• 대한기계학회논문집 C: 기술과 교육
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• 제3권4호
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• pp.241-248
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• 2015

국내 사용되고 있는 적외선 검출기 냉각용 스털링 극저온 냉동기는 상당부분 수입에 의존하고 있으며, 높은 대당 가격, 제한적인 수명 및 내구성 부족으로 지속적인 극저온 냉동기 수요가 발생하고 있다. 그런데 적외선 검출기용 극저온 냉동기 기술은 국방, 우주관련 기술로 선진국의 기술이전이나 공동 개발이 매우 제한적이다. 본 연구를 통해 개발하고자 하는 맥동관 극저온 냉동기는 저온구동부의 기계적 피스톤을 가스피스톤으로 대체하고, 압축방식을 선형압축방식으로 바꿈으로써 낮은 진동, 높은 수명 및 내구성을 확보할 수 있다. 이를 통해 맥동관 냉동기의 기술수준을 선진국에 근접시키고, 독자적인 냉각형 적외선 검출기 설계 및 제작기술에 대한 기술을 확보하고자 한다.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.15-21
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• 2008

Secondary electron detectors used in scanning electron microscope accept secondary electrons emitted from the specimen and convert them to an electrical signal that, after amplification, is used to modulate the gray-level intensities on a cathode ray tube, producing an image of the specimen. In order to acquire images with good qualities, as many secondary electrons as possible should be reached to the detector. To realize this it is very important to select an appropriate mounting position and angle of the detector inside the chamber of scanning electron microscope. In this paper, a number of numerical simulations are performed to explore the relationships between detection rates of secondary electrons and the values of some parameters, such as distances between the detector and sample, relative mounting positions of scintillator positioned inside the detector with respect to detector cover, two types of mounting angles of the detector. The relationships between detection rates and applied voltages to corona ring and faraday cage, and energies of secondary electrons are investigated as well.

• Nuclear Engineering and Technology
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• 제52권7호
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• pp.1355-1366
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• 2020

A review of the documentation and an interpretation of the NEA-1517/74 and NEA-1517/80 shielding benchmarks (measurements of photon leakage flux from a hollow sphere with a central 14 MeV neutron source) from the SINBAD database with the Monte Carlo code MCS and the most up-to-date ENDF/B-VIII.0 neutron data library are conducted. The two analyzed benchmarks describe satisfactorily the energy resolution of the photon detector and the geometry of the spherical samples with inner beam tube, tritium target and cooling water circuit, but lack information regarding the detector geometry and the distances of shields and collimators relatively to the neutron source and the detector. Calculations are therefore conducted for a sphere model only. A preliminary verification of MCS neutron-photon calculations against MCNP6.2 is first conducted, then the impact of modelling the inner beam tube, tritium target and cooling water circuit is assessed. Finally, a comparison of calculated results with the libraries ENDF/B-VII.1 and ENDF/B-VIII.0 against the measurements is conducted and shows reasonable agreement. The MCS and MCNP inputs used for the interpretation are available as supplementary material of this article.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.324-327
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• 2002

For a next generation PET that realizes high sensitivity and high resolution, we proposed a design of a depth of interaction detector. A unit of the detector is constructed of four stages rectangular blocks of 2 by 2 Gd$_2$SiO$\sub$5/: Ce (GSO) crystal array optically coupled to position sensitive photomultiplier tube (PS-PMT). The 256ch flat panel PS-PMT is under development by Hamamatsu Photonics K.K., JAPAN. It has large cathode area, 51.7 by 51.7 mm$^2$, and the ratio of the effective area to external size is about 90%. The feature will contribute high packing fraction, accordingly high sensitivity. The 256 anodes are arranged in 16 by 16 at intervals of 3.0 mm. So as to evaluate the detector capability for identifying crystal of interaction, we got positioning image histograms with coupling a 16 by 5 array of GSO crystals, 2.9 by 2.9 by 7.5 mm$^3$, to the PS-PMT by irradiating a gamma ray uniformly from a point source. Flat panel PS-PMT is a new promising device for PET. We need to evaluate it if its performance is sufficiency. The performance was compared to the one with a 16ch PS-PMT.

• 대한안전경영과학회지
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• 제17권4호
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• pp.213-221
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• 2015

The aim of this study was to set up the optimal exposure condition according to detector type considering image quality (IQ) with radiation dose in chest digital radiography. We used three detector type such as flat-panel detector (FP) and computed radiography (CR), and charge-coupled device (CCD). Entrance surface dose (ESD) was measured at each exposure condition combined tube voltage with tube current using dosimeter, after attaching on human phantom, it was repeated 3 times. Phantom images were evaluated independently by three chest radiologists after blinding image informations. Standard exposure condition using each institution was 117 kVp-AEC at FP and 117 kVp-8 mAs at CR, and 117 kVp-8 mAs at CCD. Statistical analysis was performed by One way ANOVA (Dunnett T3 test) using SPSS ver. 19.0. In FP, IQ scores were not significant difference between 102 kVp-4 mAs and 117 kVp-AEC (28.4 vs. 31.1, p=1.000), even though ESD was decreased up to 50% ($62.3{\mu}Gy$ vs. $125.1{\mu}Gy$). In CR, ESD was greatly decreased from 117 kVp-8 mAs to 90 kVp-8 mAs without significant difference of IQ score (p=1.000, 24.6 vs. 19.5). In CCD, IQ score of 117 kVp-8 mAs was similar with 109 kVp-8 mAs (29.6 vs. 29.0), with decreasing from $320.8{\mu}Gy$ to $284.7{\mu}Gy$ (about 11%). We conclude that optimal x-ray exposure condition for chest digital radiography is 102 kVp-4 mAs in FP and 90 kVp-8 mAs in CR, and 109 kVp-8 mAs in CCD.

