First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA. (arXiv:1901.03569v1 [astro-ph.IM])

First cryogenic test operation of underground km-scale gravitational-wave observatory KAGRA. (arXiv:1901.03569v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_KAGRA/0/1/0/all/0/1">KAGRA Collaboration</a>: <a href="http://arxiv.org/find/astro-ph/1/au:+Akutsu_T/0/1/0/all/0/1">T. Akutsu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ando_M/0/1/0/all/0/1">M. Ando</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arai_K/0/1/0/all/0/1">K. Arai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Arai_Y/0/1/0/all/0/1">Y. Arai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Araki_S/0/1/0/all/0/1">S. Araki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Araya_A/0/1/0/all/0/1">A. Araya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aritomi_N/0/1/0/all/0/1">N. Aritomi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Asada_H/0/1/0/all/0/1">H. Asada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aso_Y/0/1/0/all/0/1">Y. Aso</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Atsuta_S/0/1/0/all/0/1">S. Atsuta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Awai_K/0/1/0/all/0/1">K. Awai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bae_S/0/1/0/all/0/1">S. Bae</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baiotti_L/0/1/0/all/0/1">L. Baiotti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Barton_M/0/1/0/all/0/1">M. A. Barton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cannon_K/0/1/0/all/0/1">K. Cannon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Capocasa_E/0/1/0/all/0/1">E. Capocasa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chen_C/0/1/0/all/0/1">C-S. Chen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chiu_T/0/1/0/all/0/1">T-W. Chiu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cho_K/0/1/0/all/0/1">K. Cho</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chu_Y/0/1/0/all/0/1">Y-K. Chu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Craig_K/0/1/0/all/0/1">K. Craig</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Creus_W/0/1/0/all/0/1">W. Creus</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Doi_K/0/1/0/all/0/1">K. Doi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eda_K/0/1/0/all/0/1">K. Eda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Enomoto_Y/0/1/0/all/0/1">Y. Enomoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Flaminio_R/0/1/0/all/0/1">R. Flaminio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fujii_Y/0/1/0/all/0/1">Y. Fujii</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fujimoto_M/0/1/0/all/0/1">M.-K. Fujimoto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fukunaga_M/0/1/0/all/0/1">M. Fukunaga</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fukushima_M/0/1/0/all/0/1">M. Fukushima</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Furuhata_T/0/1/0/all/0/1">T. Furuhata</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hagiwara_A/0/1/0/all/0/1">A. Hagiwara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haino_S/0/1/0/all/0/1">S. Haino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hasegawa_K/0/1/0/all/0/1">K. Hasegawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hashino_K/0/1/0/all/0/1">K. Hashino</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hayama_K/0/1/0/all/0/1">K. Hayama</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirobayashi_S/0/1/0/all/0/1">S. Hirobayashi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirose_E/0/1/0/all/0/1">E. Hirose</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hsieh_B/0/1/0/all/0/1">B. H. Hsieh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_C/0/1/0/all/0/1">C-Z. Huang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ikenoue_B/0/1/0/all/0/1">B. Ikenoue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Inoue_Y/0/1/0/all/0/1">Y. Inoue</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ioka_K/0/1/0/all/0/1">K. Ioka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Itoh_Y/0/1/0/all/0/1">Y. Itoh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Izumi_K/0/1/0/all/0/1">K. Izumi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaji_T/0/1/0/all/0/1">T. Kaji</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kajita_T/0/1/0/all/0/1">T. Kajita</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kakizaki_M/0/1/0/all/0/1">M. Kakizaki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kamiizumi_M/0/1/0/all/0/1">M. Kamiizumi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kanbara_S/0/1/0/all/0/1">S. Kanbara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kanda_N/0/1/0/all/0/1">N. Kanda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kanemura_S/0/1/0/all/0/1">S. Kanemura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kaneyama_M/0/1/0/all/0/1">M. Kaneyama</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kang_G/0/1/0/all/0/1">G. Kang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kasuya_J/0/1/0/all/0/1">J. Kasuya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kataoka_Y/0/1/0/all/0/1">Y. Kataoka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawai_N/0/1/0/all/0/1">N. Kawai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawamura_S/0/1/0/all/0/1">S. Kawamura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawasaki_T/0/1/0/all/0/1">T. Kawasaki</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_C/0/1/0/all/0/1">C. Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_J/0/1/0/all/0/1">J. Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_J/0/1/0/all/0/1">J. C. Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_W/0/1/0/all/0/1">W. S. Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kim_Y/0/1/0/all/0/1">Y.-M. Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kimura_N/0/1/0/all/0/1">N. Kimura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kinugawa_T/0/1/0/all/0/1">T. Kinugawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kirii_S/0/1/0/all/0/1">S. Kirii</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kitaoka_Y/0/1/0/all/0/1">Y. Kitaoka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kitazawa_H/0/1/0/all/0/1">H. Kitazawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kojima_Y/0/1/0/all/0/1">Y. Kojima</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kokeyama_K/0/1/0/all/0/1">K. Kokeyama</a>, et al. (132 additional authors not shown)

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.

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