KAGRA Logbook

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VIS (PR2)

yuya.arai - 1:56 Friday 28 September 2018 (6335)

PR2 doesn't seem to be healthy too

Because PR3 seemed to be strange as I reported in 6291, I checked all PRs, PR2, PR3, and PRM. I measured TFs of V DoF of PRs and the result figures are shown below. The same DoF measurements are integrated in one figure (from left, PR2, PR3, PRM in each figure). From the results, I think PR2 is also unhealthy.

I also noticed BF GAS is very cyclic swinging shown in the last figure. The frequency is about 15 mHz and amplitde is about 60 um. There is no excitation signal of course. This swing continiues at least from a few days ago (I can't see second trend data further past day) . I think this is one of reason why PR2 TFs are not good because this swing amplitude is big, so the excitation signal might be buried when measuring TF of BF GAS.

One Notice : BF V of PRM cannot be measured because BF LVDT Driver is broken and waiting the repairing now.

Images attached to this report

Comments to this report:

yutaro.enomoto - 13:14 Friday 28 September 2018 (6337)

> I also noticed BF GAS is very cyclic swinging shown in the last figure. The frequency is about 15 mHz and amplitde is about 60 um. There is no excitation signal of course. This swing continiues at least from a few days ago (I can't see second trend data further past day) . I think this is one of reason why PR2 TFs are not good because this swing amplitude is big, so the excitation signal might be buried when measuring TF of BF GAS.

This behavior has started since I put some bias current to BF GAS. It is OK to remove this bias if you want; I put this so that I wanted to adjust the height.