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Shielding Experiments under JASMIN Collaboration at Fermilab (I) Overview of the Research Activities
Y. Kasugai,N. Matsuda,Y. Iwamoto,Y. Sakamoto,H. Nakashima,H. Matsumura,N. Kinoshitay,H. Iwase,T. Sanami,M. Hagiwara,H. Hirayama,H. Yashima,N. Sigyo,H. Arakawa,K. Ishibashi,N. Mokhov,A. Leveling,D. Boe 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Shielding experiments were started on 2007 using high-energy proton accelerator at Fermi National Accelerator Laboratory (Fermilab) under the collaborative study program of JASMIN: Japanese and American Study of Muon Interaction and Neutron Detection. In this series of papers entitled "Shielding experiments under JASMIN collaboration at Fermilab", the part of the results regarding neutron detection has been reported. This paper, as a first paper of the series, overview of the research activities are described, and experimental results on high-energy neutron transportation are presented in a viewpoint of neutron attenuation in steel shield and applicability of Moyer's model. In addition, deductions of a neutron spectrum in wide energy range between 1 eV and 100 MeV by means of the hybrid method using the current-readout Bonner sphere together with foil-activation technique are presented.
Evaluation of Topology Optimization Objectives in IP Networks
Y. Sinan Hanay,Shinichi Arakawa,Masayuki Murata 한국통신학회 2019 Journal of communications and networks Vol.21 No.4
In the past, various optimization objective functions havebeen proposed to help in network optimization, especially for usein traffic engineering (TE) and topology optimization. This varietyof optimization objectives resulted in the emergence of algorithmstargeting different objectives. However, the role of the objectivefunction has been largely overlooked. Because, the choiceof a particular objective function was not justified in most of thecases. Some researchers criticized this arbitrary selection of objectivefunctions. Even though some researchers intuitively suggestusing a specific objective, only few work tackled with the problemof evaluating the objectives. In this paper, we evaluate various networkoptimization objectives on topology optimization. Previously,a study analyzed the efficiency of some routing optimization objectivesusing linear programming (LP) by linear relaxation. However,some of the objective functions are nonlinear, and such a linear relaxationdoes not treat each objective equally.The difficulty arisesdue to the fact that optimization algorithms are objective functiontailored heuristics. To achieve fairness, we compare and analyzedifferent traffic optimization objectives for topology optimizationusing neural networks which are used to model nonlinear relations. By using neural networks, we strive to avoid any unfairness, suchas obviating linear approximation. Also, our work suggests whichfeatures are meaningful for machine learning in network optimization. Our method partially agrees with the previous work, and weconclude that delay is the best performing optimization objective.
The static expansion system as a new medium vacuum primary standard in KRISS
Hong, S S,Shin, Y H,Chung, K H,Arakawa, I Springer-Verlag 2005 Metrologia Vol.42 No.6
<P>A new medium vacuum primary standard using the static expansion method was developed in Korea Research Institute of Standards and Technology. We compared the system with an ultrasonic interferometer manometer using two capacitance diaphragm gauges with full-scale ranges of 133 Pa and 1333 Pa. The results showed that the two standards are coincident with each other within the range of uncertainty at calibrated pressures 3 Pa to 100 Pa.</P>
High Density and High Uniformity InAs/AlAs QDs by Using Insertion Layer
S.K Park,C.J. Park,H.Y Cho,J. Tatebayashi,Y. Arakawa 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.3
We have systematically studied the eect of a Ga(In)As insertion layer (IL) on the optical and structural properties of InAs quantum dot (QD) structures. A high density of 1.1 1011 cmက2 of InAs QDs with a Ga(In)As IL has been achieved on a GaAs (100) substrate by metal organic chemical vapor deposition. A photoluminescence linewidth of 27 meV from these QDs has been obtained. We attribute the high density and high uniformity of these QDs to the use of the IL. Our results suggest a method for obtaining high quality InAs QD structures for devices with a 1.3 m operation wavelength. Key words : high density and high uniformity dots, Ga(In)As insertion layer, InAs quantum dots
