High resolution compact vertical inertial sensor for atomic quantum gravimeter hybridizing

We present a novel design of a high-resolution compact interferometric inertial sensor intended to extend the bandwidth of an atomic quantum gravimeter. The mechanics of the sensor features fused silica glass flexure joints, allowing to produce a relatively low natural frequency mechanism of 2.8 Hz in a 10 × 10 × 10 cm3, design. We report its quality factor of 2800 in open-air. The linear translation guide allows the motion of the proof-mass to be monitored using an interferometric readout. The readout is based on a custom Michelson interferometer design, which uses laser beam propagating in phase-quadrature to allow a
long-range measurement with a relative resolution of 2 × 10−13 m/√ Hz at 1 Hz. The sensor is operated in closed-loop so as to increase the dynamic bandwidth of the sensor and improve the linearity of the readout. The actuator used for closing the loop is a homemade double-magnet voice-coil, designed to reduce the Eddy-current damping induced by the magnet. This sensor is designed to be compatible with an UHV environment.