# Vibration isolation system with a compact damping system for power recycling mirrors of KAGRA

## TL;DR

This paper presents a new vibration isolation system with a compact damping mechanism designed for the power recycling mirrors in KAGRA, improving seismic isolation and damping performance for gravitational-wave detection.

## Contribution

The development and successful implementation of a compact, passive damping vibration isolation system for KAGRA's mirrors, enhancing seismic isolation efficiency.

## Key findings

- Satisfies damping performance requirements
- Achieves effective vibration isolation ratio
- Reduces residual displacement of optics

## Abstract

A vibration isolation system called Type-Bp system used for power recycling mirrors has been developed for KAGRA, the interferometric gravitational-wave observatory in Japan. A suspension of the Type-Bp system passively isolates an optic from seismic vibration using three main pendulum stages equipped with two vertical vibration isolation systems. A compact reaction mass around each of the main stages allows for achieving sufficient damping performance with a simple feedback as well as vibration isolation ratio. Three Type-Bp systems were installed in KAGRA, and were proved to satisfy the requirements on the damping performance, and also on estimated residual displacement of the optics.