KAGRA Logbook

Reports 1-1 of 1

VIS (PRM)

takafumi.ushiba - 13:56 Monday 17 June 2024 (29936)

In-vac health check of PRM

I performed health check of PR2 and found strange behaviour.

Figure 1 shows the TF from BFGAS EXC to BFGAS.
The resonant peak at 0.3 Hz are disappeared, so suspension seems touching somewhere.

Figure 2 shows BFY EXC to BFY.
One of two resonances is disappeared and resonant frequency is shifted.
So, this TF also implies the suspension is touching somewhere.

However, TF from IMY EXC to IMY seems healthy (fig3).
Since IM TF was measured in TWR_FLOAT state, GAS position is different from the one during BFY TF measurement.
So, the situation would be recovered by offloading SF and BF GAS filters.

Images attached to this report

29936_1718598573_Screenshot from 2024-06-17 13-28-59.png

29936_1718598682_Screenshot from 2024-06-17 13-21-48.png

29936_1718599562_Screenshot from 2024-06-17 13-23-44.png

Comments to this report:

takafumi.ushiba - 11:04 Wednesday 19 June 2024 (29983)

After offloading GAS filters, suspensions seem fine.
Figure 1-33 show the TFs of each DoF excitation.

Note that IMH1 and IMV2 OSEM efficiency becomes slightly smaller because they are close to the edge of the linear range but maybe acceptable.
Figure 34 and 35 show the OSEM inputs when performing in-air health check and in-vac health check, respectively
If you would like to recover the situation, I think we can use same procedure as PR2 (klog29918) and moving BF pitch to save IMH1 OSEM.

Images attached to this comment