Showing papers by "Kangsoon Park published in 2018"
TL;DR: In this paper, the COSINE-100 experiment was used to determine whether there is evidence for an excess of events above the expected background in sodium iodide and to look for evidence of an annual modulation.
Abstract: Observations of galaxies and primordial radiation suggest that the Universe is made mostly of non-luminous dark matter1,2. Several new types of fundamental particle have been proposed as candidates for dark matter3, such as weakly interacting massive particles (WIMPs)4,5. These particles would be expected to interact with nuclei in suitable detector materials on Earth, for example, causing them to recoil. However, no definitive signal from such dark-matter interactions has been detected despite concerted efforts by many collaborations6. One exception is the much-debated claim by the DAMA collaboration of a statistically significant (more than nine standard deviations) annual modulation in the rate of nuclear interaction events. Annual modulation is expected because of the variation in Earth’s velocity relative to the Galaxy’s dark-matter halo that arises from Earth’s orbital motion around the Sun. DAMA observed a modulation in the rate of interaction events in their detector7,8,9 with a period and phase consistent with that expected for WIMPs10,11,12. Several groups have been working to develop experiments with the aim of reproducing DAMA’s results using the same target medium (sodium iodide)13,14,15,16,17. To determine whether there is evidence for an excess of events above the expected background in sodium iodide and to look for evidence of an annual modulation, the COSINE-100 experiment uses sodium iodide as the target medium to carry out a model-independent test of DAMA’s claim. Here we report results from the initial operation of the COSINE-100 experiment related to the first task18,19. We observe no excess of signal-like events above the expected background in the first 59.5 days of data from COSINE-100. Assuming the so-called standard dark-matter halo model, this result rules out WIMP–nucleon interactions as the cause of the annual modulation observed by the DAMA collaboration20,21,22,23. The exclusion limit on the WIMP–sodium interaction cross-section is 1.14 × 10−40 cm2 for 10-GeV c−2 WIMPs at a 90% confidence level. The COSINE-100 experiment will continue to collect data for two more years, enabling a model-independent test of the annual modulation observed by the DAMA collaboration.
102 citations
Sejong University1, Yale University2, University of São Paulo3, Seoul National University4, Karlsruhe Institute of Technology5, Korea Institute of Science and Technology Information6, Bandung Institute of Technology7, University of Sheffield8, Ewha Womans University9, Northwestern University10, Sungkyunkwan University11, University of Wisconsin-Madison12, Kyungpook National University13, Chiba University14, Korea Research Institute of Standards and Science15, KEK16, University of Washington17, Massachusetts Institute of Technology18, University of British Columbia19, University of Illinois at Urbana–Champaign20
TL;DR: COSINE-100 as mentioned in this paper is a dark matter search experiment based on an array of low background NaI(Tl) crystals located at the Yangyang underground laboratory in China.
Abstract: COSINE is a dark matter search experiment based on an array of low background NaI(Tl) crystals located at the Yangyang underground laboratory. The assembly of COSINE-100 was completed in the summer of 2016 and the detector is currently collecting physics quality data aimed at reproducing the DAMA/LIBRA experiment that reported an annual modulation signal. Stable operation has been achieved and will continue for at least 2 years. Here, we describe the design of COSINE-100, including the shielding arrangement, the configuration of the NaI(Tl) crystal detection elements, the veto systems, and the associated operational systems, and we show the current performance of the experiment.
89 citations
Sejong University1, Wright Laboratory2, University of São Paulo3, Seoul National University4, Bandung Institute of Technology5, University of Sheffield6, Ewha Womans University7, University of Wisconsin-Madison8, Sungkyunkwan University9, Kyungpook National University10, Korea Research Institute of Standards and Science11, Korea University12, University of Illinois at Urbana–Champaign13
TL;DR: To understand measured backgrounds in the NaI(Tl) crystals, Monte Carlo simulations using the Geant4 toolkit are performed and background models for each crystal are developed that consider contributions from both internal and external sources, including cosmogenic nuclides.
Abstract: The COSINE-100 dark matter search experiment is an array of NaI(Tl) crystal detectors located in the Yangyang Underground Laboratory (Y2L). To understand measured backgrounds in the NaI(Tl) crystals we have performed Monte Carlo simulations using the Geant4 toolkit and developed background models for each crystal that consider contributions from both internal and external sources, including cosmogenic nuclides. The background models are based on comparisons of measurement data with Monte Carlo simulations that are guided by a campaign of material assays and are used to evaluate backgrounds and identify their sources. The average background level for the six crystals (70 kg total mass) that are studied is 3.5 counts/day/keV/kg in the (2-6) keV energy interval. The dominant contributors in this energy region are found to be $^{210}$Pb and $^3$H.
39 citations
Sejong University1, Wright Laboratory2, University of São Paulo3, Seoul National University4, Bandung Institute of Technology5, University of Sheffield6, Ewha Womans University7, University of Wisconsin-Madison8, Sungkyunkwan University9, Kyungpook National University10, Korea Research Institute of Standards and Science11, Korea University12, University of Illinois at Urbana–Champaign13
TL;DR: In this article, the authors performed Monte Carlo simulations using the Geant4 toolkit and developed background models for each crystal that consider contributions from both internal and external sources, including cosmogenic nuclides.
