• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.919-926
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• 2023

To analyze the cause of the destruction of thin, carbon-backed lithium fluoride targets during a measurement of the fusion of ⁷Li and ¹⁷O, we estimate theoretically the lifetimes of carbon and LiF films due to sputtering, thermal evaporation, and lattice damage and compare them with the lifetime observed in the experiment. Sputtering yields and thermal evaporation rates in carbon and LiF films are too low to play significant roles in the destruction of the targets. We estimate the lifetime of the target due to lattice damage of the carbon backing and the LiF film using a previously reported model. In the experiment, elastically scattered target and beam ions were detected by surface silicon barrier (SSB) detectors so that the product of the beam flux and the target density could be monitored during the experiment. The areas of the targets exposed to different beam intensities and fluences were degraded and then perforated, forming holes with a diameter around the beam spot size. Overall, the target thickness tends to decrease linearly as a function of the beam fluence. However, the thickness also exhibits an increasing interval after SSB counts per beam ion decreases linearly, extending the target lifetime. The lifetime of thin LiF film as determined by lattice damage is calculated for the first time using a lattice damage model, and the calculated lifetime agrees well with the observed target lifetime during the experiment. In experiments using a thin LiF target to induce nuclear reactions, this study suggests methods to predict the lifetime of the LiF film and arrange the experimental plan for maximum efficiency.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.66-77
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• 1992

A prototype probabilistic approach to thickness design for asphalt pavement surface course was developed using first-order second moment probability model. The tensile strain (load effect) developing at the bottom of surface layer due to the wheel load and the critical strain (resistance) of asphalt concrete were used as random variables for pavement reliability analysis. Based on the parameters for load effect and resistance data collected from reference and field, simulated data were generated by Monte Carlo method for reliability evaluation of the pavement for a typical rural highway. Thickness of pavement surface course was defined in terms of target reliability of the pavement, growth factor of traffic, design life of pavement and resistance of the asphalt concrete to be placed on the pavement. According to these rationales, prototype thickness design chrats were sugested through example studies. From these, similar design charts can be developed for many pavements if appropriate data and target reliability are determined.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3026-3034
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• 2021

Multi-target X-ray tube is a new type X-ray source, and can be applied in many fields such as sensitive X-ray fluorescence analysis and medical imaging. In this work, we report an electric field modulation multi-target X-ray tube, which contains four targets (Cr, Ni, Au, Mo) coated on a Beryllium (Be) window. A four-valve electric field deflector was developed to deflect the electron beam to bombard the corresponding targets. Particle dynamics analysis software was employed to simulate the particle tracking of electron beam. The results show that the 30 keV electron beam could get a 6.7 mm displacement on the target plane by 10⁵ V/m electric field. The focus areas are about 2 mm × 5 mm and 4 mm × 2.5 mm after deflection in two directions. Thermal behavior calculated by ANSYS shows that the designed target assembly could withstand a 10 W continuous power. The optimum target thicknesses and emission spectra were obtained by Geant4 when the thickness of Be window was 300 mm and the electron beam incident angle was 0.141 rad. The results indicate that this multi-target X-ray tube could provide different X-ray sources effectively.

• Journal of the Korean Wood Science and Technology
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• v.33 no.2 s.130
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• pp.24-28
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• 2005

Monte Carlo simulation was performed on theoretical models of plywood warp for southern yellow pine plywood originating from the United States. The objective of the investigation was to determine which plywood layers was more warp sensitive to veneers that were manufactured to an undesired thickness. This study found that for a balanced panel (a panel of equal target thickness for each of five layers) manufactured veneers of undesired thickness would experience minimal warp. The veneers of undesired thickness placed in the center of the plywood panel also provided a minimum change of plywood warp properties. The panel warp was very sensitive to surface veneers constructed with undesired thickness. Conversely, this study confirms that monitoring of veneer thickness and proper allocations within the plywood lay-up were critical.

• Journal of the Korean Wood Science and Technology
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• v.24 no.4
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• pp.56-63
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• 1996

