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Radon Environment in the Korea Invisible Mass Search Experiment and Its Measurement
이명재,방형찬,김승천,김선기,이상준,Jin Li,명성숙,김영덕,김홍주 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.4
The level of radioactivity from <SUP>222</SUP>Rn in the air has to be monitored to control systematic effects on the background level at the KIMS (Korea Invisible Mass Search) dark matter search experiment. We designed and constructed a radon detector using a silicon photodiode that collects ^(218)Po and ^(214)Po daughter ions electrically and detects their α decays. Results for the detector calibration with a standard radon source, as well as the dependence of the -particle detection efficiency on the humidity, are presented. The radioactivity of radon at the YangYang underground laboratory is measured and continuously monitored.
Invariant Mass Spectroscopy for the Neutron Rich Nuclei
사토,추경호,방형찬,S. H. Choi,T. Nakamura,Y. Kondo,Y. Nakayama,N. Kobayashi,K. N. Tanaka,S. Deguchi,Y. Kawada,N. Tanaka,T. Sugimoto,T. Motobayashi,H. Sakurai,H. Otsu,N. Aoi,Y. Yanagisawa,S. Takeuchi,N. Fukuda 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The neutron-rich carbon isotopes ^(19,17)C and a boron isotope ^(14)B are investigated respectively via proton inelastic and charge-exchange reactions on a liquid hydrogen target at around 70 MeV/nucleon at RIKEN. The invariant mass method in inverse kinematics involving coincidence detection of a charged fragment and a neutron both emitted at forward angles is employed to map the energy spectrum above the neutron decay threshold. Several resonance structures are revealed in the invariant mass spectra, and the nature for some of them is discussed from comparisons of differential cross section data with predictions of microscopic DWBA calculations based on spsdpf shell model wave functions and a recent parametrization of semi-microscopic nucleon-nucleus optical model potential (JLMB). By extrapolating the (p,n) cross sections leading to the 1^+ state at 1.27 MeV in ^(141)B to zero momentum transfer the Gamow-Teller transition strength is deduced. The value is found to compare well with that reported in a β-delayed neutron emission study.
Development of the Bunch Length Detector
김종원,김준연,김도균,방형찬,윤종철 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
A bunch length detector is under construction to measure the time structure of a beam bunch based on the analysis of secondary electrons, which are produced by an ion beam hitting on a thin wire. The detector can measure the longitudinal beam shape possibly in a wide range of beam energy, intensity and ion species. A main component of the device is the rf deflector to deflect electrons in correlation with rf phase of the beam bunch. Its electromagnetic properties were analyzed using rf analysis programs, and a full-scale cold model was constructed and tested. A microchannel plate detector to measure electron currents was tested using a β-ray emitting source. With the tests of the components completed, the actual detector is being constructed based on the calculations of electron optics as well as from the test results.
A Detector System for Measurement of the Longitudinal Bunch Shape of a CW Ion Beam
김준연,김종원,김도균,방형찬 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2
To measure the bunch shape of an ion beam accelerated by an rf linear accelerator, we have designed and constructed a detector system measuring secondary electrons emitted when the beam hits a thin wire placed in the beam path. The device consists of a vacuum chamber, a target wire, an rf resonator to deflect the electrons in correlation with the rf time of the ion beam, and multi-channel plate (MCP) detector to measure the electron current. The overall design of this device was carried out based on electron optical calculations. A full-scale model of the rf deflector was used to prove its design, and the MCP detector was tested using a β-emitting source to check its performance. An actual rf deflector was constructed and tested at a low rf power. The time resolution of the system was estimated to be around 30 ps.
Study on the Injection System for Cyclotron Mass Spectrometry
김도균,J. Y. Kim,방형찬,C. C. Yun,J. W. Kim 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The accelerator mass spectrometry (AMS) based on a cyclotron can be compact and economical compared to the commercial Tandem AMS. However, AMS cyclotrons previously built suffered largely from poor transmission efficiency. To improve the efficiency, it is important for the injection system to match the beam phase space with cyclotron acceptance. We plan to adopt a sawtooth rf buncher for longitudinal phase-space matching and a flat-topping rf system in the cyclotron for a larger phase acceptance. The beam optics for the injection line was studied using TRANSPORT and TRACE-3D, keeping a minimal number of beam line elements. The shapes of extraction electrodes and Einzel lens were simulated using IGUN. A prototype beam line is being constructed so that the beam measurements in comparison with calculation results will be used to reveal an optimal design.
Measurement of Unbound Excited States of ^(24)O
추경호,사토,T. Nakamura,N. Aoi,방형찬,S. CHOI,S. Deguchi,F. Delaunay,J. Gibelin,T. Honda,M. Ishihara,Y. Kawada,Y. Kondo,T. Kobayashi,N. Kobayashi,F. M. Marques,M. Matsushita,Y. Miyashita,T. Motobayashi,Y. Nak 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The unbound excited states of the most neutron-rich oxygen isotope, ^(24)O (Z = 8, N = 16), have been investigated using the ^(24)O(p,p') ^(24)O^* → ^(23)O+n reaction at RIKEN, where a 63 MeV/neuclon secondary beam of ^(24)O was produced in a Be production target by the projectile-like fragmentation of a 95 MeV/u ^(40)Ar primary beam. The first excited 2^* state was observed in the invariant mass spectrum. This experiment will give us a deeper understanding of the new magic number at N=16 in the neutron-rich oxygen isotopes.
Observation of Air Shower in Uijeongbu Area using the COREA Prototype Detector System
조우람,신재익,권영준,양종만,남신우,Il H. Park,천병구,김항배,방형찬,박철영,김기혁,최우석,황명진,신광식 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.11
We report the study of high energy cosmic rays in Uijeongbu area using a cosmic-ray detector array system. The array consists of three detector stations, each of which contains a set of three scintillators and PMTs, a GPS antenna along with data acquisition system. To identify air shower signals originating from a single cosmic ray, time coincidence information is used. We devised a method for estimating the energy range of air shower data detected by an array of only three detectors, using air shower simulation and citing already known energy spectrum. Also, Fast Fourier Transform(FFT) was applied to study isotropy.