• Title, Summary, Keyword: NaI detector

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Study on Electrical Properties of X-ray Sensor Based on CsI:Na-Selenium Film

  • Park Ji-Koon;Kang Sang-Sik;Lee Dong-Gil;Choi Jang-Yong;Kim Jae-Hyung;Nam Sang-Hee
    • Transactions on Electrical and Electronic Materials
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    • v.4 no.3
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    • pp.10-14
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    • 2003
  • In this paper, we have introduced the x-ray detector built with a CsI:Na scintillation layer deposited on amorphous selenium. To determine the thickness of the CsI:Na layer, we have estimated the transmission spectra and the absorption of continuous x-rays in diagnostic range by using computer simulation (MCNP 4C). A x-ray detector with 65 ${\mu}m$-CsI:Na/30 ${\mu}m$-Se layer has been fabricated by a thermal evaporation technique. SEM and PL measurements have been performed. The dark current and x-ray sensitivity of the fabricated detector has been compared with that of the conventional a-Se detector with 100 ${\mu}m$ thickness. Experimental results show that both detectors exhibit a similar dark current, which was of a low value below $400 pA/cm^2$ at 10 V/${\mu}m$. However, the CsI:Na-Se detector indicates high x-ray sensitivity, roughly 1.3 times that of a conventional a-Se detector. Furthermore, a CsI:Na-Se detector with an aluminium reflective layer shows a 1.8 times higher x-ray sensitivity than an a-Se detector. The hybrid type detector proposed in this work exhibits a low dark current and high x-ray sensitivity, and, in particular, excellent linearity to the x-ray exposure dose.

A Study on the Energy and Time Characteristics of $BaF_2$ Scintillation Detector ($BaF_2$ 검출기의 시간과 에너지 특성연구)

  • Ju, Gwan-Sik;Park, Il-Jin;Kim, Jong-Ho;Nam, Gi-Yong;Baek, Seung-Hwa
    • Journal of Biomedical Engineering Research
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    • v.18 no.3
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    • pp.267-272
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    • 1997
  • he scintillation detector having $BaF^2$ crystal with 3.6cm dia${\times}$2.0 cm thick was provided. The energy and timing characteristics were measured and compared with NaI(Tl) scintillation detectors, which widely used in unclear medicine. In order to measure the energy spectrum, the radioactive sources used were $^{22}Na,\;^{54}Mn,\;^{57}Co,\;^{137}Cs$ and the source to detector distance was 7cm. For the timing characteristic, NaI(Tl)(1" ${\times}$ 1")-$BaF^2$ and NaI(Tl)(3" ${\times}$ 3")-$BaF^2$ timing coincidence systems were prepared and the used source was $^{22}Na$ emitting 511keV annihilation photons. For the 511keV gamma-ray emitted from $^{22}Na$, It was revealed that the timing response of the $BaF^2$ detector was faster than NaI(Tl)(1" ${\times}$ 1") and NaI(Tl)(3" ${\times}$ 3") detector used in this experimental investigation. The energy characteristics of the $BaF^2$ detector had a good values for about 500keV energy range.

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Design of Wide-Range radiation measurement system using GM Tube and NaI(TI) Detector (GM Tube 및 NaI(TI) 검출기를 사용한 Wide-Range 방사선 측정 시스템의 설계)

  • Ra, Seung-Tak;Lee, Joo-Hyun;Lee, Seung-Ho
    • Journal of IKEEE
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    • v.21 no.2
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    • pp.146-149
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    • 2017
  • In this paper, we propose a wide-range radiation measurement system using GM Tube and NaI(TI) detector. The proposed system is designed as a small module optimized to control and count the detector signal of NaI(Tl) Detector and GM Tube. The radiation dose is measured in a wide-range 0.1uSv/h to 10mSv/h in conjunction with two detectors, and two detectors operate simultaneously at 10uSv/h to 100uSv/h, where the measurement interval overlaps. The radiation dose was selected using a wide-range radiation measurement algorithm that controls the on/off function of the detector in the appropriate interval for the overlapped radiation measurable interval. In order to evaluate the performance of the proposed system, it has been confirmed that the measurement uncertainty of each section is measured as ${\pm}7.5%$ and it operates normally under ${\pm}15%$ of the international standard.

Determination of Spectrum-Exposure Rate Conversion Factor for a Portable High Purity Germanium Detector (휴대형 고순도 게르마늄검출기에 대한 스펙트럼-조사선량율 변환연산자의 결정)

  • Kwak, Sang-Soo;Park, Chong-Mook;Ro, Seung-Gy
    • Journal of Radiation Protection and Research
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    • v.13 no.2
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    • pp.29-40
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    • 1988
  • A spectrum-exposure rate conversion operator G(E) for a portable HPGe detector used for field environmental radiation survey was theoretically developed on the basis of a space distribution function of gamma flux emitted from a disk source and an areal efficiency of the detector. The radiation exposure rates measured using this G(E) and the portable HPGe. detector connected to a portable multichannel analyzer were compared with those measured by a 3' ${\phi}\;{\times}$3' NaI(Tl) scintillation detector with the reported G(E) and a pressurized ionization chamber. A comparison of the three results showed that the result obtained using the HPGe detector was lower than those determined using the NaI(Tl) detector and ionization chamber by 17% to 29%, The difference obtained is close to that reported in literature. The method developed here can be easily applicable to obtain a G(E) factor suitable to any detector for detecting the exposure rate of environmental gamma radiation, since the spectrum-exposure rate conversion operator can be calculated by a hand calculator.

