New Optical Layout plan

The optical layout in the central part will be changed significantly to house folded recycling cavities. The current layout plan is posted here. [attachment:40mUpgradeOpticalLayoutPlan01.pdf]

The beam size indicated by the three parallel lines in the drawing is 1" diameter. This is larger than the actual beam size. The waist size of the arm cavity is about 3mm (1/e^2 radius) and the Rayleigh range is about 27m. The beam path length inside the central part is less than the Rayleigh range. So the beam size is less than 4.2mm. If the beam is not clipped within the 1" diameter, the power loss is far less than 1ppm.

Here is the Mathematica notebook I wrote to calculate various parameters for the new recycling cavities. [attachment:NewRecCav.nb]

The PDF version is here: [attachment:NewRecCav.nb.pdf]

This notebook explains how the cavity lengths, recycling mirror ROCs, PRM reflectivity are chosen.