This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| Advanced LIGO Plus | |
|---|---|
| Name | Advanced LIGO Plus |
| Caption | Upgraded interferometer concept for Advanced LIGO Plus |
| Organization | LIGO Laboratory; National Science Foundation; Caltech; Massachusetts Institute of Technology |
| Country | United States |
| Established | planned upgrade after Advanced LIGO |
| Type | Ground-based laser interferometric gravitational wave detector upgrade |
| Wavelength | Gravitational waves (~10 Hz – 10 kHz equivalent) |
| Aperture | 4 km arm cavities at LIGO Hanford Observatory and LIGO Livingston Observatory |
| Status | Planned / commissioning |
Advanced LIGO Plus
Advanced LIGO Plus is a planned upgrade program to enhance the sensitivity and astrophysical reach of the Advanced LIGO detectors at the LIGO Hanford Observatory and LIGO Livingston Observatory. It builds on the legacy of milestones such as the first detection of gravitational waves by GW150914, the cataloging efforts of LIGO Scientific Collaboration and Virgo Collaboration, and joint multimessenger campaigns with observatories like Fermi Gamma-ray Space Telescope and IceCube. The upgrade coordinates with partner initiatives including KAGRA and the proposed LIGO-India facility to extend network capabilities.
The conception of Advanced LIGO Plus emerged from technical reviews after observing runs O1, O2, and O3, and lessons from detections such as GW190814 and GW170817. Working groups within the LIGO Scientific Collaboration, LIGO Laboratory, Caltech, and MIT evaluated subsystem limitations identified during commissioning at Hanford, Livingston, and during joint runs with Virgo. Influential reports from panels including the National Science Foundation advisory committees and community roadmaps such as the Gravitational Wave International Committee recommendations shaped the upgrade scope. Prototype testing at facilities like the 40m Prototype at Caltech and collaborations with institutes like University of Glasgow informed design choices.
Advanced LIGO Plus aims to lower quantum and thermal noise floors to increase horizon distance for compact binary coalescences and continuous-wave sources. Goals include improvements at low frequencies (~10–30 Hz) and mid-to-high frequencies (~100–1000 Hz) to enhance detection of sources similar to GW150914, GW170817, GW190425, and hypothetical heavy neutron-star–black-hole mergers studied in LIGO-Virgo-KAGRA analyses. Planned upgrades encompass higher-power lasers developed with partners such as Laser Zentrum Hannover, squeezed-light injection systems pioneered by groups at AEI Hannover, and improved coating technologies tested at NIST and University of Southampton.
Key instrumentation changes include implementation of frequency-dependent squeezed light using filter cavities inspired by demonstrations at GEO600 and Advanced Virgo, upgraded high-power laser sources with improved beam stabilization from collaborations with Thales and Laser Zentrum Hannover, and replacement or recoating of test-mass optics with low mechanical loss coatings researched at Syracuse University and University of Glasgow. Seismic isolation and suspension enhancements leverage heritage from Initial LIGO and prototype work at AEI Hannover, while thermal compensation systems draw on developments at LIGO Livingston and Caltech. Control systems interface with software frameworks maintained by the LIGO Scientific Collaboration and use timing references traceable to NIST standards.
Simulations predict Advanced LIGO Plus will increase binary neutron star range and binary black hole reach substantially compared to the A+ sensitivity curves produced by joint LSC/Virgo Collaboration studies. Quantum noise reduction via frequency-dependent squeezing targets multi-decibel improvements across the detection band, improving detection rates estimated from population models using results from LIGO-Virgo-KAGRA catalogs. Thermal noise reduction through improved coatings and heavier test masses will enhance mid-frequency performance relevant to tidal deformability measurements of objects like PSR J0348+0432 and PSR J0737−3039A. Low-frequency upgrades aim to mitigate ground motion coupling observed at LIGO Hanford during particular anthropogenic noise events.
Advanced LIGO Plus is designed to expand capabilities for observing signals similar to GW170817 enabling refined constraints on the Hubble constant using multimessenger counterparts observed by telescopes such as Hubble Space Telescope, Chandra X-ray Observatory, Very Large Telescope, and survey facilities like Zwicky Transient Facility. The program targets improved sky localization for joint campaigns with Fermi, Swift, IceCube, and electromagnetic observatories, enabling identification of hosts like NGC 4993. Enhanced sensitivity will boost detection of intermediate-mass black holes potentially related to events analogous to GW190521, continuous waves from pulsars such as Crab Pulsar and Vela Pulsar, and stochastic backgrounds constrained alongside searches by Planck and Pulsar Timing Array efforts.
Implementation follows staged installation windows coordinated with observing runs and maintenance epochs determined by the LIGO Laboratory and NSF. Early R&D and prototyping occurred at university laboratories including Caltech and MIT, with component integration planned during scheduled upgrades between observing runs in the mid-2020s. Commissioning phases will involve detector characterization teams from the LIGO Scientific Collaboration, cross-calibration with Advanced Virgo and KAGRA, and sensitivity verification through hardware injections similar to prior practices during O3. Full science operations depend on completion of filter cavities, laser upgrades, and coating replacements at both Hanford and Livingston sites.
The upgrade is managed by the LIGO Laboratory under oversight from the National Science Foundation with broad participation from the LIGO Scientific Collaboration, universities such as Caltech, MIT, Cardiff University, University of Glasgow, and national laboratories including LANL and LBNL. Funding mechanisms include NSF major facility upgrade lines supplemented by institutional contributions and in-kind efforts from partners like AEI Hannover and Laser Zentrum Hannover. Project governance uses established LIGO project offices and collaboration boards modeled after prior management frameworks deployed during the Initial LIGO to Advanced LIGO transition.