Improving LIGO calibration accuracy by tracking and compensating for slow temporal variations
Calibration of the second-generation LIGO interferometric gravitational-wave detectors employs a method that uses injected periodic modulations to track and compensate for slow temporal variations in the differential length response of the instruments. These detectors utilize feedback control loops to maintain resonance conditions by suppressing differential arm length variations. We describe how the sensing and actuation functions of these servo loops are parameterized and how the slow variations in these parameters are quantified using the injected modulations. We report the results of applying this method to the LIGO detectors and show that it significantly reduces systematic errors in their calibrated outputs.
© 2016 IOP Publishing Ltd. Received 8 August 2016, revised 21 October 2016; Accepted for publication 1 November 2016; Published 6 December 2016. LIGO was constructed by the California Institute of Technology and Massachusetts Institute of Technology with funding from the National Science Foundation (NSF) and operates under cooperative agreement PHY-0757058. This work was supported by the following NSF grants: HRD-1242090 for D Tuyenbayev, PHY-1607336 for S Karki, PHY-1404139 for S Kandhasamy and PHY-1607178 for M Wade. Fellowship support for S Karki and D Tuyenbayev from the LIGO Laboratory and for D Tuyenbayev from the UTRGV College of Sciences are also gratefully acknowledged. This paper carries LIGO Document Number LIGO-P1600063.
Submitted - 1608.05134v2.pdf