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.

Perceptions, views and opinions of university students about chemistry learning during practical work at school

The teaching of chemistry through practical experiments has long been an established practice. It forms a key component of teaching of that subject at both school and university level and students have strong views of this method of teaching. This paper reports on the view of undergraduate level 1 chemistry students in relation to their experiences of practical chemistry at school in Scotland. Almost 900 students, across two successive years at the University of Glasgow, were surveyed to determine their perceptions, views and opinions in this area. This paper initially presents the overall views of the students, and then looks in more detail at the effect the different levels to which students took the subject at school affected those views. Specifically, students who took Advanced Higher Grades are compared with those who took Higher Grades. Higher is the standard entry requirement for Scottish Universities, whilst Advanced Higher is a more advanced course. Comparison was also made between the responses of female and male students. The general picture is very encouraging, with students broadly appreciating the practical side of chemistry

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

Experimental measurements of mechanical dissipation associated with dielectric coatings formed using SiO2, Ta2O5 and Al2O3

Previous studies have quantified the mechanical dissipation associated with dielectric thin films formed from alternating layers of ion-beam-sputtered SiO2 and Ta2O5 and concluded that such dissipation could lead to potentially significant levels of thermally induced displacement noise in proposed advanced gravitational wave detectors. We report here, for the first time, measurements of the mechanical dissipation of coatings formed from alternating layers of Al2O3 and Ta2O5, and SiO2 and Al2O3, respectively, when applied to fused silica substrates. In addition, we report our measurements of the elastic properties of Al2O3/Ta2O5 and SiO2/Ta2O5 coatings, as the film elastic properties can significantly influence expected levels of coating thermal noise. In summary, our analysis suggests that SiO2/Ta2O5 coatings currently present the best option for future detectors from a thermal noise standpoint

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

Titania-doped tantala/silica coatings for gravitational-wave detection

Reducing thermal noise from optical coatings is crucial to reaching the required sensitivity in next generation interferometric gravitational-wave detectors. Here we show that adding TiO2 to Ta2O5 in Ta2O5/SiO2 coatings reduces the internal friction and in addition present data confirming it reduces thermal noise. We also show that TiO2-doped Ta2O5/SiO2 coatings are close to satisfying the optical absorption requirements of second generation gravitational-wave detectors