When the spare is not a spare... The IMC wouldn't lock. I opened the original IMC servo and it has the fast option installed, whereas the spare has not; see alog 29250. The modifications were applied to the original board. Then, the original chassis was put back in.
Also, noticed that some of the modifications were already applied, see alog 31138. However, this was never propagated to the e-traveler.
daniel.sigg@LIGO.ORG - 16:34, Tuesday 19 March 2019 (47682)
Here is the comparison with the previous version measured in alog 47485.
There is a significant improvement in IMC_I. The error signal now looks like it is limited by converter noise below 2 kHz. Strangely, there is a set of peaks around 2.5 kHz that are not in IMC-L or IMC-F. There is some loss of coherence between IMC-F and IMC-L between 1 and 10 Hz. This seems again converter noise in IMC-F.
When the spare is not a spare... The IMC wouldn't lock. I opened the original IMC servo and it has the fast option installed, whereas the spare has not; see alog 29250. The modifications were applied to the original board. Then, the original chassis was put back in.
Also, noticed that some of the modifications were already applied, see alog 31138. However, this was never propagated to the e-traveler.
Here is the comparison with the previous version measured in alog 47485.
There is a significant improvement in IMC_I. The error signal now looks like it is limited by converter noise below 2 kHz. Strangely, there is a set of peaks around 2.5 kHz that are not in IMC-L or IMC-F. There is some loss of coherence between IMC-F and IMC-L between 1 and 10 Hz. This seems again converter noise in IMC-F.
Full bandwidth spectrum.