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

One-Arm Test Yields Encouraging Results

[tms]LIGO Hanford's one-arm test closed in September 2012 with its primary goals successfully completed and with a storehouse of results that will guide future installation and commissioning. The LIGO commissioning team tasked with the test obtained a substantial list of outcomes, some highlights of which included the following.

[ey_los]The one-arm test didn't exercise some of these systems to their fullest degree and plenty of additional commissioning lies ahead. The ITM and ETM hang in four-stage suspensions that provide noise cancellation at each stage (adjacent photo), but only a subset of the controls were deployed to stabilize the mirrors. The green laser light injected at the end station wasn't synchronized to the main (infrared) laser in the corner station as will be the case for future tests. Instead, a spare infrared laser and reference cavity in the corner station sent light through a 4km optical fiber to the end station, where it was converted to green. Noise on the light from the reference system and the optical fiber was visible at higher frequencies throughout the test. Seismic noise clearly manifested itself at frequencies below 1 Hz; a more complete mitigation effort will include additional feedback that becomes available when the full arm length stabilization controls enter the mix over the next year.

Hanford will next undertake a half-interferometer test on the Y arm (HIFO-Y) that will include all of the one-arm components plus the main laser, the suspended mode cleaner and the power recycling optics that lie between the laser and the beam splitter. Installation of these items is currently underway; watch for news of HIFO-Y in the summer of 2013.



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