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ABSTRACT: The optical property of a large mirror substrate of 250 mm in diameter was successfully measured at the required resolution to meet the target sensitivity of the Large-Scale Cryogenic Gravitational Wave Telescope (LCGT) project. Although the quality of the substrate piece was not sufficient to achieve the target sensitivity, we could present how to cope with the crystal orientation for reducing any negative effect of birefringence of the substrate, and we could also produce useful data for manufacturers to improve the quality.
Classical and Quantum Gravity 08/2010; 27(18):185015. · 3.32 Impact Factor
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Masaki Ando,
Seiji Kawamura,
Naoki Seto,
Shuichi Sato,
Takashi Nakamura,
Kimio Tsubono,
Takeshi Takashima,
Ikkoh Funaki,
Kenji Numata,
Nobuyuki Kanda, [......],
Yaka Wakabayashi,
Kent Yagi,
Hiroshi Yamakawa,
Kazuhiro Yamamoto,
Toshitaka Yamazaki,
Jun'ichi Yokoyama,
Chul-Moon Yoo,
Shijun Yoshida,
Taizoh Yoshino,
Ke-Xun Sun
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ABSTRACT: A space gravitational-wave antenna, DECIGO (DECI-hertz interferometer Gravitational wave Observatory), will provide fruitful insights into the universe, particularly on the formation mechanism of supermassive black holes, dark energy and the inflation of the universe. In the current pre-conceptual design, DECIGO will be comprising four interferometer units; each interferometer unit will be formed by three drag-free spacecraft with 1000 km separation. Since DECIGO will be an extremely challenging mission with high-precision formation flight with long baseline, it is important to increase the technical feasibility before its planned launch in 2027. Thus, we are planning to launch two milestone missions. DECIGO pathfinder (DPF) is the first milestone mission, and key components for DPF are being tested on ground and in orbit. In this paper, we review the conceptual design and current status of DECIGO and DPF.
Classical and Quantum Gravity 04/2010; 27(8):084010. · 3.32 Impact Factor
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ABSTRACT: We have achieved a direct measurement of the thermal fluctuation of a pendulum in an off-resonant and wide frequency region using a laser interferometric gravitational-wave detector. These measurements have been well identified for over one decade by an agreement with a theoretical prediction, which is derived by a fluctuation-dissipation theorem. Thermal fluctuation was dominated by the contribution of resistances in coil-magnet actuator circuits. When we tuned these resistances, the noise spectrum also changed according to a theoretical prediction. The measured thermal noise level corresponds to a high quality factor on the order of 10(5) of the pendulum.
Physical Review Letters 01/2010; 104(4):040602. · 7.37 Impact Factor
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Kazuhiro Agatsuma,
Koji Arai,
Masa-Katsu Fujimoto,
Seiji Kawamura, Kazuaki Kuroda,
Osamu Miyakawa,
Shinji Miyoki,
Masatake Ohashi,
Toshikazu Suzuki,
Ryutaro Takahashi,
Daisuke Tatsumi,
Souichi Telada,
Takashi Uchiyama,
Kazuhiro Yamamoto,
CLIO collaborators
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ABSTRACT: We report on the current status of CLIO (Cryogenic Laser Interferometer Observatory), which is a prototype interferometer for LCGT (Large Scale Cryogenic Gravitational-Wave Telescope). LCGT is a Japanese next-generation interferometric gravitational wave detector featuring the use of cryogenic mirrors and a quiet underground site. The main purpose of CLIO is to demonstrate a reduction of the mirror thermal noise by cooling the sapphire mirrors. CLIO is located in an underground site of the Kamioka mine, 1000 m deep from the mountain top, to verify its advantages. After a few years of commissioning work, we have achieved a thermal-noise-limited sensitivity at room temperature. One of the main results of noise hunting was the elimination of thermal noise caused by a conductive coil-holder coupled with a pendulum through magnets. Comment: 10 pages, 6 figures, Proceedings of the 8th Edoardo Amaldi Conference on Gravitational Waves
11/2009;
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ABSTRACT: In this paper we show that information on both the differential and common mode free-mass response to a gravitational wave can provide important information on discriminating the direction of the gravitational wave source and between different theories of gravitation. The conventional Michelson interferometer scheme only measures the differential free-mass response. By changing the orientation of the beam splitter, it is possible to configure the detector so it is sensitive to the common-mode of the free-mass motion. The proposed interferometer is an adaptation of the Fox-Smith interferometer. A major limitation to the new scheme is its enhanced sensitivity to laser frequency fluctuations over the conventional, and we propose a method of canceling these fluctuations. The configuration could be used in parallel to the conventional differential detection scheme with a significant sensitivity and bandwidth.
