KAGRA Logbook

Reports 1-1 of 1

MIF (ASC)

hirose.chiaki - 14:47 Tuesday 03 October 2023 (27045)

The PZT offset in the DC centering loop of the POP WFS was off, so this was turned on and offloaded by the PICO motor.

[Hirose, Tanaka, Ushiba]

We noticed that PIT direction of PZTs(PZT1, PZT2) for DC centering loop of POP_WFS(RFQPD) were satilated.
We checked and found that the PZT offset "75V" for PZTs (PZT{1,2}_{PIT,YAW} direction) was not turned on. This offset "75V" is in the middle of the movable range of the PZT, so we need to put an offset”75V” in the digital system to set the 0 reference of the DCcentering loop to 75V.
We turned off the DCcentering loop of POP_WFS (PZT{1,2}_{PIT,YAW}) and with the offset "75V" in PZT. We offloaded the PICO motor so that the beam is centered on QPD1,2.
After that, We was able to engage the DCcentering loop successfully.

Comments to this report:

hirose.chiaki - 11:27 Friday 13 October 2023 (27168)

We noticed today that something similar was happening. We checked again and found that the offset was switched off during last Wednesday's model update.
WFS_PZT in POP is directly connected to ASC0, unlike WFS_PZT in REFL and AS, so it is likely that the offset was turned off when the model was updated.
We added "PREPARE_FOR_POP_PZT(3)" to the ASC_LOCK guardian. It will turn on OFFSETs every time ASC is attempted.

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