Showing papers by "Enrico Calloni published in 2004"
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TL;DR: The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved.
Abstract: The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved. Commissioning breaks were organized during the run which permitted improvement of the sensitivity and the robustness of the interferometer against environmental perturbations like bad weather and earthquakes. The post-run commissioning phase has now started, with the goal of preparing the next upgrade step of the detector, Virgo+.
227 citations
TL;DR: In this paper, a large ion beam sputtering deposition system was built to coat large optics up to 700 mm in diameter for the large-scale Michelson-type interferometer VIRGO.
Abstract: Large optical components (diameter 350 mm), having extremely low loss at 1064 nm, are needed for the large-scale Michelson-type interferometer VIRGO. Today, ion beam sputtering is the only deposition technique able to produce optical components having such performances. Consequently, a large ion beam sputtering deposition system was built to coat large optics up to 700 mm in diameter: two large substrates may also be coated at the same time for interferometer arm symmetry problem. The performances of this coater are described in terms of layer uniformity on a large scale (wavefront) and optical losses (absorption and scattering). The VIRGO interferometer needs six main mirrors. The first set was ready in June 2002 and they have been installed on the VIRGO site (Italy). The optical performances of this first set are discussed. The requirements at 1064 nm are all satisfied. Indeed, the absorption level is close to 1 ppm (part per million), the scattering is lower than 5 ppm and the RMS wavefront of these optics is lower than 8 nm on 150 mm in diameter. Finally, some solutions are proposed to further improve these performances, especially the absorption level and the mechanical quality factor Q of the mirrors and the substrate wavefront before coating.
41 citations
TL;DR: Virgo as discussed by the authors is a laser Michelson interferometer with 3-km long Fabry-Perot cavities in the arms, aiming at the detection of gravitational waves emitted by astrophysical sources in the frequency band from 10 Hz to few kHz.
33 citations
TL;DR: In this paper, the mirrors of interferometric detectors of GW are suspended in order to isolate them from external disturbances, and a local control system able to keep them correctly aligned and to damp the angular modes of the suspension is necessary.
31 citations
TL;DR: In this article, the first demonstration of the possibility to control an interferometer suspended from Virgo full-scale multistage seismic attenuators using information derived from the inter-ferometer locking signal was presented.
27 citations
25 Feb 2004
TL;DR: In this article, a large ion beam sputtering deposition system was built to coat large optics up to 700 mm in diameter, and the performance of this coater was described in terms of layer uniformity on large scale and optical losses (absorption and scattering characterization).
Abstract: The goal of the VIRGO program is to build a giant Michelson type interferometer (3 kilometer long arms) to detect gravitational waves. Large optical components (350 mm in diameter), having extremely low loss at 1064 nm, are needed. Today, the Ion beam Sputtering is the only deposition technique able to produce optical components with such performances. Consequently, a large ion beam sputtering deposition system was built to coat large optics up to 700 mm in diameter. The performances of this coater are described in term of layer uniformity on large scale and optical losses (absorption and scattering characterization). The VIRGO interferometer needs six main mirrors. The first set was ready in June 2002 and its installation is in progress on the VIRGO site (Italy). The optical performances of this first set are discussed. The requirements at 1064 nm are all satisfied. Indeed, the absorption level is close to 1 ppm (part per million), the scattering is lower than 5 ppm and the R.M.S. wavefront of these optics is lower than 8 nm on 150 mm in diameter. Finally, some solutions are proposed to further improve these performances, especially the absorption level (lower than 0.1 ppm) and the mechanical quality factor Q of the mirrors (thermal noise reduction).
27 citations
TL;DR: In this paper, the authors present the results of a study of the major low-frequency sources of seismic activity at the Virgo site and demonstrate that seismic noise contributed to the CITF dark fringe noise only below approximately 2 Hz.
Abstract: We present the results of a study of the major low-frequency sources of seismic activity at the Virgo site. These sources are of natural and human origin: oceanic microseism (below 1 Hz), local traffic and human activity on site (below 10 Hz). Using data collected during the commissioning of the central Virgo interferometer (CITF) we have measured the seismic coupling to the interferometer, demonstrating that seismic noise contributed to the CITF dark fringe noise only below approximately 2 Hz.
23 citations
TL;DR: In this article, the full asymptotic expansion of the Feynman photon Green function at small values of the world function, as well as its explicit dependence on the gauge parameter, are obtained without adding by hand a mass term to the Faddeev-Popov Lagrangian.
Abstract: Quantization of electrodynamics in curved spacetime in the Lorentz gauge and with arbitrary gauge parameter makes it necessary to study Green functions of non-minimal operators with variable coefficients. Starting from the integral representation of photon Green functions, we link them to the evaluation of integrals involving Γ-functions. Eventually, the full asymptotic expansion of the Feynman photon Green function at small values of the world function, as well as its explicit dependence on the gauge parameter, are obtained without adding by hand a mass term to the Faddeev–Popov Lagrangian. Coincidence limits of the second covariant derivatives of the associated Hadamard function are also evaluated, as a first step towards the energy–momentum tensor in the non-minimal case.
