-
Theoretical Characteristics of a three-point Roberts Linkage
Authors:
Munetake Otsuka,
Kohei Mitsuhashi,
Ryutaro Takahashi,
Yohei Nishino,
Yoichi Aso,
Takayuki Tomaru
Abstract:
The Roberts linkage is recognized for enabling long-period pendulum motion in a compact format. Utilizing this characteristic, we are developing a three-point Roberts linkage for vibration isolation systems, with an eye towards its potential contribution to the development of next-generation interferometric gravitational wave antennas. In this article, we derived the equations to determine the ess…
▽ More
The Roberts linkage is recognized for enabling long-period pendulum motion in a compact format. Utilizing this characteristic, we are developing a three-point Roberts linkage for vibration isolation systems, with an eye towards its potential contribution to the development of next-generation interferometric gravitational wave antennas. In this article, we derived the equations to determine the essential parameters when using this linkage as a vibration isolation system, namely the equivalent pendulum length and the relationship between translational motion of the center of mass and rigid body rotation, from size parameters. Additionally, we analyzed the behavior in response to various errors.
△ Less
Submitted 24 October, 2024;
originally announced October 2024.
-
Development of advanced photon calibrator for Kamioka gravitational wave detector (KAGRA)
Authors:
Y. Inoue,
B. H. Hsieh,
K. H. Chen,
Y. K. Chu,
K. Ito,
C. Kozakai,
T. Shishido,
Y. Tomigami,
T. Akutsu,
S. Haino,
K. Izumi,
T. Kajita,
N. Kanda,
C. S. Lin,
F. K. Lin,
Y. Moriwaki,
W. Ogaki,
H. F. Pang,
T. Sawada,
T. Tomaru,
T. Suzuki,
S. Tsuchida,
T. Ushiba,
T. Washimi,
T. Yamamoto
, et al. (1 additional authors not shown)
Abstract:
The Kamioka Gravitational wave detector (KAGRA) cryogenic gravitational-wave observatory has commenced joint observations with the worldwide gravitational wave detector network. Precise calibration of the detector response is essential for accurately estimating parameters of gravitational wave sources. A photon calibrator is a crucial calibration tool used in laser interferometer gravitational-wav…
▽ More
The Kamioka Gravitational wave detector (KAGRA) cryogenic gravitational-wave observatory has commenced joint observations with the worldwide gravitational wave detector network. Precise calibration of the detector response is essential for accurately estimating parameters of gravitational wave sources. A photon calibrator is a crucial calibration tool used in laser interferometer gravitational-wave observatory, Virgo, and KAGRA, and it was utilized in joint observation 3 with GEO600 in Germany in April 2020. In this paper, KAGRA implemented three key enhancements: a high-power laser, a power stabilization system, and remote beam position control. KAGRA employs a 20 W laser divided into two beams that are injected onto the mirror surface. By utilizing a high-power laser, the response of the detector at kHz frequencies can be calibrated. To independently control the power of each laser beam, an optical follower servo was installed for power stabilization. The optical path of the photon calibrator beam positions was controlled using pico-motors, allowing for the characterization of the detector rotation response. Additionally, a telephoto camera and quadrant photodetectors were installed to monitor beam positions, and beam position control was implemented to optimize the mirror response. In this paper, we discuss the statistical errors associated with the measurement of relative power noise. We also address systematic errors related to the power calibration model of the photon calibrator and the simulation of elastic deformation effects using finite element analysis. Ultimately, we have successfully reduced the total systematic error from the photon calibrator to 2.0 /%.
△ Less
Submitted 27 September, 2025; v1 submitted 23 February, 2023;
originally announced February 2023.
-
Control Scheme for Polarization Circulation Speed Meter Using a Dual-Retardation Waveplate
Authors:
Yohei Nishino,
Tomotada Akutsu,
Yoichi Aso,
Takayuki Tomaru
Abstract:
In interferometric gravitational wave detectors, quantum radiation pressure noise, which is a back action of the measurement, will limit their sensitivities at low frequencies. Speed meters are one of the solutions to reduce the back action noise and improve the sensitivities, and furthermore, they can surpass the standard quantum limit over a wide range of frequencies. The Polarization Circulatio…
▽ More
In interferometric gravitational wave detectors, quantum radiation pressure noise, which is a back action of the measurement, will limit their sensitivities at low frequencies. Speed meters are one of the solutions to reduce the back action noise and improve the sensitivities, and furthermore, they can surpass the standard quantum limit over a wide range of frequencies. The Polarization Circulation Speed Meter is the latest incarnation of the speed meter concept in the sense that it requires a slight modification in the conventional interferometer designs; however, its control scheme has not been developed. The main difficulty is the length and alignment control of the cavity formed by the polarization circulation mirror and the input test masses, whose round-trip phase shift should be kept to $π$. In this article, we propose a new control scheme using a dual-retardation waveplate, called Dual-Retardance Control (DRC). In addition, we compare the shot noise level of the DRC to another simpler scheme by dithering. Finally, we design the experimental setup for the demonstration of the DRC and show the expected results through the transfer function measurement.
△ Less
Submitted 7 March, 2023; v1 submitted 27 January, 2023;
originally announced January 2023.
