A known criticality of optical cavities such as Fabry–Pérot resonant cavities is the presence of non-linear effects in the build-up of the laser fields inside the cavity itself, which can spoil the ...characteristics of the error signal used to control the cavity length, usually obtained with the Pound–Drever–Hall phase modulation–demodulation technique. The non-linear effects are primarily caused by high cavity speeds prior to acquiring longitudinal control of the cavity (or “lock”), and they are due to the frequency fluctuations of the laser and to the residual seismic motion affecting the system; such effects are amplified with the increasing of the Finesse of the cavity. In order to overcome this limitation, the cavity speed is effectively slowed down before engaging the lock using a non-linear technique, known as “Guided Lock”; here an optimized version of the algorithm will be presented, which relies on a better estimation of the cavity speed based only on optical signals. The application of this technique to the high-Finesse Fabry–Pérot arm cavities of the Advanced Virgo gravitational wave detector will be described. The novel algorithm was applied for the lock acquisition of the Advanced Virgo detector during the O2 Observing Run, in August 2017; the improved algorithm, by dynamically measuring the cavity speed, allowed to implement a predictive capability in slowing down the mirrors, thus improving the efficiency of the lock acquisition procedure for the arm cavities.
We report the tilt sensitivity reached by the ARCHIMEDES tiltmeter in the 2–20 Hz frequency region, where seismic noise is expected to give an important limitation to the sensitivity in the next ...future Gravitational Waves detection, particularly through Newtonian noise. The tilt noise level
θ
~
(
f
)
is about
10
-
12
rad
/
Hz
in most of the band, reaching the minimum of
θ
~
=
7
·
10
-
13
rad
/
Hz
around 9 Hz. The tiltmeter is a beam balance with a 0.5 m suspended arm and interferometric optical readout, working in closed loop. The results have been obtained by a direct measurement of the ground tilt at the Sos Enattos site (Sardinia, Italy). This sensitivity is a requirement to use the tiltmeter as part of an effective Newtonian noise reduction system for present Gravitational Waves detectors, and also confirms that Sos Enattos is among the quietest sites in the world, suitable to host the third-generation Gravitational Waves detector Einstein Telescope.
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In this paper we study the behavior of the Casimir energy of a “multi-cavity” across the transition from the metallic to the superconducting phase of the constituting plates. Our analysis is ...carried out in the framework of the ARCHIMEDES experiment, aiming at measuring the interaction of the electromagnetic vacuum energy with a gravitational field. For this purpose it is foreseen to modulate the Casimir energy of a layered structure composing a multy-cavity coupled system by inducing a transition from the metallic to the superconducting phase. This implies a thorough study of the behavior of the cavity, in which normal metallic layers are alternated with superconducting layers, across the transition. Our study finds that, because of the coupling between the cavities, mainly mediated by the transverse magnetic modes of the radiation field, the variation of energy across the transition can be very large.
The Archimedes experiment Calloni, E.; Caprara, S.; Laurentis, M. De ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Letnik:
824
Journal Article
Recenzirano
Odprti dostop
Archimedes is an INFN-funded pathfinder experiment aimed at verifying the feasibility of measuring the interaction of vacuum fluctuations with gravity. The final experiment will measure the force ...exerted by the gravitational field on a Casimir cavity whose vacuum energy is modulated with a superconductive transition, by using a balance as a small force detector. Archimedes is two-year project devoted to test the most critical experimental aspects, in particular the balance resonance frequency and quality factor, the thermal modulation efficiency and the superconductive sample realization.
•Weight of the vacuum.•Superconductive stacks studies.•Thermal behavior studies at cryogenic temperatures.
The possibility of obtaining geophysical information from the system for controlling the position of the mirrors of the VIRGO laser-interferometric gravitational antenna and from angular ...perturbations of the vertical mirror lines is examined. Results from a study of tidal horizontal deformations are analyzed.
An ultralow resonant frequency vertical seismic activity attenuation filter prototype has been designed and built as the vertical component of a Pre-Isolation Stage (PIS) for low-frequency Seismic ...Attenuation (SA) chains. The task of the PIS is to reduce the excitation of the chain payload's resonant residual motions. A characterization and the performance of the prototype are reported along with some design considerations. An attenuation of 45
dB has been achieved in the region of interest (the SA chain resonant frequency band) and an upgrade to more than 50
dB attenuation is easily achievable. Tests of active feedback loop attenuation driven by electro magnetic actuators and controlled by a Digital Signal Processor reading a precision vertical accelerometer have been successfully performed. The filter also effectively acts as a precision positioner for the suspended payload.
In this paper we study the Casimir energy of a sample made by N cavities, with N >> 1, across the transition from the metallic to the superconducting phase of the constituting plates. After having ...characterized the energy for the configuration in which the layers constituting the cavities are made by dielectric and for the configuration in which the layers are made by plasma sheets, we concentrate our analysis on the latter. It represents the final step towards the macroscopic characterization of a "multi cavity" (with N large) necessary to fully understand the behaviour of the Casimir energy of a YBCO (or a BSCCO) sample across the transition. Our analysis is especially useful to the Archimedes experiment, aimed at measuring the interaction of the electromagnetic vacuum energy with a gravitational field. To this purpose, we aim at modulating the Casimir energy of a layered structure, the multi cavity, by inducing a transition from the metallic to the superconducting phase. After having characterized the Casimir energy of such a structure for both the metallic and the superconducting phase, we give an estimate of the modulation of the energy across the transition.
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