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Determinations of the Exposure Rate Using a NaI(Tl) Detector of the Environmental Radiation Monitor (환경방사선감시기의 NaI(Tl) 검출기를 이용한 조사선량률 결정방법)

  • Ji, Young-Yong;Lee, Wanno;Choi, Sang-Do;Chung, Kun Ho;Kang, Mun Ja;Choi, Geun-Sik
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.11 no.3
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    • pp.245-251
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    • 2013
  • The energy band and the G-factor method were compared to determine the exposure rate from the measured spectrum using a NaI(Tl) scintillation detector. First, G-factors of a 3"${\Phi}X3$" NaI(Tl) detector mounted to a EFRD 3300, which means the environmental radiation monitor, in Korea Atomic Energy Research Institute (KAERI) were calculated for several directions of incident photons through the MCNP modeling, and the optimum G-factor applicable to that monitor was then determined by comparing the results both the energy band method and the G-factor method. The results for these spectrometric determinations were also compared with the dose rate from a HPIC radiation monitor around a EFRD 3300. The measured value at the EFRD 3300 based on a 3"${\Phi}X3$" NaI(Tl) detector was $7.7{\mu}R/h$ and its difference was shown about $3{\mu}R/h$, when compared with the results from a HPIC radiation moditor. Since a HPIC is known to be able to measure cosmic rays with the relatively high energy, the difference between them was caused by cosmic rays which were not detected in a 3"${\Phi}X3$" NaI(Tl) detector.

Background reduction by Cu/Pb shielding and efficiency study of NaI(TI) detector

  • Ramadhan, Revink A.;Abdullah, Khairi MS.
    • Nuclear Engineering and Technology
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    • v.50 no.3
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    • pp.462-469
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    • 2018
  • The background spectrum of a $3^{{\prime}{\prime}}{\times}3^{{\prime}{\prime}}$ NaI(Tl) well-type scintillation SILENA detector was measured without shielding, in 6 cm thick lead shielding, and with 2 mm thick electrolytic copper covering the detector inside the lead shielding. The relative remaining background of the lead shield lined with copper was found to be ideal for low-level environmental radioactive spectroscopy. The background total count rate in the (20-2160 KeV) was reduced 28.7 times by the lead and 29 times by the Cu + Pb shielding. The effective reduction of background (1.04) by the copper mainly appeared in the energy range from X-ray up to 500 KeV, while for the total energy range the ratio is 1.01 relative to the lead only. In addition, a strong relation between the full-energy peak absolute efficiency and the detector well height was found using gamma-ray isotropic radiation point sources placed inside the detector well. The full-energy peak efficiency at a midpoint of the well (at 2.5 cm) is three times greater than that on the detector surface. The energy calibrations and the resolution of any single energy line are independent of the locations of the gamma source inside or outside of the well.

Design and Fabrication of HgI2 Sensor for Phosphor Screen based flat panel X-ray Detector (형광체 스크린 기반 평판형 X선 검출기 적용을 위한 요오드화수은 필름 광도전체 센서 설계 및 제작)

  • Park, Ji Koon;Jung, Bong Jae;Choi, Il Hong;Noh, Si Cheol
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.12
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    • pp.189-194
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    • 2014
  • In this study, from a new x-ray detector that combines a columnar CsI:Na scintillation layer with a photosensitive mercuric iodide layer was investigated. In this structure, X-rays are converted into visible light on a thick CsI:Na layer, which is then converted to electric charges in a thin $HgI_2$ bottom layer. The thin coplanar mercuric iodide films as a photosensitive converter requiring only a few tens of volts of bias, associated with a thick columnar coating of phosphor layer, were simulated and designed. The results of this research suggest that the new coplanar x-ray detector with a hybrid-type structure can resolve the following problems: high voltage from the a-Se, and low conversion efficiency from the indirect conversion method. The results of this research suggest that the new CsI:Na/$HgI_2$ x-ray detector with a double-layer type structure can resolve the following problems: high voltage from the direct conversion method, and low conversion efficiency from the indirect conversion method.

