ETpathfinder: a cryogenic testbed for interferometric gravitational-wave detectors

Abstract

The third-generation of gravitational wave observatories, such as the Einstein Telescope (ET) and Cosmic Explorer (CE), aim for an improvement in sensitivity of at least a factor of ten over a wide frequency range compared to the current advanced detectors. In order to inform the design of the third-generation detectors and to develop and qualify their subsystems, dedicated test facilities are required. ETpathfinder prototype uses full interferometer configurations and aims to provide a high sensitivity facility in a similar environment as ET. Along with the interferometry at 1550 nm and silicon test masses, ETpathfinder will focus on cryogenic technologies, lasers and optics at 2090 nm and advanced quantum-noise reduction schemes. This paper analyses the underpinning noise contributions and combines them into full noise budgets of the two initially targeted configurations: 1) operating with 1550 nm laser light and at a temperature of 18 K and 2) operating at 2090 nm wavelength and a temperature of 123 K.

Conceptual Design of a Sorption-Based Cryochain for the Etpathfinder

“…The main requirement is that the cooling system should not generate vibrations at the cold finger exceeding the level caused by seismic excitation of the ground. At the ETpathfinder site, seismic excitation with an amplitude spectral density of 4 nm∕ √ Hz has been measured in the frequency band 2 -10 Hz, corresponding to about 30 nm peak-to-peak displacement [5]. Considering that ET itself will be installed underground, its seismic levels are expected to even be one order of magnitude lower [11].…”

Research Facilities for Europe’s Next Generation Gravitational-Wave Detector Einstein Telescope

“…Due to the nature of this article, not all ETpathfinder key technologies can be described here. For an in-depth description of the project and its key technologies, further information can be found in the ETpathfinder design report [71] and the ETpathfinder reference paper [72].…”

“…ETpathfinder [71,72] is currently in its initial construction phase in Maastricht in the Netherlands. This project will develop and integrate suspended silicon mirrors with novel suspension elements in a 10 m prototype facility and aims to verify the technical readiness of subsystems, such as laser systems as well as photo-detectors, that are currently under development at new laser wavelengths applicable to ET (1550 and 2090 nm).…”