arXiv subjects

N. Kanda

Publications and source records attributed to N. Kanda.

At least 19 recordsLinked to original sources

arXiv2025

Decadal upgrade strategy for KAGRA toward post-O5 gravitational-wave astronomy

The KAGRA Collaboration has investigated a ten-year upgrade strategy for the KAGRA gravitational wave detector, considering a total of 14 upgrade options that vary in mirror mass, quantum noise reduction techniques, and the quality of cryogenic suspensions. We evaluated the scientific potential of these configurations with a focus on key targets such as parameter estimation of compact binary coalescences, binary neutron star post-merger signals, and continuous gravitational waves. Rather than aiming to improve all science cases uniformly, we prioritized those most sensitive to the detector configuration. Technical feasibility was assessed based on required hardware developments, associated R\&D efforts, cost, and risk. Our study finds that a high-frequency upgrade plan that enhances sensitivity over a broad frequency range above ~200 Hz offers the best balance between scientific return and technical feasibility. Such an upgrade would enable sky localization of binary neutron star mergers at 100 Mpc to better than 0.5 deg$^2$ in a LIGO-Virgo-KAGRA network, and improve the measurement precision of tidal deformability parameter by approximately 10% at median, compared to a network without KAGRA.

gr-qc↗

arXiv2025

Identification of Noise-Associated Glitches in KAGRA O3GK with Hveto

Transient noise ("glitches") in gravitational wave detectors can mimic or obscure true signals, significantly reducing detection sensitivity. Identifying and excluding glitch-contaminated data segments is therefore crucial for enhancing the performance of gravitational-wave searches. We perform a noise analysis of the KAGRA data obtained during the O3GK observation. Our analysis is performed with hierarchical veto (Hveto) which identifies noises based on the statistical time correlation between the main channel and the auxiliary channels. A total of 2,531 noises were vetoed by 28 auxiliary channels with the configuration (i.e., signal-to-noise threshold set to 8) that we chose for Hveto. We identify vetoed events as glitches on the spectrogram via visual examination after plotting them with Q-transformation. By referring to the Gravity Spy project, we categorize 2,354 glitches into six types: blip, helix, scratchy, and scattered light, which correspond to those listed in Gravity Spy, and dot and line, which are not found in the Gravity Spy classification and are thus named based on their spectrogram morphology in KAGRA data. The remaining 177 glitches are determined not to belong to any of these six types. We show how the KAGRA glitch types are related to each subsystem of KAGRA. To investigate the possible correlation between the main channel and the round winner - an auxiliary channel statistically associated with the main channel for vetoing purposes - we visually examine the similarity or difference in the glitch pattern on the spectrogram. We compare the qualitative correlation found through visual examination with coherence, which is known to provide quantitative measurement for the correlation between the main channel and each auxiliary channel. Our comprehensive noise analysis will help improve the data quality of KAGRA by applying it to future KAGRA observation data.

gr-qc↗

arXiv2023

Development of advanced photon calibrator for Kamioka gravitational wave detector (KAGRA)

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 /%.

astro-ph.IM↗

arXiv2022

Input optics systems of the KAGRA detector during O3GK

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.

gr-qc↗

arXiv2022

Noise subtraction from KAGRA O3GK data using Independent Component Analysis

In April 2020, KAGRA conducted its first science observation in combination with the GEO~600 detector (O3GK) for two weeks. According to the noise budget estimation, suspension control noise in the low frequency band and acoustic noise in the middle frequency band are identified as the dominant contribution. In this study, we show that such noise can be reduced in offline data analysis by utilizing a method called Independent Component Analysis (ICA). Here the ICA model is extended from the one studied in iKAGRA data analysis by incorporating frequency dependence while linearity and stationarity of the couplings are still assumed. By using optimal witness sensors, those two dominant contributions are mitigated in the real observational data. We also analyze the stability of the transfer functions for whole two weeks data in order to investigate how the current subtraction method can be practically used in gravitational wave search.

astro-ph.IM↗

arXiv2022

Performance of the KAGRA detector during the first joint observation with GEO 600 (O3GK)

KAGRA, the kilometer-scale underground gravitational-wave detector, is located at Kamioka, Japan. In April 2020, an astrophysics observation was performed at the KAGRA detector in combination with the GEO 600 detector; this observation operation is called O3GK. The optical configuration in O3GK is based on a power recycled Fabry-P\'{e}rot Michelson interferometer; all the mirrors were set at room temperature. The duty factor of the operation was approximately 53%, and the strain sensitivity was $3\times10^{-22}~/\sqrt{\rm{Hz}}$ at 250 Hz. In addition, the binary-neutron-star (BNS) inspiral range was approximately 0.6 Mpc. The contributions of various noise sources to the sensitivity of O3GK were investigated to understand how the observation range could be improved; this study is called a "noise budget". According to our noise budget, the measured sensitivity could be approximated by adding up the effect of each noise. The sensitivity was dominated by noise from the sensors used for local controls of the vibration isolation systems, acoustic noise, shot noise, and laser frequency noise. Further, other noise sources that did not limit the sensitivity were investigated. This paper provides a detailed account of the KAGRA detector in O3GK including interferometer configuration, status, and noise budget. In addition, strategies for future sensitivity improvements such as hardware upgrades, are discussed.