Abstract: The COSINE-100 dark matter search experiment is an array of NaI(Tl) crystal detectors located in the Yangyang Underground Laboratory (Y2L). To understand measured backgrounds in the NaI(Tl) crystals we have performed Monte Carlo simulations using the Geant4 toolkit and developed background models for each crystal that consider contributions from both internal and external sources, including cosmogenic nuclides. The background models are based on comparisons of measurement data with Monte Carlo simulations that are guided by a campaign of material assays and are used to evaluate backgrounds and identify their sources. The average background level for the six crystals (70 kg total mass) that are studied is 3.5 counts/day/keV/kg in the (2–6) keV energy interval. The dominant contributors in this energy region are found to be $$^{210}$$
Pb and $$^3$$
H.
35 citations
Bandung Institute of Technology1, Sejong University2, Yale University3, University of São Paulo4, Seoul National University5, Korea Institute of Science and Technology Information6, University of Sheffield7, Ewha Womans University8, Sungkyunkwan University9, University of Wisconsin-Madison10, Kyungpook National University11, Korea Research Institute of Standards and Science12, University of Illinois at Urbana–Champaign13
TL;DR: The COSINE-100 dark matter search experiment has started taking physics data with the goal of performing an independent measurement of the annual modulation signal observed by DAMA/LIBRA.
Abstract: The COSINE-100 dark matter search experiment has started taking physics data with the goal of performing an independent measurement of the annual modulation signal observed by DAMA/LIBRA. A muon detector was constructed by using plastic scintillator panels in the outermost layer of the shield surrounding the COSINE-100 detector. It detects cosmic ray muons in order to understand the impact of the muon annual modulation on dark matter analysis. Assembly and initial performance tests of each module have been performed at a ground laboratory. The installation of the detector in the Yangyang Underground Laboratory (Y2L) was completed in the summer of 2016. Using three months of data, the muon underground flux was measured to be 328 ± 1(stat.)± 10(syst.) muons/m2/day. In this report, the assembly of the muon detector and the results from the analysis are presented.
33 citations
Sejong University1, Wright Laboratory2, University of São Paulo3, Seoul National University4, Korea Institute of Science and Technology Information5, Bandung Institute of Technology6, University of Sheffield7, Ewha Womans University8, Sungkyunkwan University9, University of Wisconsin-Madison10, Kyungpook National University11, Korea Research Institute of Standards and Science12, University of Illinois at Urbana–Champaign13
TL;DR: COSINE-100 as discussed by the authors is a dark matter direct detection experiment designed to test the annual modulation signal observed by the DAMA/LIBRA experiment, which consists of 8 NaI(Tl) crystals with a total mass of 106 kg, a 2200 L liquid scintillator veto, and 37 muon detector panels.
Abstract: COSINE-100 is a dark matter direct detection experiment designed to test the annual modulation signal observed by the DAMA/LIBRA experiment. COSINE-100 consists of 8 NaI(Tl) crystals with a total mass of 106 kg, a 2200 L liquid scintillator veto, and 37 muon detector panels. We present details of the data acquisition system of COSINE-100, including waveform storage using flash analog-to-digital converters for crystal events and integrated charge storage using charge-sensitive analog-to-digital converters for liquid scintillator and plastic scintillator muon veto events. We also discuss several trigger conditions developed in order to distinguish signal events from photomultiplier noise events. The total trigger rate observed for the crystal/liquid scintillator (plastic scintillator) detector is 15 Hz (24 Hz).
26 citations
TL;DR: COSINE-100 as mentioned in this paper is a dark matter direct detection experiment designed to test the annual modulation signal observed by the DAMA/LIBRA experiment, which consists of 8 NaI(Tl) crystals with a total mass of 106 kg, a 2200 L liquid scintillator veto, and 37 muon detector panels.
Abstract: COSINE-100 is a dark matter direct detection experiment designed to test the annual modulation signal observed by the DAMA/LIBRA experiment. COSINE-100 consists of 8 NaI(Tl) crystals with a total mass of 106 kg, a 2200 L liquid scintillator veto, and 37 muon detector panels. We present details of the data acquisition system of COSINE-100, including waveform storage using flash analog-to-digital converters for crystal events and integrated charge storage using charge-sensitive analog-to-digital converters for liquid scintillator and plastic scintillator muon veto events. We also discuss several trigger conditions developed in order to distinguish signal events from photomultiplier noise events. The total trigger rate observed for the crystal/liquid scintillator (plastic scintillator) detector is 15 Hz (24 Hz).
20 citations
TL;DR: In this article, a miniature radiation portal monitor and an operation program were developed and tested for monitoring radioactive contamination of water caused by nuclear power plant accidents or unplanned release of radioactive materials.
Abstract: In this study, a miniature radiation portal monitor and an operation program were developed and tested for monitoring radioactive contamination of water caused by nuclear power plant accidents or unplanned release of radioactive materials. In order to set the optimum voltage of the detector, the voltage was increased by 1 V and the detection efficiency was measured. It was confirmed that the detector had a stable count and a high signal-to-noise ratio at 60 V. The detector response, gamma-ray energy spectrum, and energy linearity were tested using the detector with an applied voltage of 60 V. The R-square value of the detector response based on the intensity was 0.9980 and the R-square value of the channel linearity based on the energy was 0.9851, which indicates the detection characteristics to be very good. In addition, the system showed good resolution characteristics in which the gamma-ray emission energy 122 keV of the 57Co had an energy resolution of 16.02%, 662 keV of the 137Cs spectrum had 4.88%, and 1,332 keV of the 60Co had 2.02%. Based on the results from this study, it is determined that continuous research work may contribute in reducing the radioactive exposure caused by contamination of groundwater and drinking water in radioactive spill accidents.
8 citations