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153 results on '"Kii, T."'

2. Overview and Initial Results of the Very Long Baseline Interferometry Space Observatory Programme

Author

Hirabayashi, H., Hirosawa, H., Kobayashi, H., Murata, Y., Edwards, P. G., Fomalont, E. B., Fujisawa, K., Ichikawa, T., Kii, T., Lovell, J. E. J., Moellenbrock, G. A., Okayasu, R., Inoue, M., Kawaguchi, N., Kameno, S., Shibata, K. M., Asaki, Y., Bushimata, T., Enome, S., Horiuchi, S., Miyaji, T., Umemoto, T., Migenes, V., Wajima, K., Nakajima, J., Morimoto, M., Ellis, J., Meier, D. L., Murphy, D. W., Preston, R. A., Smith, J. G., Tingay, S. J., Traub, D. L., Wietfeldt, R. D., Benson, J. M., Claussen, M. J., Flatters, C., Romney, J. D., Ulvestad, J. S., D'Addario, L. R., Langston, G. I., Minter, A. H., Carlson, B. R., Dewdney, P. E., Jauncey, D. L., Reynolds, J. E., Taylor, A. R., McCulloch, P. M., Cannon, W. H., Gurvits, L. I., Mioduszewski, A. J., Schilizzi, R. T., and Booth, R. S.

Published
1998

7. A new design for generation of tunable gamma-ray with a fixed energy electron beam

Author

Ohgaki, H., Kii, T., and Toyokawa, H.

Subjects
Electron beams -- Properties, Gamma rays -- Research, Backscattering -- Research, Business, Electronics, Electronics and electrical industries
Abstract

A tunable quasi-monochromatic gamma-ray beam is indispensable not only for radiation measurements, but also for precise measurements of nuclear data. A design for generation of tunable quasi-monochromatic gamma-ray from the Compton backscattering of a laser light with a fixed energy electron beam has been investigated. We propose a new design (absorber- collimator scheme) by selecting the scattering angle of the Compton backscattered gamma-ray. Tunable gamma-ray can be obtained by changing the solid angle of the collimator (works as a low cut filter) and absorber (works as a high cut filter). A proof of principle experiment has been performed at the AIST-LCS beamline and the result showed that the absorber-collimator scheme could generate tunable gamma-rays. Numerical simulation based on the EGS4 well reproduced the experimental result. Index Terms--Compton backscattering, storage ring, tunable gamma-ray, EGS4.

Published
2009

16. Emission properties and back-bombardment for CeB6 compared to LaB6.

Author

Bakr, Mahmoud, Kawai, M., Kii, T., Zen, H., Masuda, K., and Ohgaki, H.

Subjects
THERMIONIC cathodes, ELECTRON gun, RADIO frequency, CURRENT density (Electromagnetism), COMPUTER simulation, ELECTROSTATICS
Abstract

The emission properties of CeB6 compared to LaB6 thermionic cathodes have been measured using an electrostatic DC gun. Obtaining knowledge of the emission properties is the first step in understanding the back-bombardment effect that limits wide usage of thermionic radio-frequency electron guns. The effect of back-bombardment electrons on CeB6 compared to LaB6 was studied using a numerical simulation model. The results show that for 6 ls pulse duration with input radio-frequency power of 8 MW, CeB6 should experience 14% lower temperature increase and 21% lower current density rise compared to LaB6. We conclude that CeB6 has the potential to become the future replacement for LaB6 thermionic cathodes in radio-frequency electron guns. [ABSTRACT FROM AUTHOR]

Published
2015
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21. Observations of blazars with ASCA

Author

Makino, F, Edelson, R, Fujimoto, R, Kii, T, Idesawa, E, Makishima, K, Takahashi, T, Sasaki, K, Kamae, T, Kubo, H, Mathis, D, Tashiro, M, Teraesranta, H, and Urry, C. M

Subjects
Astronomy
Abstract

The Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of 3C 279, Mkn 421, PKS 2155-304, BL Lac 0716+714 and OJ 287 blazars are presented. Blazars are a class of active galactic nuclei characterized by high variability, high polarization, flat radio spectrum and featureless spectrum. The X-ray spectra and flux variations of blazars are discussed. The inverse correlation between X-ray flux and index, soft lag, the convex curvature of the spectrum, flat gamma-ray and/or X-ray spectra, fast variability and featureless spectrum are common characteristics of blazars.

