• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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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.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.725-731
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• 2020

A radiation spectroscopy detector using a spherical scintillator was designed, and a system was developed to track the position of a radiation source using several detectors. The position tracking algorithm was designed based on the theory that the number of radiations decreases according to the inverse square law of distance, and the position of the radiation source was calculated by measuring the number of radiations generated from the radiation sources at various positions. The radiation generated from the radiation source is detected by different coefficients in each detector, and the difference between these detected coefficients varies in proportion to the inverse square of the distance. Geant4 Application for Tomographic Emission (GATE) simulation was performed to verify and evaluate the performance of the designed radiation source position tracking system, and radiation generated from radiation sources placed at different positions was counted with each detector. The number of measured radiations was tracked through the radiation source position tracking algorithm, and the error between the actual radiation source position and the position calculated by the algorithm was evaluated. The error between the position of the actual radiation source and the calculated position was measured as an average of 0.11% on the X-axis and 0.37% on the Y-axis, and it was verified that the position can be measured very accurately.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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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.

• Journal of Advanced Navigation Technology
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• v.21 no.2
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• pp.163-170
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• 2017

MLAT which is an independent cooperative surveillance system is applied to increase the positon resoultin of secondary survelliance radar. MLAT uses the hyperboic or hyperboloid position mesurement algorithm. Central processing unit of MLAT calculates target position using time difference of arrival (TDOA) which can be solved from time of arrival (TOA) information of each receivers (at least 4 receivers). To increase position resolution of MLAT which use TDOA, TOA which is transfer time from tranmitter to receiver shold be calculated with precision time resolution in receiver. This paper explained the MLAT system briefly and explained ATD which is one of means of calcuating pulse position. ATD is applied to solve the deviation of pulse position due to different amplitude of signals in mulitiple receivers. In this paper, to analysis the performance of ATD, the simulation result of LAS and CDS was compared with the simulation result of basic threshold method.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1291-1302
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• 2016

This paper presents a new and efficient scheme to determine the optimal neutron source position in a model near-equilibrium pressurized water reactor, which is based on the OPR1000 Hanul Unit 3 Cycle 7 configuration. The proposed scheme particularly assigns importance of source positions according to the local adjoint flux distribution. In this research, detailed pin-by-pin reactor adjoint fluxes are determined by using the Monte Carlo KENO-VI code from solutions of the reactor homogeneous critical adjoint transport equations. The adjoint fluxes at each allowable source position are subsequently ranked to yield four candidate positions with the four highest adjoint fluxes. The study next simulates ex-core detector responses using the Monte Carlo MAVRIC code by assuming a neutron source is installed in one of the four candidate positions. The calculation is repeated for all positions. These detector responses are later converted into an inverse count rate ratio curve for each candidate source position. The study confirms that the optimal source position is the one with very high adjoint fluxes and detector responses, which is interestingly the original source position in the OPR1000 core, as it yields an inverse count rate ratio curve closest to the traditional 1/M line. The current work also clearly demonstrates that the proposed adjoint flux-based approach can be used to efficiently determine the optimal geometry for a neutron source and a detector in a modern pressurized water reactor core.

• Korean Journal of Digital Imaging in Medicine
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• v.11 no.1
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• pp.27-33
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• 2009

In this study, we compared the alteration of test positions according to various test equipments when testing shoulder joint superoinferior axial to estimate the clinical usefulness of tiltable standing detector. Our objectives were patients who visited our hospital. Among them we chose patients who were prescribed to get a shoulder axial test, again we selected 30 patients whose abduction is more than 90 degree.(2008. Nov.$\sim$2009 Jan.) With the patients cooperation, we used CR(Agfa, Belgium), fixed-detector(Canon, japan), Tiltable-detector(Philips, Netherlands). Tested with only one equipment(tiltable detector), and posed with the other two. We surveyed 5 inspectors and 30 patients, asking them to rate the convenience of test position. Also, we checked how long it takes to have the image appear on screen after testing with the equipment We provided a standard for an assessment of the image to an expert in bone radiology, an orthopedist and a radiologist with 5 years experience. When the patients were asked about the convenience of the equipments, 15 people(50%) answered CR is convenient and 14 people(46.7%) answered the Tilting detector is convenient, showing not much difference. However, when the inspectors were asked the same question, 4people(80%) out of 5 answered that the Tilting detector is more convenient The time test showed that CR takes 2 minutes and 50 seconds, the Fixed detector 1minute and 48 seconds andor had no distortion showing the shoulder joint space. However, even though the Fixed detector showed ac the Tilting detector takes 1 minute and 43 seconds to bring the image to the screen after the position. The results of the value of image taken by each equipment, CR and the Tilting detectromion, coracoid process, due to the unstable pose, they were quite distorted and scored poor in observing glenoid fossa. By this study, we can see that testing the shoulder joint superoinferior axial projection with a detector that has a tilting device would be more convenient than testing it with a CR.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.4
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• pp.53-58
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• 2010

In this paper, the output characteristics of PSD(Position Sensetive Detector) used in measurement system are described. Most of the precision measurment systems are accomplished by a laser diode(LD), a photo diode(PD) and PSD(Position Sensetive Detector), which are used in reflection of mirror or projection of infrared spectrometer. But it is especially restricted by resolution of PD and PSD in nano-measurement. A new inclined light methods into the PSD are employed in the surface measurement system for increasing the resolution. As the results, we can know that the output characteristics of detective senser (PSD) become more than 2 or 3 times by changing inclined angle(range: 5 degree) compared with common angle. In addition, the experiment results are confirmed that the change of inclined angle is not affecting to the linearity and repeating.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.309-311
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• 2000

An advanced angular position detector (APD) for the SMART CEDM (control element drive mechanism) was designed. The APD is required to be small size with high resolution for angular displacement of rotary step motor. Unfortunately the proximity sensors can not be adopted to SMART CEDM because the motor shaft is located in the pressure boundary cylinder filled with the primary coolant under high temperature and pressure. This paper describes the electromagnetic finite element analysis for the design of advanced angular position detector for the SMART CEDM. The electromagnetic properties obtained will be used as Input for the optimization analysis of the APD.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.703-712
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• 1987

A position detection method for 2 phase bifilar permanent magnet step motors is proposed. The back emfgenerated on 2 phase windings by rotor permanent magnet is calculated using motor terminal voltage and current by analog circuit, and the rotor position output is obtained from tese back emf signals through some logical manipulation circuit. This position detector functionally acts like a 2 channel optical incremental encoder, and it is also shown by experimental results that it works well over wide range of speed or under resonant condition where the rotor rings around the detent position. Its resolution is twice of the number of steps per revolution. Bu software implemented on micro-processor, the reliability of position output is enhanced, detecting and correcting error dut to external and/ or internal noise.

• Korean Journal of Optics and Photonics
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• v.4 no.2
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• pp.157-161
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• 1993

An optical autofocus system for a DUV KrF excimer laser wafer stepper was developed by using the PSD (Position Sensitive Detector) as the position sensor. The laser beam was incident on the surface of wafer and the reflected beam was magnified optically by a lens. And the beam was directed onto the surface of PSD by a mirror system. The spatial resolution of the autofocus system was found to be $0.03{\mu}m$.