Control system for the seismic attenuation system (SAS) in TAMA300

A new seismic isolation system, TAMA Seismic Attenuation System (TAMA-SAS), was installed to TAMA300 in order to improve the sensitivity at low frequencies. Inertial damping is one of the hierarchical control systems of the TAMA-SAS which are employed to give full play to its ability. We have established two servo loops to control the Inverted Pendulum (IP) which composes the SAS. One is the servo loop using LVDT position sensors to keep the position of the IP. The other is the inertial damping which uses accelerometers to control the inertial motion of the IP for the horizontal direction. The fluctuation of the IP was reduced using our servo system. In addition, reduction of angular and longitudinal fluctuation of the mirror was also confirmed. These results indicate that the control for the IP properly works and the isolation performance of the TAMA-SAS was improved.