MDA Assessment of NaI(Tl), LaBr3(Ce), and CeBr3 Detectors for Freshly Deposited Radionuclides on the Soil (지표면 침적 방사성핵종에 대한 NaI(Tl), LaBr3(Ce) 및 CeBr3 검출기의 MDA 비교 평가)

  • Lee, Jun-Ho;Kim, Bong-Gi;Lee, Dong Myung;Byun, Jong-In
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.17 no.3
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    • pp.321-328
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    • 2019
  • The detection performances of the NaI(Tl), $LaBr_3$(Ce) and $CeBr_3$ scintillation detectors, which can be used to rapidly evaluate the major artificial radionuclides deposited on the soil surface in a nuclear accident or radiological emergency, were compared. Detection performance was assessed by calculating the minimum detectable activity (MDA). The detection efficiency of each detector for artificial radionuclides was semi-empirically determined using mathematical modelling and point-like sources having certified radioactivity. The background gamma-ray energy spectrum for MDA evaluation was obtained from relatively wide and flat grassland, and the MDA values of each detector for the major artificial radionuclides that could be released in nuclear accidents were calculated. As a result, the relative MDA values of each detector regarding surface deposition distribution at normal environmental radiation level were evaluated as high in the order of the NaI(Tl), $LaBr_3$(Ce), and $CeBr_3$ detectors. These results were compared based on each detector's intrinsic and measurement environment background, detection efficiency, and energy resolution for the gamma-ray energy region of the radionuclide of interest.

A Low-Dose High-Resolution SPECT System with CdTe for Small-Animal Imaging Applications: A GATE Simulation Study (GATE 시뮬레이션을 통한 고해상도 저선량용 소동물 영상화를 위한 CdTe 검출기 기반의 SPECT 기기 연구)

  • Park, Su-Jin;Yu, A Ram;Kim, Yeseul;Lee, Young-Jin;Kim, Hee-Joung
    • Progress in Medical Physics
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    • v.24 no.3
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    • pp.162-170
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    • 2013
  • Dedicated single-photon emission computed tomography (SPECT) systems based on pixelated semiconductors are being developed for studying small animal models of human disease. To clarify the possibility of using a SPECT system with CdTe for a high resolution low-dose small animal imaging, we compared the quality of reconstructed images from pixelated CdTe detector to those from a small SPECT system with NaI(Tl). The CdTe detector was $44.8{\times}44.8$ mm and the pixels were $0.35{\times}0.35{\times}5$ mm. The intrinsic resolution of the detector was 0.35 mm, which is equal to the pixel size. GATE simulations were performed to assess the image quality of both SPECT systems. The spatial resolutions and sensitivities for both systems were evaluated using a 10 MBq $^{99m}Tc$ point source. The quantitative comparison with different injected dose was performed using a voxelized MOBY phantom, and the absorbed doses for each organ were evaluated. The spatial resolution of the SPECT with NaI(Tl) was about 1.54 mm FWHM, while that of the SPECT with a CdTe detector was about 1.32 mm FWHM at 30 mm. The sensitivity of NaI(Tl) based SPECT was 83 cps/MBq, while that of the CdTe detector based SPECT was 116 cps/MBq at 30 mm. The image statistics were evaluated by calculating the CNR of the image from both systems. When the injected activity for the striatum in the mouse brain was 160 Bq/voxel, the CNR of CdTe based SPECT was 2.30 while that of NaI(Tl) based SPECT was 1.85. The CNR of SPECT with CdTe was overall higher than that of the NaI(Tl) based SPECT. In addition, the absorbed dose was higher from SPECT with CdTe than those from NaI(Tl) based SPECT to acquire the same quantitative values. Our simulation results indicated that the SPECT with CdTe detector showed overall high performance compared to the SPECT with NaI(Tl). Even though the validation study is needed, the SPECT system with CdTe detector appeared to be feasible for high resolution low-dose small animal imaging.

Thermoluminescent Characteristics of Newly Developed LiF:Mg,Cu,Na,Si TL Detectors

  • Lee J. I.;Kim J. L.;Chang S. Y.
    • Nuclear Engineering and Technology
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    • v.36 no.1
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    • pp.47-52
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    • 2004
  • Recently, a new sintered pellet-type LiF:Mg,Cu,Na,Si TL detector which has a high sensitivity and good reusability, named KLT-300(KAERI LiF:Mg,Cu,Na,Si TL detector), was developed by the variation of the dopants concentrations and the parameters of the preparation procedure at KAERI (Korea Atomic Energy Research Institute). In this study, the thermoluminescent characteristics of the newly developed TL detectors were investigated. The sensitivity of the TL detector was compared with that of the TLD-100 by light integration. The dose linearity of the detector was tested from $10^{-6}$ Gy up to 30 Gy. The dose response was very linear up to 10 Gy and a sublinear response was observed at higher doses. The energy response of the detector was studied for photon energies from 20 keV to 662 keV. The result shows that a maximum response of 1.004 at 53 keV and a minimum response of 0.825 at 20 keV were observed. The reproducibility study for the TL detector was also carried out. The coefficients of variation for each detector separately did not exceed 0.016, and for all the 10 detectors collectively was 0.0054. Lower limit of detection for the detector was investigated at 70 nGy by the Harshaw 4500 TLD Reader and the residual signal of the TL detector was found to be $0.57\%$.