124 research outputs found
Length sensing and control strategies for the LCGT interferometer
The optical readout scheme for the length degrees of freedom of the LCGT
interferometer is proposed. The control scheme is compatible both with the
broadband and detuned operations of the interferometer. Interferometer
simulations using a simulation software Optickle show that the sensing noise
couplings caused by the feedback control can be reduced below the target
sensitivity of LCGT with the use of feed forward. In order to improve the duty
cycle of the detector, a robust lock acquisition scheme using auxiliary lasers
will be used.Comment: 13 pages 9 figures. A proceedings paper for Amaldi9 conferenc
Ultra-Stable Beacon Source for Laboratory Testing of Optical Tracking
The ultra-stable beacon source (USBS) provides a laser-beam output with a very low angular jitter and can be used as an absolute angular reference to simulate a beacon in the laboratory. The laser is mounted on the top of a very short (approximately equal to 1 m) inverted pendulum (IP) with its optical axis parallel to the carbon fiber pendulum leg. The 85-cm, carbon fiber rods making up the leg are very lightweight and rigid, and are supported by a flex-joint at the bottom (see figure). The gimbal-mounted laser is a weight-adjustable load of about 1.5 kg with its center of rotation co-located with the center of percussion of the inverted pendulum. This reduces the coupling of transverse motion at the base of the pendulum to angular motion of the laser at the top. The inverted pendulum is mounted on a gimbal with its center of rotation coinciding with the pivot position of the inverted pendulum flexure joint. This reduces coupling of ground tilt at the inverted pendulum base to motion of the laser mounted at the top. The mass of the top gimbal is adjusted to give the pendulum a very low resonant frequency (approximately equal to 10 mHz) that filters transverse seismic disturbances from the ground where the base is attached. The motion of the IP is monitored by an optical-lever sensor. The laser light is reflected by the mirror on the IP, and then is detected by a quadrant photo-detector (QPD). The position of the beam spot on the QPD corresponds to the tilt of the IP. Damping of this motion is provided by two coil and magnet pairs. The bottom gimbal mount consists of two plates. The IP is mounted on the second plate. The first plate is supported by two posts through needles and can be rotated about the axis connecting the tips of the needles. The second plate hangs from the first plate and can be rotated about the axis perpendicular to the first plate. As a result, the second plate acts as a two-axis rotation stage. Its center of rotation is located at the effective bending point of the flex-joint. The second plate is pressed against two screw actuators by the weight of the IP. The screw actuators are orthogonal to each other and are used to adjust the inclination of the second plate. The actuators are driven by stepper motors. The whole IP system is housed in a box made of Lexan plastic plates to provide isolation from air currents and temperature variations. The signals from the sensors are processed and recorded with a PC using the xPC Target realtime environment of Math- Works. The control algorithms are written using the Simulink package from The MathWorks
Identification and Expression Analysis of Minichromosome Maintenance Proteins in the Silkworm, Bombyx mori
The minichromosome maintenance protein (MCM) family is involved in the regulatory role of DNA replication in eukaryotic organisms. A cDNA encoding of an MCM of the silkworm, Bombyx mori L. (Lepidoptera: Bombycidae), was cloned by reverse transcriptase-polymerase chain reaction (RT-PCR) and sequenced. The resultant amino acid sequence and phylogenetic analysis revealed high identity to MCM, and specifically to MCM7, of vertebrates and invertebrates. An RT-PCR showed that the bmMCM7 transcript was present in the ovaries, testes, silk glands, and fat bodies of larval silkworms. Expression plasmids were transformed into competent Escherichia coli and overexpressed. This is the first report on the identification of MCM helicase of the silkworm, B. mori
Testing Lorentz Invariance with a Double-Pass Optical Ring Cavity
We have developed an apparatus to test Lorentz invariance in the photon
sector by measuring the resonant frequency difference between two
counterpropagating directions of an asymmetric optical ring cavity using a
double-pass configuration. No significant evidence for the violation was found
at the level of . Details of our apparatus and
recent results are presented.Comment: 4 pages, 1 figure. Presented at the Sixth Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 17-21, 201
The status of DECIGO
DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential Fabry-Perot interferometer, and four units of triangular Fabry-Perot interferometers are arranged on heliocentric orbit around the sun. DECIGO is vary ambitious mission, we plan to launch DECIGO in era of 2030s after precursor satellite mission, B-DECIGO. B-DECIGO is essentially smaller version of DECIGO: B-DECIGO consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. It is hoped that the launch date will be late 2020s for the present
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