A xylophone configuration for a third-generation gravitational wave detector

Abstract

Achieving the demanding sensitivity and bandwidth, envisaged for third\ngeneration gravitational wave (GW) observatories, is extremely challenging with\na single broadband interferometer. Very high optical powers (Megawatts) are\nrequired to reduce the quantum noise contribution at high frequencies, while\nthe interferometer mirrors have to be cooled to cryogenic temperatures in order\nto reduce thermal noise sources at low frequencies. To resolve this potential\nconflict of cryogenic test masses with high thermal load, we present a\nconceptual design for a 2-band xylophone configuration for a third generation\nGW observatory, composed of a high-power, high-frequency interferometer and a\ncryogenic low-power, low-frequency instrument. Featuring inspiral ranges of\n3200Mpc and 38000Mpc for binary neutron stars and binary black holes\ncoalesences, respectively, we find that the potential sensitivity of xylophone\nconfigurations can be significantly wider and better than what is possible in a\nsingle broadband interferometer.\n