• 대한의용생체공학회:의공학회지
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• 제26권1호
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• pp.43-47
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• 2005

We have developed a small bore x-ray CT for small animal imaging with a linear x-ray detector array and small-scale slip rings. The linear x-ray detector array consists of 1024 elements of 400□m×400□m with a gadolinium oxysulfide (GOS) scintillator on top of them. To avoid use of expensive large diameter slip rings for projection data transmission from the X­ray detector to the image reconstruction system, we used the wireless LAN technology. The projection data are temporally stored in the data acquisition system residing on the rotating gantry during the scan and they are transmitted to the image reconstruction system after the scan. With the wireless LAN technology, we only needed to use small-scale slip rings to deliver the AC electric power to the X-ray generator and the power supply on the rotating gantry. The performances of the small animal CT system, such as SNR, contrast, and spatial resolution, have been evaluated through experiments using various phantoms. It has been experimentally found that the SNR is almost linearly proportional to the tube current and tube voltage, and the minimum resolvable contrast is less than 30 CT numbers at 40kVp/3.0㎃. The spatial resolution of the small animal CT system has been found to be about 0.9Ip/㎜. Postmortem images of a piglet is also presented.

• 한국방사선학회논문지
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• 제4권3호
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• pp.5-11
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• 2010

본 논문에서는 이중 에너지 디지털 래디오그래피를 위한 이중 모드 검출기 개발을 제안한다. 이중 에너지 래디오그래피 모듈의 설계를 위하여 상용 BIS(Baggage Inspection System)에서 사용되고 있는 X-선 발생장치의 스펙트럼과 이중 모드 검출기에 대한 특징 및 방사선적 특성을 분석하였다. 제안하는 영상 검출기 모듈은 BIS에서 활용되고 있는 X-선관을 대상으로 X-선 스펙트럼을 모사하고, 모사한 스펙트럼을 통하여 새롭게 제안하는 검출기 모듈의 방사선적 특성을 고찰하였다. X-ray를 이용한 실험에서 구리 필터의 두께 증가에 따라 저에너지 검출기(LED)와 고에너지 검출기(HED)의 출력신호의 차이는 같이 증가하였다. 특히 HED에서의 출력신호의 크기는 구리 필터 두께가 증가 할수록 감소함을 알 수 있었다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.318-321
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• 2002

As a part of the next generation PET project, we have developed a depth of interaction detector which is consist of three-dimensional arrays of GSO crystal elements sized 2.9mm ${\times}$ 2.9mm ${\times}$ 7.5mm. The basic structure of a detector block is 4-stages in depth, one stage is composed of 2 by 2 array of the crystal elements. The blocks are optically coupled to a position sensitive photomultiplier tube. Each crystal element can be in different conditions; rough or chemical etching for the crystal surface. The effect of the difference of crystal surface condition on the detector performance was analyzed in one-dimensional crystal array as a basic study for the three-dimensional detector by a simple model which is considered only probabilities of transmission, reflect and absorption of photons are in a crystal. As the next step, we investigated the effect of different crystal surface condition in a "U shaped detector" which is an array of stacked crystals bending at the center.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.197-201
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• 2002

A free piston and free displacer (FPFD) Stirling cryocooler and inertance pulse tube cryocooler for the cooling infrared detector and cryosensor are currently under development at Korea Institute of Machinery ＆ Materials. The pulse tube cryocooler, which has no moving parts at its cold section, is attractive for obtaining higher reliability, simpler construction and lower vibration than in any other small cryocoolers. In recent years, pulse tube cryocoolers have experienced a rapid development with the aim to eventually replace Stirling and Gifford-McMahon cryocoolers in various applications. In this study, operating characteristics of the conventional linear Stirling cryocooler was investigated by experiment. And, inertance pulse tube cryocooler with the commercial linear compressor(Leybold Polar) was designed, manufactured, and tested by the variations of the operating frequency, charging pressure and input power.

• Journal of Advanced Marine Engineering and Technology
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• 제7권1호
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• pp.14-22
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• 1983

The Bourdon tube pressure gauge is the most widely used primary detector for pressure in various kinds of fields recently. However in many cases lots of difficulties are encountered in telemetering, measuring the continuously changing pressure and recording as time goes by, etc. In this paper a Bourdon tube of flat-oval section is considered. On the basis of Wolf's theory, the very sensitive places are selected on the tube and full bridge arrangement is used. Then all of the characteristics are examined in order to use the pressure transducer practically into which the pressure gauge is converted. From the results, the error in meter reading is about $\pm$3% F.S., on the other hand, when measured with strain gauge, the error is within $\pm$1% F.S.. Also external acceleration on Bourdon tube hardly affect practical use.