[en] A group at University of Tokyo has been searching for the gravitational radiation (GR) from the Crab pulsar at 60.2 Hz. The first experiment was made in 1976-77, using a 400 kg aluminum quadrupole antenna with a quality factor Q of 4500. From 420 h of observation, upperlimits S < 14 W/m², for the GR energy flux, and h < 1.1 x 10^-19 for the root-mean-square amplitude of the non-dimensional metric tensor were set. The author reports the result of a new measurement performed from August 1978 to January 1979. In this experiment, using a larger mass, 1400-kg, and a higher Q, 65000, for the antenna, the sensitivity was improved by approximately two orders of magnitude. (Auth.)

[en] During the last years the Italian group interested in the search of gravitational waves (a collaboration between the University of Rome and the C.N.R.) has made a few experiments with small cryogenic antennas. Their purpose was, to measure the mechanical quality factor of the antenna, to test the magnetic suspensions, the electronic apparatus, the data acquisition system and finally to measure the Brownian noise by means of piezoelectric ceramics. For the first time in June 1978 the authors successfully cooled down to 4.2 K a larger aluminium bar, M=389 kg and resonance frequency 1795 Hz, equipped also with piezoelectric ceramics. This bar was cooled down again in May 1979. The main purpose was essentially to learn more about the mechanical filters for a proper design of the final large antenna, M=5000 kg. (Auth.)

[en] We are developing a detector with two laser interferometers for gravitational waves at 100 MHz. Each interferometer is a Sagnac interferometer with a 75-cm baseline synchronous recycling (or resonant recycling) cavity. Two such interferometers are constructed to perform cross-correlation analysis. The original signals at around 100 MHz are converted into electrical signals at lower frequencies before we collect the data. The output noise of each interferometer is measured to correspond to less than 1x10^-16 Hz^-1/2 in strain amplitude at around 100 MHz

[en] TAMA300 has been upgraded to improve the sensitivity at low frequencies after the last observation run in 2004. To avoid the noise caused by seismic activities, we installed a new seismic isolation system-the TAMA seismic attenuation system (SAS). Four SAS towers for the test-mass mirrors were sequentially installed from 2005 to 2006. The recycled Fabry-Perot Michelson interferometer was successfully locked with the SAS. We confirmed the reduction of both length and angular fluctuations at frequencies higher than 1 Hz owing to the SAS

[en] 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

[en] The Large-scale Cryogenic Gravitational wave Telescope (LCGT) is planned as a future Japanese project for gravitational wave detection. A 3 km interferometer will be built in an underground mine at Kamioka. Cryogenic sapphire mirrors are going to be employed for the test masses. For the demonstration of LCGT technologies, two prototype interferometers, TAMA300 and CLIO, are being developed. This paper describes the current status of the LCGT project and the two prototype interferometers.

[en] We present a data characterization method for the main output signal of the interferometric gravitational-wave detector, in particular targeting at effective detection of burst gravitational waves from stellar core collapse. The time scale of non-Gaussian events is evaluated in this method, and events with longer time scale than real signals are rejected as non-Gaussian noises. As a result of data analysis using 1000 h of real data with the interferometric gravitational-wave detector TAMA300, the false-alarm rate was improved 10³ times with this non-Gaussian noise evaluation and rejection method

[en] The objective of the TAMA 300 interferometer was to develop advanced technologies for kilometre scale interferometers and to observe gravitational wave events in nearby galaxies. It was designed as a power-recycled Fabry-Perot-Michelson interferometer and was intended as a step towards a final interferometer in Japan. The present successful status of TAMA is presented. TAMA forms a basis for LCGT (large-scale cryogenic gravitational wave telescope), a 3 km scale cryogenic interferometer to be built in the Kamioka mine in Japan, implementing cryogenic mirror techniques. The plan of LCGT is schematically described along with its associated R and D

[en] The large-scale cryogenic gravitational wave telescope (LCGT) project is the proposed advancement of TAMA, which will be able to detect the coalescences of binary neutron stars occurring in our galaxy. LCGT intends to detect the coalescence events within about 240 Mpc, the rate of which is expected to be from 0.1 to several events in a year. LCGT has Fabry-Perot cavities of 3 km baseline and the mirrors are cooled down to a cryogenic temperature of 20 K. It is planned to be built in the underground of Kamioka mine. This paper overviews the revision of the design and the current status of the R and D