KAGRA subgroup report Cryogenics T. Suzuki, Y. Sakakibara KEK/ICRR

Contents of this report Introduction of subgroup members (T.Suzuki) Status of fabrication (T.Suzuki) Installation of cryostats and duct shields (T.Suzuki) Performance of duct shield (Y.Sakakibara) Topics will be presented in 6 th Feb. Cryo-suspension design (K.Yamamoto, D.Chen, T.Miyamoto, H.Tanaka) Surveying and alignment (T. Kume)

KAGRA Cryogenics Group Toshikazu SUZUKI Chief KEK, Prof. Nobuhiro KIMURA Cryostat sub-chief KEK, Assoc. Prof. Kazuhiro YAMAMOTO Cryo-Payload sub-chief ICRR, Assist. Prof. Takayuki TOMARU Cryo-Payload KEK, Assoc. Prof. Tatsuya KUME Surveying, Alignment KEK, Assoc. Prof. Rahul KUMAR Simulation, Payload KEK, PD Yusuke SAKAKIBARA Cryostat, Scattering ICRR, Grad. Student Dan CHEN Cryo-Payload, Q ICRR, Grad. Student Ayako HAGIWARA CAD KEK, Technical Staff Shinichi TERASHIMA Machining KEK, Technical Staff Iwao MURAKAMI Welding, Assembly KEK, Technical Staff Hiroki TANAKA Cryo-Payload, Q ICRR, Grad. Student Takahiro MIYAMOTO Cryo-Payload ICRR, Grad. Student Rookie Suguru TAKADA Cryogenics NIFS, Assist. Prof.

Mr. Shigeaki KOIKE, KEK Engineer, passed away in last Nov. 15 He designed KAGRA Cryostat and gave many contribution to KAGRA. We lost a good friend, but his work will be in KAGRA.

KAGRA Cryogenics Manufacturing – Cryostats and 4K cooler units (done 4 sets in 2011~2012) – Duct-shields (done 3 in 2013, fabricating 3 in 2014, will fabricate 2 in 2015) – 80K coolers for cooling duct- shields ( fabricating 8 in 2014) Installation – Transport from the warehouse – Carry cryostats through the tunnel – Assembling on a target point Cryogenic payload – > Topic 3 6 th Feb.

Transportation of cryostats to X and Y ends

Assembling and leak test of  2400 upper flange Construct a simple clean booth around a cryostat. Set blower to supply filtered air. Put a metal gasket to the upper flange and fasten the flange. Set side port flanges. KAGRA requirement < 1x Pa*m 3 /sec Detector background 1x Pa*m 3 /sec No excess leak found above the background. Surveying and alignment -> Topic 9 6 th Feb.

Design of duct shield Duct and baffles are coated with black coating Solblack to absorb thermal radiation and scattered light – Calculated thermal radiation input < 0.38 W (<KAGRA requirement 0.5 W) Baffles are tilted to catch scattered light Cooled down by vibration-isolated cryocooler unit during observation – Cryocooler was directly connected here for testing 8 Length in mm 5 m Baffle Scattered light Duct

Calculated scattered light noise Calculated result was found to satisfy KAGRA requirement 9 Resonance 1 Hz Power inside cavity 400 kW Mass 23 kg Solblack reflectivity and scattering property: Genesia, T. Akutsu PSD of mirror surface: E. Hirose et al. Phys. Lett. D 89 (2014) D. J. Ottaway et al. OPTICS EXPRESS 20 (8) (2012) 8329

Summary Fabrication – Three duct-shields and eight 80K cooler units are fabricating in 2014fy. – Two duct-shields will be fabricated in 2015fy. Installation – Two cryostats installed to X-end and Y-end. – Another two will be installed to X-front and Y-front in Feb. and Mar – No leak was found for the cryostat in X-end. – Measurement of attitude of cryostat will be continued Duct-shield – Suppression of thermal radiation and scattered light were evaluated