Adv. LIGO Arm Length Stabilisation Design

Document #:

LIGO-T0900144-v4

Document type:

T - Technical notes

Abstract:

The design of the arm length fluctuation system. This system aids in the lock acquisition of the interferometer by stabilising the arm cavity length fluctuations to within ~1.3 nm.

Files in Document:

• T0900144_v4_ALS_Design.pdf (1.2 MB)

Topics:

• Final Design
• Sensing and Control

Authors:

• Sam Waldman
• Daniel Shaddock
• Bram Slagmolen
• John Miller
• Peter Fritschel
• Adam Mullavey
• David McClelland

Notes and Changes:

- Removed the approach section to reduce repetition.
- Inserted transmission table 2.
- Section 3.2.1, change the dynamic range from
1 um_pk to +-5 um (e.g. 10 um peak to peak).
- Included stable Quad feedback using the penultimate mass and the test mass only.
- Major reshuffle of the sections.
- Made the Quad VCO locking strategy the baseline locking approach.