Skip to content

ETpathfinder: R&D lab for gravitational wave detectors

ETpathfinder will be a test environment for gravitational wave detector technology in Maastricht. There will be a full laser interferometer, even allowing testing of different setups and the interplay between components. This is how ETpathfinder contributes to the development of better and new technologies.

Making the Einstein Telescope up to 10 times more accurate than existing observatories requires new and better technologies. These will partly be developed in the dedicated R&D lab ETpathfinder. Here, scientists and companies will work together on vacuum systems, cooling, mirrors & mirror coatings, vibration dampers and measurement and control software. Although it is about technology for gravitational wave measurements, this lab will provide new knowledge with wider applicability.

ETpathfinder: a unique R&D lab

The idea of an R&D laboratory for gravitational-wave observatories is not new. The existing LIGO and Virgo facilities could never have been so precise without R&D back-up from labs in Glasgow, Munich and California. But ETpathfinder will go one step further by making it possible to perform tests at extremely low temperatures. It is to be the first facility of its kind able to cool silicon mirrors. That is an important step in suppressing noise, for even more precise measurements. Because this is unique, it will attract scientists and businesses from all over the world.

ETpathfinder laboratorium
ETpathfinder laboratory

Co-operation between science and industry

Fifteen scientific institutions in the Netherlands, Belgium and Germany are currently involved in ETpathfinder, and committed to collaborating with industry partners. It is important that these firms come on board as soon as possible, so that they can participate actively in the lab’s R&D work and guarantee the viability of its new technologies. When companies and scientists work together, new expertise and know-how are generated. Not only are they important for the construction of the Einstein Telescope, but the businesses involved can use the technologies thus developed to create and market new products.

Testing ground for laser interferometry

ETpathfinder will be a testing ground for laser interferometry, the technique used to detect and measure gravitational waves. A laser beam is split into two and reflected by mirrors at the ends of the “arms”. The two beams then come together again and are collected on a detector. When they do so, they either cancel out one another on the detector or are amplified. This depends on the difference in length between the arms. When a gravitational wave passes it distorts space-time by a minuscule amount so that one of the arms is very briefly a tiny bit shorter than the other. This produces a flicker in the signal, which the detector picks up: the gravitational wave’s fingerprint.

Artistic impression of ETpathfinder. Bron: Marco Kraan / Nikhef
Artistic impression of ETpathfinder. Bron: Marco Kraan / Nikhef

ETpathfinder will have a cleanroom, a large dust-free hall with a stable temperature. Various configurations of the laser interferometer can be set up here over the next twenty to thirty years. The core installation will have two arms, each 20 metres long. That is not big enough to actually observe gravitational waves, but it is sufficient to develop and test all kinds of relevant techniques.

The set-up consists of a number of towers containing vibration-free tables. The laser source and detector are located in the central towers. The laser light is split into two beams, which are directed into the two “arms”. In four towers along these arms are mirrors with a special coating, which reflect the laser light back and forth. The mirrors can be cooled down to -153 °C, and in the future perhaps even to -263 °C!