Sensitivity and Performance of the Advanced LIGO Detectors in the Third Observing Run

TL;DR

This paper reports on the third observing run of Advanced LIGO and Virgo, highlighting increased sensitivity, detector upgrades, and the noise sources limiting performance, enabling better gravitational wave detection.

Contribution

It provides a detailed analysis of the detector upgrades, their impact on sensitivity, and the noise sources affecting the third observing run of Advanced LIGO and Virgo.

Findings

Higher duty cycle and sensitivity achieved

Detectors reached 111 Mpc and 134 Mpc sensitivity distances

Identified noise sources limiting detector performance

Abstract

On April 1st, 2019, the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), joined by the Advanced Virgo detector, began the third observing run, a year-long dedicated search for gravitational radiation. The LIGO detectors have achieved a higher duty cycle and greater sensitivity to gravitational waves than ever before, with LIGO Hanford achieving angle-averaged sensitivity to binary neutron star coalescences to a distance of 111 Mpc, and LIGO Livingston to 134 Mpc with duty factors of 74.6% and 77.0% respectively. The improvement in sensitivity and stability is a result of several upgrades to the detectors, including doubled intracavity power, the addition of an in-vacuum optical parametric oscillator for squeezed-light injection, replacement of core optics and end reaction masses, and installation of acoustic mode dampers. This paper explores the purposes behind these upgrades, and explains to the best of our knowledge the noise currently limiting the sensitivity of each detector.