Mechanical Dissipation in Silicon Flexures

The thermo-mechanical properties of silicon make it of significant interest as a possible material for mirror substrates and suspension elements for future long-baseline gravitational wave detectors. The mechanical dissipation in 92um thick single-crystal silicon cantilevers has been observed over the temperature range 85 K to 300 K, with dissipation approaching levels down to phi = 4.4E-7.Comment: 7 pages. Accepted by Phys Lett A, submitted for publication on 28 October 200

Detector Description and Performance for the First Coincidence Observations between LIGO and GEO

For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.Comment: 41 pages, 9 figures 17 Sept 03: author list amended, minor editorial change

Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo

We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--$1.0 M_\odot$, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.

The intrinsic mechanical loss factor of hydroxy-catalysis bonds for use in the mirror suspensions of gravitational wave detectors

This paper describes investigations into the mechanical losses of bonds created by hydroxy-catalysis bonding. Evaluation of the magnitude of such losses is important for determining thermal noise levels in bonded suspensions for gravitational wave detectors. Three samples were investigated with bonds of varying geometries and surface areas. In two cases, the bonds were between two pieces of fused silica, whilst in the third a fused silica piece was attached to a sapphire substrate. In each case sodium silicate solution was used as the bonding agent. The thickness and Young's modulus of the bond material were evaluated enabling values for the intrinsic mechanical loss factor of the bonding material to be obtained

Damping and tuning of the fibre violin modes in monolithic silica suspensions

High Q mirror suspensions are a key element of the advanced interferometric gravitational-wave detectors. In December 2002 the last of the final interferometer optics of GEO 600 were monolithically suspended, using fused silica fibres. The violin modes of the suspension fibres can have Q greater than 10(8) and can therefore interfere with the interferometer length control servo. Hence, the violin modes need to be damped, without degrading the pendulum Q itself. Furthermore, the frequency spread of the fibres used has to be small to allow for high Q notch filtering in the length control servo. ne requirements for the violin modes of the two GEO 600 inboard suspensions are Q lt 3 x 10(6) for the fundamental and Q lt 2 x 10(6) for the first harmonic mode, respectively. The frequency spread should not exceed 10% within one mode. To accomplish that, two sections of the fibres were coated with amorphous Teflon. By applying the coating, the Q of the relevant modes can be degraded to the desired values and furthermore, the frequencies of these modes can be tuned almost independently with a good accuracy over a wide range. After welding the fibres in the monolithic suspension, a corrective coating was applied to some fibres, to compensate for the frequency spread due to the tension spread of the four fibres within a suspension. We present the method and the results achieved

Mechanical loss in tantala/silica dielectric mirror coatings

Current interferometric gravitational wave detectors use test masses with mirror coatings formed from multiple layers of dielectric materials, most commonly alternating layers Of SiO2 (silica) and Ta2O5 (tantala). However, mechanical loss in the Ta2O5/SiO2 coatings may limit the design sensitivity for advanced detectors. We have investigated sources of mechanical loss in the Ta2O5/SiO2 coatings, including loss associated with the coating-substrate interface, with the coating-layer interfaces and with the coating materials. Our results indicate that the loss is associated with the coating materials and that the loss of Ta2O5 is substantially larger than that Of SiO2

Quadruple suspension design for Advanced LIGO

In this paper, we describe the conceptual design for the suspension system for the test masses for Advanced LIGO, the planned upgrade to LIGO, the US laser interferometric gravitational-wave observatory. The design is based on the triple pendulum design developed for GEO 600-the German/UK interferometric gravitational wave detector. The GEO design incorporates fused silica fibres of circular cross-section attached to the fused silica mirror (test mass) in the lowest pendulum stage, in order to minimize the thermal noise from the pendulum modes. The damping of the low-frequency modes of the triple pendulum is achieved by using co-located sensors and actuators at the highest mass of the triple pendulum. Another feature of the design is that global control forces acting on the mirrors, used to maintain the output of the interferometer on a dark fringe, are applied via a triple reaction pendulum, so that these forces can be implemented via a seismically isolated platform. These techniques have been extended to meet the more stringent noise levels planned for in Advanced LIGO. In particular, the Advanced LIGO baseline design requires a quadruple pendulum with a final stage consisting of a 40 kg sapphire mirror, suspended on fused silica ribbons or fibres. The design is chosen to aim to reach a target noise contribution from the suspension corresponding to a displacement sensitivity of 10/sup -19/ m Hz/sup -1/2/ at 10 Hz at each of the test masses

Silica research in Glasgow

The Glasgow group is involved in the construction of the GEO600 interferometer as well as in R and D activity on technology for advanced gravitational wave detectors. GEO600 will be the first GW detector using quasimonolithic silica suspensions in order to decrease thermal noise significantly with respect to steel wire suspensions. The results concerning GEO600 suspension mounting and performance will be shown in the first section. Section 2 is devoted to the present results from the direct measurement of thermal noise in mirrors mounted in the 1.0 m interferometer in Glasgow which has a sensitivity limit of 4 * 10/sup -19/ m Hz/sup -1/2/ above 1 kHz. Section 3 presents results on the measurements of coating losses. R and D activity has been carried out to understand better how thermal noise in the suspensions affects the detector sensitivity, and in section 4 a discussion on the non-linear thermoelastic effect is presented

The GEO600 gravitational wave detector: pulsar prospects

The GEO600 laser-interferometric gravitational wave detector near Hannover, Germany, is one of six such interferometers now close to operation worldwide. The UK/German GEO collaboration uses advanced technologies, including monolithic silica suspensions and signal recycling, to deliver a sensitivity comparable with much larger detectors in their initial configurations. Here we review the design and performance of GEO600 and consider the prospects for a direct detection of continuous gravitational waves from spinning neutron stars

The GEO600 gravitational wave detector: pulsar prospects

The GEO600 laser-interferometric gravitational wave detector near Hannover, Germany, is one of six such interferometers now close to operation worldwide. The UK/German GEO collaboration uses advanced technologies, including monolithic silica suspensions and signal recycling, to deliver a sensitivity comparable with much larger detectors in their initial configurations. Here we review the design and performance of GEO600 and consider the prospects for a direct detection of continuous gravitational waves from spinning neutron stars