-
Input optics systems of the KAGRA detector during O3GK
Authors:
T. Akutsu,
M. Ando,
K. Arai,
Y. Arai,
S. Araki,
A. Araya,
N. Aritomi,
H. Asada,
Y. Aso,
S. Bae,
Y. Bae,
L. Baiotti,
R. Bajpai,
M. A. Barton,
K. Cannon,
Z. Cao,
E. Capocasa,
M. Chan,
C. Chen,
K. Chen,
Y. Chen,
C-I. Chiang,
H. Chu,
Y-K. Chu,
S. Eguchi
, et al. (228 additional authors not shown)
Abstract:
KAGRA, the underground and cryogenic gravitational-wave detector, was operated for its solo observation from February 25th to March 10th, 2020, and its first joint observation with the GEO 600 detector from April 7th -- 21st, 2020 (O3GK). This study presents an overview of the input optics systems of the KAGRA detector, which consist of various optical systems, such as a laser source, its intensit…
▽ More
KAGRA, the underground and cryogenic gravitational-wave detector, was operated for its solo observation from February 25th to March 10th, 2020, and its first joint observation with the GEO 600 detector from April 7th -- 21st, 2020 (O3GK). This study presents an overview of the input optics systems of the KAGRA detector, which consist of various optical systems, such as a laser source, its intensity and frequency stabilization systems, modulators, a Faraday isolator, mode-matching telescopes, and a high-power beam dump. These optics were successfully delivered to the KAGRA interferometer and operated stably during the observations. The laser frequency noise was observed to limit the detector sensitivity above a few kHz, whereas the laser intensity did not significantly limit the detector sensitivity.
△ Less
Submitted 12 October, 2022;
originally announced October 2022.
-
Estimation of Newtonian noise from KAGRA cooling system
Authors:
Rishabh Bajpai,
Takayuki Tomaru,
Toshikazu Suzuki,
Kazuhiro Yamamoto,
Takafumi Ushiba,
Tohru Honda
Abstract:
KAGRA is the first km-scale gravitational wave detector to be constructed underground and employ cryogenics to cool down its test masses. While the underground location provides a quiet site with low seismic noise, the cooling infrastructure is known to generate large mechanical vibrations due to cryocooler operation and structural resonances of the cryostat. As cooling system components are relat…
▽ More
KAGRA is the first km-scale gravitational wave detector to be constructed underground and employ cryogenics to cool down its test masses. While the underground location provides a quiet site with low seismic noise, the cooling infrastructure is known to generate large mechanical vibrations due to cryocooler operation and structural resonances of the cryostat. As cooling system components are relatively heavy and in close proximity to the test masses, oscillation of gravity force induced by their vibration, so-called Newtonian noise, could contaminate the detector sensitivity. In this paper, we use the results from vibration analysis of the KAGRA cryostat to estimate cooling system Newtonian noise in the 1-100 Hz frequency band. Our calculations show that, while this noise does not limit the current detector sensitivity or inspiral range, it will be an issue in the future when KAGRA improves its sensitivity. We conclude that KAGRA may need to implement Wiener filters to subtract this noise in the future.
△ Less
Submitted 27 July, 2022;
originally announced July 2022.
-
Response of the underground environment of the KAGRA observatory against the air-pressure disturbance from the Tonga volcano eruption on January 15th, 2022
Authors:
T. Washimi,
T. Yokozawa,
A. Takamori,
A. Araya,
S. Hoshino,
Y. Itoh,
Y. Kobayashi,
J. Kume,
K. Miyo,
M. Ohkawa,
S. Oshino,
T. Tomaru,
J. Yokoyama,
H. Yuzurihara
Abstract:
On January 15, 2022, at 04:14:45 (UTC), the Hunga Tonga-Funga Ha'apai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, erupted and generated global seismic, shock, and electromagnetic waves, which also reached Japan, situated more than 8,000 km away. KAGRA is a gravitational wave telescope located in an underground facility in Kamioka, Japan. It has a wide variety of a…
▽ More
On January 15, 2022, at 04:14:45 (UTC), the Hunga Tonga-Funga Ha'apai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean, erupted and generated global seismic, shock, and electromagnetic waves, which also reached Japan, situated more than 8,000 km away. KAGRA is a gravitational wave telescope located in an underground facility in Kamioka, Japan. It has a wide variety of auxiliary sensors to monitor environmental disturbances which obstruct observation of gravitational waves. The effects of the volcanic eruption were observed by these environmental sensors both inside and outside of the underground facility. In particular, the shock waves made it possible to evaluate the transfer functions from the air pressure wave in the atmosphere to the underground environmental disturbances (air pressure and seismic motion).
△ Less
Submitted 5 September, 2022; v1 submitted 29 June, 2022;
originally announced June 2022.
-
A laser interferometer accelerometer for vibration sensitive cryogenic experiments
Authors:
Rishabh Bajpai,
Takayuki Tomaru,
Kazuhiro Yamamoto,
Takafumi Ushiba,
Nobuhiro Kimura,
Toshikazu Suzuki,
Tomohiro Yamada,
Tohru Honda
Abstract:
Monitoring motion originating from ultra low-temperature cooling systems like cryocoolers is important for vibration sensitive cryogenic experiments like KAGRA. Since no commercial cryogenic accelerometers are available, we developed a compact self-calibrating accelerometer with a Michelson interferometer readout for cryogenic use. Change in calibration factor and drop in interferometer output ori…
▽ More
Monitoring motion originating from ultra low-temperature cooling systems like cryocoolers is important for vibration sensitive cryogenic experiments like KAGRA. Since no commercial cryogenic accelerometers are available, we developed a compact self-calibrating accelerometer with a Michelson interferometer readout for cryogenic use. Change in calibration factor and drop in interferometer output originating from temperature drop were the main concerns which were tackled. Sensitivity of $3.38\times10^{-11}$ m/$\sqrt{\mathrm{Hz}}$ at 1 Hz was achieved at 300 K. The accelerometer was tested inside the KAGRA cryostat; showed stable operation down to 12 K in 0.1-100 Hz band with only 1% visibility drop. Our accelerometer can be employed in low vibration cryogenic environment for a multitude of applications.
△ Less
Submitted 19 March, 2022;
originally announced March 2022.
