150 research outputs found
The relationship between education and child welfare in Japanese children’s self-reliance support facilities
This is an Accepted Manuscript of an article published by Taylor & Francis in Contemporary Japan on 17 Jan 2018, available online: http://wwww.tandfonline.com/doi/full/10.1080/18692729.2018.142372
Direction-sensitive dark matter search results in a surface laboratory
We developed a three-dimensional gaseous tracking device and performed a
direction-sensitive dark matter search in a surface laboratory. By using 150
Torr carbon-tetrafluoride (CF_4 gas), we obtained a sky map drawn with the
recoil directions of the carbon and fluorine nuclei, and set the first limit on
the spin-dependent WIMP (Weakly Interacting Massive Particles)-proton cross
section by a direction-sensitive method. Thus, we showed that a WIMP-search
experiment with a gaseous tracking device can actually set limits. Furthermore,
we demonstrated that this method will potentially play a certain role in
revealing the nature of dark matter when a low-background large-volume detector
is developed.Comment: 9 figures, accepted for publication in Phys. Lett.
New readout and data-acquisition system in an electron-tracking Compton camera for MeV gamma-ray astronomy (SMILE-II)
For MeV gamma-ray astronomy, we have developed an electron-tracking Compton
camera (ETCC) as a MeV gamma-ray telescope capable of rejecting the radiation
background and attaining the high sensitivity of near 1 mCrab in space. Our
ETCC comprises a gaseous time-projection chamber (TPC) with a micro pattern gas
detector for tracking recoil electrons and a position-sensitive scintillation
camera for detecting scattered gamma rays. After the success of a first balloon
experiment in 2006 with a small ETCC (using a 101015 cm
TPC) for measuring diffuse cosmic and atmospheric sub-MeV gamma rays (Sub-MeV
gamma-ray Imaging Loaded-on-balloon Experiment I; SMILE-I), a (30 cm)
medium-sized ETCC was developed to measure MeV gamma-ray spectra from celestial
sources, such as the Crab Nebula, with single-day balloon flights (SMILE-II).
To achieve this goal, a 100-times-larger detection area compared with that of
SMILE-I is required without changing the weight or power consumption of the
detector system. In addition, the event rate is also expected to dramatically
increase during observation. Here, we describe both the concept and the
performance of the new data-acquisition system with this (30 cm) ETCC to
manage 100 times more data while satisfying the severe restrictions regarding
the weight and power consumption imposed by a balloon-borne observation. In
particular, to improve the detection efficiency of the fine tracks in the TPC
from 10\% to 100\%, we introduce a new data-handling algorithm in
the TPC. Therefore, for efficient management of such large amounts of data, we
developed a data-acquisition system with parallel data flow.Comment: 11 pages, 24 figure
Performance of a Time-Projection-Chamber with a Large-Area Micro-Pixel-Chamber Readout
A micro time-projection-chamber (micro-TPC) with a detection volume of
23*28*31 cm^3 was developed, and its fundamental performance was examined. The
micro-TPC consists of a micro pixel chamber with a detection area of 31*31 cm^2
as a two-dimensional imaging device and a gas electron multiplier with an
effective area of 23*28 cm^2 as a pre-gas-multiplier. The micro-TPC was
operated at a gas gain of 50,000, and energy resolutions and spatial
resolutions were measured.Comment: 4 pages, 7 figures, proceedings of IWORID
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