04/2009;
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Tomomi Akutsu,
Masaki Ando,
Tomiyoshi Haruyama,
Nobuyuki Kanda, Kazuaki Kuroda,
Sinji Miyoki,
Masatake Ohashi,
Yoshio Saito,
Nobuaki Sato,
Takakazu Shintomi,
Toshikazu Suzuki,
Hideyuki Tagoshi,
Hirotaka Takahashi,
Daisuke Tatsumi,
Souichi Telada,
Takayuki Tomaru,
Takashi Uchiyama,
Akira Yamamoto,
Kazuhiro Yamamoto
[show abstract]
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ABSTRACT: We search for continuous gravitational waves from PSR J0835-4510 at twice its rotational frequency using CLIO (Cryogenic Laser Interferometric Observatory) in the Kamioka mine. In this search, we use data from an observational run during 12–28 February 2007. We give a brief description of the methods used in this search. We obtain an upper limit on gravitational wave amplitude for PSR J0835-4510 as h0(UL) = 5.3 × 10−20 with 99.4% confidence level.
Classical and Quantum Gravity 09/2008; 25(18):184013. · 3.32 Impact Factor
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ABSTRACT: We investigated the noise of interferometric gravitational wave detectors due to heat energy deposited by cosmic-ray particles. We derived a general formula that describes the response of a mirror against a cosmic-ray passage. We found that there are differences in the comic-ray responses (the dependence of temperature and cosmic-ray track position) in cases of interferometric and resonant gravitational wave detectors. The power spectral density of vibrations caused by low-energy secondary muons is 100-times smaller than the goal sensitivity of future second-generation interferometer projects, such as LCGT and Advanced LIGO. The arrival frequency of high-energy cosmic-ray muons that generate enough large showers inside mirrors of LCGT and Advanced LIGO is one per a millennium. We also discuss the probability of exotic-particle detection with interferometers.
06/2008;
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Takayuki Tomaru,
Masao Tokunari, Kazuaki Kuroda,
Takashi Uchiyama,
Akira Okutomi,
Masatake Ohashi,
Hiroyuki Kirihara,
Nobuhiro Kimura,
Yoshio Saito,
Nobuaki Sato,
Takakazu Shintomi,
Toshikazu Suzuki,
Tomiyoshi Haruyama,
Shinji Miyoki,
Kazuhiro Yamamoto,
Akira Yamamoto
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ABSTRACT: A large heat load caused by thermal radiation through a metal shield pipe was observed in a cooling test of a cryostat for a prototype of a cryogenic interferometric gravitational wave detector. The heat load was approximately 1000 times larger than the value calculated by the Stefan-Boltzmann law. We studied this phenomenon by simulation and experiment and found that it was caused by the conduction of thermal radiation in a metal shield pipe. Comment: 7 pages, 4 figures, 2 tables, Submitted to Jpn. J. Appl. Phys
11/2007;
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Daisuke Tatsumi,
Ryutaro Takahashi,
Koji Arai,
Noriyasu Nakagawa,
Kazuhiro Agatsuma,
Toshitaka Yamazaki,
Mitsuhiro Fukushima,
Masa-Katsu Fujimoto,
Akiteru Takamori,
Alessandro Bertolini, [......],
Norichika Awaya,
Nobuyuki Kanda,
Akito Araya,
Souichi Telada,
Takayuki Tomaru,
Tomiyoshi Haruyama,
Akira Yamamoto,
Nobuaki Sato,
Toshitaka Suzuki,
Takakazu Shintomi
[show abstract]
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ABSTRACT: Current status of TAMA and CLIO detectors in Japan is reported in this article. These two interferometric gravitational-wave detectors are being developed for the large cryogenic gravitational wave telescope (LCGT) which is a future plan for detecting gravitational wave signals at least once per year. TAMA300 is being upgraded to improve the sensitivity in low frequency region after the last observation experiment in 2004. To reduce the seismic noises, we are installing new seismic isolation system, which is called TAMA Seismic Attenuation System, for the four test masses. We confirmed stable mass locks of a cavity and improvements of length and angular fluctuations by using two SASs. We