Negative stiffness module for highly sensitive low noise seismometer

Active vibration isolation systems rely on a true and low noise reference signal. For Einstein Telescope the lower limit of detection of vibrations needs to be reduced as far as possible, both in amplitude as in frequency. Our work is aimed at a seismometer that measures the displacement of an inertial mass, suspended with low stiffness. To achieve a low enough effective stiffness, the stiffness of the suspension is compensated by a kinematically defined mechanism.<br/>A negative stiffness module is designed and built to realize a floating mass with a decoupling frequency as low as 200 mHz.<br/>A stiffness-compensation of 1000 N/m is created, and an overall system stiffness of 2 N/m is realized.