• Journal of Radiation Protection and Research
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• v.42 no.1
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• pp.69-76
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• 2017

Background: Time-resolved optically stimulated luminescence (TR-OSL) is a very useful method for calculating the lifetimes of crystalline quartz and feldspar. Materials and Methods: A compact TR-OSL system was developed, comprising a heater assembly manufactured using Kanthal wire, 2 powerful blue light-emitting diodes (LED, LXHL-PB02) for optical stimulation equipped with VIS liquid light guides, and a photomultiplier tube combined with an optical filter for luminescence detection. A pulse generated from the data acquisition board (NI PCI 6250) was used to initiate on/off signals in LED and TR-OSL measurements. Results and Discussion: The TR-OSL and background signals measured using this TR-OSL system using quartz samples were very similar to those reported in a previous study. Additionally, the lifetimes of the build-up and TR-OSL signals were calculated as $27.4{\pm}2.2{\mu}s$ and $30.3{\pm}0.6{\mu}s$, respectively, in good agreement with the findings of a previous study. Conclusion: It was concluded that the developed TR-OSL system was very reliable for TR-OSL signal measurements and lifetime calculations.

• Journal of the Korean Society of Visualization
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• v.18 no.3
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• pp.61-68
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• 2020

Thermographic phosphor (TP) thermometry is a noncontact optical measurement method and has been applied in many fields such as combustion and heat transfer. However, due to the limitation of bonding technology and measurement method, most TP thermometry studies were conducted only on the air environment with water-soluble binders. In this paper, a temperature measurement technology in water using TP is proposed by coatings of manganese activated magnesium fluorogermanate (Mg4FGeO6:Mn4+, MFG) with Polydimethylsiloxane (PDMS). Four MFG-PDMS coatings with different thicknesses were prepared. The lifetime of MFG was not affected by the thickness of the coating as a result of the experiment and analysis of phosphor intensity using a photomultiplier tube. To measure the surface temperature field of an immerged body in water, a cylinder-type cartridge heater was coated with MFG doped PDMS. Transient surface temperature field was successfully measured even the initial temperature is higher than the boiling point of water.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.422-424
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• 2002

The accuracy of DXA(Dual Energy X-ray Absorptiometry) highly depends on the detection and separation capability of dual energy X-ray X-ray photons. In addition both of scan time and patient exposure are affected by detection efficiency. A CZT detector with a good energy resolution and high detection efficiency was evaluated for the application of bone densitometry. Its performance was compared to a photomultiplier tube with a NaI(T1) scintillator in terms of energy resolution, detection efficiency and the accuracy of bone mineral density measurement. The comparison study was performed with CZT detector and PM tube using DXA equipments(OSTEO Plus, OSTEO Prima, ISOL Technology). The energy spectrum was acquired using MCA(Multi-Channel Analyzer). The used X-ray energy ranged from 20keV to 86keV. The MCA result of the CZT detector showed a slightly sharper energy spectrum than that of NaI(T1). Detection efficiency of the CZT detector at 59.5keV was 1.4 times better. Remarkably the final results of bone mineral density measurements demonstrate only less than 1% difference. The CZT detector appears to have many benefits for the application of bone densitometry. Its excellent energy resolution can enhance the counting accuracy of dual energy X-ray spectrum. Furthermore its compactness in physical dimension and no cooling requirement will be additional benefits for a more compact and accurate bone densitometer.

• The Korean Journal of Nuclear Medicine
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• v.32 no.4
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• pp.365-373
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• 1998

Purpose: The conventional gamma camera is not ideal for scintimammography because of its large detector size (${\sim}500mm$ in width) causing high cost and low image quality. We are developing a small gamma camera dedicated for breast imaging. Materials and Methods: The small gamma camera system consists of a NaI (T1) crystal ($60 mm{\times}60 mm{\times}6 mm$) coupled with a Hamamatsu R3941 Position Sensitive Photomultiplier Tube (PSPMT), a resister chain circuit, preamplifiers, nuclear instrument modules, an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a standard resistive charge division which multiplexes the 34 cross wire anode channels into 4 signals ($X^+,\;X^-,\;Y^+,\;Y^-$). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated ana digitized via triggering signal and used to localize the position of an event by applying the Anger logic. Results: The intrinsic sensitivity of the system was approximately 8,000 counts/sec/${\mu}Ci$. High quality flood and hole mask images were obtained. Breast phantom containing $2{\sim}7 mm$ diameter spheres was successfully imaged with a parallel hole collimator The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We have succesfully developed a small gamma camera using NaI(T1)-PSPMT and nuclear Instrument modules. The small gamma camera developed in this study might improve the diagnostic accuracy of scintimammography by optimally imaging the breast.

