• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.268-271
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• 1993

Discharge pumped high power excimer laser is a very useful light source of ultraviolet region. In this paper. the design and operation characteristics of UV pre-ionized discharge pumped XeCl laser are discussed. Maximum output power of 890mJ at the efficiency of 1.4% was achieved with 35kV charging voltage, 3.4atm of total pressure and 10pps of pulse repetition rate. Optimum HCl pressure is considered to be between 2.5 and 3.5torr.

• Laser Solutions
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• v.3 no.2
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• pp.13-24
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• 2000

The weldability of dissimilar materials between sintered materials which are consisted of Co, Co＋Ni and carbon steel has been investigated using CO$_2$ laser. Autogeneous CO$_2$ laser welding were run along the butt between two alloys using sets of parameters variation-power and travel speed. In order to study weldability, mechanical tests (bending strength test, microhardness test) and metallurgical analyses (microstructure, phase transformation, fracture mode) were carried out. From the results obtained, it was found that the porosity which exists in a weld metal greatly affects the soundness of the weld. The optimum energy input to have a proper strength over than the requirement by a specification, found to be around 0.3-0.35kJ/m. There are two kinds of fracture mode in the weld metal, depending upon alloy combination, brittle fracture in the case of Co-carbon steel and a ductile fracture in the case of Co＋Ni-carbon steel. In general, Co＋Ni sintered material showed a better weld properties as compared to the Co sintered material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.84-88
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• 1992

Laser beam hardenling of 12%-Cr steel has been evaluated by using a continuous wave 3 kW CO$\_$2/ laser with a hardening mirror set. Experiment was performed on the optimum hardening condition with a laser power of 2.85kW and travel speed of 10 and 5 m/min. Multi passes have been alsotried to find the hardening characteristics of partly overlapped zone. The black paint to use at high temperature was adopted to increases the absorptivity of laser beam energy with the wavelength of 10.6 .mu. m at the surface of bese metal. The microstructure of the hardened layers was observed by using a light microscopy. SEM and TEM. A fine lamellar martensite formed in the hardened zones exhibits very high Vickers microhardness of 600 Hv, whereas the tempered martesite distributes in the base metal with Vickers microhardness of 240 Hv. It has been found that laser hardening with multi pass showed no significant drop of the hardness between adjacent passes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.816-819
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• 2000

Recently the styrofoam has been used fur material of press die pattern. The object of this research is to develope an automated laser system for manufacture of press die pattern which depends chiefly on handwork during its process. After converting 3-D CAD model into cross-sectional shape information, the unnecessary part of the section is vapored away by laser. The depth and width of cut are mainly under the control of laser power and beam feed rate. The optimum manufacturing conditions are obtained by preliminary experiments. It is necessary fur precise styrofoam pattern manufacturing to develope laser system which has sufficient motion accuracy and program or beam path generation and automatic control of this system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.659-660
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• 2006

High-aspect-ratio(max. 12.5) microchannels with excellent surface quality and good shape uniformity have been realized utilizing laser-induced etching technique. Etch width and depth variations depend largely upon process variables such as laser power and etchant concentration. Etchant concentration in association with viscosity also influence on the cross-sectional profile of the channels. The optimum process conditions for the fabrication of high-aspect-ratio microchannels applicable to micro thermal devices are demonstrated.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.96-101
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• 1989

The infrared multiphoton decomposition of trichloroethylene-H(TCE-H) and trichloroehtylene-D(TCE-D) was studied by using the high power $CO_2$ laser. The pressure dependence of TCE-H decomposition showed that the HCl elimination channel to form ClC ≡ CCl was the major step at high pressures, while the HC ≡ CCl formation step became important at low pressures. $Cl_2C$ = CHCl ${\rightarrow}$ (high pressure) ClC ${\equiv}$ CCl + HCl ${\rightarrow}$ (low pressure) HC ${\equiv}$ CCl + 2Cl${\cdot}$($Cl_2$) The IRMPD of TCE-H and TCE-D mixtures with 10P(20) laser line showed that optimum conditions of large isotope selectivity were the low system pressures and high laser powers. The experimentally observed dependence of the branching ratios on the pressure and laser fluence, and the isotope selectivity coefficients were quantitatively explained by using the modified energy grained master equations (EGME) model.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.1015-1016
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• 2006