-
Vibration Analysis of KAGRA Cryostat at Cryogenic Temperature
Authors:
Rishabh Bajpai,
Takayuki Tomaru,
Nobuhiro Kimura,
Takafumi Ushiba,
Kazuhiro Yamamoto,
Toshikazu Suzuki,
Tohru Honda
Abstract:
KAGRA uses cryogenics to cool its sapphire test masses down to 20 K to reduce the thermal noise. However, cryocooler vibration and structural resonances of the cryostat couple to test mass and can contaminate the detector sensitivity. We performed vibration analysis of the cooling system at cryogenic temperature to study its impact on detector sensitivity. Our measurement show shield vibration bel…
▽ More
KAGRA uses cryogenics to cool its sapphire test masses down to 20 K to reduce the thermal noise. However, cryocooler vibration and structural resonances of the cryostat couple to test mass and can contaminate the detector sensitivity. We performed vibration analysis of the cooling system at cryogenic temperature to study its impact on detector sensitivity. Our measurement show shield vibration below 1 Hz is not impacted by cryocooler operation or structural resonances and follows ground motion. The noise floor of the shield in 1-100 Hz was observed to be 2-3 order of magnitude larger than seismic motion even without cryocooler operation. The operation of cryocoolers does not change the noise floor, but 2.0 Hz peaks and their harmonics were observed over the entire spectrum (1-100 Hz). These results were used to calculate the coupling of cooling system vibration to the test mass. We conclude that vibration from the cooling system does not limit KAGRA design sensitivity.
△ Less
Submitted 17 March, 2022;
originally announced March 2022.
-
Cryogenic suspension design for a kilometer-scale gravitational-wave detector
Authors:
Takafumi Ushiba,
Tomotada Akutsu,
Yoichi Aso,
Sakae Araki,
Rishabh Bajpai,
Dan Chen,
Kieran Craig,
William Creus,
Yutaro Enomoto,
Yoshinori Fujii,
Masashi Fukunaga,
Ayako Hagiwara,
Sadakazu Haino,
Kunihiko Hasegawa,
Yuki Inoue,
Kiwamu Izumi,
Nobuhiro Kimura,
Keiko Kokeyama,
Rahul Kumar,
Ettore Majorana,
Yuta Michimura,
Takahiro Miyamoto,
Shinji Miyoki,
Iwao Murakami,
Yoshikazu Namai
, et al. (21 additional authors not shown)
Abstract:
We report the mirror suspension design for Large-scale Cryogenic Gravitational wave Telescope, KAGRA, during bKAGRA Phase 1. Mirror thermal noise is one of the fundamental noises for room-temperature gravitational-wave detectors such as Advanced LIGO and Advanced Virgo. Thus, reduction of thermal noise is required for further improvement of their sensitivity. One effective approach for reducing th…
▽ More
We report the mirror suspension design for Large-scale Cryogenic Gravitational wave Telescope, KAGRA, during bKAGRA Phase 1. Mirror thermal noise is one of the fundamental noises for room-temperature gravitational-wave detectors such as Advanced LIGO and Advanced Virgo. Thus, reduction of thermal noise is required for further improvement of their sensitivity. One effective approach for reducing thermal noise is to cool the mirrors. There are many technical challenges that must be overcome to cool the mirrors, such as cryocooler induced vibrations, thermal drift in suspensions, and reduction in duty cycling due to the increased number of potential failure mechanisms. Our mirror suspension has a black coating that makes radiative cooling more efficient. For conduction cooling, we developed ultra high purity aluminum heat links, which yield high thermal conductivity while keeping the spring constant sufficiently small. A unique inclination adjustment system, called moving mass, is used for aligning the mirror orientation in pitch. Photo-reflective displacement sensors, which have a large range, are installed for damping control on marionette recoil mass and intermediate recoil mass. Samarium cobalt magnets are used for coil-magnet actuators to prevent significant change of magnetism between room temperature and cryogenic temperature. In this paper, the design of our first cryogenic payload and its performance during bKAGRA Phase 1 are discussed.
△ Less
Submitted 25 January, 2021; v1 submitted 5 October, 2020;
originally announced October 2020.
-
Overview of KAGRA: Detector design and construction history
Authors:
T. Akutsu,
M. Ando,
K. Arai,
Y. Arai,
S. Araki,
A. Araya,
N. Aritomi,
Y. Aso,
S. -W. Bae,
Y. -B. Bae,
L. Baiotti,
R. Bajpai,
M. A. Barton,
K. Cannon,
E. Capocasa,
M. -L. Chan,
C. -S. Chen,
K. -H. Chen,
Y. -R. Chen,
H. -Y. Chu,
Y-K. Chu,
S. Eguchi,
Y. Enomoto,
R. Flaminio,
Y. Fujii
, et al. (175 additional authors not shown)
Abstract:
KAGRA is a newly built gravitational-wave telescope, a laser interferometer comprising arms with a length of 3\,km, located in Kamioka, Gifu, Japan. KAGRA was constructed under the ground and it is operated using cryogenic mirrors that help in reducing the seismic and thermal noise. Both technologies are expected to provide directions for the future of gravitational-wave telescopes. In 2019, KAGRA…
▽ More
KAGRA is a newly built gravitational-wave telescope, a laser interferometer comprising arms with a length of 3\,km, located in Kamioka, Gifu, Japan. KAGRA was constructed under the ground and it is operated using cryogenic mirrors that help in reducing the seismic and thermal noise. Both technologies are expected to provide directions for the future of gravitational-wave telescopes. In 2019, KAGRA finished all installations with the designed configuration, which we call the baseline KAGRA. In this occasion, we present an overview of the baseline KAGRA from various viewpoints in a series of of articles. In this article, we introduce the design configurations of KAGRA with its historical background.
△ Less
Submitted 2 July, 2020; v1 submitted 12 May, 2020;
originally announced May 2020.