20 citations
TL;DR: In this article, the authors report preliminary results of a search for inspiralling binary events, performed on data produced by the Virgo Central Interferometer during the Engineering 4 run.
Abstract: We report preliminary results of a search for inspiralling binary events, performed on data produced by the Virgo Central Interferometer during the Engineering 4 run. Given the limited sensitivity to gravitational waves, the goal was to test some of the analysis chain elements and their integration. The search method was the matched filtering, supplemented by a χ2 based method for the rejection of non-Gaussian events. The range of masses explored was [2–5] M⊙, while the frequency range considered was [24–1000] Hz. The algorithm was preliminarily tested on simulated data. On real E4 data, candidates were selected by the matched filter when the return SNR value was greater than 7; none of them survived the χ2 test. Further, it was possible to put in correspondence the candidates with precise external disturbances in the apparatus.
12 citations
TL;DR: In this paper, the use of a magnetic levitation system as a part of a multi-stage seismic attenuator for gravitational wave interferometric antennas was investigated using a MATLAB simulation code to compute the forces exerted by extended magnets.
11 citations
TL;DR: The interferometric gravitational wave detector Virgo has successfully completed the first major step of its commissioning as mentioned in this paper, which consists of a Michelson interferometer with 6 m arms with suspended mirrors.
Abstract: The interferometric gravitational wave detector Virgo has successfully completed the first major step of its commissioning. It consists of a Michelson interferometer with 6 m arms with suspended mirrors. The interferometer is tuned to the dark fringe with a recycling mirror on the other port (bright fringe) to form an equivalent 12 m long Fabry-Perot cavity. This setup has allowed us to validate the major technology choices that have been made: passive seismic attenuators, a light source with a long mode cleaner, many analogue and digital servo loops, control software, high speed data acquisition system. A sensitivity of 8 x 10 -17 m Hz -1/2 at 1 kHz together with a duty cycle of 80% has been attained during a 72 h engineering run. The data analysis allowed us to understand the noise contributions, and several improvements have been carried out while prcceeding with the end of the installation of vacuum tubes and the remaining suspensions, and before starting the commissioning of the 3 km long Fabry-Perot cavities.
TL;DR: In this article, an optical readout system for the LISA gravitational reference sensor was presented, which achieved a sensitivity of 10−8 m Hz−1/2 at 1 mHz.
Abstract: We present an optical readout system for the LISA gravitational reference sensor. Some estimations of the most relevant sources of noise are given showing that the required sensitivity can be reached with such a type of detector. Preliminary results with a bench-top experiment are also reported; a sensitivity of 10−8 m Hz−1/2 at 1 mHz and better than the specification of 10−9 m Hz−1/2 above 10 mHz has been measured. The sensitivity is probably limited, at low frequency, by drifts in the experimental set-up. A more compact and stable set-up is presently under design that should allow the demonstration of the required sensitivity down to 1 mHz.
21 Mar 2004
TL;DR: In this paper, various techniques developed in order to reach its target extreme performance are outlined, and the 3-km-long Virgo gravitational wave antenna, which will be particularly sensitive in the low frequency range (10-100 Hz) is presently in its commissioning phase.
Abstract: The interferometric gravitational wave detectors represent the ultimate evolution of the classical Michelson interferometer. In order to measure the signal produced by the passage of a gravitational wave, they aim to reach unprecedent sensitivities in measuring the relative displacements of the mirrors. One of them , the 3-km-long Virgo gravitational wave antenna, which will be particularly sensitive in the low frequency range (10-100 Hz), is presently in its commissioning phase. In this paper the various techniques developed in order to reach its target extreme performance are outlined.
Proceedings Article•
18 Oct 2004
TL;DR: In this paper, a Fabry-Perot cavity length control system for the gravitational wave detector Virgo is described. But this work was carried out with steps of increasing complexity: locking a simple Fabry perot cavity, then recycling the light beam into the interferometer.
Abstract: The gravitational wave detector Virgo is presently being commissioned A significant part of last year was spent in setting up the cavity length control system This work was carried out with steps of increasing complexity: locking a simple Fabry-Perot cavity, then a Michelson interferometer with Fabry-Perot cavities in both arms, and finally recycling the light beam into the interferometer The applied strategy and the main results obtained are described
TL;DR: In this article, the last-stage suspension for the mirrors of the Virgo CITF was studied and the effect of the holder on the internal motion of the mirror and the residual nonlinear couplings between the electromagnetic actuators and the metallic parts.
