Torsion-Bar Antenna (TOBA) is a ground-based gravitational wave detector using a torsion pendulum. The resonant frequency of torsional motion is ~1 mHz, therefore TOBA has good design sensitivity of $10^{-19} \, / \sqrt{\mathrm{Hz}}$ at 0.1 Hz in low frequencies (0.1 Hz – 10 Hz). TOBA can detect intermediate mass black hole binary mergers, Newtonian noise, and so on. A prototype detector...
As planned for its fifth observation run O5, Advanced Virgo+ will have 80 Watts in main laser. The absorption of laser power in the interferometer's core optics leads to thermal effects causing optical aberrations, ultimately preventing interferometer's operation. To recover detector's ideal operation, Thermal Compensation System (TCS) is needed to correct wavefront distortions. In particular,...
Quantum states of light are being more commonly used to increase the sensitivity of various sensors. They allow to reach high sensitivity without using significant light power, and thus find application in various fields, from biological sensing to gravitational-wave detection. At the same time, these states are very fragile, and even a small amount of decoherence can significantly reduce...
A dual-pass Fabry-Perot cavity will be used for DECIGO (DECi-hertz Interferometer Gravitational-wave observatory) and B-DECIGO. To detect gravitational waves, it is necessary to establish the method to control the dual-pass Fabry-Perot cavity. We can divide this issue in two parts, “Length control” and “Alignment control”. For Length control, it is demonstrated that we can control the length...
Changes due to gravitational waves are very small, so noise is generated due to various factors. KAGRA was built 300 meters underground to reduce ground vibrations. The groundwater generated underground is discharged through pipes. The gravity gradient generated by the universal gravitation force due to the oscillation of the water surface through the pipe may cause the mirror of KAGRA to...
Juggled interferometer (JIFO) is a novel type of earthbound gravitational wave detector targeting a frequency band of 0.1–10 Hz. By using repeatedly free-falling test masses, JIFO can in principle decouple test masses from the seismically noisy environment and avoid suspension thermal noise in a straightforward manner. Since the test masses are in a weightless state, as is the case with space...
Future terrestrial gravitational wave detectors are limited by fundamental noise sources, one of which is the thermal noise arising in the test masses and suspensions in the frequency band where ground-based detectors are sensitive. To mitigate this noise, future detectors are envisioned to operate at cryogenic temperatures using silicon optics as test masses and silicon ribbons to suspend the...
The sensitivity of 3rd generation gravitational wave detectors is currently projected to be
limited by the level of Brownian coating thermal noise produced from highly reflecting
mirror coatings. In the current detectors layers of Ta$_2$O$_5$, a material with higher
refractive index (n = 2.14), has higher levels of optical absorption compared the lower index
layers of SiO$_ {2}$ (n=1.44)....
Within gravitational wave research community (including but not limited to LIGO-Virgo-KAGRA, Einstein Telescope and LISA collaborations) a lot of work in understanding and improving the detectors involves signal processing and modelling of control systems. Historically, different software tools were used for these purposes. We believe that it is possible to create a single software tool that...
Substrate-transferred crystalline coatings made from aluminum gallium arsenide (AlGaAs) have very low thermal noise compared to the ion beam deposited amorphous oxides used until now in gravitational wave detectors. AlGaAs coatings also show excellent optical properties and both thermal noise and optical performance has been demonstrated in other precision optics applications. The primary...
Current gravitational wave detectors are limited in their most sensitive frequency range by the mirror coating thermal noise which arises from the Brownian motion of the coating materials on the interferometer test mass optics. For the next generation detector upgrades and beyond, it is imperative to find coating materials/topologies that reduce this mechanical effect, whilst still meeting the...
The Einstein Telescope pathfinder (ETpathfinder) is a cryogenic testbed for the next generation of gravitational-waves antennas. To reach the target temperature of 18 K, ETpathfinder cryogenic payloads are designed to extract heat from the test masses by integrating low stiffness and highly conductive heat-links that connect to the cryocoolers. Since the interferometer test masses are very...
Technical noise limits the low-frequency sensitivity of interferometric gravitational-wave detectors. Consequently, an effort has been made in recent decades to reduce them, which has led to the emergence of other limiting sources in the overall low-frequency noise budget. Among these noise sources there is the radiation pressure noise which, as demonstrated by LIGO and Virgo in the third...
The low-frequency interferometer in the Einstein Telescope (ET-LF) shall be operated at temperatures of 10 K to 20 K. One cooling concept provides ultra-low noise cooling for steady-state detector operation using a He-II-filled suspension capillary, in which the heat transport takes place by steady-state heat conduction.
During cool-down, the double-walled capillary enables the flow of...
Improving the low-frequency range (1 - 10 Hz) of ground-based detectors requires compact interferometric sensors with high displacement sensitivity and dynamic. We combine Deep frequency modulation and compact interferometric techniques to develop a sensor for local test mass readout. We introduce an optical head design with on-axis beam topology realized in a Quasi-Monolithic component (QMC)...
Current gravitational wave detectors are limited by local sensor noise and other related technical noise sources at low frequencies below 10 Hz. We aim to use compact displacement sensors based on deep-frequency modulation interferometry for the local readout of test-masses to overcome these limitations.
In this poster I present our work on the readout of such compact displacement sensors. We...
On January 15, 2022, at 04:14:45 (UTC), the undersea volcano of Hunga Tonga-Funga Ha’apai erupted and caused global seismic, atmospheric, and electromagnetic waves. They were transmitted to Kamioka, more than 8000 km away, and were observed by environmental sensors not only on the ground but also inside KAGRA's underground facility. In this talk, these signals measured by KAGRA's environmental...
