Australasian Science: Australia's authority on science since 1938

Tiny Detector for Gravitational Waves

A coin-sized detector might beat the giant Laser Interferometer Gravitational Wave Observatory (LIGO) to the discovery of gravitational waves, according to two Australian physicists.

Resonant-mass detectors have traditionally employed metal bars about 1 metre long and around 1 tonne in weight, which makes them sensitive to gravitational waves with frequencies up to a few kilohertz. However, any tiny vibrations induced by gravitational waves would be extremely difficult to detect above the thermal noise of the bar.

Dr Maxim Goryachev and Prof Michael Tobar of The University of Western Australia overcame this problem by targeting gravitational radiation in the 1–1000 MHz range. Operating at temperatures as low as 0.01°K above absolute zero, these devices operate at the lowest possible noise level.

Their device consists of a quartz disc about 2.5 cm in diameter hinged to another piece of quartz and placed in a vacuum chamber. A passing high-frequency gravitational wave would cause the disc to vibrate, setting up standing waves of sound across the 2 mm thickness of the disc.

The upper surface of the disc is slightly curved to trap sound quanta (phonons), which improves the signal-to-noise ratio. The nature of quartz allows the tiny vibrations to be converted into an electrical signal that is amplified by an extremely low-noise Superconducting Quantum Interference Device.

Having accounted for all known sources of noise, the researchers believe their detector would be sensitive to strains in space–time that are similar to those that the Advanced LIGO is designed to achieve.