Laser pulling and welding system
Location: Upper Switchroom
In previous generation gravitational wave detectors the test masses were suspended using metal wire. For GEO600 currently and Advanced LIGO in the future the test masses are suspended with silica fibers. These fibers can have much higher Q values (and therefore lower losses) than metal wires, together with other desirable properties. These fibers are produced by heating silica stock in rod form (diameter a few mm) to a temperature approaching the melting point, and then pulling the ends of the rod apart. This gives a fiber with the desired diameter, tapering to the original rod thickness at the ends, which can then be welded to other suspension components. This process was previously accomplished using a gas torch as the heat source, but this was not optimal for several reasons, in particular a lack of fine control. The current fiber pulling system uses a CO2 laser to heat the silica, giving much finer power and spatial control.