-
High Performance Heat Conductor with Small Spring Constant for Cryogenic Applications
Authors:
Tomohiro Yamada,
Takayuki Tomaru,
Toshikazu Suzuki,
Takafumi Ushiba,
Nobuhiro Kimura,
Suguru Takada,
Yuki Inoue,
Takaaki Kajita
Abstract:
We developed a soft and high thermal conductive heat link for cryogenic applications. The measured maximum thermal conductivity was approximately 18500 W/m/K at 10 K. This spring constant was 1/43 of that of a single thick wire with the same cross-sectional area at room temperature. We realized these performances by utilizing high purity aluminum (99.9999 %, 6N) and by stranding many thin wires th…
▽ More
We developed a soft and high thermal conductive heat link for cryogenic applications. The measured maximum thermal conductivity was approximately 18500 W/m/K at 10 K. This spring constant was 1/43 of that of a single thick wire with the same cross-sectional area at room temperature. We realized these performances by utilizing high purity aluminum (99.9999 %, 6N) and by stranding many thin wires that are 0.15 mm in diameter. The electrical Residual Resistivity Ratio (RRR) was also measured and used to estimate the thermal conductivity by Wiedemann-Franz law. We observed the size effect on the electrical conductivity, and evaluated the effect of mechanical deformation to the RRR. These evaluations allow us to design a pragmatic heat link for cryogenic application.
△ Less
Submitted 25 March, 2020;
originally announced March 2020.
-
An arm length stabilization system for KAGRA and future gravitational-wave detectors
Authors:
T. Akutsu,
M. Ando,
K. Arai,
K. Arai,
Y. Arai,
S. Araki,
A. Araya,
N. Aritomi,
Y. Aso,
S. Bae,
Y. Bae,
L. Baiotti,
R. Bajpai,
M. A. Barton,
K. Cannon,
E. Capocasa,
M. Chan,
C. Chen,
K. Chen,
Y. Chen,
H. Chu,
Y-K. Chu,
K. Doi,
S. Eguchi,
Y. Enomoto
, et al. (181 additional authors not shown)
Abstract:
Modern ground-based gravitational wave (GW) detectors require a complex interferometer configuration with multiple coupled optical cavities. Since achieving the resonances of the arm cavities is the most challenging among the lock acquisition processes, the scheme called arm length stabilization (ALS) had been employed for lock acquisition of the arm cavities. We designed a new type of the ALS, wh…
▽ More
Modern ground-based gravitational wave (GW) detectors require a complex interferometer configuration with multiple coupled optical cavities. Since achieving the resonances of the arm cavities is the most challenging among the lock acquisition processes, the scheme called arm length stabilization (ALS) had been employed for lock acquisition of the arm cavities. We designed a new type of the ALS, which is compatible with the interferometers having long arms like the next generation GW detectors. The features of the new ALS are that the control configuration is simpler than those of previous ones and that it is not necessary to lay optical fibers for the ALS along the kilometer-long arms of the detector. Along with simulations of its noise performance, an experimental test of the new ALS was performed utilizing a single arm cavity of KAGRA. This paper presents the first results of the test where we demonstrated that lock acquisition of the arm cavity was achieved using the new ALS and residual noise was measured to be $8.2\,\mathrm{Hz}$ in units of frequency, which is smaller than the linewidth of the arm cavity and thus low enough to lock the full interferometer of KAGRA in a repeatable and reliable manner.
△ Less
Submitted 28 November, 2019; v1 submitted 2 October, 2019;
originally announced October 2019.
-
J-PARC Neutrino Beamline Upgrade Technical Design Report
Authors:
K. Abe,
H. Aihara,
A. Ajmi,
C. Alt,
C. Andreopoulos,
M. Antonova,
S. Aoki,
Y. Asada,
Y. Ashida,
A. Atherton,
E. Atkin,
S. Ban,
F. C. T. Barbato,
M. Barbi,
G. J. Barker,
G. Barr,
M. Batkiewicz,
A. Beloshapkin,
V. Berardi,
L. Berns,
S. Bhadra,
J. Bian,
S. Bienstock,
A. Blondel,
S. Bolognesi
, et al. (360 additional authors not shown)
Abstract:
In this document, technical details of the upgrade plan of the J-PARC neutrino beamline for the extension of the T2K experiment are described. T2K has proposed to accumulate data corresponding to $2\times{}10^{22}$ protons-on-target in the next decade, aiming at an initial observation of CP violation with $3σ$ or higher significance in the case of maximal CP violation. Methods to increase the neut…
▽ More
In this document, technical details of the upgrade plan of the J-PARC neutrino beamline for the extension of the T2K experiment are described. T2K has proposed to accumulate data corresponding to $2\times{}10^{22}$ protons-on-target in the next decade, aiming at an initial observation of CP violation with $3σ$ or higher significance in the case of maximal CP violation. Methods to increase the neutrino beam intensity, which are necessary to achieve the proposed data increase, are described.
△ Less
Submitted 14 August, 2019;
originally announced August 2019.
