SPring-8, the large synchrotron radiation facility

Speaker : Osamu Miyakawa

Language : JAPANESE

Affiliate : ICRR, The University of Tokyo

Title : Control for Laser Interferometric Gravitational Wave Detector using Digital System

Abstract :
It is time to begin the construction of a gravitational wave detector named as LCGT (Large-Scale Cryogenic Gravitational wave Telescope) which has 3km base-line arms underground in Kamioka mine. Big gravitational waves are generated by astronomical events such as neutron star binary coalescences or supernovas, and they reach to the earth as ripples of time and space. Gravitational wave detectors using a principle of Michelson interferometer read the ripples as a difference of distance between mirrors separately located by several kilometers. We need a special control technique to keep the distance between mirrors into multiple of laser wave length for the precise measurement. We will have controls signals as ˜10 DOFs of mirror position in length direction, ˜50 DOFs in angle direction and ˜100 DOFs in local controls of multiple pendulums for seismic attenuation.

In this lecture, we introduce an effective control method using computers to deal with such an extremely many number of DOFs and complicated control topologies. Gravitational wave detectors require the very low noise environment which is limited only by principle noises such as seismic, thermal and shot noise, but generally ADC/DAC produces huge noise in the digital control. We also talk how to deal with such noisy devices in quiet detectors.

Organizer : Toru Ohata
Mail : ohata@spring8.or.jp
PHS : 3802