Abstract:
In-vac health check of ITMX BF stage was done.
The suspension mechanical transfer function at vacuum condition is not significantly changed from that at atmospheric pressure.

Detail:
Figure 1 to 6 shows the TF of BFL, BFT, BFV, BFR, BFP, BFY, respectively.
We can observe the small sprious coupling at high frequencies in TF of BFT but it is probably fine (in fact, it was there even before vacuum evacuation).
Also, the other DOF, including coupling, is not changed due to vacuum evacuation significantly.

Then, I made new suspension model for BF stage.
Figure 7 to 12 shows the model of BFL, BFT, BFV, BFR, BFP, and BFY, respectively (model: red, measured blue).
These models are stored at FM10 (SUSMod_220114) of each filter bank at BF_DAMP.
The model was based on the TFs measured on 14 of January, which are stored at /kagra/Dropbox/Measurements/VIS/PLANT/ITMX/2022/01/PLANT_ITMX_STANDBY_BF_TEST_{L,T,V,R,P,Y}_202201141937.xml.