Published
1996

27. Ginga observations of the dwarf novae BV Pup and V426 Oph

Author

Szkody, Paula, Kii, T, and Osaki, Yoji

Subjects
Astrophysics
Abstract

Ginga X-ray observations of the high excitation dwarf nova BV Pup and the suspected DQ Her dwarf nova V426 Oph are presented. The observation of BV Pup took place during optical quiescence and showed no detectable X-ray flux, implying the X-ray luminosity was below that observed by Exosat during the decline from an outburst. An optical spectrum obtained near the time of the X-ray observations showed no high-excitation He II 4686, so that it is not clear if this was an unusual low-excitation time for BV Pup or if this is a normal phase of the outburst cycle. V426 Oph was observed for four days near maximum outburst brightness with overlapping X-ray coverage on three days. The 2-10 keV flux was a factor of 2 below that observed by Exosat during a quiescent state. There is evidence for a 28 min timescale in the X-ray, and optical data which are not strictly periodic in nature.

Published
1990
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30. Optical identification of the ASCA Lynx Deep Survey: An association of quasi-stellar objects and a supercluster at z = 1.3?

Author

Ohta, K, Akiyama, M, Ueda, Y, Yamada, T, Nakanishi, K, Dalton, GB, Ogasaka, Y, Kii, T, and Hayashida, K

Abstract

Results of optical identification of the ASCA Lynx Deep Survey are presented. Six X-ray sources are detected in the 2-7 keV band using the Solid-State Imaging Spectrometer in a ∼20′ × 20′ field of view with fluxes larger than ∼4 × 10-14 ergs s -1 cm-2 in the band. Follow-up optical spectroscopic observations were made, and five out of six sources are identified with active galactic nuclei/quasi-stellar objects (AGNs/QSOs) at redshifts of 0.5-1.3. We also identify two more additional X-ray sources detected in a soft X-ray band with AGNs/QSOs. We find that three QSOs identified are located at z ∼ 1.3. Two rich clusters and several groups of galaxies are also placed at the same redshift in the surveyed field, and projected separations between the QSOs and the clusters are 3-8 Mpc at the redshift.

Published
2016

31. GENERATION OF 1-MeV QUASI-MONOCHROMATIC GAMMA-RAYS FOR PRECISE MEASUREMENT OF DELBRÜCK SCATTERING BY LASER COMPTON SCATTERING

Author

Zen, H., Kii, T., Ohgaki, H., Hayakawa, T., Shizuma, T., K. Koga, J., Salehi, E., Fujimoto, M., Hayakawa, Takehito, Shizuma, Toshiyuki, and Kevin Koga, James

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Physics::Accelerator Physics
Abstract

The nearly isolated precise measurement of the vacuum contribution, Delbrück scattering, to the elastic scattering of photons off nuclei can be realized by using high-flux linearly-polarized gamma-ray sources. An intense linearly polarized gammaray beam with an energy lower than 1 MeV should be provided. In order to examine the available gamma-ray performance at the UVSOR facility by colliding a CO2 laser with a 746-MeV electron beam, a preliminary experiment has been performed. As a result, it was confirmed that the maximum energy of the gamma-rays was slightly lower than 1 MeV and the gamma-ray flux was measured.

Published
2018

38. Nondestructive Inspection System for Special Nuclear Material Using Inertial Electrostatic Confinement Fusion Neutrons and Laser Compton Scattering Gamma-Rays.

Author

Ohgaki, H., Daito, I., Zen, H., Kii, T., Masuda, K., Misawa, T., Hajima, R., Hayakawa, T., Shizuma, T., Kando, M., and Fujimoto, S.

Subjects
NONDESTRUCTIVE testing, RADIOACTIVE substances, ELECTROSTATIC analyzers, COMPTON scattering, SHIPPING containers
Abstract

A Neutron/Gamma-ray combined inspection system for hidden special nuclear materials (SNMs) in cargo containers has been developed under a program of Japan Science and Technology Agency in Japan. This inspection system consists of an active neutron-detection system for fast screening and a laser Compton backscattering gamma-ray source in coupling with nuclear resonance fluorescence (NRF) method for precise inspection. The inertial electrostatic confinement fusion device has been adopted as a neutron source and two neutron-detection methods, delayed neutron noise analysis method and high-energy neutron-detection method, have been developed to realize the fast screening system. The prototype system has been constructed and tested in the Reactor Research Institute, Kyoto University. For the generation of the laser Compton backscattering gamma-ray beam, a race track microtron accelerator has been used to reduce the size of the system. For the NRF measurement, an array of LaBr3(Ce) scintillation detectors has been adopted to realize a low-cost detection system. The prototype of the gamma-ray system has been demonstrated in the Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology. By using numerical simulations based on the data taken from these prototype systems and the inspection-flow, the system designed by this program can detect 1 kg of highly enriched 235U (HEU) hidden in an empty 20-ft container within several minutes. [ABSTRACT FROM PUBLISHER]

Published
2017
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39. Simultaneous measurement of the photodisintegration of 4He in the giant dipole resonance region

Author

Shima, T., Naito, S., Nagai, Y., Baba, T., Tamura, K., Takahashi, T., Kii, T., Ohgaki, H., and Toyokawa, H.

