LIGO A# (A-sharp) is a proposed upgrade to the Advanced LIGO detectors to further increase their sensitivity in 2029, after the O5-observation run. It is intended to bridge the observation gap until the third-generation observatories Cosmic Explorer and Einstein Telescope come online. At the same time LIGO A# can test key aspects of the Cosmic Explorer design.
LIGO A# includes new 100 kg test masses, higher stress test mass suspension fibers, an arm cavity power increase to 1.5MW, a squeezing efficiency increased to 10 dB at high frequencies, as well as better optical coatings, for example AlGaAs crystalline coatings.
The Syracuse University Center for Gravitational-wave Astronomy and Astrophysics is involved with many aspects of the A# design, including ways to improve the squeezing efficiency, the development and integration of coatings, sensors and actuators for test mass suspension and thermal control of the optics.