This afternoon we performed some temperature scans of the OMC1 while the interferemoter was locked on the dark fringe in low noise 1. The goal was to check the content of the dark fringe beam.

A first scan was performed while the usual DARM offset: Start at 16h06 utc - End at 16h25 utc (see Fig.1)

A second scan was performed with an opposite DARM offset: Start at 16h37 utc - End at 16h57 utc (see Fig.2)

One can see in Fig.3 a full FSR for the two scans superimposed.

Aside from the fact that the power in the carrier TEM00 was larger with the opposite DARM offset (see entry 41844), the two scans are qualitatively similar.

A careful analysis of the HOM present in these scan remains to be done.