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|
Subsystem: Interferometer Sensing and Controls
This subsystem comprises the length sensing and control, the alignment sensing and control, and the overall controls coordination for the Advanced LIGO interferometer design. The most significant differences in the Advanced LIGO subsystem are the addition of the signal recycling mirror and the resulting requirements on its controls, the addition of an output mode cleaner in the output port, the implementation of homodyne, or DC, readout of the gravitational wave channel, and the use of stable optical cavities for the power and signal recycling cavities. In addition, a pre-lock length stabilization system is implemented to render the locking process faster and more predictable.
In Advanced LIGO, all of the detection will be performed in vacuum with photodetectors and auxiliary optics mounted on seismic isolation systems. This will avoid the influence of air currents and dust on the beam, and minimize the motion of the beam with respect to the photodiode. Alignment sensing and control (ASC) will be accomplished by wavefront sensing techniques similar to those employed in initial LIGO. ASC will play an important role in managing the potential instability in angle brought about by photon pressure if exerted away from the center of mass of the optic. The greater demands placed by optical powers and sensitivity are complemented by the improved seismic isolation in Advanced LIGO, leading to similar demands on the control loop gains. In general, the active isolation system and the multiple actuation points for the suspension provide an opportunity to optimize actuator authority in a way not possible with initial LIGO.
Additional Controls Photos
Explore Advanced LIGO
Instrumentation and Astrophysics
An Overview of the Upgrades
The International Partnership
LIGO Technology Transfers
LIGO Scientific Collaboration