-
First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA
Authors:
KAGRA Collaboration,
T. Akutsu,
M. Ando,
K. Arai,
Y. Arai,
S. Araki,
A. Araya,
N. Aritomi,
H. Asada,
Y. Aso,
S. Atsuta,
K. Awai,
S. Bae,
L. Baiotti,
M. A. Barton,
K. Cannon,
E. Capocasa,
C-S. Chen,
T-W. Chiu,
K. Cho,
Y-K. Chu,
K. Craig,
W. Creus,
K. Doi,
K. Eda
, et al. (179 additional authors not shown)
Abstract:
KAGRA is a second-generation interferometric gravitational-wave detector with 3-km arms constructed at Kamioka, Gifu in Japan. It is now in its final installation phase, which we call bKAGRA (baseline KAGRA), with scientific observations expected to begin in late 2019. One of the advantages of KAGRA is its underground location of at least 200 m below the ground surface, which brings small seismic…
▽ More
KAGRA is a second-generation interferometric gravitational-wave detector with 3-km arms constructed at Kamioka, Gifu in Japan. It is now in its final installation phase, which we call bKAGRA (baseline KAGRA), with scientific observations expected to begin in late 2019. One of the advantages of KAGRA is its underground location of at least 200 m below the ground surface, which brings small seismic motion at low frequencies and high stability of the detector. Another advantage is that it cools down the sapphire test mass mirrors to cryogenic temperatures to reduce thermal noise. In April-May 2018, we have operated a 3-km Michelson interferometer with a cryogenic test mass for 10 days, which was the first time that km-scale interferometer was operated at cryogenic temperatures. In this article, we report the results of this "bKAGRA Phase 1" operation. We have demonstrated the feasibility of 3-km interferometer alignment and control with cryogenic mirrors.
△ Less
Submitted 11 January, 2019;
originally announced January 2019.
-
Vibration isolation system with a compact damping system for power recycling mirrors of KAGRA
Authors:
Y. Akiyama,
T. Akutsu,
M. Ando,
K. Arai,
Y. Arai,
S. Araki,
A. Araya,
N. Aritomi,
H. Asada,
Y. Aso,
S. Bae,
L. Baiotti,
M. A. Barton,
K. Cannon,
E. Capocasa,
C-S. Chen,
T-W. Chiu,
K. Cho,
Y-K. Chu,
K. Craig,
V. Dattilo,
K. Doi,
Y. Enomoto,
R. Flaminio,
Y. Fujii
, et al. (149 additional authors not shown)
Abstract:
A vibration isolation system called Type-Bp system used for power recycling mirrors has been developed for KAGRA, the interferometric gravitational-wave observatory in Japan. A suspension of the Type-Bp system passively isolates an optic from seismic vibration using three main pendulum stages equipped with two vertical vibration isolation systems. A compact reaction mass around each of the main st…
▽ More
A vibration isolation system called Type-Bp system used for power recycling mirrors has been developed for KAGRA, the interferometric gravitational-wave observatory in Japan. A suspension of the Type-Bp system passively isolates an optic from seismic vibration using three main pendulum stages equipped with two vertical vibration isolation systems. A compact reaction mass around each of the main stages allows for achieving sufficient damping performance with a simple feedback as well as vibration isolation ratio. Three Type-Bp systems were installed in KAGRA, and were proved to satisfy the requirements on the damping performance, and also on estimated residual displacement of the optics.
△ Less
Submitted 10 January, 2019;
originally announced January 2019.
-
Finding Continuity and Discontinuity in Fish Schools via Integrated Information Theory
Authors:
Takayuki Niizato,
Kotaro Sakamoto,
Yoh-ichi Mototake,
Takenori Tomaru,
Tomotaro Hoshika,
Toshiki Fukushima
Abstract:
Collective behaviour is known to be the result of diverse dynamics and is sometimes likened to a living system. Although many studies have revealed the dynamics of various collective behaviours, their main focus was on the information process inside the collective, not on the whole system itself. For example, the qualitative difference between two elements and three elements as a system has rarely…
▽ More
Collective behaviour is known to be the result of diverse dynamics and is sometimes likened to a living system. Although many studies have revealed the dynamics of various collective behaviours, their main focus was on the information process inside the collective, not on the whole system itself. For example, the qualitative difference between two elements and three elements as a system has rarely been investigated. Tononi et al. have proposed Integrated Information Theory (IIT) to measure the degree of consciousness $Φ$. IIT postulates that the amount of information loss caused by certain partitions is equivalent to the degree of information integration in the system. This measure is not only useful for estimating the degree of consciousness but can also be applied to more general network systems. Here we applied IIT (in particular, IIT 3.0 using PyPhi) to analyse real fish schools ({\it Plecoglossus altivelis}). Our hypothesis in this study is a very simple one: a living system evolves to raise its $Φ$ value. If we accept this hypothesis, IIT reveals the existence of continuous and discontinuous properties as group size varies. For example, leadership in the fish school emerged for a school size of four or above; but not below three. Furthermore, this transition was not observed by measuring mutual information or in a simple Boids model. This result suggests that integrated information $Φ$ can reveal some inherent properties which cannot be observed using other measures. We also discuss how the fish recognition of the figure-ground relation, that is, what determines the relevant ON and OFF states, may reveal various optimal paths for obtaining the functional evolution of collective behaviour.
△ Less
Submitted 3 December, 2018;
originally announced December 2018.
