541 research outputs found
An x-ray detector using PIN photodiodes for the axion helioscope
An x-ray detector for a solar axion search was developed. The detector is
operated at 60K in a cryostat of a superconducting magnet. Special care was
paid to microphonic noise immunity and mechanical structure against thermal
contraction. The detector consists of an array of PIN photodiodes and tailor
made preamplifiers. The size of each PIN photodiode is $11\times 11\times 0.5\
{\rm mm^3}$ and 16 pieces are used for the detector. The detector consists of
two parts, the front-end part being operated at a temperature of 60K and the
main part in room temperature. Under these circumstances, the detector achieved
1.0 keV resolution in FWHM, 2.5 keV threshold and 6\times 10^{-5} counts
sec^{-1} keV^{-1} cm^{-2} background level.Comment: 8 pages, 5 figures, submitted to Nucl. Instr. Meth.
Pulse-Shape Discrimination of CaF2(Eu)
We measured the decay time of the scintillation pulses produced by electron
and nuclear recoils in CaF2(Eu) by a new fitting method. In the recoil energy
region 5-30 keVee, we found differences of the decay time between electron and
nuclear recoil events. In the recoil energy region above 20 keVee, we found
that the decay time is independent of the recoil energy.Comment: 10 pages, 4 figure
A mobile antineutrino detector with plastic scintillators
We propose a new type segmented antineutrino detector made of plastic
scintillators for the nuclear safeguard application. A small prototype was
built and tested to measure background events. A satisfactory unmanned field
operation of the detector system was demonstrated. Besides, a detailed Monte
Carlo simulation code was developed to estimate the antineutrino detection
efficiency of the detector.Comment: 23 pages, 11 figures; accepted for publication in Nuclear Instruments
and Methods in Physics Research
The Tokyo Axion Helioscope Experiment
A preliminary result of the solar axion search experiment at the University
of Tokyo is presented. We searched for axions which could be produced in the
solar core by exploiting the axion helioscope. The helioscope consists of a
superconducting magnet with field strength of 4 Tesla over 2.3 meters. From the
absence of the axion signal we set a 95 % confidence level upper limit on the
axion coupling to two photons for the axion mass eV. This is the first solar axion
search experiment whose sensitivity to exceeds the limit
inferred from the solar age consideration.Comment: 5 pages, 5 eps files included, uses espcrc2.sty, to be published in
Proc. AXION WORKSHOP, Gainesville, Florida, 13-15 March 1998, ed. by
P.Sikivi
Recent results from the Tokyo axion helioscope experiment
We have searched for axions which could have been produced in the solar core
using an axion helioscope with a 2.3m-long 4T superconducting magnet. Axion
mass region up to m_a=0.26eV was newly explored by introducing
dispersion-matching gas. Preliminary analysis sets a limit on axion-photon
coupling constant to be less than (6.4--9.6)e-10 GeV^{-1} (95%CL) for this mass
region from the absence of the axion signal. This is more stringent than the
limit inferred from the solar age consideration and also more stringent than
the recent helioseismological bound.Comment: 6 pages, 4 PostScript figures; submitted to Proceedings of IDM2000
(World Scientific
Near-infrared Brightness of the Galilean Satellites Eclipsed in Jovian Shadow: A New Technique to Investigate Jovian Upper Atmosphere
We have discovered that Europa, Ganymede and Callisto are bright around 1.5
{\mu}m even when not directly lit by sunlight, based on observations from the
Hubble Space Telescope and the Subaru Telescope. The observations were
conducted with non-sidereal tracking on Jupiter outside of the field of view to
reduce the stray light subtraction uncertainty due to the close proximity of
Jupiter. Their eclipsed luminosity was - of their uneclipsed
brightness, which is low enough that this phenomenon has been undiscovered
until now. In addition, Europa in eclipse was <1/10 of the others at 1.5
{\mu}m, a potential clue to the origin of the source of luminosity. Likewise,
Ganymede observations were attempted at 3.6 {\mu}m by the Spitzer Space
Telescope but it was not detected, suggesting a significant wavelength
dependence. The reason why they are luminous even when in the Jovian shadow is
still unknown, but forward-scattered sunlight by haze in the Jovian upper
atmosphere is proposed as the most plausible candidate. If this is the case,
observations of these Galilean satellites while eclipsed by the Jovian shadow
provide us a new technique to investigate Jovian atmospheric composition, and
investigating the transmission spectrum of Jupiter by this method is important
for investigating the atmosphere of extrasolar giant planets by transit
spectroscopy.Comment: 7 pages, 3 figures, accepted to Ap
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