The two chillers are located in the Building interstice just out of the TCS room. For the purpose of seismic isolation they have been put onto isolating supports. Indeed, the noise seems not to transmit as floor vibration (as shown in Figure 1, the seismic signal on floor is at least 100 times less intense and below the instrument intrinsic noise). We would thus forced to suspect that the vibration reaches the TCS benches through the coolant pipes, which might be carried either as vibration of the pipe itself or the fluid.
In order to definitely identify the source we shall install one accelerometer probe on the chillers. Mitigation actions shall be evaluated.