-
KAGRA: 2.5 Generation Interferometric Gravitational Wave Detector
Authors:
T. Akutsu,
M. Ando,
K. Arai,
Y. Arai,
S. Araki,
A. Araya,
N. Aritomi,
H. Asada,
Y. Aso,
S. Atsuta,
K. Awai,
S. Bae,
L. Baiotti,
M. A. Barton,
K. Cannon,
E. Capocasa,
C-S. Chen,
T-W. Chiu,
K. Cho,
Y-K. Chu,
K. Craig,
W. Creus,
K. Doi,
K. Eda,
Y. Enomoto
, et al. (169 additional authors not shown)
Abstract:
The recent detections of gravitational waves (GWs) reported by LIGO/Virgo collaborations have made significant impact on physics and astronomy. A global network of GW detectors will play a key role to solve the unknown nature of the sources in coordinated observations with astronomical telescopes and detectors. Here we introduce KAGRA (former name LCGT; Large-scale Cryogenic Gravitational wave Tel…
▽ More
The recent detections of gravitational waves (GWs) reported by LIGO/Virgo collaborations have made significant impact on physics and astronomy. A global network of GW detectors will play a key role to solve the unknown nature of the sources in coordinated observations with astronomical telescopes and detectors. Here we introduce KAGRA (former name LCGT; Large-scale Cryogenic Gravitational wave Telescope), a new GW detector with two 3-km baseline arms arranged in the shape of an "L", located inside the Mt. Ikenoyama, Kamioka, Gifu, Japan. KAGRA's design is similar to those of the second generations such as Advanced LIGO/Virgo, but it will be operating at the cryogenic temperature with sapphire mirrors. This low temperature feature is advantageous for improving the sensitivity around 100 Hz and is considered as an important feature for the third generation GW detector concept (e.g. Einstein Telescope of Europe or Cosmic Explorer of USA). Hence, KAGRA is often called as a 2.5 generation GW detector based on laser interferometry. The installation and commissioning of KAGRA is underway and its cryogenic systems have been successfully tested in May, 2018. KAGRA's first observation run is scheduled in late 2019, aiming to join the third observation run (O3) of the advanced LIGO/Virgo network. In this work, we describe a brief history of KAGRA and highlights of main feature. We also discuss the prospects of GW observation with KAGRA in the era of O3. When operating along with the existing GW detectors, KAGRA will be helpful to locate a GW source more accurately and to determine the source parameters with higher precision, providing information for follow-up observations of a GW trigger candidate.
△ Less
Submitted 20 November, 2018;
originally announced November 2018.
-
Construction of KAGRA: an Underground Gravitational Wave Observatory
Authors:
T. Akutsu,
M. Ando,
S. Araki,
A. Araya,
T. Arima,
N. Aritomi,
H. Asada,
Y. Aso,
S. Atsuta,
K. Awai,
L. Baiotti,
M. A. Barton,
D. Chen,
K. Cho,
K. Craig,
R. DeSalvo,
K. Doi,
K. Eda,
Y. Enomoto,
R. Flaminio,
S. Fujibayashi,
Y. Fujii,
M. -K. Fujimoto,
M. Fukushima,
T. Furuhata
, et al. (202 additional authors not shown)
Abstract:
Major construction and initial-phase operation of a second-generation gravitational-wave detector KAGRA has been completed. The entire 3-km detector is installed underground in a mine in order to be isolated from background seismic vibrations on the surface. This allows us to achieve a good sensitivity at low frequencies and high stability of the detector. Bare-bones equipment for the interferomet…
▽ More
Major construction and initial-phase operation of a second-generation gravitational-wave detector KAGRA has been completed. The entire 3-km detector is installed underground in a mine in order to be isolated from background seismic vibrations on the surface. This allows us to achieve a good sensitivity at low frequencies and high stability of the detector. Bare-bones equipment for the interferometer operation has been installed and the first test run was accomplished in March and April of 2016 with a rather simple configuration. The initial configuration of KAGRA is named {\it iKAGRA}. In this paper, we summarize the construction of KAGRA, including the study of the advantages and challenges of building an underground detector and the operation of the iKAGRA interferometer together with the geophysics interferometer that has been constructed in the same tunnel.
△ Less
Submitted 11 December, 2017; v1 submitted 30 November, 2017;
originally announced December 2017.
-
The status of KAGRA underground cryogenic gravitational wave telescope
Authors:
KAGRA Collaboration,
T. Akutsu,
M. Ando,
A. Araya,
N. Aritomi,
H. Asada,
Y. Aso,
S. Atsuta,
K. Awai,
M. A. Barton,
K. Cannon,
K. Craig,
W. Creus,
K. Doi,
K. Eda,
Y. Enomoto,
R. Flaminio,
Y. Fujii,
M. -K. Fujimoto,
T. Furuhata,
S. Haino,
K. Hasegawa,
K. Hashino,
K. Hayama,
S. Hirobayashi
, et al. (126 additional authors not shown)
Abstract:
KAGRA is a 3-km interferometric gravitational wave telescope located in the Kamioka mine in Japan. It is the first km-class gravitational wave telescope constructed underground to reduce seismic noise, and the first km-class telescope to use cryogenic cooling of test masses to reduce thermal noise. The construction of the infrastructure to house the interferometer in the tunnel, and the initial ph…
▽ More
KAGRA is a 3-km interferometric gravitational wave telescope located in the Kamioka mine in Japan. It is the first km-class gravitational wave telescope constructed underground to reduce seismic noise, and the first km-class telescope to use cryogenic cooling of test masses to reduce thermal noise. The construction of the infrastructure to house the interferometer in the tunnel, and the initial phase operation of the interferometer with a simple 3-km Michelson configuration have been completed. The first cryogenic operation is expected in 2018, and the observing runs with a full interferometer are expected in 2020s. The basic interferometer configuration and the current status of KAGRA are described.
△ Less
Submitted 13 October, 2017;
originally announced October 2017.
-
Mirror actuation design for the interferometer control of the KAGRA gravitational wave telescope
Authors:
Yuta Michimura,
Tomofumi Shimoda,
Takahiro Miyamoto,
Ayaka Shoda,
Koki Okutomi,
Yoshinori Fujii,
Hiroki Tanaka,
Mark A. Barton,
Ryutaro Takahashi,
Yoichi Aso,
Tomotada Akutsu,
Masaki Ando,
Yutaro Enomoto,
Raffaele Flaminio,
Kazuhiro Hayama,
Eiichi Hirose,
Yuki Inoue,
Takaaki Kajita,
Masahiro Kamiizumi,
Seiji Kawamura,
Keiko Kokeyama,
Kentaro Komori,
Rahul Kumar,
Osamu Miyakawa,
Koji Nagano
, et al. (14 additional authors not shown)
Abstract:
KAGRA is a 3-km cryogenic interferometric gravitational wave telescope located at an underground site in Japan. In order to achieve its target sensitivity, the relative positions of the mirrors of the interferometer must be finely adjusted with attached actuators. We have developed a model to simulate the length control loops of the KAGRA interferometer with realistic suspension responses and vari…
▽ More
KAGRA is a 3-km cryogenic interferometric gravitational wave telescope located at an underground site in Japan. In order to achieve its target sensitivity, the relative positions of the mirrors of the interferometer must be finely adjusted with attached actuators. We have developed a model to simulate the length control loops of the KAGRA interferometer with realistic suspension responses and various noises for mirror actuation. Using our model, we have designed the actuation parameters to have sufficient force range to acquire lock as well as to control all the length degrees of freedom without introducing excess noise.
