Young Beom Song

Characterization of OTDR based fiber-optic humidity sensor

Summary form only given. In this study, the optical time-domain reflectometer (OTDR) based fiber-optic humidity sensor (FOHS) was fabricated to measure humidity in inaccessible hazardous environments. The sensing probe of FOHS consists of a single mode optical fiber and a moisture-sensitive material (mixture of HEC and PVDF) which varies its refractive index according to the relative humidity [1, 2]; here, the end of fiber was coated with the moisture-sensitive material by using the dip coating method. By Fresnel reflection between the sensing material and the single mode fiber, the optical power of the OTDR varies with the relative humidity. To optimize the FOHS, we evaluated the variation of optical power according to the contents (0.23, 0.33, 0.43, 0.53, and 0.63 g) of PVDF in the moisture-sensitive material and wavelengths (1310 and 1550 nm) of the laser source. As the result, the moisture-sensitive material containing 0.43 g of PVDF had the highest sensitivity with 1310nm laser source.

Fiber-optic Temperature Sensor Using a Silicone Oil and an OTDR

Abstract - In this study, we developed a fiber-optic temperature sensor (FOTS) based on a silicone oil and an optical time domain reflectometer (OTDR) to apply the measurement of a coolant leakage in the nuclear power plant. The sensing probe of the FOTS consists of a silicone oil, a stainless steel cap, a FC terminator, and a single mode optical fiber. Fresnel reflection arising at the interface between the silicone oil and the single mode optical fiber in the sensing probe is changed by varying the refractive index of the silicone oil according to the temperature. Therefore, we measured the optical power of the light signals reflected from the sensing probe. The measurable temperature range of the FOTS using a Cu-coated silica fiber is from 70℃ to 340℃ and the maximum operation temperature of the FOTS is sufficient for usage at the secondary system in the nuclear power plant.Key Words : Fiber-optic temperature sensor, Silicone oil, OTDR, Fresnel reflection, Coolant leakage †Corresponding Author : School of Biomedical Engineering,College of Biomedical & Health Science, BK21 Plus Research Institute of Biomedical Engineering, Konkuk University, KoreaE-mail : bslee@kku.ac.kr* School of Biomedical Engineering, College of Biomedical & Health Science, BK21 Plus Research Institute of Biomedical Engineering, Konkuk University, Korea** Department of Organic Materials & Fiber Engineering, College of Engineering, Soongsil University, KoreaReceived : August 11, 2015; Accepted : October 29, 2015

Feasibility study on remote gamma spectroscopy system with fiber-optic radiation sensor

In this study, we developed a remote gamma spectroscopy system based on fiber-optic radiation sensor (FORS) to detect species of gamma-emitting sources at large distances. In order to evaluate the performance of the gamma spectroscopy system, we measured the scintillating light intensity and gamma energy spectra as a function of the length of the plastic optical fiber (POF) and radioactivity of the gamma-ray source. Using the obtained experimental results, we selected the optimal inorganic scintillator as the FORS sensing material and measured the energy spectra. In addition, the photopeaks of the gamma-emitting sources were detected for different lengths of the POF and radioactivity of the 137Cs gamma-ray source. It is expected that the remote gamma spectroscopy system based on FORS can be an effective and convenient tool that can detect gamma-emitting sources at large distances, and can identify species of radioactive sources by measuring gamma energy spectra in nuclear facilities.

Real-time detection of 192Ir gamma-ray source positon using organic scintillator array sensor in HDR brachytherapy

In this study, we fabricated an organic scintillator array sensor (OSAS) based the array of organic scintillators. The scintillator array of OSAS for detecting positions of 192Ir gamma-ray source was fabricated using four types of organic scintillators, which emit the scintillating lights of different wavelength, respectively. To evaluate the performance of the OSAS, 192Ir gamma-ray source employed in a HDR brachytherapy was used. In this research, the spectra were measured with positions of 192Ir gamma-ray source which was moved at intervals of 5 mm and 10 mm using the OSAS. The experimental results show that the proposed OSAS can measure and discriminate the wavelength of scintillating lights generated in the OSAS according to the positions of 192Ir gamma-ray source. It is expected that the OSAS can used to detect positions of 192Ir gamma-ray source during a HDR brachytherapy. Further studies are planned to fabricate the OSAS with the different intervals of movements and the small size of organic scintillators.

Dual type fiber-optic radiation sensor for measuring alpha and beta particles

In this study, we fabricated a dual type fiber-optic radiation sensor (DFORS) system using a spectroscopic technique to measure alpha and beta particles simultaneously and separately. The DFORS is composed of a sensing probe, a plastic optical fiber (POF), a photomultiplier tube (PMT)-amplifier system, and a multichannel analyzer (MCA). As sensing probes, a ZnS(Ag) film and CaF2(Eu) crystal were used for alpha and beta spectroscopy. And, we measured the alpha and beta energy spectra using the proposed DFORS system to discriminate species of the radioisotopes emitting alpha or beta particle. From the experimental results, we demonstrated that the small-sized, flexible, and insertable DFORS system can measure and discriminate the alpha and beta successfully with the spectral information of each radioisotope.

Performance Evaluation of a Multichannel All-In-One Phantom Dosimeter for Dose Measurement of Diagnostic X-ray Beam.

We developed a multichannel all-in-one phantom dosimeter system composed of nine sensing probes, a chest phantom, an image intensifier, and a complementary metal-oxide semiconductor (CMOS) image sensor to measure the dose distribution of an X-ray beam used in radiation diagnosis. Nine sensing probes of the phantom dosimeter were fabricated identically by connecting a plastic scintillating fiber (PSF) to a plastic optical fiber (POF). To measure the planar dose distribution on a chest phantom according to exposure parameters used in clinical practice, we divided the top of the chest phantom into nine equal parts virtually and then installed the nine sensing probes at each center of the nine equal parts on the top of the chest phantom as measuring points. Each scintillation signal generated in the nine sensing probes was transmitted through the POFs and then intensified by the image intensifier because the scintillation signal normally has a very low light intensity. Real-time scintillation images (RSIs) containing the intensified scintillation signals were taken by the CMOS image sensor with a single lens optical system and displayed through a software program. Under variation of the exposure parameters, we measured RSIs containing dose information using the multichannel all-in-one phantom dosimeter and compared the results with the absorbed doses obtained by using a semiconductor dosimeter (SCD). From the experimental results of this study, the light intensities of nine regions of interest (ROI) in the RSI measured by the phantom dosimeter were similar to the dose distribution obtained using the SCD. In conclusion, we demonstrated that the planar dose distribution including the entrance surface dose (ESD) can be easily measured by using the proposed phantom dosimeter system.