A. Moylan

Gingin High Optical Power Test Facility

The Australian Consortium for Gravitational Wave Astronomy (ACIGA) in collaboration with LIGO is developing a high optical power research facility at the AIGO site, Gingin, Western Australia. Research at the facility will provide solutions to the problems that advanced gravitational wave detectors will encounter with extremely high optical power. The problems include thermal lensing and parametric instabilities. This article will present the status of the facility and the plan for the future experiments.

Status of the Australian Consortium for Interferometric Gravitational Astronomy

We report the status of research and development being undertaken by the members of the Australian Consortium for Interferometric Gravitational Astronomy.

Functional programming framework for GRworkbench

The software tool GRworkbench is an ongoing project in visual, numerical General Relativity at The Australian National University. Recently, the numerical differential geometric engine of GRworkbench has been rewritten using functional programming techniques. By allowing functions to be directly represented as program variables in C++ code, the functional framework enables the mathematical formalism of Differential Geometry to be more closely reflected in GRworkbench. The powerful technique of ‘automatic differentiation’ has replaced numerical differentiation of the metric components, resulting in more accurate derivatives and an order-of-magnitude performance increase for operations relying on differentiation.

Technology developments for ACIGA high power test facility for advanced interferometry

The High Optical Power Test Facility for Advanced Interferometry has been built by the Australian Consortium for Interferometric Gravitational Astronomy north of Perth in Western Australia. An 80 m suspended cavity has been prepared in collaboration with LIGO, where a set of experiments to test suspension control and thermal compensation will soon take place. Future experiments will investigate radiation pressure instabilities and optical spring effects in a high power optical cavity with ~200 kW circulating power. The facility combines research and development undertaken by all consortium members, whose latest results are presented.

Numerical Wave Optics and the Lensing of Gravitational Waves by Globular Clusters

We consider the possible effects of gravitational lensing by globular clusters on gravitational waves from asymmetric neutron stars in our galaxy. In the lensing of gravitational waves, the long wavelength, compared with the usual case of optical lensing, can lead to the geometrical optics approximation being invalid, in which case a wave optical solution is necessary. In general, wave optical solutions can only be obtained numerically. We describe a computational method that is particularly well suited to numerical wave optics. This method enables us to compare the properties of several lens models for globular clusters without ever calling upon the geometrical optics approximation, though that approximation would sometimes have been valid. Finally, we estimate the probability that lensing by a globular cluster will significantly affect the detection, by ground-based laser interferometer detectors such as LIGO, of gravitational waves from an asymmetric neutron star in our galaxy, finding that the probability is insignificantly small.

Developments in GRworkbench

AbstractThe software tool GRworkbench is an ongoing project in visual,numerical General Relativity at The Australian National University.Recently, GRworkbench has been significantly extended to facilitatenumerical experimentation in analytically-defined space-times. Thenumerical differential geometric engine has been rewritten using func-tional programming techniques, enabling objects which are normallydefined as functions in the formalism of differential geometry and Gen-eral Relativity to be directly represented as function variables in theC++ code of GRworkbench. The new functional differential geometricengine allows for more accurate and efficient visualisation of objects inspace-times and makes new, efficient computational techniques avail-able. Motivated by the desire to investigate a recent scientific claimusing GRworkbench, new tools for numerical experimentation havebeen implemented, allowing for the simulation of complex physicalsituations. 1 Introduction Physically important exact solutions of the Einstein field equationare often difficult to work with algebraically because of their com-

Status of ACIGA High Power Test Facility for advanced interferometry

The Australian Consortium for Gravitational Astronomy has built a High Optical Power Test Facility north of Perth, Western Australia. Current experiments in collaboration with LIGO are testing thermal lensing compensation, and suspension control on an 80m baseline suspended optical cavity. Future experiments will test radiation pressure instabilities and optical spring in a high power optical cavity with ~200kW circulating power. Once issues of operation and control have been resolved, the facility will go on to assess the noise performance of the high optical power technology through operation of an advanced interferometer with sapphire tests masses, and high performance suspension and isolation systems. The facility combines research and development undertaken by all consortium members, which latest results are presented.