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|
Advanced LIGO News
Livingston Places the End Mirrors, Nears Completion of aLIGO Installation
Advanced LIGO personnel at LIGO Livingston (LLO) are now undertaking the final major installation activity on the site's aLIGO installation schedule, the insertion of the mirrors and supporting equipment at the ends of the L1 detector's long arms. Once the end station vacuum chambers (BSC's) receive their payloads, LLO will seal the vacuum system and begin commissioning the full interferometer as LIGO continues to point to 2015 for the first data run of LIGO's advanced detector era. By design, Livingston leads Hanford (LHO) in the aLIGO schedule by several months; LHO anticipates vacuum closure in the summer of 2014.
LLO has rebuilt L1 on the path that the light takes into the detector, starting with the main laser system (PSL) and then moving to the input optics (input mode cleaner and power recycling chain), the output optics (signal recycling chain and output mode cleaner), and the beam splitter and inner test masses. In addition to these principal pieces, a large number of auxiliary components required time and attention in the schedule such as stray light controls (baffles), global controls optics and electronics such as angle-sensing and length-sensing instrumentation, auxiliary control systems like optical levers and thermal compensation, calibration hardware (in the adjacent photo) and the software capability to integrate and optimize the subsystems.
In November 2013 the LLO teams inserted the X end station "cartridge" into the vacuum. The cartridge consists consists of the vibration isolation platform, the transmission monitor suspension and the large optic (end test mass) suspension. View the suspensions inthe adjacent photo. Shortly after installation, the X arm was brought into resonance with green light (see photo below). Small errors in pointing could cause commissioners to spend considerable time trying to find the beam spot after it travels 4km; LIGO personnel didn't need to play the beam-hunting game very long on L1's X arm before steering the beam onto its target optic and improving the alignment to obtain an arm locked on a resonant state.
As LLO now moves to the completion of the remaining end station, combinations of crews continue to step through a lengthy list of tasks on the way to placing the Y end cartridge in the vacuum. 1) The internal seismic isolation platform (ISI) needed to make the 4km trip from its assembly area near the corner station to the end of an arm and onto a test stand in the end station vacuum equipment area. 2) The large optic end test mass suspension likewise migrated to the end station onto another test stand. The ISI and suspension must undergo full testing on their test stands. 3) The large optic suspension then moves to the underside of the ISI. 4) The suspension then undergoes a partial breakdown to permit the replacement of metal placeholder masses with the glass masses, including the hanging of the mirror (ETM) from the upper glass mass by welded glass fibers. 5) The transmission monitor suspension, having been assembled in a clean lab at the end station, moves onto the ISI adjacent to the large optic suspension. 6) The completed cartridge, wrapped in shed-free fabric for travel, will then ride the crane into the vacuum chamber, where it will undergo additional testing before crews open the light path along the arm.
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