Advligorts: The Advanced LIGO real-time digital control and data acquisition system

Rolf Bork,Jonathan Hanks,David Barker,Joseph Betzwieser,Jameson Rollins,Keith Thorne,Erik Von Reis

doi:10.1016/j.softx.2020.100619

Abstract

The Advanced LIGO detectors are sophisticated opto-mechanical devices. At the core of their operation is feedback control. The Advanced LIGO project developed a custom digital control and data acquisition system to handle the unique needs of this new breed of astronomical detector. The advligortsis the software component of this system. This highly modular and extensible system has enabled the unprecedented performance of the LIGO instruments, and has been a vital component in the direct detection of gravitational waves.

Highlights

The advligorts software consists of three primary components: a patched version of the standard Linux kernel, a real-time code generator (RCG), and a suite of data acquisition daemons (DAQD)
The data acquisition daemon provides a Network Data Service (“NDS”) which can be used to access all data acquired by the system in real-time, or to access archival data that has been stored to disk
The Japanese project KAGRA [13] has adopted the full Advanced LIGO digital control and data acquisition system for control of their underground gravitational wave detector. advligorts is used in the GEO 600 project, the Caltech 40m prototype, the MIT LASTI prototype, the AEI 10m prototype, as well as in dozens of smaller laboratories around the world to control a variety of table-top opto-mechanical experiments

Summary

Motivation and significance

The development of long baseline gravitational wave detectors over the last 40 years has been of groundbreaking scientific impact. While prototype interferometer gravitational wave detectors paved the way, their relative simplicity could not provide a clear roadmap for the ultimate design of the LIGO detectors. This was true for the interferometer feedback control systems at the core of the instruments’ operation. The feedback controllers needed to be flexible to account for uncertainty in the final feedback control scheme This motivated a critical decision early in the LIGO design process: to use digital instead of analog feedback control. At the time, it was unclear if digital control was feasible for this application. EPICS provides a standard interface for operator interfaces (LIGO uses the “MEDM” GUI tool) and supervisory control, such as guardian, the Advanced LIGO automation platform [? ]

Software Architecture

Illustrative Examples

Impact

Conclusions and future development