• Journal of Korean Society for Atmospheric Environment
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• v.17 no.2
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• pp.223-231
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• 2001

In order to provide some insights into the influence of electric field, gas composition, and gas temperature on electron energy distribution and electron transport characteristics, the Boltzmann equation was solved by using cross section data for electron collisions, Critical electric fields for the corona development in dry air and flue gas are 150 and 80 Td, respectively. It was seen that the decrease of critical electric field in flue gas is mainly caused by the $H_2O$ addition through the comparison of ionization and attachment coefficients of gas components. Increase of $O_2$, $H_2O$, and $CO_2$ contents in gas affected discharge characteristics according to their reciprocal characteristics between lowering the ionization threshold and increasing the electro-negativity. As electric field increases, electrons with higher energies in the electron energy distribution also increase. The mean and characteristic electron energies also linearly increase with electric field. The variation of flue gas temperature did rarely affect on the electron energy distribution function and electron transport characteristics, because the gas temperature is several hundreds or thousands times lower than the electron temperature.

• Journal of Radiation Protection and Research
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• v.41 no.3
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• pp.286-290
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• 2016

Background: Activation of air and water in the electron linear accelerator for medical use has not been considered severely. By the new Japanese regulation for protection of radiation hazard, it became indispensable to evaluate of activation of air and water in the accelerator room. The measurement of induced activity in air and water components in the electron energy region of 10 to 20 MeV is very difficult, because this energy region is close to the threshold energy region of photonuclear reactions. Then, we measured the photonuclear reaction yields of $^{13}N$, $^{15}O$, and $^{11}C$ by using the electron linear accelerator. Obtained data were compared with the data calculated by the Monte Carlo method. Materials and Methods: An activation experiment was performed at the Research Center for Electron Photon Science, Tohoku University. Highly purified $SiO_2$, $Si_3N_4$, and carbon disks were irradiated for 10 minutes by bremsstrahlung converted by a tungsten plate. Induced activity from C, N, and O was obtained. Monte Carlo calculation was performed using MCNP5 and AERY (DCHAIN-SP) to simulate the experimental condition. Cross section data were adopted the KAERI dataset. Results and Discussion: In our experiment in hospital, calculated values were not agreed with experimental values. It might be three possible reasons as the cause of this deference, such as irradiation energy, calculation procedure and cross section data. Obtained data of this work, calculated and experimental values were good agreement with each other within one order. In this work, we used KAERI dataset of photonuclear reaction instead of JENDL. Therefore, it was found that the photonuclear cross section data of light elements are most important for yield calculation in these reactions. Conclusion: Further improvement for calculation using a new dataset JENDL/PD-2015 and considering electron energy spreading will be needed.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1224-1226
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• 2007

• Nuclear Engineering and Technology
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• v.54 no.2
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• pp.666-673
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• 2022

The optimization of a transmission type bremsstrahlung conversion target was carried out with Monte Carlo code FLUKA for intense pulsed electron beams with electron energy of several hundred keV for maximum photon fluence. The photon emission intensity from electrons with energy ranging from 300 keV to 1 MeV on tungsten, tantalum and molybdenum targets was calculated with varied target thicknesses. The research revealed that higher target material element number and electron energy leads to increased photon fluence. For a certain target material, the target thickness with maximum photon emission fluence exhibits a linear relationship with the electron energy. With certain electron energy and target material, the thickness of the target plays a dominant role in increasing the transmission photon intensity, with small target thickness the photon flux is largely restricted by low energy loss of electrons for photon generation while thick targets may impose extra absorption for the generated photons. The spatial distribution of bremsstrahlung photon density was analyzed and the optimal target thicknesses for maximum bremsstrahlung photon fluence were derived versus electron energy on three target materials for a quick determination of optimal target design.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.266-272
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• 2021

In the pulsed electron beam generators, such as plasma focus devices and linear induction accelerators whose electron pulse width is in the range of nanosecond and less, as well as in cases where there is no direct access to electron beam, like runaway electrons in Tokamaks, measurement of the electron energy spectrum is a technical challenge. In such cases, the indirect measurement of the electron spectrum by using the bremsstrahlung radiation spectrum associated with it, is an appropriate solution. The problem with this method is that the matrix equation between the two spectrums is an ill-conditioned equation, which results in errors of the measured X-ray spectrum to be propagated with a large coefficient in the estimated electron spectrum. In this study, a method based on the neural network and the MCNP code is presented and evaluated to recover the electron spectrum from the X-ray generated by collision of the electron beam with a target. Multilayer perceptron network showed good accuracy in electron spectrum recovery, so that for the X-ray spectrum with errors of 3% and 10%, the network estimated the electron spectrum with an average standard error of 8% and 11%, on all of the energy intervals.