are currently optimizing the performance of the third and fourth SASs. We continue TAMA300 operation and R&D studies for LCGT. Next data taking in the summer of 2007 is planned. CLIO is a 100-m baseline length prototype detector for LCGT to investigate interferometer performance in cryogenic condition. The key features of CLIO are that it locates Kamioka underground site for low seismic noise level, and adopts cryogenic Sapphire mirrors for low thermal noise level. The first operation of the cryogenic interferometer was successfully demonstrated in February of 2006. Current sensitivity at room temperature is close to the target sensitivity within a factor of 4. Several observation experiments at room temperature have been done. Once the displacement noise reaches at thermal noise level of room temperature, its improvement by cooling test mass mirrors should be demonstrated.
05/2007;
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ABSTRACT: While the thermomechanical properties of sapphire make it an excellent candidate of test mass for advanced laser interferometers, its optical quality is not well understood or well controlled. We have studied the results from high-resolution measurements of scattering, absorption, and birefringence in test-mass samples to better understand issues of quality. Samples show large-scale scattering structures clearly linked to the crystal-growth process. Samples characterized by the presence of point defects have significantly lower scattering (except at the point defects). In general on a large scale, high scattering also correlates with higher absorption and higher average birefringence inhomogeneity. However, on a smaller scale there is not a clear point-to-point correlation between scattering and absorption. Often a large-scale scattering structure is spatially displaced by tens of millimeters from a similar absorption structure, indicating that quite separate microscopic mechanisms give rise to scattering and absorption. The spatial displacements indicate that absorption centers and scattering centers are laid down during crystal growth at different distances from the solid-liquid interface. We suggest that absorption may be linked to F centers, while scattering may be linked to impurities such as iron.
Applied Optics 05/2006; 45(12):2631-7. · 1.41 Impact Factor
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ABSTRACT: The current status of LCGT is described. The physical target of LCGT is to detect every year at least one event of gravitational wave signal produced at the coalescence of a binary neutron star. To attain this objective, LCGT is built underground by adopting cryogenic mirrors with a high power laser. To assure the reliable detection, two independent sets of interferometers are installed in a common vacuum system.
Classical and Quantum Gravity 03/2006; 23(8):S215. · 3.32 Impact Factor
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Kazuhiro Yamamoto,
Shinji Miyoki,
Takashi Uchiyama,
Hideki Ishitsuka,
Masatake Ohashi, Kazuaki Kuroda,
Takayuki Tomaru,
Nobuaki Sato,
Toshikazu Suzuki,
Tomiyoshi Haruyama,
Akira Yamamoto,
Takakazu Shintomi,
Kenji Numata,
Koichi Waseda,
Kazuhiko Ito,
Koji Watanabe
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ABSTRACT: We have measured the mechanical loss of a dielectric multilayer reflective coating (ion-beam sputtered SiO$_2$ and Ta$_2$O$_5$) in cooled mirrors. The loss was nearly independent of the temperature (4 K $\sim$ 300 K), frequency, optical loss, and stress caused by the coating, and the details of the manufacturing processes. The loss angle was $(4 \sim 6) \times 10^{-4}$. The temperature independence of this loss implies that the amplitude of the coating thermal noise, which is a severe limit in any precise measurement, is proportional to the square root of the temperature. Sapphire mirrors at 20 K satisfy the requirement concerning the thermal noise of even future interferometric gravitational wave detector projects on the ground, for example, LCGT.
