Advanced LIGO subsystems
are the organizational units of the overall project. Follow the links below to view the mission and progress of each subsystem.
Subsystem: Auxiliary Optics
Auxiliary optics include a number of systems that support the alignment, control and calibration of LIGO's gravitational wave interferometers. The unifying theme for the AOS work is in-vacuum optical layout and beam transport. AOS components include the following:
- Stray light control. In-vacuum baffles along the input path, output path and arm cavities will absorb stray laser light to reduce internal detector noise.
- Thermal compensation. The thermal compensation system (TCS) provides auxilliary heating on the arm cavity test masses (mirrors) to control their profile in the face of heating caused by absorption of the main interferometer beam. Ring heaters on the test masses will provide coarse heating. CO2 lasers will heat compensation plates which in turn will radiate heat to the test masses for fine control. TCS wave front sensing, a new feature in aLIGO, will improve TCS servo controls.
- Optical levers. Optical lever lasers and photodiodes create an alignment reference system that stabilizes the angular alignments of interferometer optics.
- Initial alignment procedures and equipment. High-precision surveying techniques will verify the alignments of seismic isolation systems and optic suspensions at the time of installation, ensuring the integrity of interferometer beam paths.
- Photon calibrator. Auxiliary laser beams, modulated at audio frequencies, will accelerate the test masses by known amounts via radiation pressure. Readouts of the resulting test mass oscillations will provide a means of calibrating the detector.
- Arm length stabilization. AOS will provide the suspensions for transmission monitors (part of the arm length stabilization system).
![[aos]](graphics/5166_20130118181106_IMG_1472_lho_tcs_ringheaters_baking_thumb.jpg)
TCS ring heater bake load
![[aos]](graphics/ReferenceMeasurement_WavefrontNoTilt_llo_ofi_thumb.png)
Output Faraday isolator measurement
![[aos]](graphics/21073pre_61446efddcd109e_hamaux_thumb.jpg)
HAM auxiliary suspensions
![[aos]](graphics/7094_20130715190830_blade_h1_ex_cpb_mount_thumb.jpg)
Cryopump baffle suspension spring
![[aos]](graphics/19322pre_65100249bb7943b_tcs_pm_thumb.jpg)
Thermal compensation picomoters
![[aos]](graphics/8238_20130809134845_IMG_0775_llo_ey_pcal_scope_thumb.jpg)
Photon calibrator periscope
![[aos]](graphics/Sep12103932AM_ring_heater_llo_thumb.jpg)
Ring heater on large optic
![[aos]](graphics/IMG_1462_llo_tcs_sm_thumb.jpg)
Covered TCS steering mirror
![[aos]](graphics/6723_20130612174903_XendInstall3_h1_pcal_scope_thumb.jpg)
Photon calibrator periscope
![[aos]](graphics/aos_ringheater_thumb.jpg)
TCS ring heater assembly
![[aos]](graphics/aos_oplevpier_thumb.jpg)
Optical lever pier
![[aos]](graphics/aos_mcbaffle_thumb.jpg)
Mode cleaner baffle installation
![[aos]](graphics/RS1046_00001_thumb.jpg)
Early TCS Hartmann sensor
![[aos]](graphics/aos_tcs1.jpg)
TCS ring heater
![[aos]](graphics/aos_tcs2.jpg)
Heat distribution on eLIGO ITM