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

Initial LIGO Input and Output Tubes Undergo Removal

Photos courtesy of Rodney Haux

[news]A LIGO interferometer forms the familiar enormous "L," but each segment of the L projects for two dozen meters on the opposite sides of the vertex where the beam splitter rests. One of these projections forms the input side of the detector; laser light approaches the beam splitter along this line. The perpendicular output line carries the interference pattern downstream from the beam splitter to the sensing photodiodes. On the input side, Initial LIGO (iLIGO) laser light entered the vacuum from the PSL and traveled through a mode cleaner cavity and a set of mode-matching telescopes that increased the beam diameter. The light then passed through a power recycling mirror before reaching the beam splitter. The path on the output side was simpler, although it became more complex in Enhanced LIGO due to the insertion of an output mode cleaner in the terminal chamber along the output line.

Advanced LIGO (aLIGO) will employ input and output (IO) beam paths of greater complexity. The sizes of aLIGO optics and their suspensions along these paths will increase in comparison to similar iLIGO parts. The IO beams themselves will increase in diameter over iLIGO. These changes will require beam tube segments of greater diameter along the IO beam lines. The photos below show the removal of an Initial LIGO output tube segment to make way for its wider replacement. The length of the tube created several challenges for the extraction crews as they craned the unit through the Laser Vacuum and Equipment Area (LVEA). Approximately 3000 pounds, the tube eventually made its way outside the building then off-site for recycling. The new tubes will arrive from the manufacturer clean and baked and ready for installation once received at the Observatories.

Image 1:  View of the H2 output tube looking towards the beam splitter.

Image 2:  Loosening the O-ring.

Image 3:  Sliding in the temporary chamber cover.

Image 4:  This HAM chamber will wait for the new tube.

Image 5:  The view from 90 deg clockwise. The H2 input tube appears on the right.

Image 6:  The tube on its way out of the LVEA.

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