Vacuum pipe - The Pilot Sector
The Einstein Telescope (ET, https://www.et-gw.eu/) is a proposed underground infrastructure to host a third-generation, gravitational-wave observatory. It builds on the success of current, second-generation laser-interferometric detectors Advanced Virgo and Advanced LIGO, whose breakthrough discoveries of merging black holes (BHs) and neutron stars over the past 5 years have ushered scientists into the new era of gravitational-wave astronomy.
The Einstein Telescope will achieve a greatly improved sensitivity by increasing the size of the interferometer from the 3km arm length of the Virgo detector to 10km, and by implementing a series of new technologies. With a total budget of 1,7 billion euros, the ET will contribute towards breakthrough technological innovations in the areas of ultra-high vacuum, cryogenics, computing, precision mechanics, lasers or optics. Some of these are for example a cryogenic system to cool some of the main optics to 10 – 20K, new quantum technologies to reduce the fluctuations of the light, and a set of infrastructural and active noise-mitigation measures to reduce environmental perturbations.
As a consequence of ET being included in the ESFRI roadmap in its 2021 update, the project entered its preparatory phase, with the Horizon Europe ET-PP project. The ET-PP project addresses a number of fundamental prerequisites for the approval, construction and operation of the Einstein Telescope, one of which is the industrial involvement in the design and construction of the Einstein Telescope.
The vacuum arm system of the Einstein Telescope (ET) gravitational wave interferometer will probably be the world's largest ultra-high vacuum (UHV) system for a long time to come (120 km). For a gravitational wave interferometer like ET, the cost is important and proportional to its length. The construction of a vacuum system of this size requires an enormous effort to optimise the choice of materials, manufacturing processes and tube treatments to reduce costs, as it is estimated to account for 1/3 of the total cost of ET.
For the construction of a pilot sector under the leadership of CERN, industrial partners are being sought for the production of ultra-high vacuum (UHV) tubes, based on the solution adopted for the VIRGO observatory (smooth pipe) and corrugated tubes compatible with high vacuum. The tube material will be ferritic stainless steel (AISI 441). The pilot section, with a total length of 50m, is divided into modules with a length of 6-12m and a diameter of 1m.
