Development of Narrow-band Laser Interferometer Gravitational Wave Antenna

• Project/Area Number: 10440083
• Research Category: Grant-in-Aid for Scientific Research (B).
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 素粒子・核・宇宙線
• Research Institution: National Astronomical Observatory
• Principal Investigator: SEIJI Kawamura Astrometry and Celestial Mechanics Divisoin National Astronomical Observatory Associate Professor, 位置天文・天体力学研究系, 助教授 (40301725)
• Co-Investigator(Kenkyū-buntansha): TOSHITAKA Yamazaki Astrometry and Celestial Mechanics Divisoin National Astronomical Observatory Research Associate, 位置天文・天体力学研究系, 助手 (90182485) ; RYUTARO Takahasi Astrometry and Celestial Mechanics Divisoin National Astronomical Observatory Research Associate, 位置天文・天体力学研究系, 助手 (60270451) ; 大橋 正健 東京大学, 宇宙線研究所, 助教授 (80213833)
• Project Period (FY): 1998 – 2000
• Project Status: Completed (Fiscal Year 2000)
• Budget Amount: ¥13,000,000 (Direct Cost: ¥13,000,000); Fiscal Year 2000: ¥1,700,000 (Direct Cost: ¥1,700,000); Fiscal Year 1999: ¥1,300,000 (Direct Cost: ¥1,300,000); Fiscal Year 1998: ¥10,000,000 (Direct Cost: ¥10,000,000)
• Keywords: Gravitational Wave / Resonant Sideband Extraction / TAMA Project

Research Abstract

There are several projects going on which aim at gravitational wave detection using laser interferometers : the Japanese TAMA project, the American LIGO project, the French-Italian VIRGO project, and the German-British GEO project. It is quite possible that gravitational waves could be detected in several years. However, it is necessary to improve the sensitivity of the antennas further in order to establish the gravitational wave astronomy. The resonant sideband extraction (RSE) is one of the advanced technologies which could improve the sensitivity of the interferometer in a limited frequency band. In this program we performed a basic research to investigate the performance of the RSE interferometer.
The RSE interferometer requires an additional mirror placed at the detection port of the conventional power-recycled Fabry-Perot Michelson interferometer. This signal extraction mirror makes it possible to extract the gravitational wave signal from the arm cavity, which would be cancelled out otherwise. The RSE interferometer has an advantage that the laser power in the recycling cavity is lower compared with the conventional interferometer, which could avoid the degradation of sensitivity due to the heating lens effect of the mirrors. Moreover, the RSE interferometer can be operated with better sensitivity in a limited frequency band by simply displacing the signal extraction mirror by a fraction of the wavelength of the light.
There has been several basic experiments on the RSE interferometer so far, but they were all performed as table-top experiments in the air, as well as they were all using multi-modulation schemes for signal extraction. Since the RSE interferometer requires an extremely high finesse of the arm cavity, thus, extremely high reflectivty of the mirrors, it is not preferable to operate the interferometer in the air because of possible degradation of the mirrors in the air. Also the table-top experiment uses mirrors fixed to the table, which are very different from the suspended mirrors in a real gravitational wave antenna. Moreover the multi-modulation scheme makes the interferometer control even more complicated.
Therefore in this research, we performed the experiment in the vacuum system using a small suspension system, which made it possible to have a better and more realistic environment. Also we invented a single modulation method for signal extraction, which ensures the simplicity of the control system. In the last year we finally succeeded in operating the RSE interferometer using the single modulation method in a vacuum system using suspended mirrors for the first time in the wotld. After that we found a better way for signal extraction using the third harmonic demodulation maintaining the single modulation scheme. We analyzed this new method theoretically and using the simulation we found that the method would work even better without losing the simplicity of tlte system. We plan to verify this new scheme by experiment next year.
In the last year we finally succeeded in operating the RSE interferometer using the single modulation method in a vacuum system using suspended mirrors for the first time in the wotld. After that we found a better way for signal extraction using the third harmonic demodulation maintaining the single modulation scheme. We analyzed this new method theoretically and using the simulation we found that the method would work even better without losing the simplicity of the system. We plan to verify this new scheme by experiment next year.

Research Products

• [Publications] Osamu Miyakawa,Gerhard Heinzel,Seiji Kawamura,and Kazuaki Kuroda: "Development of a Narrow-band Laser Interferometer using Resonant Sideband Extraction"Proc.of Gravitational Wave Detection II. 361 (1999)
  • Description: 「研究成果報告書概要(和文)」より
• [Publications] Osamu Miyakawa, Gerhard heinzel, Seiji Kawamura, and Kazuaki Kuroda: "Development of a Narrow-band Laser Interferometer using Resonant Sideband Extraction"Proc.of Gravitational Wave Detection II. 361 (1999)
  • Description: 「研究成果報告書概要(欧文)」より