arXiv subjects

H. Katayama

Publications and source records attributed to H. Katayama.

5 recordsLinked to original sources

arXiv2020

COMET Phase-I Technical Design Report

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminium nucleus ($μ-e$ conversion, $μ^- N \to e^- N$); a lepton flavor violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90 % upper limit of branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the \mue conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

physics.ins-det↗

arXiv2011

High-precision CTE measurement of hybrid C/SiC composite for cryogenic space telescopes

This paper presents highly precise measurements of thermal expansion of a "hybrid" carbon-fiber reinforced silicon carbide composite, HB-Cesic\textregistered - a trademark of ECM, in the temperature region of \sim310-10K. Whilst C/SiC composites have been considered to be promising for the mirrors and other structures of space-borne cryogenic telescopes, the anisotropic thermal expansion has been a potential disadvantage of this material. HB-Cesic\textregistered is a newly developed composite using a mixture of different types of chopped, short carbon-fiber, in which one of the important aims of the development was to reduce the anisotropy. The measurements indicate that the anisotropy was much reduced down to 4% as a result of hybridization. The thermal expansion data obtained are presented as functions of temperature using eighth-order polynomials separately for the horizontal (XY-) and vertical (Z-) directions of the fabrication process. The average CTEs and their dispersion (1σ) in the range 293-10K derived from the data for the XY- and Z-directions were 0.805$\pm$0.003\times10$^{-6}$ K$^{-1}$ and 0.837\pm0.001\times10$^{-6}$ K$^{-1}$, respectively. The absolute accuracy and the reproducibility of the present measurements are suggested to be better than 0.01\times10$^{-6}$ K$^{-1}$ and 0.001\times(10)^{-6} K^{-1}, respectively. The residual anisotropy of the thermal expansion was consistent with our previous speculation regarding carbon-fiber, in which the residual anisotropy tended to lie mainly in the horizontal plane.

astro-ph.IM↗

arXiv2004

An X-ray measurement of Titan's atmospheric extent from its transit of the Crab Nebula

Saturn's largest satellite, Titan, transited the Crab Nebula on 5 January 2003. We observed this astronomical event with the {\it Chandra} X-ray Observatory. An ``occultation shadow'' has clearly been detected and is found to be larger than the diameter of Titan's solid surface. The difference gives a thickness for Titan's atmosphere of 880 $\pm$ 60 km. This is the first measurement of Titan's atmospheric extent at X-ray wavelengths. The value measured is consistent with or slightly larger than those estimated from earlier Voyager observations at other wavelengths. We discuss the possibility of temporal variations in the thickness of Titan's atmosphere.

astro-ph↗

arXiv2002

Properties of the background of EPIC-pn onboard XMM-Newton

We have investigated the background properties of EPIC-pn onboard XMM-Newton to establish the background subtraction method. Count rates of the background vary violently by two orders of magnitude at the maximum, while during the most quiet period, these are stable within 8 % at a 1 $σ$ level. The overall spectrum is dominated by particle events above 5 keV, and its spatial variation is also found. The long-term variation of the background is also investigated with CAL CLOSED data, where the filter wheel was in closed position with the internal calibration source illuminating the sensitive area. The average background count rate decreased by 20 % from March 2000 to January 2001, but it regained in February 2001. For the modeling of the background spectrum, we investigate relations between the 2.0--7.0 keV count rate and some characteristic parameters. The 2.0--7.0 keV background count rate shows a good correlation with the count rate of events outside the field of view. This correlation is usable for the modeling of the background.

astro-ph↗

arXiv2002

Properties of the background of EPIC onboard XMM-Newton

Understanding a background is crucial in particular for a study of low surface brightness objects. In order to establish the background subtraction method, we have studied properties of the EPIC background. Count rates of the background vary violently by two order of magnitude at the maximum, while during the most quiet period, these are stable within 8 % at a 1 $σ$ level. The overall spectrum is dominated by particle events above 5 keV, and its spatial variation is also found. The long-term variation of the background is also investigated with CAL CLOSED data, which is the data of calibration source with filter closed. The average background count rate decreased by 20 % from March 2000 to January 2001, but it regained in February 2001. For the modeling of the background spectrum, we investigate correlations between the 2-10 keV count rate and some characteristic parameters. The PN background shows a good correlation with some parameters. On the other hands, the MOS background does not shows a clear correlation. Further investigation is needed for the MOS background. Our final goal is to establish a method to predict the background, for which these results will be reflected in the background generator.

astro-ph↗