1,491 research outputs found
Acceleration disturbances due to local gravity gradients in ASTROD I
The Astrodynamical Space Test of Relativity using Optical Devices (ASTROD)
mission consists of three spacecraft in separate solar orbits and carries out
laser interferometric ranging. ASTROD aims at testing relativistic gravity,
measuring the solar system and detecting gravitational waves. Because of the
larger arm length, the sensitivity of ASTROD to gravitational waves is
estimated to be about 30 times better than Laser Interferometer Space Antenna
(LISA) in the frequency range lower than about 0.1 mHz. ASTROD I is a simple
version of ASTROD, employing one spacecraft in a solar orbit. It is the first
step for ASTROD and serves as a technology demonstration mission for ASTROD. In
addition, several scientific results are expected in the ASTROD I experiment.
The required acceleration noise level of ASTROD I is 10^-13 m s^-2 Hz^{-1/2} at
the frequency of 0.1 mHz. In this paper, we focus on local gravity gradient
noise that could be one of the largest acceleration disturbances in the ASTROD
I experiment. We have carried out gravitational modelling for the current
test-mass design and simplified configurations of ASTROD I by using an
analytical method and the Monte Carlo method. Our analyses can be applied to
figure out the optimal designs of the test mass and the constructing materials
of the spacecraft, and the configuration of compensation mass to reduce local
gravity gradients.Comment: 6 pages, presented at the 6th Edoardo Amaldi Conference (Okinawa
Japan, June 2005); to be published in Journal of Physics: Conference Serie
Sensitivity differences in the successive stages of spermatogenesis in Drosophila after irradiation in nitrogen or air
Universal scaling for the spin-electricity conversion on surface states of topological insulators
We have investigated spin-electricity conversion on surface states of
bulk-insulating topological insulator (TI) materials using a spin pumping
technique. The sample structure is Ni-Fe|Cu|TI trilayers, in which magnetic
proximity effects on the TI surfaces are negligibly small owing to the inserted
Cu layer. Voltage signals produced by the spin-electricity conversion are
clearly observed, and enhanced with decreasing temperature in line with the
dominated surface transport at lower temperatures. The efficiency of the
spin-electricity conversion is greater for TI samples with higher resistivity
of bulk states and longer mean free path of surface states, consistent with the
surface spin-electricity conversion
Development of a low-mass and high-efficiency charged particle detector
We developed a low-mass and high-efficiency charged particle detector for an
experimental study of the rare decay . The
detector is important to suppress the background with charged particles to the
level below the signal branching ratio predicted by the Standard Model
(O(10)). The detector consists of two layers of 3-mm-thick plastic
scintillators with wavelength shifting fibers embedded and Multi Pixel Photon
Counters for readout. We manufactured the counter and evaluated the performance
such as light yield, timing resolution, and efficiency. With this design, we
achieved the inefficiency per layer against penetrating charged particles to be
less than , which satisfies the requirement of the KOTO
experiment determined from simulation studies.Comment: 20 pages, 18 figure
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