J. R. Taylor

The AEI 10 m prototype interferometer

A 10 m prototype interferometer facility is currently being set up at the AEI in Hannover, Germany. The prototype interferometer will be housed inside a 100 m 3 ultra-high vacuum envelope. Seismically isolated optical tables inside the vacuum system will be interferometrically interconnected via a suspension platform interferometer. Advanced isolation techniques will be used, such as inverted pendulums and geometrical anti-spring filters in combination with multiple-cascaded pendulum suspensions, containing an all-silica monolithic last stage. The light source is a 35 W Nd:YAG laser, geometrically filtered by passing it through a photonic crystal fibre and a rigid pre-modecleaner cavity. Laser frequency stabilisation will be achieved with the aid of a high finesse suspended reference cavity in conjunction with a molecular iodine reference. Coating thermal noise will be reduced by the use of Khalili cavities as compound end mirrors. Data acquisition and control of the experiments is based on the AdvLIGO digital control and data system. The aim of the project is to test advanced techniques for GEO 600 as well as to conduct experiments in macroscopic quantum mechanics. Reaching standard quantum-limit sensitivity for an interferometer with 100 g mirrors and subsequently breaching this limit, features most prominently among these experiments. In this paper we present the layout and current status of the AEI 10 m Prototype Interferometer project.

Towards a Suspension Platform Interferometer for the AEI 10 m Prototype Interferometer

Currently, the AEI 10 m Prototype is being set up at the Albert Einstein Institute in Hannover, Germany. The Suspension Platform Interferometer (SPI) will be an additional interferometer set up inside the vacuum envelope of the AEI 10 m Prototype. It will interferometrically link the three suspended in-vacuum tables. The inter-table distance will be 11.65 m. The SPI will measure and stabilise the relative motions between these tables for all degrees of freedom, except roll around the optical axis. In this way, all tables can be regarded as one large platform. The design goal is 100 pm/ differential distance stability between 10mHz and 100Hz.

Designs of the frequency reference cavity for the AEI 10 m Prototype interferometer

The AEI 10 m Prototype is in its designing phase and will provide a test-bed for very sensitive interferometric experiments, such as the sub-SQL interferometer. It will test new techniques to reach – and even surpass – the Standard Quantum Limit. The experience and knowledge that can be gained from this experiment can be applied to large-scale interferometric gravitational detectors to improve the detector sensitivities. In order for the sub-SQL interferometer to achieve the required sensitivity all limiting noise sources need to be suppressed sufficiently. Noise sources can include seismic noise, thermal noise, and laser noise; laser frequency noise will be the main focus of this document. The laser frequency noise will be suppressed to a level of 10−4 Hz/ at 20 Hz dropping to below 10−6 Hz/ at 1kHz. The proposed design to suppress the laser frequency noise with a ring cavity is described in this paper.