Optimization of Design Parameters for Gravitational Wave Detector DECIGO Including Fundamental Noises

The DECi-hertz Interferometer Gravitational-Wave Observatory (DECIGO) is a space gravitational wave (GW) detector. DECIGO was originally designed to be sensitive enough observe primordial GW background (PGW). However, due the lowered upper limit of PGW by Planck observation, further improvement target sensitivity required. In previous studies, DECIGO’s parameters were optimized maximize signal-to-noise ratio (SNR) quantum noise including effect diffraction loss. To simulate SNR more realistically, we optimize considering GWs from double white dwarfs (DWDs) and thermal test masses. We consider two cases cutoff frequency DWDs. addition, kinds noise: in residual gas internal noise. investigate how mirror geometry affects sensitivity, calculate it changing mass, keeping thickness, vice versa. As result, obtained optimums for that depends on radius. This result shows thick with large radius gives good enables us design based feasibility study size future.