물을 용매로 하는 액체섬광검출기 개발을 위한 연구

이주영,소중호,김홍주 한국물리학회 2012 새물리 Vol.62 No.3

Large sized water Cerenkov detectors or liquid scintillators have been used for neutrino or neutron detection. We developed a liquid scintillator based on water with different liquid scintillator loadings. We used a linear alkyl benzene (LAB) based liquid scintillator because it is less toxic and its flash point is higher than those of other scintillators. We added a scintillator solute and a wavelength shifter to the LAB. We also added Triton X-100 to load the liquid scintillator into the water. Different concentrations of the liquid scintillator were loaded into the water, and the developed material was characterized using X-ray luminescence and scintillation light yield measurements with a radioactive gamma-ray source. A commercial liquid scintillator of Ultima Gold LLT was used for comparison with the developed liquid scintillator. This low cost water-based liquid scintillator detector can be applied for particle-astrophysics and nuclear experiments for neutrino detection and for radiation dose monitoring. 중성미자 및 중성자 검출을 위하여 물 또는 섬광액을 이용한 대용량의검출기가 사용되고 있다. 본 연구에서는 다량의 물에 섬광액을 혼합하여섬광체의 특성 변화에 대한 연구를 수행하였다. 기존에 사용되는섬광액의 경우 독성을 띠거나 발화점이 낮으므로 이에 따른 제약을극복하기 위하여 Linear Alkyl Benzene과 같이 독성이 현저히 낮고발화점은 높은 안전한 유기용매를 선택하였고, 여기에 용매로부터에너지를 전달받아 빛을 내는 섬광체 및 파장변환물질을 첨가하였다. 이러한 섬광액에 물을 섞기 위하여 유화제를 사용하여 다량의 물과혼합하여 가면서 X-선 및 감마선을 이용하여 섬광 방출 스펙트럼 및섬광량의 변화에 대한 연구를 수행하였고 상용의 Ultima-Gold LLT 섬광액과 비교하였다. 개발된 검출기는 저가이면서 대용량의 검출기가필요한 입자 천체 물리 및 핵물리실험, 또는 방사선량 모니터링에 응용될수 있다.

Spectra Responsibility of Quantum Dot Doped Organic Liquid Scintillation Dosimeter for Radiation Therapy

Kim, Sung-woo,Cho, Byungchul,Cho, Sangeun,Im, Hyunsik,Hwang, Ui-jung,Lim, Young Kyoung,Cha, SeungNam,Jeong, Chiyoung,Song, Si Yeol,Lee, Sang-wook,Kwak, Jungwon Korean Society of Medical Physics 2017 의학물리 Vol.28 No.4

The aim is to investigate the spectra responsibilities of QD (Quantum Dot) for the innovation of new dosimetry application for therapeutic Megavoltage X-ray range. The unique electrical and optical properties of QD are expected to make it a good sensing material for dosimeter. This study shows the spectra responsibility of toluene based ZnCd QD and PPO (2.5-diphenyloxazol) mixed liquid scintillator. The QDs of 4 sizes corresponding to an emission wavelength (ZnCdSe/ZnS:$440{\pm}5nm$, ZnCdSeS:470, 500, $570{\pm}5nm$) were utilized. A liquid scintillator for control sample was made of toluene, PPO. The Composition of QD loaded scintillators are about 99 wt% Toluene as solvent, 1 wt% of PPO as primary scintillator and 0.05, 0.1, 0.2 and 0.4 wt% of QDs as solute. For the spectra responsibility of QD scintillation, they were irradiated for 30 second with 6 MV beam from a LINAC ($Infinity^{TM}$, Elekta). With the guidance of 1.0 mm core diameter optical fiber, scintillation spectrums were measured by a compact CCD spectrometer which could measure 200~1,000 nm wavelength range (CCS200, Thorlabs). We measured the spectra responsibilities of QD loaded organic liquid scintillators in two scintillation mechanisms. First was the direct transfer and second was using wave shifter. The emission peaks from the direct transfer were measured to be much smaller luminescent intensity than based on the wavelength shift from the PPO to QDs. The emission peak was shifted from PPO emission wavelength 380 nm to each emission wavelength of loaded QD. In both mechanisms, 500 nm QD loaded samples were observed to radiate in the highest luminescence intensity. We observed the spectra responsibility of QD doped toluene based liquid scintillator in order to innovate QD dosimetry applicator. The liquid scintillator loading 0.2 wt% of 500 nm emission wavelength QD has most superior responsibility at 6 MV photon beam. In this study we observed the spectra responsibilities for therapeutic X-ray range. It would be the first step of innovating new radiation dosimetric methods for radiation treatment.

