Inventing the ultimate suspension system

To hear tiny vibrations from half a galaxy away, first you need to filter out the Earth’s constant rumbling.

At gravitational wave observatories such as the European Advanced Virgo in Italy, scientists try to detect ripples in spacetime caused by colliding black holes and other stellar cataclysms.

The detectors work by measuring tiny changes in the paths of laser beams fired through kilometres-long vacuum tubes. These changes are about 100 billion times smaller than the effects of background seismic rumbling, so the detector components must be extremely well isolated from outside vibrations.

Joris van Heijningen worked on vibration isolation systems for the Advanced Virgo detector during his PhD at the Dutch National Institute for Subatomic Physics (Nikhef). Now based at the University of Western Australia (UWA), Joris is working on a kind of spring that he hopes will add a new dimension to the “vibration isolation toolkit” for the next generation of gravitational wave detectors.

“The first ultra-low frequency stage of many isolation systems is an inverted pendulum,” says Joris, “but that works in the horizontal direction. The device we are proposing isolates from low-frequency vertical vibrations.”

At the heart of the proposed design—based on previous work by Joris’ UWA colleague John Winterflood—is an Euler spring, a flat metal strip that buckles and flexes to absorb jitters.

Joris is part of a team that is developing an improved design that is lighter and protects against vibrations of a wider range of frequencies.

If all goes well, these Euler springs will be used in the Einstein Telescope, a proposed European gravitational wave observatory that will be 10 times more sensitive than Advanced Virgo.

“At Nikhef they are planning to build an Einstein Telescope Pathfinder to test all the technologies they want to use for the Einstein Telescope. I hope our ideas can be part of it.”

Banner image: Advanced Virgo is Europe’s gravitational wave observatory. Credit: Virgo