1. ET-meeting, 22 th Oct. 2013 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,

2. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK 2 Outline Over View of KAGRA Cryogenics Time Line Performance Tests Cryostat with Cryocooler-units 1/2 Dummy Payload Vibration in the cryostat ( Mr. D. Chen presented at poster session) Prototype Duct Shield ( Preliminary results ) Summary

3. ET-meeting, 22 th Oct. 2013 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)

4. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK Temperature of the test mass/mirror < 23 [K] Inner radiation shield have to be cooled to < 8 [K] The test mass have to be cooled without introducing excess noise, especially vibration due to cryocoolers. Easy access and enough capacity to installation work around the mirror. Allowable size as large as possible under public transport regulation and KAGRA tunnel. Meets ultra high vacuum specification < 10 -7 [Pa] The requirements for KAGRA Cryogenic Adopt Pulse Tube-type Cryo-cooler units with very low vibration mount based on the CLIO type. Adopt conduction cooling technique with high pure metal such as 6N class Aluminum. No use cryogenic fluid cause of vibration noise such as liquid helium flow. Analyzed the cryostat response to ground motion @ Kamioka-mine. Heat load from components as low as possible. Adopt very low outgas super insulation system for under ultra high vacuum < 10 -7 [Pa], and polish by Electrical Chemical Baffling for inner surface of the vacuum chambers. Meets the requirements for the KAGRA Cryogenics

5. ET-meeting, 22 th Oct. 2013 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 < 1.0 W (< 0.5 W x 2) Baffles

6. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK 80K Cooling passage 5N8 8K Conduction Bar Valve Unit Structure view of the Low Vibration Cryo-cooler Unit バルブ台 Flexible Heat Links Bellows Vacuum Vessel (Support: Conduction Paths) Support Frame (Support: Cold Head) 2m 1m Part of Vibration Reduction Stage

7. 77 TM RM IM RM for IM Platform Cooling Time Reduction with Black Coating To accelerate cooling down by radiation, plated black coating with Diamond Like Carbon on outer surface of the payload and inner surface of 8K shield. S.Koike TM : Test Mass RM : Recoil Mass IM : Intermediate Mass ItemsMaterialsMass Comparison of Cooling Time with & without DLC Almost half ! Without DLC With DLC By courtesy of Mr. Y. Sakakibara/ICRR

8. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK Time Line 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 22th/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

9. ET-meeting, 22 th Oct. 2013 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 10 -4 - Total 94 (116) 125 W/unit 24 (29) 31 8K Shield Esti. (W) Meas. (W) ◦ View Ports (0.4)* - ◦ Radiation From 80 K 2.2 - ◦ Support post and Rods 2.4 - ◦ Electrical wires 3 x 10 -4 - ◦ Duct Shields (~ 5m) ( < 1.0 ?) - Total4.6 (6.0 ?) <2.0 W/unit2.3 (3.0 ?) <1.0 Cryo-payload Esti. (W) Meas. (W) ◦ Payload (~1.0?)- ◦ Mirror Adsorption(~1.0?)- Total(2.0 ?) - W/unit(1.0 ?) 0.4

10. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK Emissivity Sapphire: 0.5 Platform: 0.3*(T/300K) IM: 0.4*(T/300K) Cryo-coolers for payloads didn’t cool down completely (2nd stage stayed at 20 K) Thermal conductivity of heat links calculated from results: one fifth of literature! – Thermal contact resistance between payloads and heat links, etc. Results (with copper heat links) By courtesy of Mr. Y. Sakakibara/ICRR

11. Heat Load Response Test 11 Pulse tube cryocoolers Heater and thermometer Sapphire mirror Cooling test in Toshiba

12. 2 W~ 5 ppm 0 W ~0 ppm 10 W ~25 ppm 5 W ~ 12.5 ppm Mirror Operation (~23K) Q radiation < α(T 4 8K -T 4 mirror ) Result of Heat Load Response @ 8K Radiation Shield 12 Cooling test @ Toshiba Scatted light power is 4 W @400 kW beam power when scattered loss on the mirror surface is 10 ppm. It is confirmed that 25 ppm (10 W) @400 kW of scattered loss is acceptable as heat load for the cryocoolers via the 8 K radiation shield.

13. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK Measurement of thermal radiation Two aluminum plates suspended 1.600 mm plate (Left side) is heated up to 300 K and emits thermal radiation 2.250 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 Mr. Y. Sakakibara/ICRR 1.1313 1.Thermal Radiation 1.600 mm 1.250 mm 1.150 K1.250 K 1.40 K 1.17 m Performance Test of the Prototype Duct Shield

14. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK Preliminary 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 14 Reflectivity at 10 um Duct0.94±0.02 Solblack0.3±0.1 Reduced by Duct Shield It was confirmed duct shield could reduce 99.9 % of heat to cryogenic payload. Preliminary courtesy By courtesy of Mr. Y. Sakakibara/ICRR

15. ET-meeting, 22 th Oct. 2013 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 Sakakibara15 ~200 ppm of laser light came back to camera 635 nm, 4.5 mW Background

16. F17 77.16 Hz F18 94.00 Hz F19 96.18 Hz F20 99.86 Hz Resonant Frequency F1 18.85 Hz F2 25.48 Hz F3 38.52 Hz F4 40.28 Hz F5 40.99 Hz F6 43.65 Hz F7 44.20 Hz F8 46.31 Hz F9 49.01 Hz F10 59.07 Hz F11 63.66 Hz F12 64.58 Hz F13 68.25 Hz F14 68.69 Hz F15 73.87 Hz F16 77.00 Hz F17 77.16 Hz F18 94.00 Hz F19 96.18 Hz F20 99.86 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.

17. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEK Structure view of the Production Duct Shield 80 K Duct Shield Bellows Vacuum Vessel Support Frame 5 m Baffles Specification L=5 m -> Q input < 0.5 W

18. ET-meeting, 22 th Oct. 2013 N. KIMURA/KEKSummary 18 1. 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. Finally, we could achieve the big mile stone which completed the cryostats on time!