• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.27-32
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• 2008

This paper describes a contact atomic force microscope (AFM) that can be used for high-speed precision measurements of microstructured surfaces. The AFM is composed of an air-bearing X stage, an air-bearing spindle with the axis of rotation in the Z direction, and an AFM probe unit. The traversing distance and maximum speed of the X stage are 300 mm and 400 mm/s, respectively. The spindle has the ability to hold a sample in a vacuum chuck with a maximum diameter of 130 mm and has a maximum rotation speed of 300 rpm. The bandwidth of the AFM probe unit in an open loop control circuit is more than 40 kHz. To achieve precision measurements of microstructured surfaces with slopes, a scanning strategy combining constant height measurements with a slope compensation technique is proposed. In this scanning strategy, the Z direction PZT actuator of the AFM probe unit is employed to compensate for the slope of the sample surface while the microstructures are scanned by the AFM probe at a constant height. The precision of such a scanning strategy is demonstrated by obtaining profile measurements of a microstructure surface at a series of scanning speeds ranging from 0.1 to 20.0 mm/s.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.39-39
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• 1999

The KSTAR (Korea Superconducting Tokamak Advanced Research) tokamak is a nuclear fusion experimental device for a long pulse/steady-state plasma operation, adopting fully superconducting magnets. In accordance with completion of the basic design of the torus vacuum vessel and the enclosing cryostat, the vacuum pumping and gas fueling basic design has been developed to fulfil the physics requirements. The ultra-high vacuum pumping and sophisticated gas fueling system of the machine is essential to achieve such roles for optimized plasma performance and operation. Recently the vacuum exhaust system using dedicated pumping ports for the vacuum vessel and cryostat has been modified to meet more reliable and successful performance of the KSTAR[Fig. 1].In order to achieve the required base pressure of 5 x 10-9 torr, the total impurity load to the vessel internal is limited to ~5 x 10-5 torr-1/x, while the cryostat base pressure is kept as ~5 x 105 torr to mitigate the thermal load applied to the superconducting magnets. Each KSTAR fueling system will be separately capable of fueling gas at a rate of 50 torr-1/x, consistent with the given pumping throughput. In order to initiate a plasma discharge in KSTAR, the vacuum vessel is filled to a gas pressure of few 10-6 to few 10-4 torr, and additional gas injection is required to maintain and increase the plasma density during the course of the discharge period.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.359-359
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• 2014

In this study, surface plasmon resonance structures for the selective and the enhanced transmission of infrared light were designed. In order to relieve the large discontinuity of refractive index between air and metal hole array, $Si_3N_4$ was used as the impedance matching layer. Experimental parameter were calculated and determined in advance by the rigorous coupled wave analysis (RCWA) simulation, and then the experiment was carried out. A 2-dimensional metal hole array structures were patterned on the size of $1{\times}1cm^2$ GaAs substrate using photolithography process, and 5 nm thick Ti, 50 nm thick Au were deposited by E-beam evaporator, respectively. Subsequently, $Si_3N_4$ films with various thicknesses (150, 350, 550, and 750 nm) were deposited by plasma enhanced chemical vapor deposition (PECVD). For the comparison, transmittance of specimens with and without $Si_3N_4$ was measured using Fourier transform infrared spectroscopy (FTIR) in the range of $2.5-15{\mu}m$. Furthermore, the surface and the cross-sectional images were collected from the specimens by scanning electron microscopy (SEM). From the results, it was demonstrated that the transmittance was enhanced up to 80% by the deposition of 750 nm $Si_3N_4$ at $6.23{\mu}m$. It has advantage of enhanced transmission despite the simple fabrication process.

• Progress in Medical Physics
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• v.33 no.4
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• pp.72-79
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• 2022

Purpose: The proficiency test was conducted to assess the performance of the dosimetry audit service provider in the readout practice of the dose delivered to patients in medical institutions. Methods: A certain amount of the absorbed dose to water for the high-energy X-ray from the medical linear accelerator (LINAC) installed in the Korea Research Institute of Standards and Science (KRISS) was delivered to the postal dose audit package given by the dosimetry audit service provider, in which the radio-photoluminescence (RPL) glass dosimeters were mounted. The dosimetry audit service provider read the RPL glass dosimeters and sent the readout dose value with its uncertainty to KRISS. The performance of the dosimetry audit service provider was evaluated based on the E_n number given in ISO/IEC 17043:2010. Results: The evaluated E_n number was -0.954. Based on the ISO/IEC 17043, the performance of the dosimetry service provider is "satisfactory." Conclusions: As part of the conformity assessment, the KRISS performed the proficiency test over the postal dose audit practice run by the dosimetry audit service provider. The proficiency test is in line with confirming the traceability of the medical institutions to the primary standard of absorbed dose to the water of the KRISS and ensuring the confidence of the dosimetry audit service provider.

