• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4167-4172
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• 2023

Miniaturized tissue equivalent proportional counters (mini-TEPCs) are proper for radiation dosimetry in medical application because the small size of the dosimeter could prevent pile-up effect under the high intensity of therapeutic beam. However, traditional methods of calibrating mini-TEPCs using internal alpha sources are not feasible due to their small size. In this study, we investigated the use of electron and proton edges on Monte Carlo-generated lineal energy spectra as markers for calibrating a 0.9 mm diameter and length mini-TEPC. Three possible markers for each spectrum were calculated and compared using different simulation tools. Our simulations showed that the electron edge markers were more consistent across different simulation tools than the proton edge markers, which showed greater variation due to differences in the microdosimetric spectra. In most cases, the second marker, y_δδ, had the smallest uncertainty. Our findings suggest that the lineal energy spectra from mini-TEPCs can be calibrated using Monte Carlo simulations that closely resemble real-world detector and source geometries.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.130-135
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• 2000

We have analyzed characteristics for the structure of $Al_{0.25}/Ga_{0.75}/As/In_{0.15}/Ga_{0.85}$/AS/GaAS pseudomorphic high electron mobility transistor (PHEMT) by photoluminescence (PL) and photoreflectance (PR) measurements. By the PL measurement at 10 K, we observed el-hl transition peak at 1.322 eV and e2-hl transition peak at 1.397 eV in the InGaAs quantum well. We calculated value of 23 meV, the difference between the first energy level and the second energy level of a valence band by dependence of temperatures. Also, (e2-h2) transition signal was observed at 300 K by PR measurement. From the PR measurement, we recognized that the transition was dominated the second energy level of conduction band than the first energy level of conduction band due to band filling. The other hand, PL signal of the first energy level of conduction band was dominated because of the electron screening effect.

• Journal of Radiation Protection and Research
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• v.38 no.1
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• pp.22-28
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• 2013

The skyshine effect is an essential and important phenomenon in the shielding design of the high energy accelerator. In this study, a new estimation method of neutron skyshine was proposed and was verified by comparison with existing methods. The effective dose of secondary neutrons and photons at the locations that was far away from high-energy electron accelerator was calculated using FLUKA and PHITS Monte Carlo code. The transport paths of secondary radiations to reach a long distance were classified as skyshine, direct, groundshine and multiple-shine. The contribution of each classified component to the total effective dose was evaluated. The neutrons produced from the thick copper target irradiated by 10 GeV electron beam was applied as a source term of this transport. In order to evaluate a groundshine effect, the composition of soil on the PAL-XFEL site was considered. At a relatively short distance less than 50 m from the accelerator tunnel, the direct and groundshine components mostly contributed to the total effective dose. The skyshine component was important at a long distance. The evaluated dose of neutron skyshine agreed better with the results using Rindi's formula, which was based on the experimental results at high energy electron accelerator. That also agreed with the estimated dose using the simple evaluation code, SHINE3, within about 20%. The total effective dose, including all components, was 10 times larger than the estimated doses using other methods for this comparison. The influence of multiple-shine path in this evaluation of the estimation method was investigated to be bigger than one of pure skyshine path.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.240-241
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• 2002

Propagation of an intense laser pulse through fully ionized plasma has been an interesting topic in many fields. It includes laser-driven electron accelerators,(1) generation of high harmonics,(2) soft x-ray laser development(3) and so on. Specifically, in the application of laser-driven electron accelerators a large laser-plasma interaction length is required to get sufficient acceleration energy of electron. (omitted)

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.208-213
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• 1999

Space Physics Sensor (SPS) on-board the KOMPSAT-1 consists of the High Energy Particle Detector (HEPD) and the Ionospheric Measurement Sensor (IMS). The HEPD is to characterize the low altitude high energy particle environment and the effects on the microelectronics due to these high energy Particles. It is composed of four sensors: Proton and Electron Spectrometer(PES), Linear Energy Transfer Spectrometer (LET), Total Dose Monitor (TDM), and Single Event Monitor(SEM). 35MeV proton beam from the medical KCCH cyclotron, at Korea Cancer Center Hospital in Seoul, is used to calibrate the PES. Primary proton beam of 35MeV scattered by polypropylene target is converted to various energy Protons according to the elastic collision kinematics. In this calibration, the threshold level of the proton in the PES can be determined and the energy ranges of PES channels are also calibrated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.10
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• pp.923-929
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• 2006

