Length sensing and control strategies for the LCGT interferometer

TL;DR

This paper proposes a length sensing and control scheme for the LCGT interferometer, demonstrating through simulations that noise couplings can be minimized and a robust lock acquisition method can improve operational duty cycle.

Contribution

It introduces a compatible control scheme for broadband and detuned operations and a lock acquisition method using auxiliary lasers for the LCGT interferometer.

Findings

Sensing noise couplings can be reduced below target sensitivity with feed forward.

The proposed control scheme is compatible with different operational modes.

A robust lock acquisition method improves the detector's duty cycle.

Abstract

The optical readout scheme for the length degrees of freedom of the LCGT interferometer is proposed. The control scheme is compatible both with the broadband and detuned operations of the interferometer. Interferometer simulations using a simulation software Optickle show that the sensing noise couplings caused by the feedback control can be reduced below the target sensitivity of LCGT with the use of feed forward. In order to improve the duty cycle of the detector, a robust lock acquisition scheme using auxiliary lasers will be used.