Investigation of crackling noise in the vibration isolation systems of the KAGRA gravitational wave detector

TL;DR

This study investigates crackling noise in KAGRA's suspension system, demonstrating it is unlikely to affect gravitational wave detection sensitivity above 60 Hz through experimental scaling laws.

Contribution

The paper introduces a scaling law linking miniature and actual GAS systems, enabling estimation of crackling noise impact in KAGRA.

Findings

Crackling noise in KAGRA's suspension is below sensitivity limits above 60 Hz.

Experimental results from miniature GAS can predict noise levels in the full-scale system.

Crackling noise is unlikely to interfere with gravitational wave detection in the target frequency band.

Abstract

Gravitational wave detectors, such as KAGRA, require complex mirror suspension systems to reach high sensitivity. One particular concern in these suspensions is the presence of crackling noise, where motion of the steel crystal structure disturbs material defects, causing impulse force release and exciting mirror motion. Crackling in the Geometric Anti Spring filters (GAS) in KAGRA's suspension system could introduce noise in the gravitational wave detection band. We investigate crackling noise in a miniature GAS with a low-frequency cyclical stress. We developed a scaling law between miniature and KAGRA GAS. Applying experimental results to the scaling law allows us to estimate the upper limit of crackling noise in KAGRA. It is found that crackling noise should be below the target sensitivity for gravitational waves above 60 Hz.