astro-ph.IM↗

arXiv2021

Charge-changing cross sections for $^{42\textrm{--}51}$Ca and effect of charged-particle evaporation induced by neutron removal reaction

Charge-changing cross sections $\sigma_\mathrm{CC}$ for $^{42\textrm{--}51}$Ca on a carbon target at around 280~MeV/nucleon have been measured. The measured $\sigma_\mathrm{CC}$ values differ significantly from the previously developed calculations based on the Glauber model. However, through introduction of the charged-particle evaporation effect induced by the neutron-removal reaction in addition to the Glauber-model calculation, experimental $\sigma_\mathrm{CC}$ values on $^{12}$C at around 300~MeV/nucleon for nuclides from C to Fe isotopes are all reproduced with approximately 1\% accuracy. This proposed model systematically reproduces $\sigma_\mathrm{CC}$ data without phenomenological corrections, and can also explain experimental $\sigma_\mathrm{CC}$ values obtained in other energy regions.

nucl-ex↗

arXiv2021

Application of the Hilbert-Huang transform for analyzing standing-accretion-shock-instability induced gravitational waves in a core-collapse supernova

Through numerical simulations, it is predicted that the gravitational waves (GWs) reflect the characteristics of the core-collapse supernova (CCSN) explosion mechanism. There are multiple GW excitation processes that occur inside a star before its explosion, and it is suggested that the GWs originating from the CCSN have a mode for each excitation process in terms of time-frequency representation. Therefore, we propose an application of the Hilbert-Huang Transform (HHT), which is a high-resolution time-frequency analysis method, to analyze these GW modes for theoretically probing and increasing our understanding of the explosion mechanism. The HHT defines frequency as a function of time, and is not bound by the trade-off between time and frequency resolutions. In this study, we analyze a gravitational waveform obtained from a three-dimensional general-relativistic CCSN model that showed a vigorous activity of the standing-accretion-shock-instability (SASI). We succeed in extracting the SASI induced GWs with high resolution on a time-frequency representation using the HHT and we examine their instantaneous frequencies.

astro-ph.HE↗

arXiv2020

Overview of KAGRA: Calibration, detector characterization, physical environmental monitors, and the geophysics interferometer

KAGRA is a newly built gravitational wave observatory, a laser interferometer with a 3 km arm length, located in Kamioka, Gifu, Japan. In this series of articles, we present an overview of the baseline KAGRA, for which we finished installing the designed configuration in 2019. This article describes the method of calibration (CAL) used for reconstructing gravitational wave signals from the detector outputs, as well as the characterization of the detector (DET). We also review the physical environmental monitors (PEM) system and the geophysics interferometer (GIF). Both are used for characterizing and evaluating the data quality of the gravitational wave channel. They play important roles in utilizing the detector output for gravitational wave searches. These characterization investigations will be even more important in the near future, once gravitational wave detection has been achieved, and in using KAGRA in the gravitational wave astronomy era.

gr-qc↗

arXiv2020

Overview of KAGRA : KAGRA science

KAGRA is a newly build gravitational-wave observatory, a laser interferometer with 3 km arm length, located in Kamioka, Gifu, Japan. In this paper in the series of KAGRA-featured articles, we discuss the science targets of KAGRA projects, considering not only the baseline KAGRA (current design) but also its future upgrade candidates (KAGRA+) for the near to middle term (~5 years).

gr-qc↗

arXiv2020

Overview of KAGRA: Detector design and construction history

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.

physics.ins-det↗

arXiv2019

Swelling of doubly magic $^{48}$Ca core in Ca isotopes beyond $N=28$

Interaction cross sections for $^{42\textrm{-}51}$Ca on a carbon target at 280 MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number $N=28$. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and the Mean-Field calculations point out that this anomalous enhancement of the nuclear size beyond $N=28$ results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare $^{48}$Ca core in Ca isotopes beyond $N=28$.

nucl-ex↗

arXiv2019

An arm length stabilization system for KAGRA and future gravitational-wave detectors

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.

physics.ins-det↗

arXiv2019

Application of the independent component analysis to the iKAGRA data

We apply the independent component analysis (ICA) to the real data from a gravitational wave detector for the first time. Specifically we use the iKAGRA data taken in April 2016, and calculate the correlations between the gravitational wave strain channel and 35 physical environmental channels. Using a couple of seismic channels which are found to be strongly correlated with the strain, we perform ICA. Injecting a sinusoidal continuous signal in the strain channel, we find that ICA recovers correct parameters with enhanced signal-to-noise ratio, which demonstrates usefulness of this method. Among the two implementations of ICA used here, we find the correlation method yields the optimal result for the case environmental noises act on the strain channel linearly.

astro-ph.IM↗

arXiv2019

First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA

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.

astro-ph.IM↗

arXiv2019

Vibration isolation system with a compact damping system for power recycling mirrors of KAGRA

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.

physics.ins-det↗

arXiv2018

KAGRA: 2.5 Generation Interferometric Gravitational Wave Detector

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.

gr-qc↗

arXiv2017

Construction of KAGRA: an Underground Gravitational Wave Observatory

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.

gr-qc↗