2025/10/25 by Yuki Inoue, Inoue, Yuki, Daiki Tanabe +9 · 2 citations
#physics.ins-det #astro-ph.CO #astro-ph.IM #gr-qc
paper · pdf · doi:10.48550/arxiv.2510.24780
We present the optical design and sensitivity modeling of the Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter (CHRONOS), a triangular Sagnac speed-meter interferometer incorporating power and signal recycling. Using ABCD-matrix analysis and Finesse3 simulations, we obtain stable optical eigenmodes with mode-matching efficiencies above 99.5%. The optimized configuration achieves a quantum-noise-limited strain sensitivity of h ≃ 3×10-18,\mathrmHz-1/2 at 1 Hz, with a ring-cavity finesse of F≃3.1×104 and a round-trip Gouy phase of ψ≈153∘. The low-frequency quantum noise is primarily governed by the power-recycling cavity detuning, while the signal-recycling cavity produces an approximately uniform quadrature rotation. An optimal homodyne angle of ζ≃46∘ provides the best sensitivity near 1 Hz. Assuming an end-mirror reflectivity of RETM=99.9999% at 10 K, CHRONOS can achieve quantum-noise-limited performance on a laboratory scale. Its projected science reach includes intermediate-mass black-hole binaries out to approximately 271,Mpc, a 10-year stochastic-background sensitivity of ΩGW≃4.7×10-4 at 2.15,Hz, constraints on Yukawa-type deviations from Newtonian gravity, and prompt gravity-gradient signals from nearby earthquakes.