Niobium Bar



The first Southern Hemisphere Gravitational Wave Detector

The search for gravitational waves began in the 1990s and this detector, Niobe, was one of 5 set up around the world as part of that search.  It came into operation in 1993 after 16 years, 12 PhD projects and several million dollars to build. This worldwide experiment set limits to the strength of gravitational waves and paved the way for the next generation of detectors.

Gravitational waves are ripples in the curvature of spacetime that mark the beginning of time in the Big Bang and the end of time at the birth of black holes.

Niobe is exquisite technology based on superconductivity and microwaves that was developed entirely in Western Australia. It was designed to ring like a bell when struck by the feather-touch of gravitational waves. It set world records for the smallest amount sound energy ever detected, about 10-26 joules and the longest ringing time ever measured for a metallic object, several days. Niobe has at its heart a very sophisticated superconducting microwave microphone able to detect vibrations ten million times smaller than an atom.

Niobe is the world’s largest bar of the element Niobium. It was suspended inside a double walled liquid tank where it was cooled to minus 269 degrees Celsius. This is about 4 degrees more than absolute zero – the coldest temperature possible. Niobium is the best superconducting element and at this temperature it loses all electrical conductivity and repels all magnetic fields.

Vibration isolation is critical for detection of gravitational waves. Niobium’s vibration isolator was so effective it could operate through earthquakes. The first stage of this isolation uses a long titanium rod hanging from a stack of lead and rubber. This then supports a massive steel block that contains further isolation stages of masses and tapered springs beside and beneath the niobium bar. The bar itself is supported underneath by a pure titanium catherine wheel suspension.

Sapphire clocks were invented for its readout system. These were shown to be the most accurte in the world and have now been commercialised.