LIGO Document G1500456-v4

CARM / ALS Electro-Optical Controls Diagram

Document #:
LIGO-G1500456-v4
Document type:
G - Presentations (eg Graphics)
Other Versions:
LIGO-G1500456-v2
06 Mar 2018, 13:53
LIGO-G1500456-v1
26 Aug 2017, 15:08
Abstract:
The CARM / ALS system is arguably one of the most complicated control systems in the LIGO IFOs, and spanning the most subsystems. A combination of ISC, PSL, IOO, CDS, and ALS, designed and documented by many, it's rare to get the "whole" picture on one page. Not mention it has evolved constantly as both sites commissioned their lock aquisition sequence. This is my attempt to capture it all, as a post-published supplement to P1400105.

Note that all RF frequencies have been rounded for legibility and compactness. Check out referenced documentation for exact frequencies.

-v4 REDLINES
  1. The connections to the summing node are out of date (and confusingly labeled). For LHO, as of the addition of a second REFL LSC PD (ECR E1800316) the connections match the wiring diagram D1900511-v12; the REFL AIR PD has been depricated, and the summing node connections are
    • A IN1 -- TR CARM (the sqrt(TRX+TRY) signal that's in "2b" in -v4)
    • A IN2 -- In-Vac REFL A (the f_{REFL}^{VAC} signal that's in "1b" in -v4)
    • B IN1 -- ALS COMM (the blue COMM signal that's in "1a" in -v4)
    • B IN2 -- In-vac REFL B (the f_{REFL}^{AIR} signal that's in "2a" in -v4)

    LLO's connections are unclear to the author as of 2025-12-11.
Topics:
Referenced by:

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