Maximising opportunities: the Einstein Telescope in a triangular or L-shaped configuration

The Einstein Telescope EMR Task Force has asked the Project Office to also investigate the feasibility of an L-shaped configuration. What does this mean? Here are a few key points.

Does investigating the feasibility of the L-configuration mean that the triangle is no longer being considered?

No, quite the opposite. The first results of the noise measurements for the triangle have recently come in, and the results are positive. The feasibility study for the triangle is continuing as planned and will be completed by the end of this year.

And what about the L-configuration?

The L-shaped configuration consists of a gravitational-wave detector with two perpendicular arms forming an L, rather than a triangular structure. To operate as a complete observatory, two L-shaped detectors need to be located at a considerable distance from each other. By contrast, a triangular configuration can independently carry out research into gravitational waves.

Why, then, also investigate an L-configuration in the Meuse-Rhine Euroregion?

Last year, the European Einstein Telescope Organisation (ETO) had already asked the EMR project office to investigate an L in addition to the feasibility study for the triangle that was already underway. ETO requested this study in order to properly compare both configurations. At the time, this became a desk study so that priority could be given to the triangle.

In July 2026, the recently established Scientific Advisory Committee (SAC) of the EMR recommended expanding the desk study into a full feasibility study. By broadening the scope of the study, the EMR region is maximising its flexibility and its chances of bringing the Einstein Telescope to the Meuse-Rhine Euroregion.

If we know that one L-shaped detector requires another L-shaped detector in another location to be able to function, what does that imply?

If, at the end of all the studies and comparisons, the conclusion is that an L is feasible in the Meuse-Rhine Euroregion, this L could preferably be combined with an L-shaped detector in Sardinia, because of the longer distance required.

What will the feasibility study for the L-configuration look like?

The project office is currently mapping this out. Initially, the focus will be on the physical feasibility of an L in our Euroregion. We will examine the geology and subsurface conditions at potential locations that have not yet been investigated. The same applies to seismology. In any case, additional drilling, technical studies and environmental studies will be required.

Where and when will this take place?

As mentioned, the project office is currently preparing a proposal for this. Once the drilling locations are known and agreements have been reached with landowners, municipalities and other authorities, we will of course communicate this. The project office will also invite local residents and other interested parties to an information meeting, as has always been the case.

What does this mean for the deadlines, which are still set for the end of this year?

As mentioned, the study of the triangle is proceeding according to schedule and will be completed this year. Preparations for the bid book have also begun. The European selection procedure is expected to start next spring.

In the meantime, the EMR will begin the feasibility study for the L.

What factors will determine which configuration the Euregio Meuse-Rhine ultimately puts forward?

At present, the EMR is preparing to submit a bid book for the triangle. At the same time, the feasibility study for the L is being launched.

Depending on the outcome of the feasibility studies and the prioritisation process, a 2L proposal with Italy could also be submitted. In October, the European Einstein Telescope Organisation (ETO) will publish a comparative report on the triangle and the 2L configuration. This could provide important insight into international preferences.

It will then be up to the European countries and the countries behind the EMR proposal to make a final decision.

It sounds like a difficult choice…

Ultimately, we will go for the option with the best prospects. By also investigating the double-L configuration in cooperation with Italy, we are maximising the EMR region’s chances of bringing the Einstein Telescope to this region.

This is not a decision to be made overnight, but rather a process involving the necessary considerations to arrive at a well-founded and carefully considered decision.

At the same time, we are seeing tremendous energy developing across the Meuse-Rhine Euroregion, extending far beyond the scientific field alone. Within the innovative business community, 100 companies are now working on the technologies required for the Einstein Telescope.

In education, the ETEC (Einstein Telescope Centre), the Einstein Academy, student tours of universities and school visits are helping to stimulate interest in STEM/STEAM education. Young people are seeing opportunities for a future in science and technology at all levels.

The ongoing participatory research in the search region shows that residents are interested in the Einstein Telescope and have questions about its potential impact, but above all, they also see the opportunities it could create for the future of their own region.

So there is one thing we know for certain: whatever happens, we want to bring an Einstein Telescope to the Meuse-Rhine Euroregion.

Which leaves one question: when?

It is not possible to say precisely at this stage. Carefulness takes precedence over speed. We know that the European decision on the location must be made in the second half of 2027. There therefore needs to be clarity before then.