Hong, S S,Chung, K H,Shin, Y H,Arakawa, I IOP Pub 2006 Measurement Science and Technology Vol.17 No.1
<P>The present study generated an extremely high vacuum of 10<SUP>−10</SUP> Pa by very common methods such as using SUS304 chamber material, electropolishing surface treatment and turbomolecular pumping technology. We examined the gas phase and electron-stimulated desorption ions of the ion gauges, the effect of ambient temperature, total pressure and H<SUB>2</SUB> partial pressure. One of the results showed that, as is well known, most of the residual gas in the extremely high vacuum chamber was H<SUB>2</SUB> but there was also a little F, which is not so well known.</P>
스테인레스 스틸 고진공용기에 부착된 열음극 전리진공게이지의 주변 온도변화에 따른 압력요동
홍승수(S. S. Hong),임인태(I. T. Lim),신용현(Y. H. Shin),정광화(K. H. Chung),이치로 아라카와(Ichiro Arakawa) 한국진공학회(ASCT) 2004 Applied Science and Convergence Technology Vol.13 No.2
스테인레스 스틸로 가공된 진공용기에 제조회사와 사양이 각각 다른 세 개의 열음극 전리진공게이지를 부착하고 실험실 온도변화에 따른 게이지들의 압력요동 특성을 조사하였다. 상온 근방의 최소 20℃와 최대 26 ℃에서의 압력 편차는 각각 IG1은 5.0%, IG2는 5.3 %, 그리고 IG3은 10.3%이었다. 그러나 온도 21.5℃에서 22.5℃ 구간에서의 압력변화는 모두 게이지들의 불확도 보다 작고 안정한 성능을 보였다. 본 연구결과 상온 고진공에서 열음극 전리진공게이지의 압력변화는 게이지 자체의 특성 때문에 아니고 실험실 온도 때문에 변화는 압력변화에 기인한 것임을 알 수 있었다. Three hot cathode ionization gauges (HCIG) were used to study their responses of pressure measurements at the stainlee steel high vacuum (HV) chamber around room temperatures. The pressure variations of HV measured by the three HCIGs between 20 ℃ and 26 ℃ were 5.0 %, 5.3 %, and 10.3 %, respectively. However, pressure differences between 21.5 ℃ and 22.5 ℃ were lower than the gauges uncertainly limits. The pressure variations of the HCIGs at the<br/> HV chamber was not directly affected by gauge characteristics, but pressure changes due to room temperatures.
T. Kajimoto,N. Shigyo,K. Ishibashi,D. Moriguchi,Y. Nakamura,H. Arakawa,S. Kunieda,T. Watanabe,R. C. Haight 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
We measured neutron-production double-differential cross-sections by neutron incidence from 50 to 150 MeV. A ^(238)U fission ionization chamber was set to take the incident-neutron flux. Six NE213 liquid scintillators which had a thickness of 12.7 cm and 12.7 cm in diameter, were placed at 15˚, 30˚, 60˚, 90˚, 120˚, and 150˚ to detect neutrons emitted from a sample. The energy of incident neutron was determined by the time of flight (TOF) technique. The energy spectra of neutron emitted from the sample were derived by the unfolding their light output spectra with the response functions of the detectors. The response functions were measured with the spallation neutrons above 25 MeV. In the unfolding process, we assumed that neutron energy spectra reproduced the shape by the moving source model. The neutron-induced neutron-production double-differential cross sections were parameterized with the moving source model by the least-square method. The experimental results were compared with calculations of the PHITS and the TALYS codes.
크라이오 펌프를 이용한 스테인레스 스틸 고진공용기 배기에서 2차 냉각판 온도와 용기 내부의 기체 부분압 관계
홍승수,임종연,신용현,정광화,Hong S. S.,Lim J. Y.,Shin Y. H.,Chung K. H.,Arakawa Ichiro 한국진공학회 2004 Applied Science and Convergence Technology Vol.13 No.4
Recently, the importance of clean vacuum and partial pressure measurement of gas species has been increased in the vaccum process. In this study, the partial pressures of $H_2$, He, C, N, $O_2$, $H_2O $, Ar/2, $N_2$(CO), Ar, $CO_2$ were measured by residual gas analyzer according to temperature of cryogenic pump which is used to clean vacuum generation and compared. The experimental results showed that the cryopanel temperature was reached to 12K after 72 minutes of pumping and after 25hours, the partial pressures in percent were 24.9 %, 6.6%, 5.5 %, 2.2 %, 3.8%, 30.7%, 6.5%, 6.1 %, 5.5%, 8.2% for $H_2$, He, C, N, $O_2$, $H_2O $, Ar/2, $N_2$, Ar, $CO_2$ respectively. The dominant gases were $H_2$ and $H_2O $, and the partial pressures were relatively high compare to other gases. 최근에는 진공공정에서 용기내의 청정도와 잔류기체의 부분압에 대한 관심이 높아지고 있다. 본 연구에서는 청정진공 발생에 많이 사용되고 있는 크라이오 펌프의 냉각판 온도에 따른 $H_2$, He, C, N, $O_2$, $H_2O$, Ar/2, $N_2$(CO), Ar, $CO_2$의 부분압을 잔류기체분석기로 측정하여 비교하였다. 크라이오 펌프를 켜고 약 72분이 지났을 때 펌프의 냉각판 온도가 12K에 도달하였으며, 25시간이 경과하여 온도가 충분하게 낮아졌을 때 부분압은 $H_2$, He, C, N, $O_2$, $H_2O$, Ar/2, $N_2$, Ar, $CO_2$순으로 24.9%, 6.6%, 5.5%, 2.2%, 3.8%, 30.7%, 6.5%, 6.1%, 5.5 %, 8.2%로 $H_2$와 $H_2O $압력이 상대적으로 높은 것을 알 수 있었다.