Single crystalline ZnO films were successfully grown on R-plane sapphire substrates by plasma-assisted molecular beam epitaxy. Epitaxial relationship between the ZnO film and the R-plane sapphire was determined to be $[-1101]Al_2O_3{\parallel}[0001]ZnO,\;[11-20]Al_2O_2{\parallel}[-1100]ZnO$ based on the in-situ reflection high-energy electron diffraction analysis and confirmed again by high-resolution X-ray diffraction measurements. Grown (11-20) ZnO films surface showed mound-like morphology along the <0001>ZnO direction and the RMS roughness was about 4 nm for $2{\mu}m{\times}2{\mu}m$ area.

• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05a
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• pp.6-6
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• 1992

Ionized cluster beam deposition (ICBD) technique has been employed to fabricate high-purity crystalline polyimide (PI) film. The pyromellitic dianhydride (PMDA) and oxydianiline (ODA) were deposited using dual ICB sources, Fourier trans forminfraredspectroscopy (FT-IR), X-ray photoemission spectroscopy (XPS), and Transmission electron microscopy (TEM)study show that the bulk and surface chemical properties and the crystalline structure are very sensitive to the ICBD conditions such as cluster ion acceleration voltage and ionization voltage, At optimum ICBD conditions, the PI films have a maximum imidization, negligible impurities(∼1% isoimide), and a good crystalline structure probably due to the high surface migration energy and surface cleaning effect. These characteristics are superior to those of films deposited by other techniques such as colvent cast, vapowr deposition, or sputtering techniques.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.31-34
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• 2002

Imaging techniques using x-ray beam at high energies (>6KeV) such as contact radiography, projection microscopy, and tomography have been used to nondestructively discern internal structure of objects in material science, biology, and medicine. This paper introduces the x-ray micro-imaging method using 1B2 micro-probe line of PAL (Pohang Accelerator Laboratory). Cross-sectional information on low electron density materials can be obtained by probing a sample with coherent synchrotron x-ray beam in an in-line holography setup. Living organism such as plants, insects are practically transparent to high energy x-rays and create phase shift images of x-ray wave front. X-ray micro-images of micro-bubbles of $20\~120\;{\mu}m$ diameter in an opaque tube were recorded. Clear phase contrast images were obtained at Interfaces between bubbles and surrounding liquid due to different decrements of refractive index.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.214-216
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• 2005

The PAL (Pohang Accelerator Laboratory) is persuading to construct a SASE-XFEL facility (PAL XFEL) that supplies coherent X-rays. The bright and stable electron beam is essential for the PAL XEL. The electron beams has to have an emittance of 1.0 mm-mrad, a peak current of 3 kA, and a low energy spread of 1.0 MeV. In order to provide reasonably stable SASE output, the RF stability of 0.02% rms is required for both RF phase and amplitude. This is a technologically challenging issue for PAL XFEL. An inverter technology is to be applied to charge the PFN of a new modulator. Therefore, a new inverter system should provide very stable charging performances. This paper presents the development of an ultra stable klystron-modulator with an inverter power supply.

• Nuclear Engineering and Technology
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• v.22 no.4
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• pp.380-388
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• 1990

The MM-22 medical microtron at Korea Cancer Center Hospital is now operational for high energy electron and photon therapy, This microtron is designed to produce 5.3-22.5 MeV electron beams and deliver these to the treatment head through beam transport system with an intensity and stability suitable for cancer treatment. The availability of high quality radiation modalities from the MM-22 shows new possibilities in the treatment of deep seated tumours. Principle of operation, system structures and operating characteristics of the MM-22 are described in this paper.