알코올 기반 액체섬광검출용액 개발 및 적용 연구

김병찬,박선영,송예성,우희진,주경광,최지영 한국물리학회 2021 새물리 Vol.71 No.1

Liquid scintillators are widely used in various fields because they give a high light yield. In addition, the development of stable liquid scintillator for particle detectors and medical applications is very important. This paper proposes a new base material, a mixture of alcohol and water, for a liquid scintillator. The development of this alcohol-based liquid scintillator and the experimental result for various physical and optical properties are described. Until now, R&D studies on such detectors or no market products of this type have been available. Thus, room exists for improvement. Therefore, various possibilities for detection solutions were studied by varying the mixing ratio of each component constituting the liquid scintillator. Finally, as an example of usage in medical physics, a range (=beam-path-length) measurement using an electron beam is briefly described. The measurement results obtained by changing the energy of the incident electron beam were compared with Monte Carlo simulation, Novalis-Tx and the phantom results. 액체섬광검출용액은 높은 빛 방출량을 주기 때문에 물리학을 비롯한 여러 타 분야에서 널리 사용하고있다. 또한 검출기와 의학적 활용을 위해서는 안정된 액체섬광검출용액의 개발은 매우 중요하다. 본논문은 알코올을 용매로 사용해 물과 혼합한 새로운 형태의 액체섬광검출용액을 제안한다. 알코올을기반으로 한 액체섬광검출용액 개발 과정과 여러 물리 광학적 측정 결과에 대해 설명하였는데, 현재까지직접 제조해 검출기에 사용하거나, 이런 조합으로 구성된 상업적 제품은 없어 액체섬광검출용액 분야에서발전 가능성을 여전히 존재한다. 따라서 액체섬광검출용액을 구성하고 있는 각 성분들의 배합 비율을달리 하여 검출용액으로써 여러 가지 가능성 연구를 수행하였다. 최종적으로는 본 연구에서 개발한액체섬광검출용액을 활용한 한 예시로 의학물리에서 전자선을 사용한 비정 측정에 대해 간략히 기술하였다. 몬테카를로 시뮬레이션을 통한 전산모사 결과, 측정 결과, 팬텀 결과 및 Novalis-Tx 결과를 서로 비교하였다

Pulse Shaping Analysis with LAB-based Liquid Scintillators

J. S. Lee,김용함,K. B. Lee,M. K. Lee,K. J. Ma,E. J. Jeon,J. Y. Kim,김남영,김영덕,J. Y. Lee 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.3

We report on a pulse shaping analysis for alpha-beta discrimination using a linear alkylbenzene (LAB)-based liquid scintillator developed for reactor neutrino experiments. The scintillation properties are measured with an internal alpha source diluted in the same scintillator and an external gamma source. The comparison of the fast and the slow parts in the signal waveforms provide clear separations of alpha and gamma events in the liquid scintillator. The discrimination power is compared between the LAB-based liquid scintillator and other commercially available liquid scintillators. The potential use of this scintillator when loaded with 6Li is discussed with regard to neutron measurements.

