Advanced LIGO subsystems
are the organizational units of the overall project. Follow the links below to view the mission and progress of each subsystem.
Auxiliary Optics | Core Optics |
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Data Acquisition | Data and Computing Systems |
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Facilities Modifications |
Input Optics |
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Interferometer Control |
Pre-Stabilized Laser |
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Seismic Isolation |
Suspensions |
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Advanced LIGO News
Arm Length Stabilization Takes Shape
May 2013
Arm length stabilization (ALS) refers to the LIGO detector subsytem that will bring the long detector arms to a controlled and quiet state, ready to integrate into a fully controlled interferometer in which the light resonates in all parts. New for Advanced LIGO, ALS has required extensive installation at the Livingston and Hanford sites. These installation activities are nearing completion at Hanford and will continue at Livingston into 2014 as LLO completes work at the detector end stations. The key parts of ALS include 1) An out-of-vacuum table at each end station on which a green laser will inject light into the vacuum; 2) An in-vacuum transmission monitor suspension at each end station that routes the green light through the neighboring end test mass (mirror - ETM) and toward the inner test mass (ITM) 4km away; 3) a set of optics in HAM 1, the vacuum chamber in the corner station that's next to the main laser enclosure, that will reflect each arriving long-arm green beam through a viewport and out of the vacuum onto (4) an optical table adjacent to HAM 1 that receives and processes the green beams from each arm; 5) Hardware on the main laser table (photo above) that directs a small portion of the main laser beam into HAM 1 where it's changed to green and compared to the green light from the arms, and 6) Equipment that directs another portion of the main beam into a pair of 4km optical fibers where it travels to each end station and serves to synchronize the green beam that was mentioned in (1).
The in-vacuum ALS transmission monitor (shown on a test stand in the adjacent photo) fastens to the underside of the large-chamber vibration isolation platforms (ISI's) in the same manner as the nearby end test mass large optic suspensions -- a single ISI bears the load of both units. HAM 1's tip-tilt mirrors and other optical components don't require a level of vibration isolation that necessitates an ISI; their isolation specifications are a bit more relaxed. LIGO then chooses to deploy Initial LIGO passive vibration isolation stacks in HAM 1 of each detector (photo below right). HAM 1 represents the only re-use of HAM passive stacks in Advanced LIGO.
ALS exists to facilitate rapid and reliable locking of the advanced detectors. Once locked, the interferometers won't use the out-of-vacuum ALS photodiode signals. Better-isolated in-vacuum sensors will take over and provide the angle-sensing and length-sensing control signals needed to maintain the resonating detector on its high-sensitivity operating point.
Beam diverters awaiting optics
aLIGO News Archive
August 2016 -- LIGO Reports O1 Results
June 2016 -- Another Black Hole Merger
Feburary 2016 -- First Gravitational Wave Detection
November 2015 -- O1 Progress Report
August 2015 -- Final Preparations for the O1 Run
February 2015 -- Hanford's H1 Achieves Two-Hour Lock
July 2014 -- Livingston Commissioning Progress
June 2014 -- Livingston Locks the L1 Interferometer
December 2013 -- Livingston Installs End Station Payloads
September 2013 -- Half-interferometer Test Closes
June 2013 -- DRMI Test at Livingston
May 2013 -- Arm Length Stabilization
November 2012 -- One-arm Test at Hanford
September 2012 -- LIGO Begins Locking Optical Cavities
August 2012 -- Installation of Stray Light Controls
July 2012 -- Small Optic Suspenions Enter L1
April 2012 -- First Cartridges Enter the Vacuum
November 2011 -- Glass Fiber Suspensions in Production
October 2011 -- Continued Suspension Development
July 2011 -- Hanford's H2 Becomes a 4K
May 2011 -- LLO Laser Installation Completed
March 2011 -- Input and Output Tubes Undergo Removal
February 2011 -- New Laser Enclosure Takes Shape
December 2010 -- Initial LIGO Comes Out of the Vacuum
October 2010 -- S6 Yields to Advanced LIGO
Explore Advanced LIGO
Construction Schedule
Instrumentation and Astrophysics
An Overview of the Upgrades
The International Partnership
Science Impacts
LIGO Technology Transfers
LIGO Scientific Collaboration
Public Outreach
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