728 research outputs found
Parametric instabilities in the LCGT arm cavity
We evaluated the parametric instabilities of LCGT (Japanese interferometric
gravitational wave detector project) arm cavity. The number of unstable modes
of LCGT is 10-times smaller than that of Advanced LIGO (U.S.A.). Since the
strength of the instabilities of LCGT depends on the mirror curvature more
weakly than that of Advanced LIGO, the requirement of the mirror curvature
accuracy is easier to be achieved. The difference in the parametric
instabilities between LCGT and Advanced LIGO is because of the thermal noise
reduction methods (LCGT, cooling sapphire mirrors; Advanced LIGO, fused silica
mirrors with larger laser beams), which are the main strategies of the
projects. Elastic Q reduction by the barrel surface (0.2 mm thickness
TaO) coating is effective to suppress instabilities in the LCGT arm
cavity. Therefore, the cryogenic interferometer is a smart solution for the
parametric instabilities in addition to thermal noise and thermal lensing.Comment: 6 pages,3 figures. Amaldi7 proceedings, J. Phys.: Conf. Ser.
(accepted
Current status of the CLIO project
CLIO (Cryogenic Laser Interferometer Observatory) is a Japanese gravitational
wave detector project. One of the main purposes of CLIO is to demonstrate
thermal-noise suppression by cooling mirrors for a future Japanese project,
LCGT (Large-scale Cryogenic Gravitational Telescope). The CLIO site is in
Kamioka mine, as is LCGT. The progress of CLIO between 2005 and 2007 (room- and
cryogenic-temperature experiments) is introduced in this article. In a
room-temperature experiment, we made efforts to improve the sensitivity. The
current best sensitivity at 300 K is about
around 400 Hz. Below 20 Hz, the strain (not displacement) sensitivity is
comparable to that of LIGO, although the baselines of CLIO are 40-times shorter
(CLIO: 100m, LIGO: 4km). This is because seismic noise is extremely small in
Kamioka mine. We operated the interferometer at room temperature for
gravitational wave observations. We obtained 86 hours of data. In the cryogenic
experiment, it was confirmed that the mirrors were sufficiently cooled (14 K).
However, we found that the radiation shield ducts transferred 300K radiation
into the cryostat more effectively than we had expected. We observed that noise
caused by pure aluminum wires to suspend a mirror was suppressed by cooling the
mirror.Comment: 8 pages, 9 figures. Amaldi7 proceedings, J. Phys.: Conf. Ser.
(accepted
Mechanical quality factor of a sapphire fiber at cryogenic temperatures
A mechanical quality factor of was obtained for the 199
Hz bending vibrational mode in a monocrystalline sapphire fiber at 6 K.
Consequently, we confirm that pendulum thermal noise of cryogenic mirrors used
for gravitational wave detectors can be reduced by the sapphire fiber
suspension.Comment: To be published to Physiscs Letters A. Number of pages: 10 Number of
figures: 5 Number of tables:
Force measurements of a superconducting-film actuator for a cryogenic interferometric gravitational-wave detector
We measured forces applied by an actuator with a YBCO film at near 77 K for
the Large-scale Cryogenic Gravitational-wave Telescope (LCGT) project. An
actuator consisting of both a YBCO film of 1.6 micrometers thickness and 0.81
square centimeters area and a solenoid coil exerted a force of up to 0.2 mN on
a test mass. The presented actuator system can be used to displace the mirror
of LCGT for fringe lock of the interferometer.Comment: 9 pages, 3 figure
Indium joints for cryogenic gravitational wave detectors
A viable technique for the preparation of highly thermal conductive joints between sapphire components in gravitational wave detectors is presented. The mechanical loss of such a joint was determined to be as low as 2 × 10−3 at 20 K and 2 × 10−2 at 300 K. The thermal noise performance of a typical joint is compared to the requirements of the Japanese gravitational wave detector, KAGRA. It is shown that using such an indium joint in the suspension system allows it to operate with low thermal noise. Additionally, results on the maximum amount of heat which can be extracted via indium joints are presented. It is found that sapphire parts, joined by means of indium, are able to remove the residual heat load in the mirrors of KAGRA
Does timing of decisions in a mixed duopoly matter?
We determine the endogenous order of moves in a mixed pricesetting duopoly. In contrast to the existing literature on mixed oligopolies we establish the payo equivalence of the games with an exogenously given order of moves if the most plausible equilibrium is realized in the market. Hence, in this case it does not matter whether one becomes a leader or a follower. We also establish that replacing a private firm by a public firm in the standard Bertrand-Edgeworth game with capacity constraints increases social welfare and that a pure-strategy equilibrium always exists
Search for continuous gravitational waves from PSR J0835-4510 using CLIO data
We search for continuous gravitational waves from PSR J0835-4510 at twice its rotational frequency using CLIO (Cryogenic Laser Interferometric Observatory) in the Kamioka mine. In this search, we use data from an observational run during 12–28 February 2007. We give a brief description of the methods used in this search. We obtain an upper limit on gravitational wave amplitude for PSR J0835-4510 as h0(UL) = 5.3 × 10−20 with 99.4% confidence level
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