◽  
Vol 48 (1) ◽  
pp. 198-199
Author(s):  
Ryo Iiyoshi ◽  
Susumu Maruse ◽  
Hideo Takematsu
Keyword(s):  
Electron Beam ◽  
Tungsten Wire ◽  
Local Heating ◽  
Electron Gun ◽  
Original Position ◽  
Beam Power ◽  
Radius Of Curvature ◽  
High Brightness ◽  
Beam Focusing ◽  
Time Operation

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.

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