Skip to main content

The Einstein Telescope (ET) will be one of the most important European research infrastructures of the coming decades. The project involves the construction of a large underground facility that will house a gravitational wave detector at a depth of between 100 and 300 meters, with the aim of isolating it from all noise sources (both natural and anthropogenic) that could interfere with the measurements the detector will carry out. The construction of ET will take approximately 10 years and will require significant engineering efforts, especially due to the need to adapt underground construction techniques to the scientific community’s requirements. Regardless of the final site (or sites, should the decision be made to build two detectors in Europe) and the experiment’s geometry, which is still under discussion, the project will be based on the principles of sustainability, aimed at minimizing the environmental and energy impact of the infrastructure throughout its entire lifecycle. This is a key aspect, already guiding the early study phases of ET.

We discussed this with Maria Marsella, professor of geomatics at the Department of Civil and Environmental Engineering (DICEA) of Sapienza University of Rome and deeply involved in the Einstein Telescope project, both at the international and national levels. Within the Einstein Telescope Organisation (ETO), she is responsible for the civil engineering group and serves as the coordinator of Work Package 6 (dedicated to sustainable design) of the PNRR ETIC project, promoted by the Ministry of University and Research (MUR) and coordinated by the National Institute for Nuclear Physics (INFN).

 

Maria Marsella

What are the main engineering challenges of the Einstein Telescope?
The project involves the underground construction of over 30 kilometers of tunnels, each more than six meters in diameter, along with three large caverns about 20 meters high, all connected to surface infrastructures supporting the underground systems. Of course, the first challenge is in choosing the construction techniques for excavation and defining the strategy for managing the extracted material, which will be quite significant: it is currently estimated at between three and four million cubic meters.
In fact, modern civil engineering techniques make the construction of such works a well-established practice, posing no particular problems. The real engineering challenge for a project like ET lies elsewhere: in meeting the scientific requirements, which are, of course, very different from those of any ordinary underground civil work.

What are these requirements?
The construction of the infrastructure must take place far from sources of acoustic or mechanical vibrations, or in conditions that allow for adequate shielding. Effective solutions for water collection and disposal are also necessary, as water can generate noise in an underground setting. Additionally, there are many other complex aspects related to the logistics of assembling large underground vacuum tubes, the cryogenic systems, and various control and safety systems. In some cases, civil engineers will need to draw on the experience gained from constructing existing infrastructures, such as the LHC accelerator at CERN in Geneva or current gravitational wave observatories, and adapt it to this new, even more complex challenge. In other cases, it will be necessary to come up with entirely new solutions from scratch, such as the connections between underground and surface infrastructures.

The engineering challenges go hand in hand with environmental and sustainability challenges. What are the prospects from this perspective?
The preparatory phase of the Einstein Telescope project is being carried out within the context of the European ET-PP (Einstein Telescope Preparatory Phase) project, funded by the European Commission following the approval of ET by the European ESFRI body. One of the most important actions of the project is precisely the definition of a strategy for the long-term sustainability of the ET infrastructure. This strategy must take into account all aspects that could impact the environment and sustainability, starting with the management and treatment of the excavation materials – which requires thorough preparation in the design phase and a focus on the most sustainable solutions – and extending to more intangible but equally crucial aspects, such as the energy impact of the computing centers.

Also in this case, would it be useful to refer to successful experiences already in progress?
Absolutely: CERN, for example, is a model of excellence with the goal of zero emissions impacting the environment by 2050. However, in the context of ET, we have a huge competitive advantage: we can think of sustainable solutions already in the design phase, envisioning them throughout the entire lifecycle of the infrastructure, from the construction phase to its operational phase, up to the decommissioning, when the infrastructure will cease to operate and all built structures will need to be sustainably repurposed. This is a process that must be intrinsic to the entire technological and engineering design.

How do these strategies fit into the context of the Sos Enattos candidate site?
One of the key actions of the ETIC project is a preliminary study for the sustainable design of ET at the Sardinian site. Sos Enattos is a site of great natural and cultural value, with low human impact and few infrastructures. We now know its geological characteristics very well, which allows us to foresee the necessary treatment for the excavation materials. All the solutions we adopt must be guided by principles of sustainability, environmental respect, and territorial enhancement. In particular, one of the fundamental goals will be to preserve the landscape: the surface infrastructures will have to blend into the environment, be energy self-sufficient, and have a low environmental impact. Moreover, the activities will also be designed to promote entrepreneurial or local technological innovation initiatives. For example, supply chains could be created to facilitate the reuse of excavation materials.

What ideas are being considered for ET’s energy supply?
It is, of course, still too early to have an accurate assessment of the energy budget required for the infrastructure, which will come after the in-depth geological investigations currently underway. However, contrary to what one might think, we already know that a facility like ET will not require a massive energy input, especially when compared to other large research infrastructures like particle accelerators. It will be important to design a smart network of energy systems, which could range from solar power, wind power (outside of protected areas), or even geothermal energy (to be evaluated after the geological surveys), while also enhancing the local standard grid, with clear benefits for the area concerned.

(ms)