Advanced LIGO stable recycling cavities
by
Stefan Hild
—
last modified
2008-08-30 20:21
A brief collection of the ALIGO design parameter can be found on this page.
The values collected on this page are taken from the following two LIGO notes:
- LIGO E080033-00-D: "Core Optics Components Preliminary Design" (ROCs, beam sizes, substrate dimensions)
- LIGO T080078-00-D: "Stable Recycling Cavity Mirror Coordinates and Recycling Cavity lengths" (distances and lengths)
Mirror ROCs
- PRM1 = 8.95m
- PRM2 = -2.335m
- PRM3 = 35.048m
- SRM1 = 107.29m
- SRM2 = -2.155m
- SRM3 = 35.048m
- ITM = 1973m
Mirror dimensions
- PRM1, PRM2, SRM1, SRM2 = 150x75mm
- PRM3, SRM3 = 265x100mm
Beam sizes
- ITM = 55.5mm
- SRM3, PRM3 = 56.5mm
- SRM2, PRM2 = 3.4mm
- SRM3, PRM3 = 1.85mm
Distances
These values are derived from page 17 of LIGO T080078-00-D. I didn't take any lateral beam position change inside the recycling cavities into account. For the PR cavity I only took the X-coordinates into account, while in the SR cavity I only looked at the Y-coordinates. Therefore the lengths given on this wikipage are not very accurate. However, since the lateral position shift between the individual recycling mirrors is of the order tens of centimeters, the given values should not be wrong by more than half a meter or so.- BS-HR => ITMX about 8.8m
- BS-HR => ITMY about 8.8m
- BS-HR => PRM3 about 19.8m
- PRM3 => PRM2 about 15.0m
- PRM2 => PRM1 about 15.8m
- BS-HR => SRM3 about 20.2m
- SRM3 => SRM2 about 16.3m
- SRM2 => SRM1 about 15.6m
For comparison the values given in the original LIGO note are 60.4m for PRC length and 62.1m for SRC length 62.1m. This discrepancy of about 1m each originates from the fact that I first didn't take the BS and the ITM substrate into account and second also neglected any lateral beam shift.