The ET (Einstein Telescope) project aims to the realization of a crucial research infrastructure in Europe: a third generation Gravitational Wave observatory.
ET has been supported as Design Study by the European Commission under the Framework Programme 7 (FP7, Grant Agreement 211743). This phase is concluded and a Conceptual Design Document has been released; currently a new phase is open focused on the needed technologies development. For this reason a new project, embedded in the ET framework, is now supported by the European Commission, still under FP7 (People, IRSES): ELiTES, focused on the development of the cryogenic technologies for LCGT (now KAGRA) and ET. The aim of the ET project is the realization of a future European third generation gravitational wave detector; in fact the evolution of the gravitational wave detectors is well defined: after the initial phase, terminated in 2011, the detectors are evolving toward their second generation: the advanced (Virgo and LIGO) detector. According to the current gravitational sources modeling, when these apparatuses will reach their nominal sensitivity, the detection of the gravitational waves seems assured in few months of data taking. But the sensitivity needed to test the Einstein’s gravity in strong field condition or to realize a precision gravitational wave astronomy, mainly of massive stellar bodies or of highly asymmetric (in mass) binary stellar systems goes beyond the expected performances of the advanced detectors and of their subsequent upgrades. In fact, for example, the fundamental limitations at low frequency of the sensitivity of the 2nd generation detectors are given by the seismic noise, the related gravitational gradient noise (so-called Newtonian noise) and the thermal noise of the suspension last stage and of the test masses. To circumvent these limitations new infrastructures are necessary: an underground site for the detector, to limit the effect of the seismic noise, and cryogenic facilities to cool down the mirrors to directly reduce the thermal vibration of the test masses. The ET-FP7 project is addressing the basic questions in the realization of this new observatory: site location and characteristics, suspension design and technologies, detector topology and geometry, detection capabilities requirements and Astrophysics potentialities, The physicists directly involved in the ET project are aware of the difficulty of designing such as new observatory and for this reason the project is open to all the scientists willing to collaborate to the ET adventure. An appropriate body, the science team, has been created to support the scientists, not belonging to the original 8 partners, interested to contribute to our effort.
The ASPERA organization, a network of national government agencies responsible for coordinating and funding national research efforts in Astroparticle Physics, includes ET in the “Magnificent Seven” list in its roadmap.