Distributed state machine supervision for long-baseline gravitational-wave detectors

Abstract

The Laser Interferometer Gravitational-wave Observatory (LIGO) consists of two identical yet independent, widely separated, long-baseline gravitational-wave detectors. Each Advanced LIGO detector consists of complex optical-mechanical systems isolated from the ground by multiple layers of active seismic isolation, all controlled by hundreds of fast, digital, feedback control systems. This article describes a novel state machine-based automation platform developed to handle the automation and supervisory control challenges of these detectors. The platform, called Guardian, consists of distributed, independent, state machine automaton nodes organized hierarchically for full detector control. User code is written in standard Python and the platform is designed to facilitate the fast-paced development process associated with commissioning the complicated Advanced LIGO instruments. While developed specifically for the Advanced LIGO detectors, Guardian is a generic state machine automation platform that is useful for experimental control at all levels, from simple table-top setups to large-scale multi-million dollar facilities.

Characterization of systematic error in Advanced LIGO calibration

“…for that t k since the data at that time are not qualified for astrophysical analyses. In O3B, we apply an additional, fixed, frequency-dependent error calculated as described in section 4.1 to each estimate η R (f ; t k ) with t k falling within an hour after the laser power increases and the automated lock acquisition system [8] reports that it has achieved the nominal low-noise state. Using this method, roughly 10% of the Hanford detector hourly estimates have this extra error applied throughout O3B (consistent with the detector duty cycle [6]), affecting all of the Hanford epochs in table 2.…”

Review of the Advanced LIGO Gravitational Wave Observatories Leading to Observing Run Four

“…The interferometer is supported by several auxiliary subsystems required to detect gravitational waves. Auxiliary subsystems include the core optics length controls [17][18][19][20][21][22][23], angular controls [24][25][26][27][28][29][30][31], high-powered stabilized laser [32][33][34], vacuum system [35][36][37], optics suspensions [38][39][40], seismic isolation [41][42][43][44], and electronics and data acquisition systems [45][46][47][48]. This review will focus on the optical configuration and operation of the interferometers.…”

Review of the Advanced LIGO gravitational wave observatories leading to observing run four

“…The interferometer is supported by several auxiliary subsystems required to detect gravitational waves. Auxiliary subsystems include the core optics length controls [17][18][19][20][21][22][23], angular controls [24][25][26][27][28][29][30][31], high-powered stabilized laser [32][33][34], vacuum system [35][36][37], optics suspensions [38][39][40], seismic isolation [41][42][43][44], and electronics and data acquisition systems [45][46][47][48]. This review will focus on the optical configuration and operation of the interferometers.…”

“…The lock acquisition process is coded using the Guardian finite state machine [47]. During O3 the lock acquisition sequence took roughly 25 minutes, but depends strongly on environmental factors including seismic activity and wind speed [8].…”