Subjects
FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

We have performed for the first time the simultaneous measurement of the two-body and three-body photodisintegration cross-sections of 4He in the energy range from 21.8 to 29.8 MeV using monoenergetic pulsed photons and a 4-pi time projection chamber containing 4He gas as an active target in an event-by-event mode. The photon beam was produced via the Compton backscattering of laser photons with high-energy electrons. The 4He(gamma,p)3H and 4He(gamma,n)3He cross sections were found to increase monotonically with energy up to 29.8 MeV, in contrast to the result of a recent theoretical calculation based on the Lorentz integral transform method which predicted a pronounced peak at around 26-27 MeV. The energy dependence of the obtained 4He(gamma,n)3He cross section up to 26.5 MeV is marginally consistent with a Faddeev-type calculation predicting a flat pattern of the excitation function. The cross-section ratio of 4He(gamma,p)3H to 4He(gamma,n)3He is found to be consistent with the expected value for charge symmetry of the strong interaction within the experimental uncertainty in the measured energy range. The present results for the total and two-body cross-sections of the photodisintegration of 4He are compared to previous experimental data and recent theoretical calculations., 19 pages, 24 figures, accepted for publication in Phys. Rev. C

Published
2005

41. Non-resonant direct p- and d-wave neutron capture by 12C

Author

Kikuchi, T., Nagai, Y., Suzuki, T. S., Shima, T., Kii, T., Igashira, M., Mengoni, A., and Otsuka, T.

Subjects
Nuclear Theory (nucl-th), Nuclear Theory, FOS: Physical sciences
Abstract

Discrete gamma-rays from the neutron capture state of 13C to its low-lying bound states have been measured using pulsed neutrons at En = 550 keV. The partial capture cross sections have been determined to be 1.7+/-0.5, 24.2+/-1.0, 2.0+/-0.4 and 1.0+/-0.4 microb for the ground (1/2-), first (1/2+), second (3/2-) and third (5/2+) excited states, respectively. From a comparison with theoretical predictions based on the non-resonant direct radiative capture mechanism, we could determine the spectroscopic factor for the 1/2+ state to be 0.80 +/- 0.04, free from neutron-nucleus interaction ambiguities in the continuum. In addition we have detected the contribution of the non-resonant d-wave capture component in the partial cross sections for transitions leading to the 1/2- and 3/2- states. While the s-wave capture dominates at En < 100 keV, the d-wave component turns out to be very important at higher energies. From the present investigation the 12C(n,gamma)13C reaction rate is obtained for temperatures in the range 10E+7 - 10E+10 K., Accepted for publication in Phys. Rev. C. - 16 pages + 8 figures

Published
1998

42. Multiwavelenght observations of a dramatic high energy flare in the blazar 3C279

Author

Wehrle, A. E., Pian, E., Urry, C. M., Maraschi, L., Ghisellini, G., Hartman, R. C., Madejski, G. M., Makino, F., Marscher, A. P., Mchardy, I. M., Wagner, S. J., Webb, J. R., Aldering, G. S., Aller, M. F., Aller, H. D., Backman, D. E., Balonek, T. J., Boltwood, P., Bonnell, J., Caplinger, J., Celotti, Anna Lisa, Collmar, W., Dalton, J., Drucker, A., Falomo, R., Fichtel, C. E., Freudling, W., Gear, W. K., Gonzalez Perez, N., Hall, P., Inoue, H., Johnson, W. N., Kazanas, D., Kidger, M. R., Kii, T., Kollga, Ard, R. I., Kondo, Y., Kurfess, J., Lawson, A. J., Lin, Y. C., Mccollum, B., Mcnaronbrown, K., Nair, A. D., Penton, S., Pesce, J. E., Pohl, M., Raiteri, C. M., Renda, M., Robson, E. I., Sambruna, R. M., Schirmer, A. F., Shrades, C., Sikora, M., Sillanpa, A. A., Smith, P. S., Stevens, J. A., Stocke, J., Takalo, L. O., Terasranta, H., Thompson, D. J., Thompson, R., Tornikoski, M., Tosti, G., Turcotte, P., Treves, A., Unwin, S. C., Valtaoja, E., Villata, M., Xu, W., and Zook, A.

Published
1998

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