A xylophone configuration for a third-generation gravitational wave detector

Abstract

Achieving the demanding sensitivity and bandwidth, envisaged for third generation gravitational wave (GW) observatories, is extremely challenging with a single broadband interferometer. Very high optical powers (Megawatts) are required to reduce the quantum noise contribution at high frequencies, while the interferometer mirrors have to be cooled to cryogenic temperatures in order to reduce thermal noise sources at low frequencies. To resolve this potential conflict of cryogenic test masses with high thermal load, we present a conceptual design for a 2-band xylophone configuration for a third generation GW observatory, composed of a high-power, high-frequency interferometer and a cryogenic low-power, low-frequency instrument. Featuring inspiral ranges of 3200 Mpc and 38000 Mpc for binary neutron stars and binary black holes coalesences, respectively, we find that the potential sensitivity of xylophone configurations can be significantly wider and better than what is possible in a single broadband interferometer.PACS numbers: 04.80. Nn, 07.60.Ly, 95.75.Kk, 95.55.Ym

Unified picture of the post-merger dynamics and gravitational wave emission in neutron star mergers

“…Depending on the highly uncertain binary NS merger rate, a detection may succeed with Advanced LIGO/Virgo [40] or with discussed upgrades [42][43][44] (the latter may yield a sensitivity increase at high frequencies of a factor three). Since the strength of the secondary features is somewhat lower than that of the dominant peak (in relation to the anticipated instrument noise curves), direct detections of the secondary GW peaks can be expected for the planned Einstein Telescope [36,37,40,41,45], unless the merger rate is on the more optimistic side as defined in [3], which may enable an earlier observation. The exact detection rate of secondary peaks is hard to quantify not only because of the uncertain merger rate, but also because of the varying strength and prominence of the secondary peaks depending on the exact model.…”

Velocity and Attenuation Characterization of the LIGO Site near Livingston, Louisiana

“…The interferometric detectors measure strain by observing the phase of laser light that is reflected between two suspended mirrors separated by several kilometers. The current strain sensitivities of the LIGO detectors are close to 10 23 Hz 1=2 at 100 Hz, and design studies of future-generation detectors envision strain sensitivities of about 10 24 Hz 1=2 down to 3 Hz (Hild et al, 2009). The suspension systems decouple the motion, especially the horizontal motion of the mirrors, from the motion of the ground.…”

Optical absorption of ion-beam sputtered amorphous silicon coatings

“…The 1st and 2nd generations of GWDs operate at room temperature, using a laser wavelength of 1064 nm. Future, more sensitive detectors such as upgrades to Advanced LIGO [2] and the low frequency detector within the Einstein Telescope (ET) [3,4] may be operated at cryogenic temperatures to reduce thermal noise. The presently used test-mass material fused silica becomes unsuitable at low temperatures due to high mechanical loss and thus high thermal displacement noise [5].…”