02/2006;
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Hirotaka Takahashi,
Hideyuki Tagoshi,
Masaki Ando,
Koji Arai,
Peter Beyersdorf,
Nobuyuki Kanda,
Seiji Kawamura,
Norikatsu Mio,
Shinji Miyoki,
Shigenori Moriwaki, [......],
Ken-ichi Ueda,
Fumihiko Usui,
Koichi Waseda,
Yuko Watanabe,
Hiromi Yakura,
Kazuhiro Yamamoto,
Akira Yamamoto,
Toshitaka Yamazaki,
Tatsuo Yoda,
Zong-Hong Zhu
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ABSTRACT: Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor ∼10-4 compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 [1/h] (C.L.=90%) to the galactic event rate within 1 kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.
Phys. Rev. D. 08/2004; 70(4).
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Shigeo Nagano,
Seiji Kawamura,
Masaki Ando,
Ryutaro Takahashi,
Koji Arai,
Mitsuru Musha,
Souichi Telada,
Masa-Katsu Fujimoto,
Mitsuhiro Fukushima,
Yoshihide Kozai, [......],
Takashi Nakamura,
Misao Sasaki,
Masaru Shibata,
Hideyuki Tagoshi,
Takahiro Tanaka,
Ken-ichi Nakao,
Ken-ichi Oohara,
Yasufumi Kojima,
Toshifumi Futamase,
Hideki Asada
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ABSTRACT: Laser frequency stabilization is essential for interferometric gravitational-wave detectors to attain their target sensitivity. We have designed a multistage laser frequency stabilization system which has been applied in the development of the TAMA 300 gravitational-wave detector in Japan. The control topology consisting of two cascaded loops were employed to secure high feedback gain and reliable detector operation and thus allow the best frequency stability and uninterrupted long-term observation. We achieved simultaneously a frequency stability of 5×10−5 Hz/, and a common-mode rejection ratio (which reduces the coupling of frequency noise to spurious signals in the detector) of 37 dB. The developed system enabled us to operate TAMA 300 with sufficient sensitivity and stability that it had the potential to register gravitational-wave events. The system was confirmed to be suitable for a gravitational-wave detector from the observation run of TAMA 300. © 2003 American Institute of Physics.
Review of Scientific Instruments 08/2003; 74(9):4176-4183. · 1.37 Impact Factor
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Takayuki Tomaru,
Shinji Miyoki,
Masatake Ohashi, Kazuaki Kuroda,
Takashi Uchiyama,
Toshikazu Suzuki,
Akira Yamamoto,
Takakazu Shintomi,
Akitoshi Ueda,
Daisuke Tatsumi, [......],
Koji Arai,
Masaki Ando,
Koji Watanabe,
Kenji Nakamura,
Masahiko Watanabe,
Kazuhiko Ito,
Izumi Kataoka,
Hiroaki Yamamoto,
Brett Bochner,
Yaron Hefetz
Applied Optics 04/2003; 42(7):1306-7. · 1.41 Impact Factor
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Takayuki Tomaru,
Shinji Miyoki,
Masatake Ohashi, Kazuaki Kuroda,
Takashi Uchiyama,
Toshikazu Suzuki,
Akira Yamamoto,
Takakazu Shintomi,
Akitoshi Ueda,
Daisuke Tatsumi, [......],
Koji Arai,
Masaki Ando,
Koji Watanabe,
Kenji Nakamura,
Masahiko Watanabe,
Kazuhiko Ito,
Izumi Kataoka,
Hiroaki Yamamoto,
Brett Bochner,
Yaron Hefetz
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ABSTRACT: We evaluated the performance of polished mirror surfaces for the TAMA interferometric gravitational wave detector by comparing the experimental results with a wave-front tracing simulation. The TAMA mirror surfaces were polished to a roughness of a few nanometer rms. We confirmed that these polished mirrors do not limit the present TAMA sensitivity and that the target shot-noise sensitivity will be achieved with these mirrors, even if a power-recycling technique is introduced in the next stage of the TAMA.
