Twente consortium develops vibration-free cooling for measuring gravitational waves First award from R&D scheme Einstein Telescope for high-tech companies

A consortium of the University of Twente, Demcon kryoz and Cooll will develop an advanced cooling system for the Einstein Telescope. The consortium will receive €2.6 million over a three-year period from the Einstein Telescope R&D scheme, funded by the National Growth Fund.

The Einstein Telescope will be a huge observatory that will measure gravitational waves that Albert Einstein predicted more than 100 years ago. Those gravitational waves are so weak that even the smallest vibrations make it impossible to detect the waves. Detecting these very weak signals from the universe requires vibration-free cooling to very low temperatures.

Measuring Gravitational waves

Observations of gravitational waves by existing observatories and the new Einstein Telescope are made with laser beams. These are sent into ten-kilometre-long tunnels in two directions and reflected by mirrors at the ends to be collected at the starting point by a detector. The measurement signal depends on the difference in the path travelled by the two laser beams. University lecturer Michiel van Limbeek explains: "A passing gravity wave influences that difference on the measurement signal. You can extract information from that, for example about how that gravitational wave was formed."

To fund the research, the R&D scheme was created as part of the ET valorisation programme with a financial contribution from the National Growth Fund. The scheme has five calls; the first was for vibration-free cooling, which is needed to make measurements much more accurate. That call was awarded to the Twente consortium.

Three-stage cooling system

The Twente consortium will receive €2.6 million over three years to make its cooling technology suitable for the Einstein Telescope. To do so, they will develop a three-stage cooling system that works with three different coolants, neon, hydrogen and helium. The cooling process starts at -195 °C, the temperature reached with liquid nitrogen. Two intermediate steps are needed to reach the final, trickiest step to -263 °C: the coldest point in the cooling system. Eventually, they will build three copies of the cooling system, one for research at the University of Twente and two for the ETpathfinder in Maastricht.

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Dr Michiel van Limbeek is an Associate Professor in the Department of Energy, Materials & Systems (EMS; Faculty of S&T). Among other things, the research group has been conducting research on vibration-free cooling based on a sorption technology using activated carbon for over 20 years. Besides research on cryogenic techniques, the EMS group also works on high-current superconductivity. Applications are in the field of renewable energy (including nuclear fusion and high-power electricity transmission) and scientific research. EMS contributes to CERN (elementary particles), ESA (space exploration) and the Einstein Telescope (gravitational waves), among others.