Analysis of 90 days operation of the gyroscope GINGERINO

Abstract: GINGERINO is a square ring-laser prototype, which has been built to investigate the level of noise inside the Gran Sasso underground laboratory. It Is meant for fundamental physics, but it provides suitable data for geophysics and seismology. Since May 2017 it is continuously acquiring data. The analysis of the first $90$ days shows that the duty cycle is higher than $95\%$, and the quantum shot noise limit is of the order of $ 10^{-10}(\mathrm{rad}/s)/\sqrt{\mathrm{Hz}}$. It is located in a seismically active area, and it recorded part of the of central Italy earthquakes. Its high sensitivity in the frequency band of fraction of Hz makes it suitable for seismology studies. The main purpose of the present analysis is to investigate the long term response of the apparatus. Simple and fast routines to eliminate the disturbances coming from the laser have been developed. The Allan deviation of the raw data reaches $10^{-7}$ after about $10^6s$ of integration time, while the processed data shows an improvement of one order of magnitude. Disturbances at the daily time scale are present in the processed data and the expected signal induced by polar motion and solid Earth tide is covered by those disturbances.