• Radiation Oncology Journal
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• v.1 no.1
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• pp.41-45
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• 1983

To obtain 7 MeV electron beam which is suitable for treatment of the chest wall after radical of modified radical mastectomy, the authors reduced the energy of electron beam by means by Lucite plate inserted in the beam. To determine the proper thickness of the Lucite plate necessary to reduce the energy of 9 MeV electron beam to 6 MeV, dosimetry was made by using a parallel plate ionization chamber in polystyrene phantom. Separation between two adjacent fields, 7 MeV for chest wall and 12 MeV for internal mammary region, was studied by means of film dosimetry in both polytyrene phantom and Humanoid phantom. The results were as follows. 1. The average energy of 9 MeV electron beam transmitted through the Lucite plate was reduced. Reduction was proportional to the thickness of the Lucite plate in the rate of 1.7 MeV/cm. 2. The proper thickness of the Lucite plate necessary to obtain 6 MeV electron beam from 9 MeV was 1.2 cm. 3. 7 MeV electron beam, 80% dose at 2cm depth, is adequate for treatment of the chest wall. 4. Proper separation between two adjacent electron fields, 7 MeV and 12 MeV, was 5mm on both flat surface and sloping surface to produce uniform dose distribution.

• Journal of the Korean Vacuum Society
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• v.13 no.1
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• pp.1-8
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• 2004

The SOI wafer fabrication technique has been developed by using ion-cut process, based on proton implantation and wafer bonding techniques. It has been shown by TRIM simulation that 65 keV proton implantation is required for the standard SOI wafer (200 nm SOI, 400 nm BOX) fabrication. In order to investigate the optimum proton dose and primary annealing condition for wafer splitting, the surface morphologic change has been observed such as blistering and flaking. As a result, effective dose is found to be in the 6∼$9\times10^{16}$ $H^{+}/\textrm{cm}^2$ range, and the annealing at $550^{\circ}C$ for 30 minutes is expected to be optimum for wafer splitting. The depth distribution of implanted hydrogen has been experimentally confirmed by ERD and SIMS measurements. The microstructure evolution in the damaged layer was also studied by X-TEM analysis.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.251-257
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• 2014

This research is focused on coagulation and sand filtration process as a pretreatment of RO seawater desalination. RO systems require sufficient and reliable pretreatment process to produce superior quality of RO feedwater that can mitigate RO membrane fouling. This experiment was conducted to investigate the effectiveness of coagulation and filtration process under various experimental conditions including different coagulant dose, flocculation mixing intensity and time, turbidity, and filtration rate. The experimental results showed that the optimum pretreatment conditions resulting in lower SDI value suitable for RO feedwater were coagulation pH 6.5, raw water turbidity greater than 4 NTU, and media bed depth greater than 550 mm. However, flocculation mixing intensity, coagulant dose, and filtration rate relatively affected little on the filtration efficiency.

• Nuclear Engineering and Technology
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• v.6 no.4
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• pp.239-247
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• 1974

A human phantom of polyethylene has been designed and sculptured for studying the effective radiation safety control. The phantom has the approximate size of the Korean adult and was sliced into thirty-five transverse slabs, 2.5 cm thick, The relative dose at the specified position was determined from the exposure that a TLD badge worn on the surface of the phantom body received from external ${\gamma}$-ray. The variation of the exposure as a function of depth in the phantom was measured for uncollimated ${\gamma}$-ray using TLD rods, and also isodose curves were obtained for the anatomical cross-section of the critical organs of the body. To simulate radiation exposure condition in the nuclear facility, measurements were made for given angles of incident ${\gamma}$-ray. The front to back attenuation factor for human phantom of thickness 20 cm was 0.439 for Cs$^{137}$ ${\gamma}$-ray which is in reasonable agreement with the published data.

• Nuclear Engineering and Technology
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• v.52 no.6
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• pp.1243-1251
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• 2020

Irradiation-induced damage of binderless nanoporous-isotropic graphite (NPIG) prepared by isostatic pressing of mesophase carbon microspheres for molten salt reactor was investigated by 3.0 MeV He⁺ irradiation at room temperature and high temperature of 600 ℃, and IG-110 was used as the comparation. SEM, TEM, X-ray diffraction and Raman spectrum are used to characterize the irradiation effect and the influence of temperature on graphite radiation damage. After irradiation at room temperature, the surface morphology is rougher, the increase of defect clusters makes atom flour bend, the layer spacing increases, and the catalytic graphitization phenomenon of NPIG is observed. However, the density of defects in high temperature environment decreases and other changes are not obvious. Mechanical properties also change due to changes in defects. In addition, SEM and Raman spectra of the cross section show that cracks appear in the depth range of the maximum irradiation dose, and the defect density increases with the increase of irradiation dose.