△ Less
Submitted 21 June, 2019; v1 submitted 8 September, 2017;
originally announced September 2017.
-
Adaptation of frequency-domain readout for Transition Edge Sensor bolometers for the POLARBEAR-2 Cosmic Microwave Background experiment
Authors:
Kaori Hattori,
Kam Arnold,
Darcy Barron,
Matt Dobbs,
Tijmen de Haan,
Nicholas Harrington,
Masaya Hasegawa,
Masashi Hazumi,
William L. Holzapfel,
Brian Keating,
Adrian T. Lee,
Hideki Morii,
Michael J. Myers,
Graeme Smecher,
Aritoki Suzuki,
Takayuki Tomaru
Abstract:
The POLARBEAR-2 CosmicMicrowave Background (CMB) experiment aims to observe B-mode polarization with high sensitivity to explore gravitational lensing of CMB and inflationary gravitational waves. POLARBEAR-2 is an upgraded experiment based on POLARBEAR-1, which had first light in January 2012. For POLARBEAR-2, we will build a receiver that has 7,588 Transition Edge Sensor (TES) bolometers coupled…
▽ More
The POLARBEAR-2 CosmicMicrowave Background (CMB) experiment aims to observe B-mode polarization with high sensitivity to explore gravitational lensing of CMB and inflationary gravitational waves. POLARBEAR-2 is an upgraded experiment based on POLARBEAR-1, which had first light in January 2012. For POLARBEAR-2, we will build a receiver that has 7,588 Transition Edge Sensor (TES) bolometers coupled to two-band (95 and 150 GHz) polarization-sensitive antennas. For the large array's readout, we employ digital frequency-domain multiplexing and multiplex 32 bolometers through a single superconducting quantum interference device (SQUID). An 8-bolometer frequency-domain multiplexing readout has been deployed on POLARBEAR-1 experiment. Extending that architecture to 32 bolometers requires an increase in the bandwidth of the SQUID electronics to 3 MHz. To achieve this increase in bandwidth, we use Digital Active Nulling (DAN) on the digital frequency multiplexing platform. In this paper, we present requirements and improvements on parasitic inductance and resistance of cryogenic wiring and capacitors used for modulating bolometers. These components are problematic above 1 MHz. We also show that our system is able to bias a bolometer in its superconducting transition at 3 MHz.
△ Less
Submitted 4 July, 2013; v1 submitted 7 June, 2013;
originally announced June 2013.
-
Measurements of the T2K neutrino beam properties using the INGRID on-axis near detector
Authors:
K. Abe,
N. Abgrall,
Y. Ajima,
H. Aihara,
J. B. Albert,
C. Andreopoulos,
B. Andrieu,
M. D. Anerella,
S. Aoki,
O. Araoka,
J. Argyriades,
A. Ariga,
T. Ariga,
S. Assylbekov,
D. Autiero,
A. Badertscher,
M. Barbi,
G. J. Barker,
G. Barr,
M. Bass,
M. Batkiewicz,
F. Bay,
S. Bentham,
V. Berardi,
B. E. Berger
, et al. (407 additional authors not shown)
Abstract:
Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure o…
▽ More
Precise measurement of neutrino beam direction and intensity was achieved based on a new concept with modularized neutrino detectors. INGRID (Interactive Neutrino GRID) is an on-axis near detector for the T2K long baseline neutrino oscillation experiment. INGRID consists of 16 identical modules arranged in horizontal and vertical arrays around the beam center. The module has a sandwich structure of iron target plates and scintillator trackers. INGRID directly monitors the muon neutrino beam profile center and intensity using the number of observed neutrino events in each module. The neutrino beam direction is measured with accuracy better than 0.4 mrad from the measured profile center. The normalized event rate is measured with 4% precision.
△ Less
Submitted 14 November, 2011;
originally announced November 2011.
-
The T2K Experiment
Authors:
T2K Collaboration,
K. Abe,
N. Abgrall,
H. Aihara,
Y. Ajima,
J. B. Albert,
D. Allan,
P. -A. Amaudruz,
C. Andreopoulos,
B. Andrieu,
M. D. Anerella,
C. Angelsen,
S. Aoki,
O. Araoka,
J. Argyriades,
A. Ariga,
T. Ariga,
S. Assylbekov,
J. P. A. M. de André,
D. Autiero,
A. Badertscher,
O. Ballester,
M. Barbi,
G. J. Barker,
P. Baron
, et al. (499 additional authors not shown)
Abstract:
The T2K experiment is a long-baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ_{13} by observing ν_e appearance in a ν_μ beam. It also aims to make a precision measurement of the known oscillation parameters, Δm^{2}_{23} and sin^{2} 2θ_{23}, via ν_μ disappearance studies. Other goals of the experiment include various neutrino cross…
▽ More
The T2K experiment is a long-baseline neutrino oscillation experiment. Its main goal is to measure the last unknown lepton sector mixing angle θ_{13} by observing ν_e appearance in a ν_μ beam. It also aims to make a precision measurement of the known oscillation parameters, Δm^{2}_{23} and sin^{2} 2θ_{23}, via ν_μ disappearance studies. Other goals of the experiment include various neutrino cross section measurements and sterile neutrino searches. The experiment uses an intense proton beam generated by the J-PARC accelerator in Tokai, Japan, and is composed of a neutrino beamline, a near detector complex (ND280), and a far detector (Super-Kamiokande) located 295 km away from J-PARC. This paper provides a comprehensive review of the instrumentation aspect of the T2K experiment and a summary of the vital information for each subsystem.
