- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dark matter signals on a laser interferometer
摘要： WIMPs are promising dark matter candidates. A WIMP occasionally collides with a mirror equipped with interferometric gravitational wave detectors such as LIGO, Virgo, KAGRA and the Einstein Telescope (ET). When WIMPs collide with a mirror of an interferometer, we expect that characteristic motions of the pendulum and mirror are excited, and those signals could be extracted by highly sophisticated sensors developed for gravitational wave detection. We analyze the motions of the pendulum and mirror, and estimate the detectability of these motions. For the “Thin-ET” detector, the signal-to-noise ratio may be 1.7e mDM T, where mDM is the mass of a WIMP. We may set a more strict upper limit on the cross section between a WIMP and a nucleon than the limits obtained by other experiments so far when mDM is approximately lower than 0.2 GeV. We find an order-of-magnitude improvement in the upper limit around mDM 100 GeV ? 0.2 GeV.
关键词： Dark matter,Laser interferometer,Signal-to-noise ratio,WIMPs,Gravitational wave detectors
更新于2025-09-23 15:19:57
-
Silicon nitride and silica quarter-wave stacks for low-thermal-noise mirror coatings
摘要： This study investigates a multilayer high reflector with new coating materials for next-generation laser interferometer gravitational wave detectors operated at cryogenic temperatures. We use the plasma-enhanced chemical vapor deposition method to deposit amorphous silicon nitride and silica quarter-wave high-reflector stacks and studied the properties pertinent to the coating thermal noise. Room- and cryogenic-temperature mechanical loss angles of the silicon nitride and silica quarter-wave bilayers are measured using the cantilever ring-down method. We show, for the first time, that the bulk and shear loss angles of the coatings can be obtained from the cantilever ring-down measurement, and we use the bulk and shear losses to calculate the coating thermal noise of silicon nitride and silica high-reflector coatings. The mechanical loss angle of the silicon nitride and silica bilayer is dispersive with a linear weakly positive frequency dependence, and, hence, the coating thermal noise of the high reflectors show a weakly positive frequency dependence in addition to the normal 1/sqrt(f) dependence. The coating thermal noise of the silicon nitride and silica high-reflector stack is compared to the lower limit of the coating thermal noise of the end test mirrors of ET-LF, KAGRA, LIGO Voyager, and the directly measured coating thermal noise of the current coatings of Advanced LIGO. The optical absorption of the silicon nitride and silica high reflector at 1550 nm is 45.9 ppm. Using a multimaterial system composed of seven pairs of ion-beam-sputter deposited Ti:Ta2O5 and silica and nine pairs of silicon nitride and silica on a silicon substrate, the optical absorption can be reduced to 2 ppm, which meets the specification of LIGO Voyager.
关键词： quarter-wave stacks,silica,silicon nitride,gravitational wave detectors,thermal noise,mechanical loss,cryogenic temperatures,optical absorption,mirror coatings
更新于2025-09-19 17:15:36
-
Implications of Dedicated Seismometer Measurements on Newtonian-Noise Cancellation for Advanced LIGO
摘要： Newtonian gravitational noise from seismic fields will become a limiting noise source at low frequency for second-generation, gravitational-wave detectors. It is planned to use seismic sensors surrounding the detectors’ test masses to coherently subtract Newtonian noise using Wiener filters derived from the correlations between the sensors and detector data. In this Letter, we use data from a seismometer array deployed at the corner station of the Laser Interferometer Gravitational Wave Observatory (LIGO) Hanford detector combined with a tiltmeter for a detailed characterization of the seismic field and to predict achievable Newtonian-noise subtraction levels. As was shown previously, cancellation of the tiltmeter signal using seismometer data serves as the best available proxy of Newtonian-noise cancellation. According to our results, a relatively small number of seismometers is likely sufficient to perform the noise cancellation due to an almost ideal two-point spatial correlation of seismic surface displacement at the corner station, or alternatively, a tiltmeter deployed under each of the two test masses of the corner station at Hanford will be able to efficiently cancel Newtonian noise. Furthermore, we show that the ground tilt to differential arm-length coupling observed during LIGO’s second science run is consistent with gravitational coupling.
关键词： gravitational-wave detectors,LIGO,Newtonian noise,Wiener filters,seismic fields
更新于2025-09-09 09:28:46
-
Magnetic coupling to the advanced Virgo payloads and its impact on the low frequency sensitivity
摘要： We study the electromagnetic coupling of the Advanced Virgo (AdV) input mirror payload in response to a slowly time-varying magnetic field. As the problem is not amenable to analytical solution, we employ and validate a finite element (FE) analysis approach. The FE model is built to represent as faithfully as possible the real object, and it has been validated by comparison with experimental measurements. The intent is to estimate the induced currents and the magnetic field in the neighbourhood of the payload. The procedure found 21 equivalent electrical configurations that are compatible with the measurements. These have been used to compute the magnetic noise contribution to the total AdV strain noise. At the current stage of development, AdV seems to be unaffected by magnetic noise, but we foresee a non-negligible coupling once AdV reaches the design sensitivity.
关键词： finite element analysis,low frequency sensitivity,gravitational-wave detectors,magnetic coupling,Advanced Virgo
更新于2025-09-04 15:30:14