• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.400-403
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• 2002

The fundamental experiments for measuring soft x-ray characteristics from the vacuum capillary are described. These experiments were primarily performed in order to generate line spectra such as x-ray lasers. The generator consists of a high-voltage power supply, a polarity-inversion ignitron pulse generator, a turbo-molecular pump, and a radiation tube with a capillary. A high-voltage condenser of 200 nF in the pulse generator is charged up to 20 kV by the power supply, and the electric charges in the condenser are discharged to the capillary in the tube after closing the ignitron. During the discharge, weakly ionized plasma forms on the inner and outer sides of a capillary. In the present work, the pump evacuates air from the tube with a pressure of about 1 mPa, and a demountable capillary was developed in order to measure x-ray spectra according to changes in the capillary length. In this capillary, the anode (target) and cathode elements can be changed corresponding to the objectives. The capillary diameter is 2.0 mm, and the length is adjusted from 1 to 50 mm. When a capillary with aluminum anode and cathode electrodes was employed, both the cathode voltage and the discharge current almost displayed damped oscillations. The peak values of the voltage and current increased when the charging voltage was increased, and their maximum values were -10.8 kV and 4.7 kA, respectively. The x-ray durations observed by a 1.6 ${\mu}$m aluminum filter were less than 30 ${\mu}$s, and we detected the aluminum characteristic x-ray intensity using a 6.8 ${\mu}$m aluminum filter. In the spectrum measurement, two sets of aluminum and titanium electrodes were employed, and we observed multi-line spectra. The line photon energies seldom varied according to changes in the condenser charging voltage and to changes in the electrode element. In the case where the titanium electrode was employed, the line number decreased with corresponding decreases in the capillary length. Compared with incoherent visible light, these rays from the capillary were diffracted and diffused greatly after passing through two slits.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.91-92
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• 2006

Liquid crystal (LC) alignment on $a-SiO_x$ thin film was investigated by means of X-ray photoemission spectroscopy and optical transmittance as we varied the deposition temperature and the target-to-substrate distance. LC molecules can be aligned vertically on $a-SiO_x$ film when the stoichiometric parameter x of $a-SiO_x$ is smaller than 1.56, but they can be aligned homogeneously when x is larger than 1.56. We also found that whether liquid crystals can be aligned vertically or homogeneously on $a-SiO_x$ film can be predicted simply by measuring the change in optical transmittance by deposition of $a-SiO_x$ thin film layers.

• Journal of Radiation Protection and Research
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• v.27 no.3
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• pp.155-164
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• 2002

Methodology to evaluate the effective doses to adults undergoing various diagnostic x-ray examinations were established by Monte Carlo simulation of the x-ray examinations. Anthropomorphic mathematical phantoms, the MIRD5 male phantom and the ORNL female phantom, were used as the target body and x-ray spectra were produced by the x-ray spectrum generation code SPEC78. The computational procedure was validated by comparing the resulting doses to the results of NRPB studies for the same diagnostic procedures. The effective doses as well as the organ doses due to chest, abdomen, head and spine examinations were calculated for x-rays incident from AP, PA, LLAT and RLAT directions. For instance, the effective doses from the most common procedures, chest PA and abdomen AP, were 0.029 mSv and 0.44 mSv, respectively. The fact that the effective dose from PA chest x-ray is far lower than the traditional value of 0.3 mSv(or 30 mrem), which results partly from the advances of technology in diagnostic radiology and partly from the differences in the dose concept employed, emphasizes necessities of intensive assessment of the patient doses in wide ranges of medical exposures. The methodology and tools established in this study can easily be applied to dose assessments for other radiology procedures; dose from CT examinations, dose to the fetus due to examinations of pregnant women, dose from pediatric radiology.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.272.2-272.2
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• 2016

