Collaborating institutes

Mirrors that hang on glass threads

Advanced LIGO Documentary Project

LIGO: A discovery that shook the world - Episode 1

Triple Pendulum Suspension

The central elements in all gravitational wave detectors are mirrors weighing up to 10 kg, which are used to direct the laser beams. These mirrors are suspended as pendulums, so that they are isolated from various disturbances. The mirror suspensions must meet several special requirements: they have to hold the heavy mirrors securely and must not cause disturbances of their own.
Monolithic suspension Zoom Image
Monolithic suspension

The Institute for Gravitational Research (IGR) of the University of Glasgow has developed suspensions meeting these requirements: thin threads made of quartz glass – fused silica fibres. Such fibres have far less internal losses than equivalent steel wires, for instance. They are bonded directly onto the mirrors and a second pendulum mass, which means there is no friction at the point of contact. This increases the overall sensitivity of GEO600 through reduced mechanical loss.

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