E-TEST prototype design report

E-TEST (Einstein Telescope Euregio-Meuse-Rhin Site and Technology) is a
project recently funded by the European program Ineterreg Euregio Meuse-Rhine.
This program is dedicated to innovative cross boarder activities between
Belgium, The Netherlands and Germany. With a total budget of15MC and a
consortium of 11 partners from the three countries, the objective of the
project is twofold. Firstly, to develop an eco-friendly and non-invasive
imaging of the geological conditions as well as the development of an
observatory of the underground in the EMR region. Secondly, to develop
technologies necessary for 3rd generation gravitational wave detectors. In
particular, it is proposed to develop a prototype of large suspended cryogenic
silicon mirror, isolated from seismic vibrations at low frequency. The total
budget of the project is equally spread over the two activities. The first
activity is not discussed at all in this report. The E-TEST prototype will have
some key unique features: a silicon mirror of 100 kg, a radiative cooling
strategy (non contact), a low-frequency hybrid isolation stage, cryogenic
sensors and electronics, a laser and optics at 2 microns, a low thermal noise
coating.