Copper-Tin (CuSn) thin films were synthsized by rf magnetron co-sputtering method with pure Cu and Sn metal targets with various rf powers and sputtering times. The obtained CuSn thin films were characterized by a surface profiler (alpha step), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), and contact angle measurement. The deposition rates were calculated by the thickness of CuSn thin films and sputtering times. We observed hexagonal Cu20Sn6 and cubic Cu39Sn11 phases from the films by XRD measurement. From the survey XPS spectra, the Cu and Sn main peaks were observed. Therefore, we could conclude CuSn thin films were successfully fabricated on the substrate in this study. The changes of oxidation states and chemical environment of the films were investigated with high resolution XPS spectra in the regions of Cu 2p, Cu LMM, and Sn 3d. Surface free energy (SFE) and wettability of the CuSn thin films were studied with distilled water (DW) and ethylene glycol (EG) using the contact angle measurement. The total SFE of CuSn thin films decreased as rf power on Cu target increased. The contribution to the total SFE of dispersive SFE was relatively superior to polar SFE.

• Progress in Medical Physics
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• v.10 no.1
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• pp.55-62
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• 1999

In an effort to study the characteristics of x-rays utilized in radiation therapy, we calculated the energy distribution and the mean energy of x-rays generated from a tungsten target bombarded by 6, 10, and 15 MeV electron beams, using a Monte Carlo technique. The average photon energies calculated as a function of the beam radius lied in 1.4 ∼ 1.6, 2.1 ∼ 2.5 and 2.8 ∼ 3.3 MeV ranges for 4, 10, and 15 MV electron beams, respectively, which turned out to have no strong dependence on the radius. Using the energy distributions of 6,10, and 15 MV x-rays obtained for the target distance of 100 cm, percentage depth doses were determined using Monte Carlo calculations. For the case 10 MV, a comparison was made between our calculation and measurement performed by others. The calculated percentage depth dose appeared somewhat smaller than the measured one except in the surface region. We conclude that this is due to the fact that the beam hardening effect resulting from the flattening filter was not properly allowed for in our Monte Carlo calculations.

• Journal of Surface Science and Engineering
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• v.43 no.6
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• pp.266-271
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• 2010

Ternary Mo-Cu-N films were deposited on Si wafer substrates with various copper contents by magnetron sputtering method using Mo target and Cu target in $Ar/N_2$ gaseous atmosphere. As increasing $N_2$ pressure, the microstructure of Mo-N films changed from ${\gamma}-Mo_2N$ of (111) having face-centered-cubic (FCC) structure to $\delta$-MoN of (200) having hexagonal structure. Detailed the microstructures of the Mo-Cu-N coatings were studied by X-ray diffraction, scanning electron microscopy and field emission transmission electron microscope. The results indicated that the incorporation of copper into the growing Mo-N coating led to the $Mo_2N$ and MoN crystallites were more well-distributed and refined and the copper existed in grain boundary. Ternary Mo-Cu-N films had a composite microstructure of the nanosized crystal crystalline ${\gamma}-Mo_2N$ and $\delta$-MoN surrounded by amorphous $Cu_3N$ phase.

• Journal of radiological science and technology
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• v.30 no.2
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• pp.113-119
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• 2007

It is important to consider the contrast of object in Mammography because an absorption gap between tissues of body and breast in breast is low. This study is to evaluate MTF image with resolution chart according to change of combination of target and filter. The results were as follows : 1. There were significant differences in X-ray energy according to combination of filter(Mo/Mo, Mo/Rh. Mo/Al, Rh/Rh, Rh/Al) and acrylic thickness(2 cm, 3 cm, 4 cm). 2. The value of lp/mm on MTF to 0.5 showed that the sharpness in MTF curve was 2.4 compared to Mo/Mo and 2cm acryl, 2.63 in Mo/Rh and 4 cm acryl, and 2.9 in Rh/Rh and 6cm acryl. 3. The value of lp/mm on MTF showed that the resolution in MTF curve was 6.0 compared to Mo/Mo and 2 cm acryl, 4.60 in Rh/Al and 4cm acryl, and 6.03 in Rh/Al and 6 cm acryl. 4. The value of MTF on 2.5 lp/mm distinguishable visually was 0.48 compared to Mo/Mo and 2 cm acryl, 0.53 in Mo/Rh and 4cm acryl, and 0.59 in Rh/Rh and 6cm acryl. 5. For the evaluation of an image of the mammo-phantom, the score of Mo/Mo was 12 points, Mo/Rh 11, Rh/Rh 10.5, Mo/Al 10, Rh/Al 9.0, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2000.11a
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• pp.12-12
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• 2000