This study was to manufacture thinned wood of Larix leptolepis Gordon into Oriented Strand Board(OSB) with Urea-Formaldehyde Resin. The OSB was made of four kinds of strand in slenderness ratio 150 ; thickness $0.3{\pm}0.05mm$, $0.4{\pm}0.05mm$, $0.5{\pm}0.05mm$ and $0.6{\pm}0.05mm$, respectively length 45mm, 60mm, 75mm and 90mm. Target densities were 0.65gr/$cm^3$, 0.75gr/$cm^3$ and 0.85gr/$cm^3$. The stepwise 9 minutes-multi-pressing schedule in the maximum pressure 40kgf/$cm^2$, the minimum pressure 10kgf/$cm^2$ was applied for $400mm{\times}390mm{\times}12mm$ board at the temperature of $150^{\circ}C$ in a hot press. In MOR The OSB of thin strand thickness $0.3{\pm}0.05mm$(length 45mm) and density 0.85gr/$cm^3$ was the highest. The strand thickness had more effect on MOR than the strand length. In strand thickness $0.4{\pm}0.05mm$(length 60mm) and density 0.85gr/$cm^3$ was the highest MOE. The strand thickness and length had adverse effects on MOE each other. At internal bonding. The OSB of strand thickness $0.3{\pm}0.05mm$(length 45mm) and board density 0.75gr/$cm^3$ showed the highest value. OSB had higher IB value with thinner strand thickness. The thinner strand thickness showed the lower thickness swelling in turn $0.3{\pm}0.05mm$(length 45mm), $0.4{\pm}0.05mm$(length 60mm), $0.5{\pm}0.05mm$(length 75mm). $0.6{\pm}0.05mm$(length 90mm). Target densities 0.75gr/$cm^3$ 0.65gr/$cm^3$, 0.85gr/$cm^3$ showed in turn lower value. Finally, The OSB made of thinned wood of Larix leptolepis Gordon showed good results in laboratory experiment.

• Advances in nano research
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• v.1 no.4
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• pp.219-228
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• 2013

We report on the preparation of iron pyrite ($FeS_2$) using pulsed electron ablation of two targets, namely, a mixture of sulfur and iron compound target, and a natural iron pyrite target. Thin films of around 50 nm in thickness have been deposited on glass substrates under Argon background gas at 3 mTorr, and at a substrate temperature of up to $450^{\circ}C$. The thin films have been analyzed chemically and examined structurally using x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and visible Raman spectroscopy. The morphology and thickness of the films have been assessed using scanning electron microscopy (SEM) and visible spectroscopic reflectance. The preliminary findings, using a synthetic target, show the presence of iron pyrite with increasing proportion as substrate temperature is increased from $150^{\circ}C$ to $250^{\circ}C$. The data have not shown any evidence of pyrite in the deposited films from a natural target.

• Transactions on Electrical and Electronic Materials
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• v.6 no.5
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• pp.225-228
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• 2005

In this work, we studied the optimized copper thickness in Cu ECP (Electrochemical Plating). In order to select an optimized Cu ECP thickness, we examined Cu ECP bulge (bump, hump or over-plating amount), Cu CMP dishing and electrical properties of via hole and line trench over dual damascene patterned wafers split into different ECP Cu thickness. In the aspect of bump and dishing, the bulge increased according as target plating thickness decreased. Dishing of edge was larger than center of wafer. Also in case of electrical property, metal line resistance distribution became broad gradually according as Cu ECP thickness decreased. In conclusion, at least $20\%$ reduced Cu ECP thickness from current baseline; $0.8\;{\mu}m$ and $1.0\;{\mu}m$ are suitable to be adopted as newly optimized Cu ECP thickness for local and intermediate layer.

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.160.2-160
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• 2002

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.252-255
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• 2009

The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of roll gap to compensate thickness variation due to top-end temperature drop. The off-line simulation of compensated roil gap significantly decreases top-end thickness variation.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.106-109
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• 2012

Purpose : The KOTRON-13 cyclotron was developed and installed in regional cyclotron centers to produce short-lifetime medical radioisotopes. However, this cyclotron has limited capacity to produce $^{11}C$ so far. In present study, we developed an effective $^{11}C$ target system combining with fluorine-18 target and applied to the production of various $^{11}C$ radiopharmaceuticals. Materials and Methods : To develop the optimal $^{11}C$ target system and effective its cooling system, we designed the $^{11}C$ target system by Stopping and Range of Ions in Matter (SRIM) simulation program and considered the cavity pressure during irradiation at target grid. In this investigation, we modified target materials, cavity shapes and the position of cooling system in $^{11}C$ target and then evaluated $[^{11}C]CO_2$ production at different beam currents, thickness of the target foil, oxygen content of nitrogen gas and target gas loading pressure. Also, we evaluate the production of several $^{11}C$ radiopharmaceuticals such as [$^{11}C$]PIB, [$^{11}C$]DASB, and [$^{11}C$]Clozapine. Results : $[^{11}C]CO_2$ was produced about 74 GBq for 30min irradiation at 60 ${\mu}A$ of beam current as following conditions: thickness of the target foil: 19 nm HAVAR, oxygen content of nitrogen: under 50 ppb, target gas loading pressure: 24 bar. Additionally, the cooling system was stable to produce $[^{11}C]CO_2$ at high beam current. The radiochemical yields of [$^{11}C$]PIB, [$^{11}C$]DASB, and [$^{11}C$]Clozapine showed about 26-38% with over 127 GBq/umol of specific activity. Conclusion : The carbon-11 target system in the KOTRON-13 cyclotron was successfully developed and showed stable production of $[^{11}C]CO_2$. These results showed that our $^{11}C$ target system will be compatible with other commercial system for the routine $^{11}C$ radiopharmaceuticals production in the KOTRON-13 cyclotron.