• Journal of Korean Ophthalmic Optics Society
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• v.17 no.2
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• pp.135-141
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• 2012

Purpose: Polymerization of HEMA(2-hydroxyethyl methacrylate) which can be used in the soft contact lens has been performed by using electron beam(EB) irradiation, and examined the best condition for the polymerization. Comparing the physical properties of the contact lenses to the one fabricated by thermal polymerization method, we check the use possibility of the EB irradiation to the fabrication of the soft contact lens. Methods: We investigated the degree of polymerization of the HEMA according to the composition of the monomer, the additive ratio and the dose of electron beam (0~120 kGy). The degree of polymerization was measured depending on the EB dose to research the best synthetic condition under the EB irradiation. The physical properties of the contact lens such as water content(%), oxygen transmissibility(Dk/t) and optical transmittance were analysed by using the FT-IR results with comparing the two different polymerization method (thermal and electron beam polymerization) with same additive ratio. Results: When the dose of electron beam was above 100 kGy, the degree of polymerization of HEMA was above 99% with regardless using cross-linker and initiator. The water content of the lens fabricated by EB method showed 10% higher than the one by the thermal method which was 40%. The lens fabricated by EB method also showed higher oxygen transmissibility(Dk/t) as same with the water content, and showed twice higher value in the lens fabricated by pure HEMA. According to the FT-IR results, hydrophilic property of the lens fabricated by EB method was increased due to increasing the intermolecular hydrogen bonding. It showed above 90% optical transmittance in the visible range of wavelength on the contact lenses fabricated by the both of two different polymerization method. Conclusions: The polymerization of HEMA without cross-linker and initiator was successful above 100 kGy of EB irradiation. Moreover the lens fabricated from the polymer synthesized by pure HEMA with 100 kGy of EB showed the highest water content and oxygen transmissibility. Therefore EB irradiation is another possible method to synthesize the polymer which can be used for the soft contact lens.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.2
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• pp.24-29
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• 2006

The use electron-beam(E-beam) manufacturing system provides a means to alleviate optic exposure equipment's problems. We are developing an E-beam manufacturing system with scanning electron microscope(SEM) function. The E-beam manufacturing system consist of high voltage generator, beam blanker, condenser lenses, object lenses, stigmator and stage. The development of E-beam manufacturing system is used on the method of remaking SEM's structure. The functions of SEM are developed. It is important for the test of E-beam performance. In E-beam manufacturing system and SEM, beam focus is important function. In this paper, we propose intelligent remote control function for beam focus in E-beam manufacturing system. The function extends the user's function and gives convenience.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.517-522
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• 2011

Most of SEM is double condenser lens system. Two condenser lenses are required to provide the high demagnification ratios necessary for forming nanometer probes. The thin lens concept provides a highly useful basis for preliminary calculations in a broad range of situations. It is an easy way to understand the electron beam paths in column. Demagnification is easily calculated by this method. In this paper, we present design processes for condenser lens's demagnification by using thin lens combination model. Also, we verify the reliability of our design processes by comparing the modeled demagnification with these of corrected condenser lens.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.354-358
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• 2006

A silicon lens and an insulator of pyrex, components of a micro-electron column, should be assembled by aligning and stacking simultaneously. An optical alignment of a diffraction beam and a laser welding were employed for the assembly of a source lens and an Einzel lens with precision within $\pm$4% for the maximum aperture size. The experimental condition for optical alignment and laser welding are explained. Anodic bonding was used to assist in stacking lenses. A micro-electron column of smaller apertures assembled with precise alignment and fabrication was tested with a current image of a Cu grid of 9$\mu$m in linewidth, and showed a higher resolution in acceleration mode.

• Vacuum Magazine
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• v.2 no.2
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• pp.24-28
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• 2015

The brightness of an electron source, along with the aberrations of an objective lens, determines the image resolution and beam current on samples, which are two important parameters for evaluating the performance of an electron microscope. Here we introduce thermal electron source, Schottky emitter and cold field electron emitter. Thermal electron source is the cheapest and stable electron source but it has the lowest brightness. Schottky emitter is 10000 times brighter than tungsten thermal electron source, but requires ultrahigh vacuum operating condition. Cold field electron emitter is 10 times brighter than Schottky emitters, but it is rather unstable and its operation requires most stringent vacuum condition, hindering its widespread use.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1288-1293
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• 2007

The present study covers the design and analysis of a thermionic scanning electron microscope (SEM) column. The SEM column contains an electron optical system in which electrons are emitted and moved to form a focused beam, and this generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system mainly consists of a thermionic electron gun as the beam source, the lens system, the electron control unit, and the vacuum unit. In the design process, the dimension and capacity of the SEM components need to be optimally determined with the aid of finite element analyses. Considering the geometry of the filament, a three-dimensional (3D) finite element analysis is utilized. Through the analysis, the beam emission characteristics and relevant trajectories are predicted from which a systematic design of the electron optical system is enabled. The validity of the proposed 3D analysis is also discussed by comparing the directional beam spot radius. As a result, a prototype of a thermionic SEM is successfully developed with a relatively short time and low investment costs, which proves the adoptability of the proposed 3D analysis.

• Journal of the Optical Society of Korea
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• v.15 no.4
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• pp.368-372
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• 2011

An advanced microcolumn is proposed which adopts a modified einzel lens structure. The newly designed einzel lens is composed of four electrodes. The two center electrodes are specially designed electrostatic quadrupole (EQ) einzel lenses having keyhole instead of circular apertures. We constructed the advanced microcolumn with the EQ-einzel lenses, and operated the newly designed microcolumn in single lens mode and double-lens mode. The preliminary results show that the EQ-einzel lens can improve the performance of the micro-column for large sample applications.

• Journal of the Korean Society of Radiology
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• v.18 no.3
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• pp.283-292
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• 2024

Radiation side effects and complications on the ocular adnexa during electron beam therapy for orbital lymphoma can increase the incidence of posterior subcapsular cataracts. This study simulated a medical linear accelerator and a mathematical model of the eye using monte carlo simulations to evaluate the dose to the ocular adnexa and compare the shielding effectiveness on different parts of the ocular adnexa based on lens shield thickness. The dose assessment results of the ocular adnexa showed that the lens's sensitive area had the highest absorbed dose distribution when no shield was used, followed by the lens's non-sensitive area, the anterior chamber, vitreous humor, cornea, and eyelid in descending order. With the use of a shield, a 2 mm thick shield demonstrated a dose reduction effect of over 90% in the lens's sensitive area, over 83% in the non-sensitive area and anterior chamber, and a dose reduction effect of 30 to 62% in the vitreous body, cornea, and eyelid. For dose reduction in the lens's sensitive area during electron beam therapy for orbital lymphoma, it is necessary to use a shield of at least 2 mm thickness. Additionally, shielding strategies considering the thickness and area of the shield for other ocular adnexa besides the lens are required.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.461-462
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• 2007

• Korean Journal of Materials Research
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• v.11 no.9
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• pp.792-796
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• 2001

For electron beam lithography and SEM(scanning electron microscopy) applications, miniaturized electrostatic lenses called a microcolumn have been fabricated. In this paper, we report the fabrication technique for 20~30$\mu\textrm{m}$ apertures of electron lenses based on silicon and Mo membrane using an active Q-switched Nd:YAG laser. Experimental conditions of laser micromachining for silicon and Mo membrane are improved. The geometrical structures, such as the diameter and the preciseness of the micron-size aperture are dependent upon the total energy of the laser pulse train, laser pulse width, and the diameter of laser spot.