• Korean Journal of Optics and Photonics
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• v.35 no.2
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• pp.61-70
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• 2024

We demonstrate a laser power meter calibration system based on 12-diode laser sources coupled to single-mode fibres in a wavelength range from 400 to 1,600 nm. In our system, three laser power controllers ensure that the output power uncertainty of all laser sources is less than 0.1% (k=2). In addition, all laser beams are adjusted to have similar beam sizes of approximately 2 mm (1/e²-width) at the measurement position to minimise unmeasured laser power on a detector. As a reference detector, we use an integrating sphere combined with silicon and indium gallium arsenide photodiodes to minimise the non-uniformity and non-linearity of responsivity. The minimum uncertainty of the calibration system is estimated to be 1.1% (k=2) for most laser wavelengths.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.335-343
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• 2024

This paper came up with the theoretical modelling of the metrology for the acoustic power using ultrasonic radiation force and showed some theoretical results. In order to do this, a scattering model for a rigid circular cone based upon the Kirchhoff approximation was made, which was followed by the calculation of acoustic power, and then, was converted to the radiation force. From these works, it provided the accuracy and limitation of the conventional method using a circular cone, and the expanded metrology modelling that can be applied to a circular cone with arbitrary apex angle. Using these, this study provided the dependence of the metrology for the acoustic power using ultrasonic radiation force on the frequency and the size of the target. As a result, the correction was yielded in the value of the acoustic power calculated by the suggested International Electrotechnical Commission (IEC) method, which needs to be added when the frequency and the size of the target was considered.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.282-285
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• 2004

Every year, the last products from most important builders of high bandwidth digitizers are tested in our laboratory which is specialized in the design and the characterization of fast links used in large laser facility. The purpose of this article is to describe the series of tests conducted during the characterization of such digitizers. More particularly, it takes an interest in the metrology of instruments with more than 5 GHz of bandwidth. It presents the different methods used and the kind of conclusion that we can give after such study. Such metrology campaign which usually takes one month of work, allows us to observe the smallest details and characteristics that usually builders don't give in their tables specifications. After the campaign, a copy of our technical report is written and sends to the builder. This report can be used by the technical team to ameliorate the points we noted.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.24-32
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• 1994

A force sensor of 30 MN capacity using build-up technique in which three load cells of 10 MN capacity are arranged in parallel was fabricated. A column spring element was adopted as a shape of a strain gage type load cell. Temperature compensation circuits were used to reduce the error of a load cell. It was estimated that the total error of the fabricated force sensor is less than 0.1 %. The force sensor may be used to calibrate or test material testing machines above 4.5 MN capacity in industries.

• IE interfaces
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• v.23 no.3
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• pp.229-238
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• 2010

Virtual metrology (VM), a critical component of semiconductor manufacturing, is an efficient way of assessing the quality of wafers not actually measured. This is done based on a model between equipment sensor data (obtained for all wafers) and the quality characteristics of wafers actually measured. This paper considers principal component regression (PCR), partial least squares regression (PLSR), kernel PCR (KPCR), and kernel PLSR (KPLSR) as VM models. For each regression model, two cases are considered. One utilizes all explanatory variables in developing a model, and the other selects significant variables using the genetic algorithm (GA). The prediction performances of 8 regression models are compared for the short- and long-term etch process data. It is found among others that the GA-KPLSR model performs best for both types of data. Especially, its prediction ability is within the requirement for the short-term data implying that it can be used to implement VM for real etch processes.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.369-370
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• 2004

초음파의 조차에 의한 인체내부의 온도상승의 측도로 열지수(thermal index)가 사용되고 있으며, 이는 주파수 및 음향파워에 의존한다. 초음파 조사에 의한 인체내부의 온도상승을 평가하는데 사용되는 재료를 조직 모사 물질이라 한다. 본 논문아사는 단위 음향파워에 대한 온도 변화인 열 감도(thermal sensitivity)를 새로이 정의하였으며, 이 물리량으로 조직모사물질의 성능을 평가 할 수 있다는 것을 제안하고자 한다.