Accurate calibration of test mass displacement in the LIGO interferometers

TL;DR

This paper presents three different calibration methods for LIGO test mass displacement actuators, demonstrating that systematic errors are within expected uncertainties across a range of frequencies and amplitudes.

Contribution

It introduces and compares three fundamentally different calibration techniques to verify and ensure the accuracy of LIGO's gravitational-wave detector responses.

Findings

Calibration coefficients agree within 4% across methods

Systematic errors are within the stated uncertainties

Calibration is reliable over tested frequency and amplitude ranges

Abstract

We describe three fundamentally different methods we have applied to calibrate the test mass displacement actuators to search for systematic errors in the calibration of the LIGO gravitational-wave detectors. The actuation frequencies tested range from 90 Hz to 1 kHz and the actuation amplitudes range from 1e-6 m to 1e-18 m. For each of the four test mass actuators measured, the weighted mean coefficient over all frequencies for each technique deviates from the average actuation coefficient for all three techniques by less than 4%. This result indicates that systematic errors in the calibration of the responses of the LIGO detectors to differential length variations are within the stated uncertainties.