We've tested a new tripod mounting system for the magnetometers with aims to decrease artifacts from motion of the magnetometer on the tripod. The iLIGO mounting scheme resulted in peaks in the magnetometer spectra that were not from real magnetic fields but from the magnetometer moving in the earth's field at tripod resonances. We tap tested both tripods to study their resonances and damping. The flagpole resonance of the current tripod is at 7.9 Hz. The new system, designed at Cal State Fullerton, is more damped and rigid. 

Attached is the power spectrum of both setups, side to side (see photo). The red trace is the magnetometer mounted on the current tripod, the blue trace is the magnetometer mounted on the Fullerton prototype tripod. The flagpole resonance of current tripod is seen at 7.9 Hz, the one place the blue Fullerton trace does not follow. Most other peaks seen are from nearby cleanroom fans and the expected 60 Hz. 

Terra, Robert