This entry reports the behavior of the BF and IM-V transfer functions at frequencies above several Hz. As shown in the first picture, in the case of BF the transfer function stops decreasing at about 7.5 Hz and after a resonance at 11.4 Hz it begins to increase. In the second picture it is possible to see the same resonance in the IM-V transfer function, but the increase happens until 47 Hz. For the BF case the measurement with the cable disconnected is also depicted. In the case of IM-V the picture also shows the measurement with the IM-V1, IM-V2 and IM-V3 cables disconnected and yet a third measurement with the satellite amplifier disconected from the rack.

The third and fourth pictures show the amplitude spectral densities corresponding to the transfer function measurements. In both devices the noise levels are lower than the displacements and, therefore, do not explain the increase of the transfer functions. The measurements that might be able to provide useful information would be that of the transfer functions with the IM and BF keystone locked. In such cases an assessment of the electromagnetic pick up from the actuation coils into the readout would be possible. However, it's not possible to lock the BF within the vacuum chamber. See, for example, entry 7500 where this type of measurement is reported for the F0 filter.

Files:

• Directory: /users/enzo/SRM_insidetank/
• SRM_BF_GAS_20181225.xml
• SRM_IM_V_20181227.xml