Improving gravitational-wave interferometers with fast cooling

Gravitational wave astronomy exposes the universe in new ways, but the detectors are limited by sensitivity. Using radiative cooling to maintain a frigid, 124 Kelvin temperature within the gravitational wave interferometer would reduce thermal noise and increase sensitivity. However, achieving the necessary low temperature through radiative cooling alone could take weeks.

During the long cooldown process, ice may deposit on the test mass, harming the optics. The long turnaround time also lengthens the iterative process to improve detectors. Bonilla et al. devised and tested a cryo-cooling system that significantly reduces the gravitational wave interferometer’s cooldown time and allows flexibility for handling ice deposition.

Radiative cooling is contactless, so it provides vibration isolation. The authors’ fast-cooling system adds to the existing cooling to quickly switch from room temperature to operating temperature.

“The technique is super simple: we put a bit of nitrogen near the mass that is cooling. The nitrogen gas molecules will bounce back and forth between the surfaces to carry the thermal energy across the gap,” said author Edgard Bonilla.

Finding the right balance of added gas is crucial: more gas improves energy transfer, but too much might damage other equipment.

The authors achieved cooling 3.5 times faster than radiation only. This rapid cooling can help mitigate damage and facilitate more research into increasing the sensitivity of gravitational wave interferometers.

“Better sensitivity helps to get more, longer duration, and clearer detections for the astrophysical events we have grown to know and love,” said Bonilla. “We can learn about big-scale things like the rate of expansion of the universe or about tiny-scale things like the properties of nuclear matter.”

Source: “Improving the cooldown times for next-generation cryocooled gravitational-wave interferometers,” by Edgard Bonilla, Jaimi Salone, Brian Lantz, Aaron Galper, and Faith Stults, Applied Physics Letters (2023). The article can be accessed at https://doi.org/10.1063/5.0143940 .

This paper is part of the Gravitational Wave Detectors Collection, learn more here .