Estimating Uncertainties in the Reactor Neutrino Directionality Using Liquid Scintillator with Monte Carlo Simulation

Jun Hu Seo,Kyung Kwang Joo,신창동,Atif Zohaib 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.2

This paper describes in detail the uncertainties due to several factors that may affect the direction vector of a reactor neutrino in a liquid scintillation detector. The reactor neutrino direction vector was reconstructed through a charge weighting method. The paper simulates the response of gadolinium-loaded, liquid scintillator detector to reactor electron anti-neutrinos. The reaction is based on neutrino capture on hydro-genic protons of inverse beta decay process in the scintillator. A Cherenkov radiation detector can reconstruct the directional information of incident neutrinos relatively well, compared to the liquid scintillation detector. Statistics, spatial resolution, neutrino energy, and multi-reactor and multi-detectors are examined by using Monte Carlo simulation based on the cylindrical liquid scintillating detector model. Furthermore, this simulated model is detailed down to the optical processes, and the source of reactor fuel composition. Finally, one of the main goals is to provide the potential of the detector to measure the origin direction of the incident neutrino. Furthermore, our intention is to help understanding of various uncertainties of the neutrino directionality study for the future massive liquid scintillating neutrino detectors.

Neutron Spectrometer with a Capture-Gated Liquid Scintillator

김정호,박현서,K.-O. Choi 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.1

We have developed a capture-gated neutron spectrometer with a liquid scintillator and a lithium glass scintillator. The neutron-scattering signals from the liquid scintillator and the neutron-capture signals from the lithium glass scintillator were processed and collected separately by using a digital pulse processing technique. Neutron and gamma separation was performed using a pulse shape discrimination technique, which showed a 98 % selection capability above a neutron energy of 1MeV. The correlation between the incident neutron energy and analogue-to-digital converter (ADC)values of the liquid scintillation counter was obtained by using a time-of-flight method to measure the neutrons emitted from a 252Cf source. The correlation function of the ADC values and the neutron energy allowed us to determine the neutron energy by using only the ADC values of the liquid scintillation detector for capture-gated events. This work shows that the capture-gated neutron spectrometer can be used in neutron dosimetry.

가돌리늄이 0.5% 용해된 선형알킬벤젠 기반 액체섬광검출용액의 시간에 따른 농도와 물함량 측정

송숙형,주경광 한국물리학회 2013 새물리 Vol.63 No.9

Neutrinos can be detected using inverse beta decay (IBD) in a detecter filled with a liquid scintillator. Commonly, because neutrino experiments take a long time, the gadolinium concentration of a gadolinium (Gd)-loaded linear alkyl benzene (LAB)-based liquid scintillator must be stable. Also, if the water content in a liquid scintillator is high, the optical property of the liquid scintillator may change and contamination may easily occur. Therefore, the gadolinium concentration and the water content of the liquid scintillator should be optimized for the experiment. In this study, we the gadolinium concentration was measured by using EDTA (ethylene diamine tetraacetic acid) titration, and the water content was measured by using the Karl-Fischer titration method. 액체섬광검출용액 (LS, liquid scintillator)이 채워진 검출기에역베타붕괴 반응 (IBD, inverse beta decay)을 이용하면 중성미자를 검출할 수 있다. 일반적으로 중성미자 실험은 오랜 시간 동안 진행되기때문에, 가돌리늄 (Gd)이 용해된 선형알킬벤젠 (LAB, linear alkyl benzene) 기반 액체섬광검출용액의 가돌리늄 농도는 안정 해야 한다. 또한 액체섬광검출용액 안의 물함량이 높으면 물에 의해 용액의 광학적성질이 변하게 되고 오염 또한 쉽게 진행 될 수 있다. 그러므로액체섬광검출용액은 실험에 맞게 농도와 물함량을 최적화해야한다. 본연구에서는 EDTA (ethylene diamine tetraacetic acid) 적정법을이용하여 가돌리늄 농도를 측정 하였고, 물함량 측정은 칼피셔 수분적정(karl fischer titration) 방법을 사용하였다.

