First observations of gravitational waves stimulated several astrophysics fields, opening to the era of gravitational wave imaging of the universe. The natural outcome of the efforts spent on current detectors in the last five years is the rekindling of the planning concerning the next generation of ground-based detectors, whose target is to detect coalescence gravitational-wave emission from the whole universe and extending the bandwidth to the lowest frequency technically possible with ground-based devices. Concepts and ideas on viable solutions leading that target were reflected on the literature in the last ten years , but the science case for 3rd generation detector (3G) network was fully motivated only after first observations. Compared to present detectors, 2nd generation (2G), 3G interferometers will have longer baselines, ranging from 10 to 40 km depending on the optical layout adopted. In the specific case of the Einstein Telescope, conceived under worldwide voluntary effort and sustained by European auspices through dedicated R&D programs (FP6-7, Horizon2020), other two relevant features are foreseen: underground and cryogenics.
Gravitational wave group at Sapienza pioneered concerned cryogenics R&D and through the years tightly collaborated with KAGRA on payload, seismic suspension and control issues. Now we have a great opportunity to further contribute to the design of core solutions leading to ET. We apply for a support that will be finalised along two main lines, both concerning payload cryogenics: A) test-mass suspension material performance at low temperature and B) Vibration and Structural-dynamics studies of large cryostat, which are meant to host 500 kg payloads. Indeed, the two themes of this research are tightly interlaced. We have matured specific expertise and worldwide collaboration with the most advanced groups pursuing this research and plan to let it further grow-up at Sapienza towards ET technical design.
