Dutch sensor technology helps the Einstein Telescope establish vibration-free measurements

A Dutch consortium is developing extremely sensitive sensors designed to help protect the Einstein Telescope’s mirrors from vibrations as effectively as possible. The first major milestones have now been reached: an initial sensor prototype is operational and a new test setup has been commissioned at NIKHEF. The technology focuses on very low frequencies, for which existing sensors are not yet accurate enough.

Every movement counts

In order to measure gravitational waves, the mirrors of the Einstein Telescope must be virtually motionless. This presents a major technical challenge. The mirrors can be affected by all manner of disturbances, ranging from human activity and ground movements to thermal and quantum noise.

In order to actively correct the position of the mirrors, even the tiniest movements must be measurable: with an accuracy of one billionth of a metre or one billionth of a degree of angle. Suitable sensors already exist for fast, high-frequency vibrations, but not yet for low-frequency vibrations. It is precisely these that are important because the Einstein Telescope must also be able to detect gravitational waves at low frequencies, between 1 and 10 Hz. This will enable scientists to study more cosmological processes and more massive astronomical objects.

Six Dutch partners in collaboration

The SENVIDET consortium – Sensor Engineering for Noise and Vibration Isolation and Damping in the Einstein Telescope – is therefore working on a new generation of sensors.

Three Dutch SMEs are developing the technology. Innoseis Sensor Technologies is focusing on rotation sensors, Somni Solutions on displacement sensors, and Quantified Air is developing a new technique for reading out the rotation sensors. Demcon HTS Delft is providing support with the integration of the sensors into the control system, VSL is working on the necessary calibration, and Nikhef is testing and validating the sensors.

First sensor prototype works

A significant milestone has now been reached. Somni Solutions has developed an initial version of its sensor and had it calibrated at VSL. The sensor was then tested at NIKHEF to see how it responds to movement. The results are promising.

Hedde van Hoorn, Senior Project Lead at Somni Solutions and consortium coördinator, states: “We have now carried out static calibration of the first version at VSL; this has demonstrated that the sensor works and has a very high sensitivity. We then tested the dynamic response at Nikhef; compared to a seismometer, it appears to perform very well.”

The next step is to further reduce the noise level so that the sensor can meet the requirements of the Einstein Telescope.

State-of-the-art Dutch sensor technology

NIKHEF has also recently commissioned the OmniSens 6D in Amsterdam: a new setup for testing the sensors under high vacuum.

According to Albert van Dorssen, business developer with the Einstein Telescope Valorisation & Impact team, sensor technology with the required precision was not yet commercially available. Dutch companies are now developing technology that may well be able to meet the requirements.

Opportunities beyond the Einstein Telescope

The technology can also be applied outside the Einstein Telescope. Examples include the semiconductor industry, quantum technology and nuclear fusion. The technology can also be used to measure seismic vibrations with great precision, for example to monitor earthquakes.

SENVIDET is one of six consortia in which Dutch high-tech companies and research institutions are developing technology for the Einstein Telescope. The projects are made possible in part by funding from the Dutch National Growth Fund. In this way, they not only deliver technology for the Einstein Telescope, but also create new opportunities for the Dutch high-tech sector.