Influence of nonuniformity in sapphire substrates for a gravitational wave telescope

Somiya, K.; Hirose, E.; Michimura, Yuta

doi:10.1103/physrevd.100.082005

Cited by 16 publications

(8 citation statements)

References 15 publications

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“…The coupling between CARM and DARM was measured and observed to be larger than the expected level derived using the simulation model that included known or assumed differences in the transmittance of the ITMs, finesse of the arm cavities (as depicted in Table 1), reflected light phase map, and transmission wavefront error map that essentially displays the non-uniformity of the optical thickness of the mirror [48]. A possible cause of the larger CARM-DARM coupling is the birefringence of the test mass mirrors.…”

Section: Laser Frequency Noisementioning

confidence: 85%

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

Abe,

Adhikari,

Akutsu

et al. 2022

Preprint

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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 5/37 Fabry-Pérot 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 × 10 −22 / √ 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.

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Section: Laser Frequency Noisementioning

confidence: 85%

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

Abe,

Adhikari,

Akutsu

et al. 2022

Preprint

Self Cite

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“…Also, fabrication of larger sapphire mirrors would be feasible in the next few years, but it remains uncertain at this point whether larger mirror with required quality is feasible or not. Recently, in KAGRA, it is found that nonuniformity of the transmission map and inhomogeneous birefringence of the input test masses were larger than the expectation, partly due to the use of light with wrong polarization to measure the transmission map to correct the map [31, 59,60]. These issues need to be investigated further for realizing the upgrade of KAGRA.…”

Section: Discussionmentioning

confidence: 99%

Prospects for improving the sensitivity of the cryogenic gravitational wave detector KAGRA

Michimura,

Komori,

Enomoto

et al. 2020

Preprint

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Upgrades to improve the sensitivity of gravitational wave detectors enable more frequent detections and more precise source parameter estimation. Unlike other advanced interferometric detectors such as Advanced LIGO and Advanced Virgo, KAGRA requires different approach for the upgrade since it is the only detector which employs cryogenic cooling of the test masses. In this paper, we describe possible KAGRA upgrades with technologies focusing on different detector bands, and compare the impacts on the detection of compact binary coalescences. We show that either fivefold improvement in 100M⊙-100M⊙ binary black hole range, a factor of 1.3 improvement in binary neutron star range, or a factor of 1.7 improvement in the sky localization of binary neutron stars is well feasible with upgrades which do not require changes in the existing cryogenic or vacuum infrastructure. We also show that twofold broadband sensitivity improvement is possible by applying multiple upgrades to the detector.

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“…The inhomogeneity of the refractive index of a material is not usually categorized as its topography, but we introduce sapphire's inhomogeneity here since the measurement technique is essentially the same as the figure measurement. Inhomogeneity of the substrate is especially important in the ITMs since wave-front phase distortion while the beam propagates through the substrate degrades the sensitivity [14]. Sapphire is known to have inhomogeneity about 1 order of magnitude greater than that of fused silica.…”

Section: E Inhomogeneity Of the Substratementioning

confidence: 99%

“…The situation will become worse with inhomogeneity of the ITM substrate. The transfer function from frequency noise to strain sensitivity was independently simulated with the measured inhomogeneity maps, and it was found that the transfer function increases by more than 1 order of magnitude in the observation band [14]. Moreover, the inhomogeneity in the c plane acts as a polarization coupler that converts a linearly polarized incident beam to the opposite polarization state to some extent.…”

Section: Impact On the Detectormentioning

confidence: 99%

Characterization of Core Optics in Gravitational-Wave Detectors: Case Study of KAGRA Sapphire Mirrors

et al. 2020

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We report the characterization of superlow-loss optics used in the second-generation gravitational-wave detectors currently in operation. The sapphire test-mass mirrors in the KAGRA detector are introduced as an example, but the techniques here are common to all detectors. In this work, we discuss mainly the surface topography obtained by interferometric techniques and the optical properties obtained with special setups.

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Influence of nonuniformity in sapphire substrates for a gravitational wave telescope

Cited by 16 publications

References 15 publications

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

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

Prospects for improving the sensitivity of the cryogenic gravitational wave detector KAGRA

Characterization of Core Optics in Gravitational-Wave Detectors: Case Study of KAGRA Sapphire Mirrors

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