• Progress in Medical Physics
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• v.17 no.4
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• pp.224-231
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• 2006

The electron energy spectra for 6 MeV electron beam were calculated using a MCNPX code. The head of the linear accelerator (ML6M; Mitsubishi, Japan) was modelled for this study. The energy spectrum of the initial electron beam was assumed to be Gaussian and the mean energy was determined by evaluating the measured and calculated values of $R_{50}$ and dose profiles in air. The energy distributions for electrons and photons at the interested points in the head of the linear accelerator were calculated by appling the Initial beam parameters. The effect of contaminant photons on depth dose curves were estimated by the photon energy spectra at the end of the applicator.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.274-274
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• 2012

We have researched on controlling an electron temperature and a plasma collision frequency to study the effect of collisions on helicon plasmas. So, we have designed and constructed an electron cyclotron resonance (ECR) heating system in the helicon device as an auxiliary heating source. Since then, we have tried to optimize experimental designs such as a magnetic field configuration for ECR heating and 2.45GHz microwave launching system for its power transfer to the plasma effectively, and have characterized plasma parameters using a Langmuir probe. For improving an efficiency of the ECR heating with R-wave in the helicon plasma, we would understand an effect of R-wave propagation with ECR heating in the helicon plasma, because the efficiency of ECR heating with R-wave depends on some factors such as electron temperature, electron density, and magnetic field gradient. Firstly, we calculate the effect of R-wave propagation into the ECR zone in the plasma with those factors. We modify the magnetic field configuration and this system for the effective ECR heating in the plasma. Finally, after optimizing this system, the plasma parameters such as electron temperature and electron density are characterized by a RF compensated Langmuir probe.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.75-78
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• 2003

Energy distribution function for electrons in $SF_6$-Ar mixtures gas used by MCS-BEq algorithm has been analysed over the E/N range $30\sim300$[Td] by a two term Boltzmann equation and by a Monte Carlo Simulation using a set of electron cross sections determined by other authors, experimentally the electron swarm parameters for 0.2[%] and 0.5[%] $SF_6$-Ar mixtures were measured by time-of-flight(TOF) method. The results show that the deduced electron drift velocities, the electron ionization or attachment coefficients, longitudinal and transverse diffusion coefficients and mean energy agree reasonably well with theoretical for a rang of E/N values. The transport coefficients for electrons in (0.2[%])$SF_6$-Ar and (0.5[%]$SF_6$ - Ar mixtures were measured by time-of-flight method, and the electron energy distribution function and the parameters of the velocity and the diffusion were determined by the variation of the collision cross-sections with energy. The results obtained from Boltzmann equation method and Monte Carlo simulation have been compared with present and previously obtained data and respective set of electron collision cross sections of the molecules.

• KSBB Journal
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• v.29 no.4
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• pp.297-302
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• 2014

The autoclaving assisted by an irradiation pretreatment method was developed without toxic chemicals to produce fermentable sugars for their conversion to bioethanol. In the first step, electron beam irradiation (EBI) of rice straw was performed at various doses. The electron beam-irradiated rice straw was then autoclaved with DI water at $120^{\circ}C$ for 1 h. A total sugar yield of 81% was obtained from 300 kGy electron beam-irradiated rice straw after 72 h of enzymatic hydrolysis by Cellulase 1.5L (70 FPU/mL) and Novozyme-188 (40 CbU/mL). Also, the removal of hemicellulose and lignin was 32.0% and 32.5%, respectively. This result indicates that the environmentally-friendly pretreatment method of rice straw by an electron beam irradiation could be applied for bioethanol production in plant.

• Journal of Radiation Industry
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• v.9 no.1
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• pp.15-20
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• 2015

Carbon fiber has received much attention owing to its properties, including a large surface-to-volume ratio, chemical and thermal stability, high thermal and electrical conductivity, and high mechanical strengths. In particular, magnetic nanopowder dispersed carbon fiber has been attractive in technological applications such as the electrochemical capacitor and electromagnetic wave shielding. In this study, the nickel-oxide-nanoparticle dispersed polyacrylonitrile (PAN) fibers were prepared through an electrospinning method. Electron beam irradiation was carried out with a 2.5 MeV beam energy to stabilize the materials. The samples were then heat-treated for stabilization and carbonization. The nanofiber surface was analyzed using a field emission scanning electron microscope (FE-SEM). The crystal structures of the carbon matrix and nickel nanopowders were analysed using X-ray diffraction (XRD). In addition, the magnetic and electrical properties were analyzed using a vibrating sample magnetometer (VSM) and 4 point probe. As the irradiation dose increases, the density of the carbon fiber was increased. In addition, the electrical properties of the carbon fiber improved through electron beam irradiation. This is because the amorphous region of the carbon fiber decreases. This electron beam effect of PAN fibers containing nickel nanoparticles confirmed their potential as a high performance carbon material for various applications.