Applied Optics 11/2002; 41(28):5913-20. · 1.41 Impact Factor
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Shigeo Nagano,
Mark A. Barton,
Hideki Ishizuka, Kazuaki Kuroda,
Sumihiro Matsumura,
Osamu Miyakawa,
Shinji Miyoki,
Daisuke Tatsumi,
Takayuki Tomaru,
Takashi Uchiyama, [......],
Takahiro Tanaka,
Misao Sasaki,
Hideyuki Tagoshi,
Toshifumi Futamase,
Nobuki Kawashima,
Eiichi Mizuno,
Yasufumi Kojima,
Namio Matsuda,
Ken-ichi Oohara,
Nobuhiro Tsuda
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ABSTRACT: We have developed a light source suitable for laser interferometric gravitational-wave detectors. The developed light source has high power, TEM00 mode, linear polarization, high frequency stability, and low intensity noise. The light source with the quality is essential for attaining the goal sensitivity in the TAMA 300 and was found to be available for a observation run of a gravitational-wave detector. © 2002 American Institute of Physics.
Review of Scientific Instruments 04/2002; 73(5):2136-2142. · 1.37 Impact Factor
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ABSTRACT: We report the reduction of the thermal lensing in cryogenic sapphire mirrors, which is planed to be used in the Large scale Cryogenic Gravitational wave Telescope (LCGT) project. We measured three key parameters of sapphire substrate for thermal lensing at cryogenic temperature. They are optical absorption coefficient, thermal conductivity and temperature coefficient of refractive index at cryogenic temperature. On basis of these measurements, we estimated the shot noise sensitivity of the interferometer with thermal lensing by using a wave-front tracing simulation. We found that thermal lensing in cryogenic sapphire mirrors is negligible. Comment: 6 pages, 3 figures, Proceedings of 4th Edoaldo Amaldi Conference of Gravitational Waves, 8 - 13 July 2001, The University of Western Australia. Accepted to Classical and Quantum Gravity (Special Issue)
02/2002;
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ABSTRACT: We have extended to two dimensions a previously developed vibration isolation table using crossed wire suspensions (X mechanisms). A load table is suspended using a combination of normal and upside-down X mechanisms so that it moves freely with a very long period in both horizontal directions but is moderately stiff in all other degrees of freedom. Periods of 5 s are easily achievable. The transfer function of the prototype reported here contains a number of elastic mode resonance peaks, but it is shown by analysis how to reduce or eliminate nearly all of these. © 1999 American Institute of Physics.
Review of Scientific Instruments 03/1999; 70(4):2150-2154. · 1.37 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In this paper we show that information on both the differential and common mode free-mass response to a gravitational wave can provide important information on discriminating the direction of the gravitational wave source and between different theories of gravitation. The conventional Michelson interferometer scheme only measures the differential free-mass response. By changing the orientation of the beam splitter, it is possible to configure the detector so it is sensitive to the common-mode of the free-mass motion. The proposed interferometer is an adaptation of the Fox-Smith interferometer. A major limitation to the new scheme is its enhanced sensitivity to laser frequency fluctuations over the conventional, and we propose a method of cancelling these fluctuations. The configuration could be used in parallel to the conventional differential detection scheme with a significant sensitivity and bandwidth.
Phys. Rev. D. 03/1999; 59(10).
