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hirose.chiaki - 17:40 Friday 17 November 2023 (27658) Print this report
Placed dark offset on POP WFS QPDs and replaced the gain double Dsub-BNC converter for POP DC centering loop

[kTanaka, Hirose]

This is continued from klog27045.

In order to get the full range of the PZT, the amplification of the power supply of Dsub-BNC converter should have been doubled.
However this Dsub-BNC converter(S2214287)that it was used for POP DC centering loop was not modified. 
So another Dsub-BNC converter( S2214289) was modified and replace with this.

And for placing dark offset of POP WFS QPDs, we measured this with the shutters closed. (FIg1)
In this case, we did it with the PRM in the state "MISALIGNED_BF". (FIg2,3) ("MISALIGNED_BF" is state for reflected light from misaligned PRMs to hit the beam dump in the IMMT2 chamber. )
After this, the offsets was placed.(FIg4)

We put the 75 V offset in the DC centring loop of the POPWFS to see if the movement is doubled. The movement has doubled compared to before.

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takafumi.ushiba - 9:19 Monday 20 November 2023 (27672) Print this report

In this morning, POP PZT for POP WFS2 PIT is not working well (fig1).
So, e need to investigate what happened.

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takafumi.ushiba - 11:33 Monday 20 November 2023 (27673) Print this report

[kTanaka, Ushiba]

We checked PZT driver and found that the one of the PZT driver output was about 4V though al PZT driver output should be around 75V.
After that, we disconnected the PZT for POP WFS2 PIT and see the output: then, the output became about 75V.
So, it is very likely that one of PZTs is short electrically.

Though we looked for the spare of mirror mount with PZTs, we could not find it, so we keep the PZT disconnected ad turn off the PZT feedback for temporal measure.
We will soon purchase new mounts and recover it after the delivery.

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