GINGER and GINGERINO

GINGER (Gyroscopes IN General Relativity) is a proposal aiming at measuring the Lense-Thirring effect with an Earth based experiment, using an array of ringlasers, which are the most sensitive inertial sensors to measure the rotation rate of the Earth. The long term stability of the apparatus plays a crucial role for this experiment, and an underground location is advantageous from this point of view. GINGERINO is a single axis ring laser located inside the Gran Sasso laboratory. Gingerino has demonstrated that the very high thermal stability of the underground laboratory allows a continuous operation, sensitivity well below fractions of nrad/s, and with a duty cycle above 90% even in free running operation, without stabilisation of the scale factor of the ring laser.