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
Input Optics

Advanced LIGO News

Small Optic Suspenions Enter the L1 Interferometer

[IO]When LIGO's laser light first enters the vacuum system, the light undergoes purification in a 14-meter mode cleaner cavity. The beam experiences an increase in diameter after leaving the mode cleaner by interacting with several suspended optics in a system known as a mode-matching telescope. The resulting light, stripped of undesired modes and sized for entry into the main interferometer, is named input light. LIGO Livingston Observatory has completed the installation of the L1 input optics chain.

[IO]Unlike the large optic (core optic) suspension frames that consist of numerous joined parts, the frames for Advanced LIGO input optics (small optics such as those in the mode cleaner) are single welded units. In other respects, the small optic suspensions resemble their larger counterparts in design and functionality. Blade springs at the top of a suspension provide vertical vibration isolation. Voice-coil actuators similar to those used in Initial LIGO populate the all three stages of the suspension. The face of a small suspended optic possesses tiny glued-on magnets that protrude into copper coils for magnetic force actuation similar to the Initial LIGO system. Thin wire loops suspend one stage from another.

[IO]Small optic suspensions such as those in the mode cleaner cavity occupy vacuum chambers known as Horizontal Access Modules (HAM's). A pair of HAM's along the input arm, between the laser and the beam splitter, contain the input optics system, a dense array of hardware that includes the mode cleaner and mode-matching optics along with other components such as a Faraday isolator to prevent light that's leaving the interferometer to pass back into the main laser. The left photo shows the contents of an input HAM. Nearly all of the aLIGO input components require more table space than their Initial LIGO predecessors. The implementation of a chain of power recycling optics in aLIGO instead of a single power recycling mirror as before creates an entirely new 14m reflected path parallel to the mode cleaner path. These factors create the need for additional in-vacuum width between the input HAM's, a need that aLIGO previously addressed by replacing the exisitng 86cm diameter input tube sections with 213cm diameter tubes.


      Using an installation arm to install a small optic suspension


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