Cryogenic system installation and update on the cryo-payload system for the KAGRA detector Rahul Kumar1, T. Takayuki1, K. Yamamoto2, H. Tanaka2,T. Miyamoto2, T. Suzuki1, N. Kimura1, T. Kume1 and The Cryogenics Group High Energy Accelerator Research Organisation (KEK) 1, The University of Tokyo (ICRR) 2, Japan 11th Edoardo Amaldi Conference on Gravitational Waves June 21 – 26, 2015, Gwangju, South Korea

Outline KAGRA project (status talk by R. Flaminio) Cryostat installation Design status: Cryogenic payload system Conclusions The next slide shows the outline of my talk. I will give a brief introduction about the KAGRA detector which is currently being constructed in Japan for the detection of gravitational waves Next I will give the present status of the ongoing installation activities at the KAGRA site in the Kamioka mine. Then I will discussing the design of the cryogenic payload system for the kagra detector And finally I will be concluding my talk

Cryostat Installation 2.6 m 4.3 m Cryostats were the first to be installed. The cryostats are 4.6 m in height and 2.6 m in diameter without the flanges. This is almost the same size as that of the arm tunnel and hence it had to be installed first. They were transported by special carts. All the cryostats have been installed and assembled. Installation video link : https://www.youtube.com/watch?v=6n6nuxA_xlY

Cryostat Assembly All the cryostats have been installed and assembled. These images were taken during the cryostat installation All the cryostats have been installed and assembled. All the cryostats have been installed and assembled. 2.6m

Tests for vacuum leakage ongoing Vacuum Tubes and Tanks Installation Beam tubes: φ800mm x12m x 478 Mode cleaner and BS tanks After the cryostat installation to both the ends, vaccum tubes of total 478 in number were installed in the arm tunnels. This work was recently completed in March 2015. Tests for vacuum leakage ongoing

Teething problems ~ 3x10-9 Vertical Vibration Measurement Results by Seismometer Seismic vibration at X-end cryostat is expected level, comparable with CLIO site. In front of water pit where is about 10m from the cryostat location, we found excess over 10Hz. ~ 3x10-9 Vertical Measurement by T. Takayuki A big issue is water leakage in the tunnel. During spring time when the snow melts about 1200 tons of water leaks every hour. KAGRA site has a gradient of 1/300 to counter underground water. The water flows in the side pits in the tunnel. The water can affect the seismic vibrations. Recently Takayuki measured the vibrations at the kagra site using seismometers and the results can been in this plot. The vibration levels are at 3*e-9 m/sqrtHz. We observed a peak above 10 Hz in front of the water pit, however near the cryostat location there was no such effect. A large micro-seismic peak at 0.2 Hz was observed. This peak has seasonal variations and is due to the rough sea during the winter. The sea shore ijust 30 km from the karga site. Underground water much more than expected especially during the spring season when snow starts to melt

Vibration isolation system Cryostat housing cryogenic payload Total height 14m Room temperature Cryo-duct Cryostat housing cryogenic payload Cryo-payload Cryo-cooler Cryo-shield Laser beam Cryogenic payload system 4 cryogenic mirrors X-end Y-end

Cryogenic Payload system CuBe blades Moving mass Platform stage Marionette Upper intermediate mass (IM) w/ moving mass Bottom IM w/ sapphire blades The mechanical design of cryogenic payload for sapphire mirror can been seen. This cryogenic payload consists of semi-monolithic sapphire suspension, recoil mass, intermediate mass with sapphire vertical blade springs, control stage named Marionette, Marionette recoil mass and Geometric Anti-Spring (GAS) filter Sapphire suspension fibers Sapphire Mirror IM recoil mass and heat link are not shown. Recoil Mass

Design and TN discussed yesterday Marionette for control Sapphire suspensions Design and TN discussed yesterday Optimising the overall design FEA modelling of TN from the platform stage and intermediate mass Since we know that the TN is inversely proportional to Q, hence the lowermost part of the suspension is of sapphire which has a very high Q of e7 at cryogenic temp. Also it has good optical properties like high thermal conductivity and youngs modulus. The cryogenic payload current weighs around 200 kg and we working on the optimizing the design to reduce the weight and size. FEA modelling is ongoing to improve the design and to estimate the thermal noise contributions from these parts as well. Sapphire suspensions

Metal prototype: lowermost stage Marionette CuBe blades Dummy mirror 23 kg Intermediate mass Pitch/roll measurements @ KEK Using dial gauge and laser displacement meter Measure displacement by degree of leaning Marionette inclined => 3 degrees Test performed by Takahiro Miyamoto (MSc student)

Fabrication: Cryogenic payload Sapphire fibres Sapphire blades 350 mm Sapphire mass (23 kg) with side cuts for ear attachment We have plans to fabricate and test the cryogenic payload system in this financial year. We already have a 23 kg sapphire mass with side cuts for ear attachments. A dummy mass is currently being used for prototype testing of various components. Sapphire fibres and sapphire blade springs are currently being ordered from Shinkosha and Impex. Sapphire nail head 10 mm Sapphire ear 1st Cryogenic payload system to be fabricated in 2015-16

Ongoing work (KEK and ICRR) Q measurements: sapphire fibres, sapphire blades ANSYS modelling to improve/optimize the Cryo- payload design Discussions with IMPEX (Germany) and Shinkosha (Japan) for the fabrication of sapphire parts Next I will report the ongoing work in KEK and ICRR Sapphire fibres fabricated by impex are currently being tested for theire Q values in ICRR. We will also be measuring the Q of the sapphire blade springs There are plans to fabricate and test a small single fibre with blade pendulum suspending a mass of 5.6 kg. The aim of this experiment is to test the clamps, Indium bonds and ease of assembly. ANSYS modelling is ongoing to improve the design of the cryogenic payload system Discussion with shinkosha and Impex for the fabrication of sapphire parts.

Conclusions KAGRA Tunnel excavation completed: cryostat, beam tubes have been installed Underground water an issue! Design and testing of the components for cryogenic payload system currently ongoing We plan to fabricate the first cryogenic payload system in this FY (2015-16) Here is my conclusion of the talk. As discussed, Kagra is the 2nd gen GWD currently under construction Kagra uses challenging technologies like cryogenic mirror system and an underground site We reported that tunnel excavation completed last year Ikragra will begin observation this year Cryogenic payload design is currently under study First cryopaylod to be fabricated in this FY.