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 |
![]() |
![]() |
Data Acquisition | Data and Computing Systems |
![]() |
![]() |
Facilities Modifications |
Input Optics |
![]() |
![]() |
Interferometer Control |
Pre-Stabilized Laser |
![]() |
![]() |
Seismic Isolation |
Suspensions |
![]() |
![]() |
Advanced LIGO News
Large Optic Suspensions and Vibration Isolation Systems Enter the Vacuum
April 2012
Multi-stage suspensions and noise-cancelling vibration isolation platforms represent two major thrusts of the Advanced LIGO program. Four-stage quadruple suspensions are the most complex of the aLIGO family of optic suspensions. These "quads" and the large optics that populate them will occupy the vacuum chambers that form the reflective boundaries of the four-kilometer arm cavities on each interferometer. Quad suspensions attach to the undersides of aLIGO vibration isolation platforms named ISI's (internal seismic isolation). The 3900kg ISI's can only enter LIGO's large vacuum chambers (BSC's) through the top of the chamber. Rather than lower the ISI into the BSC and then bring the quad through the side of the chamber for attachment, LIGO chooses to mate the quad to the ISI outside of the BSC. The photo above shows a quad/ISI assembly, known as a cartridge, resting on a test stand. Crews then then lower the entire wrapped cartridge into a BSC through the chamber top. LIGO has now accomplished two cartridge installations on the Hanford H1 detector.
The installation process must safely land the cartridge in the BSC while preserving the hardware alignments that assembly crews have taken great care to produce and verify. When inside the chamber, the large optic on the lowermost quad stage must rest within a millimeter of its position specification and within a milliradian of its angle specification. After the installation, LIGO's alignment specialists use precision surveying to assess the quality of the placement. The BSC ISI's consist of two suspended stages; this means that the large optics (also known as the test masses) are the terminal masses in a chain of six suspended stages. Alignment errors at any stage will take their toll on the final result.
Each of the several thousand suspension and ISI parts underwent cleaning and baking prior to inclusion in the assemblies. Cartridge installation must not degrade the clean state of the assemblies. HEPA-filtered air in LIGO's large instrument areas and portable clean rooms with additional filtering provide the main defense against particulate contamination. Shed-free custom-tailored fabric wraps protect the cartridge once the portable clean room moves aside to allow the craning to occur. All craning and rigging equipment must be free of contamination, including moisture and hydrocarbon contamination. The industrial scale of the cartridge installation creates challenges for the installation team at every step.
Now that LIGO Hanford has installed two cartridges at opposite ends of a single detector arm, the focus moves toward the single-arm test. Soon LIGO will send light from a green laser through the back of the mirror at the end of the arm. This light will need to strike the face of the inner cavity mirror four kilometers away, then resonate in the cavity during multiple reflections along the arm. LIGO's single-arm team will perform a variety of tests on the new Advanced LIGO hardware in both of these chambers to assess the performance of the suspensions, the vibration isolation systems and the control systems that regulate these components. The single-arm test represents a key intermediate stage on the path toward full interferometers.
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
LIGO Magazine
aLIGO Home