Low Frequency - High Sensitivity Horizontal Inertial Sensor based on Folded Pendulum

This paper describes a new implementation of monolithic horizontal sensor, developed at the University of Salerno, based on the Folded Pendulum architecture, configurable both as seismometer and as accelerometer. The large low-frequency band (10-6 ÷ 10 Hz), the high sensitivity (10-12 m/sqrt(Hz) in the band 0.1 ÷ 10 Hz) and the high quality factor in air (Q > 1500) are largely better than all the previous Folded Pendulum implementations. Moreover its monolithic implementation of the whole mechanics, coupled with a full tunability of its resonance frequency (70 mHz ÷ 1.2 Hz) obtained with a specially designed calibration procedure and with an integrated laser optical readout, guarantees both compactness, robustness and immunity to environmental noises. This makes this sensor suitable for a large number of scientific applications, also in high vacuum and cryogeny. Applications of this sensor are already started in the field of geophysics, including the study of seismic and newtonian noise for characterization of suitable sites for future underground interferometric detectors of gravitational waves.