Describe LCGT/subgroup/ifo/ISC/TaskList/SpatialMode/SpatialModeDesign here.
Preliminary (base) desisn of folded stable cavities
The task is to determine the locations and the ROCs of the folding mirrors given the following constraints.
The boundary conditions for the design of the folded RCs are the following.
- The TEM00 mode in the RCs should match the arm cavity modes.
- Out of 73m of the RC length, 25m should be allocated between the BS and the ITMs for radiation shield.
- The Gouy phase shift in the RC (one-way) must be about 20deg.
- The beam spot sizes on the optics should not be too small (what is the tolerance ?).
- The incident angle of the beam to the folding mirrors should be as small as possible, to avoid astigmatism (1deg max).
- There is a minimum distance between two optics (e.g., the PRM and PR2) coming from the size of the SAS.
Design of folded stable cavities
ROC_ERROR_v2.pdf (revised on 2010-07-14)
Design of unfolded stable cavities
Current design of marginally stable cavities
Some limitations in the view of vacuum and seismic attenuation group
- maximum beam shift
- minimum tank separation
Higher order mode check
Higher order modes of the arm cavities should not overlap with sidebands and their harmonics.
This was checked here.
Old (current) layout of vacuum tanks