• Journal of Sensor Science and Technology
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• v.21 no.4
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• pp.287-292
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• 2012

A fiber-optic radiation sensor was fabricated using a sensing probe, a plastic optical fiber, a photomultiplier tube, and a multichannel analyzer for gamma-ray spectroscopy. As an inorganic scintillator of the sensing probe, a LYSO crystal was used. In this study, we obtained the relationship between the photon counts of the fiber-optic radiation sensor and the activity of the radioactive isotope. In addition, the gamma-ray energy spectra were also measured using a fiber-optic radiation sensor to discriminate species of gamma-ray emitters.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.3
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• pp.1-14
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• 1974

The gain stability of the nuclear pulse linear amplifiers with feedback for such a fast pulse input as the step voltage or the nuclear radiation detector pulse is analysed in detail. The expression is derived which describes the waveform at the anode circuit of the photomultiplier tube which is a part of the nuclear radiation detector. It is analysed and compared when the feedback amplifier has one and two time-constants. When these fast input pulse voltages are applied to the feedback amplifier, the effects of feedback in linearity and stability of the output voltage appear only after two or three rise-times of the amplifier, And it is proved that in order to reduce this limitation, the rise time of the feedback amplifier shou1d be less than the input pulse width. It is also shown that the above theory can be applied directly to the voltage-shunt feedback amplifier stages designed as the basic amplifier of the linear amplifier, and that the gain stability is more improved for the smaller input impedance of this amplifier stage.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.365-368
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• 1997

We are developing a small gamma camera or imaging malignant breast tumors. The small scintillation camera system consists of NaI(Tl) crystal ($60\;{\times}\;60\;{\times}\;6\;mm^3$) coupled to position sensitive photomultiplier tube (PSPMT), nuclear instrument module (NIM), analog to digital converter (ADC), and personal computer. High quality flood source image and hole mask image were obtained using the gamma camera developed in this study. Breast phantom containing $2{\sim}7\;mm$ diameter spheres was successfully imaged with parallel hole collimator. The obtained image displayed accurate activity distribution over the imaging field of view. Linearity and uniformity correction algorithms are being developed. It is believed that the developed small gamma camera could be useful or detection of malignant breast cancer.

• Journal of Sensor Science and Technology
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• v.21 no.5
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• pp.367-373
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• 2012

We fabricated a fiber-optic alpha/beta detector, which is composed of a sensing probe, a plastic optical fiber, a photomultiplier tube, and a multichannel analyzer, to obtain the energy spectra of radioactive isotopes. As inorganic scintillators of a sensing probe, a ZnS(Ag) film was coupled with a $CaF_2$(Eu) crystal for alpha and beta spectroscopy. In this study, $^{210}Po$ and $^{90}Sr$ were used as alpha and beta sources, respectively, and we measured the radiation energy spectra using a fiber-optic alpha/beta detector to identify alpha and beta emitting radionuclides for nuclear medicine application. Also, the variations of energy spectrum were obtained according to the length of plastic optical fiber.

• Journal of Radiation Protection and Research
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• v.29 no.4
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• pp.257-261
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• 2004

A coded-aperture gamma camera was developed to increase the sensitivity of a pin hole camera made with a pixellated CsI(Tl) scintillator and a position-sensitive photomultiplier tube. The modified round-hole uniformly redundant array of pixel size $13{\times}11$ was chosen as a coded mask considering the detector spatial resolution. The performance of the coded-aperture camera was compared with the pin hole camera using various forms of Tc-99m source to see the improvement of signal-to-noise ratio or the improvement of the sensitivity. The image quality is much improved despite of a slight degradation of the spatial resolution. Though the camera and the test were made for low energy case, but the concept of the coded-aperture gamma camera could be effectively used for the radioactive environmental monitoring and other applications.

• Korean Journal of Optics and Photonics
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• v.20 no.4
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• pp.201-206
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• 2009

In this study, we have fabricated a fiber-optic radiation sensor for detection of tritium using inorganic scintillators and optical fibers. We have tested various kinds of inorganic scintillators such as $Gd_2O_2S$ : Tb, $Y_3Al_5O_{12}$ : Ce, and CsI : Tl to select the most effective sensor tip. In addition, we have measured the scintillating lights using a photomultiplier tube as a function of distance between sensor tips to the source with the different activities of hydride tritium. The final results are compared with those which are obtained using a surface activity monitor.