△ Less
Submitted 8 June, 2011; v1 submitted 6 June, 2011;
originally announced June 2011.
-
Current status of the CLIO project
Authors:
K Yamamoto,
T Uchiyama,
S Miyoki,
M Ohashi,
K Kuroda,
H Ishitsuka,
T Akutsu,
S Telada,
T Tomaru,
T Suzuki,
N Sato,
Y Saito,
Y Higashi,
T Haruyama,
A Yamamoto,
T Shintomi,
D Tatsumi,
M Ando,
H Tagoshi,
N Kanda,
N Awaya,
S Yamagishi,
H Takahashi,
A Araya,
A Takamori
, et al. (5 additional authors not shown)
Abstract:
CLIO (Cryogenic Laser Interferometer Observatory) is a Japanese gravitational wave detector project. One of the main purposes of CLIO is to demonstrate thermal-noise suppression by cooling mirrors for a future Japanese project, LCGT (Large-scale Cryogenic Gravitational Telescope). The CLIO site is in Kamioka mine, as is LCGT. The progress of CLIO between 2005 and 2007 (room- and cryogenic-temper…
▽ More
CLIO (Cryogenic Laser Interferometer Observatory) is a Japanese gravitational wave detector project. One of the main purposes of CLIO is to demonstrate thermal-noise suppression by cooling mirrors for a future Japanese project, LCGT (Large-scale Cryogenic Gravitational Telescope). The CLIO site is in Kamioka mine, as is LCGT. The progress of CLIO between 2005 and 2007 (room- and cryogenic-temperature experiments) is introduced in this article. In a room-temperature experiment, we made efforts to improve the sensitivity. The current best sensitivity at 300 K is about $6 \times 10^{-21} /\sqrt{\rm Hz}$ around 400 Hz. Below 20 Hz, the strain (not displacement) sensitivity is comparable to that of LIGO, although the baselines of CLIO are 40-times shorter (CLIO: 100m, LIGO: 4km). This is because seismic noise is extremely small in Kamioka mine. We operated the interferometer at room temperature for gravitational wave observations. We obtained 86 hours of data. In the cryogenic experiment, it was confirmed that the mirrors were sufficiently cooled (14 K). However, we found that the radiation shield ducts transferred 300K radiation into the cryostat more effectively than we had expected. We observed that noise caused by pure aluminum wires to suspend a mirror was suppressed by cooling the mirror.
△ Less
Submitted 15 May, 2008;
originally announced May 2008.
-
Conduction Effect of Thermal Radiation in a Metal Shield Pipe in a Cryostat for a Cryogenic Interferometric Gravitational Wave Detector
Authors:
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
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 conduc…
▽ More
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.
△ Less
Submitted 6 November, 2007;
originally announced November 2007.
-
Pulse tube cryocooler with self-cancellation of cold stage vibration
Authors:
T. Suzuki,
T. Tomaru,
T. Haruyama,
N. Sato,
A. Yamamoto,
T. Shintomi,
Y. Ikushima,
R. Li
Abstract:
We experimentally demonstrated a new method for reducing the vibration of the cold stage of a cryocooler. Comparing the RMS amplitude with the case of no phase shift of the driving gas pressure between the two pairs, the longitudinal vibration of the cold stage was reduced by 96.1% at 126 K by supplying gas pressure with 180 degrees of phase shift.
We experimentally demonstrated a new method for reducing the vibration of the cold stage of a cryocooler. Comparing the RMS amplitude with the case of no phase shift of the driving gas pressure between the two pairs, the longitudinal vibration of the cold stage was reduced by 96.1% at 126 K by supplying gas pressure with 180 degrees of phase shift.
△ Less
Submitted 3 November, 2006;
originally announced November 2006.
-
Thermal lensing in cryogenic sapphire substrates
Authors:
Takayuki Tomaru,
Toshikazu Suzuki,
Shinji Miyoki,
Takashi Uchiyama,
C. T. Taylor,
Akira Yamamoto,
Takakazu Shintomi,
Masatake Ohashi,
Kazuaki Kuroda
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 cryog…
▽ More
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.
△ Less
Submitted 12 February, 2002;
originally announced February 2002.
-
Cryogenic measurement of the optical absorption coefficient in sapphire crystals at 1.064(micro)m for the Large-scale Cryogenic Gravitational wave Telescope
Authors:
Takayuki Tomaru,
Takashi Uchiyama,
Daisuke Tatsumi,
Shinji Miyoki,
Masatake Ohashi,
Kazuaki Kuroda,
Toshikazu Suzuki,
Akira Yamamoto,
Takakazu Shintomi
Abstract:
We have applied laser calorimetry to the measurement of optical absorption in mono-crystalline sapphire at cryogenic temperatures. Sapphire is a promising candidate for the mirror substrates of the Large-scale Cryogenic Gravitational wave Telescope. The optical absorption coefficients of different sapphire samples at a wavelength of 1.064(micro)m at 5K were found to average 90ppm/cm.
We have applied laser calorimetry to the measurement of optical absorption in mono-crystalline sapphire at cryogenic temperatures. Sapphire is a promising candidate for the mirror substrates of the Large-scale Cryogenic Gravitational wave Telescope. The optical absorption coefficients of different sapphire samples at a wavelength of 1.064(micro)m at 5K were found to average 90ppm/cm.
△ Less
Submitted 8 March, 2001; v1 submitted 17 January, 2001;
originally announced January 2001.