Prospects for improving the sensitivity of the cryogenic gravitational wave detector KAGRA

TL;DR

This paper explores potential upgrades to the cryogenic KAGRA gravitational wave detector, aiming to enhance its sensitivity across different frequency bands without major infrastructure changes.

Contribution

It identifies feasible upgrade strategies that significantly improve KAGRA's detection range and localization capabilities, tailored to its cryogenic design.

Findings

Fivefold increase in black hole binary detection range

1.3 times better neutron star binary detection range

1.7 times improved sky localization for neutron star binaries

Abstract

Upgrades to improve the sensitivity of gravitational wave detectors enable more frequent detections and more precise source parameter estimation. Unlike other advanced interferometric detectors such as Advanced LIGO and Advanced Virgo, KAGRA requires different approach for the upgrade since it is the only detector which employs cryogenic cooling of the test masses. In this paper, we describe possible KAGRA upgrades with technologies focusing on different detector bands, and compare the impacts on the detection of compact binary coalescences. We show that either fivefold improvement in the $100 M_{\odot}$--$100 M_{\odot}$ binary black hole range, a factor of 1.3 improvement in the binary neutron star range, or a factor of 1.7 improvement in the sky localization of binary neutron stars is well feasible with upgrades that do not require changes in the existing cryogenic or vacuum infrastructure. We also show that twofold broadband sensitivity improvement is possible by applying multiple upgrades to the detector.