# Prospects for improving the sensitivity of KAGRA gravitational wave detector

## TL;DR

This paper discusses potential upgrade strategies for the KAGRA gravitational wave detector, focusing on increasing sensitivity through various technical modifications and their implications for gravitational-wave science.

## Contribution

It presents novel upgrade plans for KAGRA, considering its unique cryogenic cooling system, and evaluates their impact on detector performance and scientific outcomes.

## Key findings

- Increasing input laser power improves high-frequency sensitivity.
- Larger mirror mass enhances low-frequency detection capabilities.
- Injecting frequency-dependent squeezed vacuum reduces quantum noise.

## Abstract

KAGRA is a new gravitational wave detector which aims to begin joint observation with Advanced LIGO and Advanced Virgo from late 2019. Here, we present KAGRA's possible upgrade plans to improve the sensitivity in the decade ahead. Unlike other state-of-the-art detectors, KAGRA requires different investigations for the upgrade since it is the only detector which employs cryogenic cooling of the test mass mirrors. In this paper, investigations on the upgrade plans which can be realized by changing the input laser power, increasing the mirror mass, and injecting frequency dependent squeezed vacuum are presented. We show how each upgrade affects to the detector frequency bands and also discuss impacts on gravitational-wave science. We then propose an effective progression of upgrades based on technical feasibility and scientific scenarios.