ET-meeting, 22 th Oct N. KIMURA/KEK The Latest Status of the KAGRA Cryogenics N. KIMURA A, D. CHEN B, T. KUME A, S. KOIKE A, Y. SAKAKIBARA B, T. SUZUKI A, C. TOKOKU B, K. YAMAMOTO B, M. OHASHI B, and K. KURODA B A High Energy Accelerator Research Organization, KEK B ICRR, University of Tokyo,

ET-meeting, 22 th Oct N. KIMURA/KEK 2 Outline Over View of KAGRA Cryogenics Actual Work Schedule Performance Tests Cryostat 1/2 Dummy Payload Prototype Duct Shield ( Preliminary tests ) Summary

ET-meeting, 22 th Oct N. KIMURA/KEK Gate valve Connection Port to SAS Mirror a cryostat Location of Four Mirror Cryostats in Kamioka Mine Constructed at the position of 1 km in depth. Mozumi-End Atotsu-End X-Front Room Y-Front Room L=5 m Vacuum duct 800 with radiation shield

ET-meeting, 22 th Oct N. KIMURA/KEK Conceptual Design of the Cryogenics Four 4K cryocooler units per one cryostat Baffles against wide scattering is cooled via 8K shield. Main Beam Cooling 8K shield Cooling Cryo-Payload Duct Shield 400kW 4W? ~1W Cryostat 80K shield 8K shield two units 80K PTC with Vibration reduction 4K PTC with Vibration reduction two units 2 units for cool cryo-payload 2 units cool for 8K shield 4 units cool for 80K shield Low vibration in U. H. Vacuum Stop propagation of 300K radiation Prevent heating by scattered beam 300K Radiation Baffles

ET-meeting, 22 th Oct N. KIMURA/KEK Overview of KAGRA Cryogenics S.Koike 5 m Duct Shield Main Laser Beam Four Cryocooler Units Radiation Shields Seismic Attenuation System (SAS) Cryogenic Payload Sapphire Mirror ( -alumina crystal) 5 m Duct Shield Stainless steel t=20mm Diameter 2.4 m Height ~4.3 m M ~ 11 ton Cold Mass: 8K shield ~455 kg 80 K shield ~590 kg Cryocoolers Pulse tube, 60Hz 0.9 W at 4K (2nd) 36 W at 50K (1st)

ET-meeting, 22 th Oct N. KIMURA/KEK Actual Work Schedule of KAGRA Cryogenics Manufacture components Assemble and factory test with cryo-coolers Transport to storage near Kamioka 2011 Jfy2012 Jfy2013 Jfy Apr./12Apr./13Apr./14Apr./11. Design by KEK Bidding We are here 22 th /Oct. Four Mirror Cryostats Cryo-cooler units Design by KEK Production of seven cryo-cooler units with performance test Production of nine cryo-cooler units with performance test Transport to Kamioka Custody at Kamioka Duct shield units Design by KEK Production of three ducts shield units without cryo-coolers Performance test

ET-meeting, 22 th Oct N. KIMURA/KEK Performance of the Cryostat It took 12.5 days to cool down from 300 K to 8K. Cool down time of the cryostat was almost consistent with the predicted cooing time by Calculation model. Performance test at Toshiba Keihin Product 80K Shield Est. (W) Meas. (W) Eleven View Ports (22) - Radiation From 300 K 70 - Support post and Rods 24 - Electrical wires 3 x Total 94 (116) 125 W/unit 24 (29) 31 8K Shield Esti. (W) Meas. (W) View Ports (0.4)* - Radiation From 80 K Support post and Rods Electrical wires 3 x Duct Shields ( < 0.05 ?) - Total4.6 (5.0 ?) <2.0 W/unit2.3 (2.5 ?) <1.0 Cryo-payload Esti. (W) Meas. (W) Payload (~1.0?)- Mirror Adsorption(~1.0?)- Total(2.0 ?) - W/unit(1.0 ?) 0.4

8 Heat load Test Pulse tube cryocoolers Heater and thermometer Sapphire mirror Cooling test in Toshiba

W 10 W 0 W According to our design, temperature should be below 8 K when heat absorption in mirror is 1 W. Result of Heat Load Cryo-payload line Cooling test in Toshiba It is confirmed that 2.5 ppm (1 kW of mirror deposition is acceptable as heat load for the cryocoolers connected with cryo-payload line.

ET-meeting, 22 th Oct N. KIMURA/KEK Results (with copper heat links) Cryo-coolers for payloads didnt cool down completely (2nd stage stayed at 20 K) Thermal conductivity of heat links calculated from results: 1/5 of literature – Thermal contact resistance between payloads and heat links Yusuke Sakakibara Emissivity Sapphire: 0.5 Platform: 0.3*(T/300K) IM: 0.4*(T/300K)

ET-meeting, 22 th Oct N. KIMURA/KEK Measurement of thermal radiation Two aluminum plates suspended mm plate (Left side) is heated up to 300 K and emits thermal radiation mm plate (Right side) absorbs radiation and is heated up 3.Calibration is conducted using heater on 250 mm plate 4.Coated with Solblack to enhance emissivity or absorptivity Done by Y. Sakakibara Thermal Radiation mm mm K1.250 K 1.40 K 1.17 m Performance Test of the Prototype Duct Shield

ET-meeting, 22 th Oct N. KIMURA/KEK Results Calculated value has error of several times Measured reflectivity at 10 μm of shield has error Rays are reflected by shield many times Measured value is within the error 12 Reflectivity at 10 um Duct0.94±0.02 Solblack0.7±0.1 Reduced by Duct Shield

ET-meeting, 22 th Oct N. KIMURA/KEK Measurement of scattered light Red light from laser diode Photographs of scattered light when angle changes Calibration by changing exposure time Future work: Vibration measurement, calculation of equivalent GW amplitude Yusuke Sakakibara13 ~200 ppm of laser light came back to camera 635 nm, 4.5 mW Background

5 Fixed points Modal analysis for KAGRA Duct Shield Φ800 Gravitational Direction We analyzed the resonance peaks of the vacuum chamber without bellows and the inner shield. Mode frequency are calculated from 20 Hz to 100 Hz.

F Hz F Hz F Hz F Hz Resonant Frequency F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz F Hz Shape of duct shield at each resonant frequency. It was confirmed that the most of resonant frequencies are cause of strength of the vacuum chamber, and weaker than that of inner shield. These results have been feedback to the duct shield design.

ET-meeting, 22 th Oct N. KIMURA/KEK Structure view of the Production Duct Shield 80 K Duct Shield Bellows Vacuum Vessel Support Frame 5 m Baffles

ET-meeting, 22 th Oct N. KIMURA/KEKSummary KAGRA cryogenics consisting of cryostat and cryo- cooler units was designed, fabricated, and tested their performances during 2011JFY and 2012JFY. 2. At the performance test, following items were confirmed and verified; The cooling and vibration performance of sixteen cryocooler units. The cooling performance of all the four cryostats. Vibration on the surface of inner radiation shield. Experiment with half size of dummy cryo-payload 3. Experiment with proto type duct shield was conducted, and result was agreed with predicted heat load. But, need more analysis work. 4. Design of the production of duct shield were almost finished. Now, We are focusing our work on fabrication of the duct shields and preparing performance test.