The important parameters deciding the fluctuation of Accumulation style surgical operation of ventriculus laser beam are smoothing capacitor, frequency and he characteristics of laser resonator. In this thesis, we control the fluctuation of medical $CO_2C$ laser in realtime by changing Duty-Ratio of IGBT and switching frequency with fixed the smoothing capacitor to improve the fluctuation of laser beam. We detect the light on laser resonator using a CdS photo sensor to improve ripple factor of laser beam and feedback fluctuated signals refined by a band pass filter into the control circuit to stabilize fluctuation actively. There is much to be desired in the realtime controlling technique of the light on Accumulation style surgical operation of ventriculus laser discharge tube in electrical signal. We propose switching control technique with microprocessor and photo sensing technique by controlling switch devices optimum operation and feedback signals detected by a photo sensor into the laser power supply in order to improve ripple factor of the $CO_2$ laser beam.

• Laser Solutions
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• v.17 no.4
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• pp.14-19
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• 2014

Laser beam was applied on the boundary of the polyurethane and biodegradable polyacetate polymers. The distributed laser passed through the polyurethane layer and heated the polyacetate layer, then the soften acetate was squeezed thorough the 1mm square slots of polyurethane for the mechanical joining. The surface roughness ranging between $0.28{\mu}m$ and $3.06{\mu}m$ had almost no effect on joining strength, but the optical properties of HD (High Definition) and UHD (Ultra High Definition) mode affected laser beam transmittance. The optimum laser power was found to be between 8watt and 10watt with 500mm/min of scanning speed. The joining boundary was characterized by optical and SEM analysis. Based on the experiment and characterization results, the laser energy was effective for the polymer joining and efficiency of joining.

• Nuclear Engineering and Technology
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• v.33 no.2
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• pp.175-183
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• 2001

Various welding processes are now available for end cap closure of nuclear fuel element such as TG(Tungsten Inert Gas) welding, magnetic resistance welding and laser welding. Even though the resistance and TIG welding processes are widely used for manufacturing commercial fuel elements, they can not be recommended for the remote seal welding of a fuel element at a hot cell facility due to the complexity of electrode alignment, difficulity in the replacement of parts in the remote manner and a large heat input for a thin sheath. Therefore, the Nd:YAG laser system using optical fiber transmission was selected for Zircaloy-4 end cap welding inside hot cell. The laser welding apparatus was developed using a pulsed Nd:YAG laser of 500 watt average power with optical fiber transmission. The weldability of laser welding was satisfactory with respect to the microstructures and mechanical properties comparing with TIG and resistance welding. The optimum operation processes of laser welding and the optical fiber transmission system for hot cell operation in a remote manner have been developed The effects of irradiation on the properties of the laser apparatus were also being studied.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1733-1735
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• 2002

The important parameters deciding the fluctuation of laser beam are smoothing capacitor, frequency and the characteristics of laser resonator. In this thesis, we control the fluctuation of $CO_2$ laser in realtime by changing Duty-Ratio of IGBT and switching frequency with fixed the smoothing capacitor to improve the fluctuation of laser beam. We detect the light on laser resonator using a CdS photo sensor to improve ripple factor of laser beam and feedback fluctuated signals refined by a band pass filter into the control circuit to stabilize fluctuation actively. There is much to be desired in the realtime controlling technique of the light on laser discharge tube in electrical signal. We propose switching control technique with microprocessor and photo sensing technique by controlling switch devices optimum operation and feedback signals detected by a photo sensor into the laser power supply in order to improve ripple factor of the $CO_2$ laser beam.