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AdV-COM (AdV commissioning (1st part) )
Allocca, Chiummo - 23:33 Wednesday 23 January 2019 (44501) Print this report
ITF stuck at MICH_SET_0_1

Tonight we tried again the ITF recovery, but we experienced lots of IMC instabilities (this will be described in a dedicated entry).

The few times that the IMC was quiet and collaborative, we tried to go to LN1, but we could reach this state only once over 3 attempts, and the other two times we got stuck at MICH_SET_0_1 with the warning: "WAITING FOR PR ALIGNMENT TO BE STABLE".

Looking at the signals, there is something strange in the corrections of the PR (see attached figures). It seems that they are active for few seconds and then they go back to zero.

To be investigated by the experts.

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Comments to this report:
bersanetti - 1:57 Thursday 24 January 2019 (44504) Print this report

Looking at Figure 1 it can be seen that despite the PR loop was enabled (column 2), it was actually off (column 3) because the trigger was off; the trigger looks at the _Sum power of B1p_QD2 (column 4, bottom plot), which was below zero probably because of some issues with the Galvo loops of the QPD which were not closed (column 5). The spikes of the control signals sent to the DSP (column 1) were due to the trigger going occasionally above zero (zoom in Figure 2) for electronic/digital causes.

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