KAGRA Logbook

Reports 1-1 of 1

VIS (OMM)

takafumi.ushiba - 21:17 Friday 21 June 2024 (30057)

Health check of OSTM

I performed OSTM health check.
Figure 1-7 show the TFs from each DoF.

Compared with the TFs in 2023 (klog25967), phases are flipped.
Though phases are flipped now, they seem correct phase, which means phase in previous measurement was flipped from the nominal ones.
So, they seems fine.

Note:

Though current actuator signs are correct locally, actuator signs were flipped from the ones during O4a.
So, OMC ASC signs should be flipped, so it is necessary to treat ASC signs.

Images attached to this report

30057_1718971992_Screenshot from 2024-06-21 21-08-25.png

30057_1718971994_Screenshot from 2024-06-21 21-08-33.png

30057_1718971997_Screenshot from 2024-06-21 21-08-42.png

30057_1718971999_Screenshot from 2024-06-21 21-08-50.png

30057_1718972001_Screenshot from 2024-06-21 21-09-00.png

30057_1718972003_Screenshot from 2024-06-21 21-09-10.png

30057_1718972005_Screenshot from 2024-06-21 21-09-17.png

Comments to this report:

ryutaro.takahashi - 20:28 Thursday 14 November 2024 (31639)

[Ushiba, Takahashi]

We went to a health check of OSTM suspension.
Figures 1-7 show the TFs from each DoF.

Compared with the TFs measured last time, the DC gains were reduced by about -2dB. The coherence of the H4 TF was low around 10Hz.

Images attached to this comment

ryutaro.takahashi - 17:02 Monday 18 November 2024 (31675)

This is a consideration of the low coherence in the H4 TF around 10Hz. There are some possibilities.

The TF gain was about 5dB smaller than the last measurement. The low coherence is due to low SNR.
The pitch TF of the last measurement has a well-damped resonance at 8Hz. The low coherence is due to changed damping conditions in the IM stage.
The low coherence is due to parasitic resonances from the upper structures excited by natural disturbance.