Just like the real thing, the scale model has several towers, pillars actually, set up in the form of a horizontal V. A laser beam runs from the point and immediately splits into two, going through two tunnels and crashing onto deeply cooled mirrors and then bounced back. If both beams don’t return at the same moment, that can be an indication of a gravitational wave. Although ETpathfinder is too small to pick them up.
The experiments will take place in the spotless white clean room. “That was the greatest challenge,” says Ralph Herben, project leader at Facility Services, who is giving Observant a tour. “We engaged a Belgian contractor, who also builds clean rooms for chip manufacturers. These spaces have hardly any temperature differences and practically no dust particles. People and materials enter through an airlock.”
Cost: two million euro.
Even the cement floor was anything but a routine job. “It is 45 centimetres thick and rests on 178 columns of eight metres long. The floor is not attached to the walls in order to limit vibrations from trains and cars.”
The real Einstein Telescope will not be troubled by that either, because it will be three hundred metres underground. Whether that will be under the South Limburg loess, we will not know until 2025. Sardinia is also still in the running.
The choice of where it will be makes no difference to ETpathfinder. This testing facility will be used for dozens of years anyway. The first experiments are scheduled to start in the summer of 2022.