During yesterday evening shift (Nov 13), we worked on 2 topics: we checked the DIFFp TY signal symmetry with the OMC now better aligned (see results posted in entry 43571), and we worked on the OMC lock acquisition on single bounce beam.

Here is the list of measurements performed:

LOW NOISE 3:

• At 16h34m46 UTC we put an offset of +10 um in the SDB1_B5_QD2_H error signal which displaced the bench in TY by about +1.5 urad. The transition to this new angular position was achieved towards 16:37:05 UTC. Starting from this time we collected about 2 Min of data with an on-going scan of the DIFFp TY degree of freedom.

• At 16:41:34 UTC the SDB1_B5_QD2_H offset was put back to 0, and another scan of the DIFFp was started. However the ITF unlocked about  ~1 min after the beginning of this measurement.
• Low noise 3 was finally recovered and around 20h42 UTC we took another ~2 min of data with the scan on the DIFFp, and SDB1_B5_QD2_H offset to 0. ITF unlocked again at the end of the measurement.

SINGLE BOUNCE BEAM:

Michal fixed the OMC lock acquisition on the single bounce beam, and we could test it once successfully.

Then a scan of OMC1 was performed  at 21:37:40 (2 min) in order to recheck the misalignment defect and mode mismatch (see attached Figure). Peak power was 11.8 mW on TEM00, 0.12 mW on 1st order mode (only 0.06 mW after subtraction of the tail of the TEM00), and about 0.1 mW on the 2nd order mode. This corresponds to about 0.5% of misalignment defect, and a bit less than 1% of mode mismatch between the single bounce beam and the OMC1.