Advanced LIGO detector performance in the fourth observing run

Authors

E. Capote
W. Jia
N. Aritomi
M. Nakano
V. Xu
R. Abbott
I. Abouelfettouh
R. X. Adhikari
Francisco Llamas Villarreal, The University of Texas Rio Grande Valley
Volker Quetschke, The University of Texas Rio Grande ValleyFollow

Document Type

Article

Publication Date

3-3-2025

Abstract

On May 24, 2023, the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), joined by the Advanced Virgo and KAGRA detectors, began the fourth observing run for a two-year-long dedicated search for gravitational waves. The LIGO Hanford and Livingston detectors have achieved an unprecedented sensitivity to gravitational waves, with an angle-averaged median range to binary neutron star mergers of 152 and 160 Mpc, and duty cycles of 65.0% and 71.2%, respectively, with a coincident duty cycle of 52.6%. The maximum range achieved by the LIGO Hanford detector is 165 Mpc and the LIGO Livingston detector 177 Mpc, both achieved during the second part of the fourth observing run. For the fourth run, the quantum-limited sensitivity of the detectors was increased significantly due to the higher intracavity power from laser system upgrades and replacement of core optics, and from the addition of a 300 m filter cavity to provide the squeezed light with a frequency-dependent squeezing angle, part of the A+ upgrade program. Altogether, the A+ upgrades led to reduced detector-wide losses for the squeezed vacuum states of light which, alongside the filter cavity, enabled broadband quantum noise reduction of up to 5.2 dB at the Hanford observatory and 6.1 dB at the Livingston observatory. Improvements to sensors and actuators as well as significant controls commissioning increased low frequency sensitivity. This paper details these instrumental upgrades, analyzes the noise sources that limit detector sensitivity, and describes the commissioning challenges of the fourth observing run.

Comments

© 2025 American Physical Society

Recommended Citation

Capote, E., W. Jia, N. Aritomi, M. Nakano, V. Xu, R. Abbott, I. Abouelfettouh et al. "Advanced LIGO detector performance in the fourth observing run." Physical Review D 111, no. 6 (2025): 062002. https://doi.org/10.1103/PhysRevD.111.062002

Publication Title

Physical Review D

DOI

10.1103/PhysRevD.111.062002