There has been some development work on a new metal triangular mode cleaning cavity (a la PMC) to be tested out in bridge (initially in the CryoLab).

= What can a PMC to do?  =

* Acts as a (poor) length reference if we lock to it
* Filters out the laser noise above the pole of the cavity
* Gives a fixed reference point for the beam pointing and location w.r.t. the optical table
* Turns beam jitter and frequency noise into intensity noise
* Can be mounted on a base so that you can remove and replace it very accurately

== Some Questions One Might Ask ==

* The initial LIGO PMC