Abstract: We present the last-stage suspension for the mirrors of the gravitational wave antenna Virgo. We studied some problems encountered during the commissioning of the Virgo central interferometer (CITF) and solved them with the aim of achieving the target sensitivity of the detector in its final configuration. We measured the effect of the holder on the internal motion of the mirror, and the residual nonlinear couplings between the electromagnetic actuators and the metallic parts present on the last-stage suspension. The limits experienced on the Virgo CITF have helped us to define some important modifications to be applied to the last-stage suspension. Moreover, we present the experimental study of west input mirror internal modes after it was dismounted from the Virgo central interferometer. The results were useful to identify, in the data of the engineering run 4 of the CITF, the thermal peaks of such a mirror.
TL;DR: In this paper, the lock acquisition algorithm used for the central interferometer of the gravitational wave detector Virgo (CITF) was presented. But the lock selection was not considered in this paper.
Posted Content•
TL;DR: The French-Italian interferometric gravitational wave detector VIRGO is currently being commissioned and its principal instrument is a Michelson laser interferometer with 3 km long optical cavities in the arms and a power-recycling mirror.
Abstract: The French-Italian interferometric gravitational wave detector VIRGO is currently being commissioned. Its principal instrument is a Michelson laser interferometer with 3 km long optical cavities in the arms and a power-recycling mirror. The interferometer resides in an ultra-high vacuum system and the mirrors are suspended from multistage pendulums for seismic isolation. This type of laser interferometer reaches its maximum sensitivity only when the optical setup is held actively very accurately at a defined operating point: control systems using the precise interferometer signals stabilise the longitudinal and angular positions of the optical component. This paper gives an overview of the control system for the angular degrees of freedom; we present the current status of the system and report the first experimental demonstration of the Anderson technique on a large-scale interferometer.
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05 Aug 2004
TL;DR: Virgo as discussed by the authors is a 3 km arm laser interferometer aiming at the detection of gravitational waves in a range of frequency between 5 Hz and 5 kHz, built in the vicinity of Pisa -Italy, by a collaboration among several laboratories of CNRS (France) and INFN (Italy).
Abstract: Virgo is a 3 km arm laser interferometer aiming at the detection of gravitational waves in a range of frequency between 5 Hz and 5 kHz. Virgo has been built in the vicinity of Pisa – Italy, by a collaboration among several laboratories of CNRS (France) and INFN (Italy). The construction has been completed in 2003. 2004 has been devoted to commissioning the detector, with the aim to start the acquisition of scientifically interesting data in 2005. The status of advancement of the commissioning will be reported and the present sensitivity will be discussed.
TL;DR: In this article, a method to search for and extract the parameters of binary pulsars with Doppler shift was proposed, and a preliminary test of this method was performed on the Virgo data recorded during the E4 engineering run.
Abstract: Most of the known pulsars with frequencies lying in the best sensitivity range of the Virgo/LIGO/TAMA interferometers belong to binary systems. Accordingly their frequencies are Doppler shifted in an unknown way. We investigate a new method to search for and extract the parameters of such pulsars. A first preliminary test of this method, performed on the Virgo data recorded during the E4 engineering run, is presented.
TL;DR: In this paper, an adaptive optics (AO) system for the control of geometrical fluctuations in a laser beam based on the interferometric detection of phase front is presented.
Abstract: We present an adaptive optics (AO) system for the control of geometrical fluctuations in a laser beam based on the interferometric detection of phase front. By comparison with the usual Shack–Hartman-based AO system, we show that this technique is of particular interest when high sensitivity and high band-pass are required for correction of small perturbations such as, for instance, the control of the input beam of gravitational waves interferometric detectors.
TL;DR: In this paper, a prototype of Adaptive Optics for the control of geometrical fluctuations in a laser beam, based on the interferometric detection of phase front, is presented.
Abstract: In this paper we briefly discuss the possibility to use Adaptive Optics in long baseline interferometric gravitational wave detectors. Analisys is carried out to demonstrate the usefulness of Adaptive Optics as a method to integrate double-mode-cleaner systems, presently used or foreseen in the next generation detectors as systems for the reduction of geometrical fluctuations of input laser beam. Finally a prototype of (AO) system for the control of geometrical fluctuations in a laser beam, based on the interferometric detection of phase front, is presented. By comparison with the usual Shack-Hartmann based AO system, we show that this technique is of particular interest when high sensitivity and high band-pass are required for correction of small perturbations like, for instance, the control of the input beam of gravitational waves interferometric detectors.
01 Feb 2004-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the first adaptive optics system for laser beam geometrical fluctuations correction, based on interferometric detection of aberrations, is presented and the resulting feed-back is of several hundreds Hz and the residual fluctuations, measured on the error signal, are better than what can be obtained by typical Shack-Hartmann technique.
Abstract: The first adaptive optics system for laser beam geometrical fluctuations correction, based on interferometric detection of aberrations, is presented. The bandwidth of the resulting feed-back is of several hundreds Hz and the residual fluctuations, measured on the error signal, are better than what can be obtained by typical Shack–Hartmann technique, encouraging for use in long baseline interferometers for GW detection.