• Radiation Oncology Journal
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• v.2 no.1
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• pp.11-20
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• 1984

The renewed interest in the use of hyperthermia in cancer therapy is bases on radiobiological and clinical evidence indicated that there may be a significant therapeutic advantage with the use of heat alone or combined with radiation or chemotherapy, There are many methods for generating heat for localized tumor as like radiofrequency, microwave, electromagnetic induction and ultrasound. But it is very difficult to be even thermal dose distribution and stable output of power and then the detection of temperature in tumor is difficult to be precise with thermocouples and semiconductor sensors. We designed the microwave heating generator, dipole antenna applicators and autometic temperature controlled thermocouples for localized hyperthermia on skin and in cavities. 1. The microwave generator with 120 W, 2,450MHz magnetron could be heating up to $40^{\circ}C\~50^{\circ}C\;for\;1\~2$ hours in living tissues. 2. The thermal dose distribution in tissue with microwave was described $42^{\circ}C\~44^{\circ}C$ with in 3 cm depth and $2\~6cm$ diameter area. 3. Skin surface heating applicator with spiral 3 times wave length antenna radiated high Power of microwave. 4, Intracavitary heating applicator with dipole antenna with autometic control temperature sensor kept up continuously constant temperature in tissue. 5. For constant thermal distribution, applied two steps power with 10W microwave after $17\~20W$ during first 10 minutes. 6. The cooling rate by blood flew in living tissue was rised as $10\%$ then meats.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.537-558
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• 2005

This paper addresses the results of HAUSAT-2 radiation environment and effect analyses, including TID and SEE analyses. Trapped proton and electron, solar proton, galactic cosmic ray models were considered for HAUSAT-2 TID radiation environment analysis. TID was analyzed through total dose-depth curve and the radiation tolerance of TID for HAUSAT-2 components was verified by using DMBP method and sectoring analysis. HAUSAT-2 LET spectrum for heavy ion and proton were also analyzed for SEE investigation. SEE(SEU, SEL) analyses were accomplished for MPC860T2B microprocessor and K6X8008T2B memory. It was estimated that several SEUs may occur without SEL during the HAUSAT-2 mission life(2 years). Software Hamming Code EDAC has been implemented to detect and correct the SEU. In this study, all radiation analyses were conducted by using SPENVIS software.

• Progress in Medical Physics
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• v.23 no.4
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• pp.229-233
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• 2012

A small water phantom (dual-window phantom) was developed to improve the output measurement efficiency of medical linacs. This phantom is suitable for determining the quality index and output dose for high-energy photon beams. The phantom has two opposite windows and two independently rotating axes. The two axes measure the tissue phantom ratio (TPR) and the percentage depth dose (PDD) simply without requiring chamber movement by rotating the phantom around its axis. High-energy photon beams from a Co-60 irradiator and a medical linac were used to evaluate the phantom. The measured quality index is in good agreement with the reference values; the measured and reference values are within 0.2% of each other for the Co-60 gamma rays and within 1.4% for 6 and 10 MV X-rays. This phantom is more practical for routine output measurements, resulting in the prevention of potential human errors.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.180-180
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• 2000

Plasma source ion implantation is a new doping technique for the formation of shallow junction with the merits of high dose rate, low-cost and minimal wafer charging damage. In plasma source ion implantation process, the wafer is placed directly in the plasma of the appropriate dopant ions. Negative pulse bias is applied to the wafer, causing the dopant ions to be accelerated toward the wafer and implanted below the surface. In this work, inductively couples plasma was generated by anodized Al antenna that was located inside the vacuum chamber. The outside wall of Al chamber was surrounded by Nd-Fe-B permanent magnets to confine the plasma and to enhance the uniformity. Before implantation, the wafer was pre-sputtered using DC bias of 300B in Ar plasma in order to eliminate the native oxide. After cleaning, B2H6 (5%)/H2 plasma and negative pulse bias of -1kV to 5 kV were used to form shallow p+/n junction at the boron dose of 1$\times$1015 to 5$\times$1016 #/cm2. The as-implanted samples were annealed at 90$0^{\circ}C$, 95$0^{\circ}C$ and 100$0^{\circ}C$during various annealing time with rapid thermal process. After annealing, the sheet resistance and the junction depth were measured with four point probe and secondary ion mass spectroscopy, respectively. The doping uniformity was also investigated. In addition, the electrical characteristics were measured for Schottky diode with a current-voltage meter.

• Progress in Medical Physics
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• v.25 no.1
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• pp.46-52
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• 2014

Liquid ionization chamber is filled with liquid equivalent material unlike air filled ionization chamber. The high density material allow very small-volume chamber to be constructed that still have a sufficiently high sensitivity. However liquid ionization chamber should be considered for both initial recombination and general recombination. We, therefore, studied using the Co-60 beam as the continuous beam and the microLion chamber (PTW) for comparing the ion collection efficiency by Greening theory, two-dose rate method and our experiment method. The measurements were carried out using Theratron 780 as the cobalt machine and water phantom and 0.6 cc Farmer type ionization chamber was used with microLion chamber in same condition for measuring the charge of microLion chamber according to the dose rates. Dose rate was in 0.125~0.746 Gy/min and voltages applied to the microLion chamber were +400, +600 and +800 V. As the result, the collection efficiency by three method was generally less than 1%. In particular, our experimental collection efficiency was in good agreement within 0.3% with Greening theory except the lowest two dose rates. The collection efficiency by two-dose rate method also agreed with Greening theory generally less than 1%, but the difference was about 4% when the difference of two dose rates were lower. The ion recombination correction factors by Greening theory, two-dose rate method and our experiment were 1.0233, 1.0239 and 1.0316, respectively, in SSD 80 cm, depth 5 cm recommended by TRS-398 protocol. Therefore we confirmed that the loss by ion recombination was about 3% in this condition. We think that our experiment method for ion recombination correction will be useful tool for radiation dosimetry in continuous beam.