This paper investigated the effect of the film deposition rate for $CrN_x$ microstructure and mechanical properties. For these purpose, pure Cr an stoichiometric CrN films were deposited with various target power density on Si hardened M2 tool steel. The variation of ni trogen concentration in $CrN_x$ f analyzed by AES and deposition rate was calculated by measuring of thickness using ${\alpha}-step$ profilometer. The microstructure was analyzed by X-Ray Diffract and Scanning Electron Microscopy(SEM), and mechanical properties were evalua residual stress, microhardness and adhesion tests. Deposition rate of Cr and CrN increased as an almost linear function of target power density from $0.25\mu\textrm{m}/min$ and $0.15\mu\textrm{m}/min$ to $0.43\mu\textrm{m}/min$. Residual stresses of Cr and CrN films were from tensi Ie to compressive stress with an increase of deposi tion rate a compressive stresses were increased as more augmentation of deposition r maximum hardness value of $2300kg/\textrm{mm}^2$ and the best adhesion strength correspond HF 1 were obtained for CrN film synthesized at the highest target densitY($13.2W/\textrm{mm}^2$) owing to high residual compressive stress and increasing mobility.

• Journal of the Korean Vacuum Society
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• v.4 no.2
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• pp.172-176
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• 1995

$YBa_2Cu_3O_{7-y}$ thin films have been prepared on MgO(100)substrates placed on-axis to the target by dc magnetron sputtering in a variety of oxygen/argon gas pressures with different substrate-target distances. We found that films with the c-axis perpendicular to the substrate deposited in an optimally high gas pressure with on-axis substrate-target configuration do. Increasing the substrate-target distance was found to be effetive in reducing the resputtering effect and enhancing superconductivity of films, but not so much $\alpha$-and c-axis growth of YMCO films on MgO substrates. Dependences of the Tc, the rationj of resistances at 300K and 100K, and the X-ray diffraction pattern on the gas pressure and the substrate target distance are described.

• The Journal of the Korea Contents Association
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• v.10 no.9
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• pp.267-275
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• 2010

Quality management of an x-ray unit drastically differs according to the type of establishment of medical institutions. Many primary medical institutions have it, but they do not pay much attention to quality management. In the study, Gyeongbuk area has been divided into four zones from January 4, 2010 to September 3, 2010, and four places were designated by city. Among medical institutions located at a total of 16 sites, the target was 8 places with X-ray emission equipment 10 years or more in use as well as 8 places with X-ray emission equipment less than 10 years in use. The 5 essential items of quality control were tested. In the test that checked for equipment it was found that sites with X-ray emission equipment 10 years or more in use didn't have ground connection (6.25%) while all of them passed the current leak test. In the exposure dose reproducibility test 4 sites with X-ray emission equipment 10 years or more in use (25%) and 1 site with X-ray emission equipment less than 10 years in use didn't pass the test. In the KVp accuracy test 5 sites with X-ray emission equipment 10 years or more in use (31.25%) and 2 sites with X-ray emission equipment less than 10 years in use (12.5%) didn't pass the test. In the tube current and tube current amount test 3 sites with X-ray emission equipment 10 years or more in use (18.75%) and 1 site with less than 10 years in use (6.25%) didn't pass the test. According to the findings of the present research, quality control at medical institutions with X-ray equipment 10 years or more in use was poorer than medical institutions with X-ray equipment less than 10 years in use. In this regard, administrative and technical measures need to be taken as soon as possible. In addition, owners of medical clinics or unit managers need to raise awareness, and it is necessary to revise a regular test cycle every year or every two years if they have old equipment or if the equipment is not used on a frequent basis. And it is also important to provide regular educational programs for quality management.