A search for 0νββ decay of ¹²⁴Sn with tin-loaded liquid scintillator

KIMS Collaboration,Hwang, M.J.,Kwon, Y.J.,Kim, H.J.,Kwak, J.W.,Kim, S.C.,Kim, S.K.,Kim, T.Y.,Kim, S.Y.,Lee, H.S.,Lee, M.J.,Myung, S.S.,Kim, Y.D.,Lee, J.I.,Kang, W.G.,Hahn, I.S.,Lee, M.H. North-Holland ; Elsevier Science Ltd 2009 Astroparticle physics Vol.31 No.6

<P>A search for the neutrinoless double-beta decay of Sn-124 was carried out using the tin-loaded liquid scintillator for an active source-detector technique. Tin (32.6%) in weight was successfully loaded into the liquid scintillator, and light output was as high as 57% of the unloaded liquid scintillator. A tin-loaded liquid scintillator with 1.1 l volume was installed at the 700 m underground laboratory in YangYang. and data were taken for 5285 h. No evidence for the O nu beta beta decay was found and a lower limit on the Sn-124 half-life was obtained to be 2.0 x 10(19) year with 90% C.L The new limit represents a significant improvement with respect to those previously available for Sn-124. (C) 2009 Elsevier B.V. All rights reserved.</P>

RENO 실험에서 액체섬광검출용액의 특성 변화에 의한 이벤트 위치 구성 연구

신창동,주경광 한국물리학회 2017 새물리 Vol.67 No.7

The RENO (Reactor Experiment for Neutrino Oscillation) uses a liquid scintillator for neutrino detection. The vertex reconstruction is important for separating the signal from the background in the neutrino experiment. Especially, vertex reconstruction is more difficult for a cylindrical detector than for a spherical detector. Vertex reconstruction requires a correction for the vertex position because the properties of the liquid scintillator can change over time. In this paper, we study the vertex reconstruction method and the differences in the reconstructed vertex caused by changes in the properties of the liquid scintillator. Reactor Experiment for Neutrino Oscillation (RENO) 실험은 한빛 원자력 발전소에서 생성된 중성미자의 진동변환을 확인하기 위한 실험이다. 액체섬광검출용액을 이용한 중성미자 검출실험에서 우리가 관측하려는 신호를 구분하기 위해서 이벤트의 위치를 구성하는 것이 중요하게 사용된다. 특히 구형이 아닌 원통형의 검출기에서의 이벤트의 위치 구성은 간단하지 않다. 또한 액체섬광검출용액은 시간에 대해서 성질이 변할 수 있기 때문에, 그에 따른 위치 구성 방법의 보정이 필요하다. 이 논문에서는 몬테카를로를 이용하여 이벤트의 기본적인 위치 구성 방법과 액체섬광검출용액의 특성 변화에 따른 위치 구성 결과의 차이를 기술하였다.

Study of Pulse Shape Discrimination of Sub-MeV Neutrons From Gamma-Rays with Liquid Scintillator

M. Yoshioka,M. Ueyama,Y. Koba,Y. Nakamura,T. Kajimoto,D. Moriguchi,Y. Uozumi,N. Shigyo 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

We have studied pulse shape discrimination of sub-MeV neutron from spallation nuclear reactions. Neutron measurements were carried out with a 2-inch NE213 scintillator viewed by a phototube (HAMAMATSU H1949) for the carbon-carbon reaction at 290 MeV/n. Neuron energies were measured with the TOF technique by using a timing pick-up plastic scintillator. Output signals of detectors were digitized and stored with a digitizer (Acqiris DC282). The digital pulse shape discrimination (DPSD) has been investigated through comparison between three different analyzing algorithms. Effects on the neutron-gamma (n/g) discrimination were also investigated after the subtraction of background and abnormal events. Moreover, in order to realize better n/g discrimination the detector system was cooled down to about zero degrees centigrade by Peltier devices to suppress the dark current of the phototube which would be the main cause distorting pulse shapes. Experimental studies were made in terms of the temperature dependence of detector performance including pulse shape.