1. 1 Kazuhiro Yamamoto Institute for Cosmic Ray Research (ICRR) the University of Tokyo ELiTES first collaboration meeting Sanjo conference hall, the University of Tokyo, Tokyo, Japan 4 October 2012 Current status of KAGRA cryogenic payload

2. 2 0. Abstract Outlines and current status of KAGRA cryogenic payload KAGRA cryogenic payload in ELiTES program

3. 3 Contents 1.Introduction 2.Issues 3.Outline of strategy 4.Current status 5.KAGRA payload in ELiTES 6.Summary

4. 44 Cryogenic mirror Cryostat Vibration Isolation Outline of vibration isolation and cryostat 1. Introduction

5. 5 to SAS View ports Remote valve unit 4 Low vibration cryocooler unit Main LASER beam Cryostat Stainless steel t20mm Diameter 2.6m Height ~3.6m M ~ 10 ton Cryo-coolers Pulse tube, 60Hz 0.9 W at 4K (2nd) 36 W at 50K (1st) Outline of cryostat Cryogenic payload Mirror 1. Introduction S. Koike

6. 6 Progress of assembly of cryostat at Toshiba Keihin Product Operations Main body (Φ2.6m, H3.6m) 1. Introduction

7. Progress of assembly of cryostat at Toshiba Keihin Product Operations Vacuum chamber 7 1. Introduction

8. Progress of assembly of cryostat Vacuum chamber 8 1. Introduction at Toshiba Keihin Product Operations

9. Progress of assembly of cryostat Shield 9 1. Introduction at Toshiba Keihin Product Operations

10. 10 Outline of cryogenic payload Sapphire fiber Sapphire mirror (About 20K) Inner shield (8K) 1. Introduction Y. Sakakibara et al., Classical and Quantum Gravity 29(2012)205019. Outer shield (80K) Heat links (pure Al) Vacuum chamber (300K)

11. 11 2. Issues (1)How to assemble Details of construction, clean room …. (2)Strength Tensile strength, development of clamp, sapphire bonding … (3)Control and damping system to reduce fluctuation and instability Actuators (what and where), resonant mode (frequency and Q) and so on

12. 12 2. Issues (4)Cooling Temperature of mirror (below 20 K), initial cooling time, heat resistance of clamp … (5)Noise Thermal noise, vibration via vibration isolation system and heat links …

13. 13 3. Outline of strategy The development should be in progress for bKAGRA (2016-) in iKAGRA phase. In iKAGRA phase (before installation in mine) (a) Experiment of 1/4 cryostat in ICRR to check payload performance 1/4 means number of cryocooler, not size. (b) Other R&D Progress of investigations for (4) Cooling and (5) Noise are mainly introduced here.

14. 14 4. Current status (a) Preparation for 1/4 cryostat Design and discussion for 1/4 cryostat to check payload is in progress. Preliminary.

15. 15 4. Current status 15 At beginning of initial cooling, heat transfer is dominated by radiation. Initial cooling time of KAGRA cryostat and cryogenic payload is about 2 months (if no tricks). Diamond Like Carbon (DLC) coating (High emissivity, Large radiation) on shields and payload (except for mirror) Details were explained by Y. Sakakibara yesterday. (b)Initial cooling time

16. 16 4. Current status 16 Initial cooling time with DLC (shield and mass) Calculation by Y. Sakakibara Almost half ! Other tricks are welcomed ! (b)Initial cooling time

17. 17 4. Current status 17 We must check the effect of radiation (and DLC coating) on the initial cooling time experimentally. Y. Sakakibra proceeds with small experiment in ICRR. (His talk yesterday) Experiment in Toshiba Toshiba has the plan of cooling test in this autumn and winter. During this cooling test, some samples (sapphire bulk, dummy payload and so on) without heat link are suspended inside shield and the temperature will be monitored to check calculation result (radiation effect). (Y. Sakakibra’s talk yesterday) (b)Initial cooling time

18. 18 4. Current status 18 Test sample (T. Uchiyama) (c) Sapphire fibers with nail heads

19. 19 4. Current status 19 Length = 350 mm diameter = 1.8 mm Almost as needed in bKAGRA. Need to check the quality and improvement. T. Uchiyama asked MolTech GmbH (Germany). Sapphire fibers have already come ! (c) Sapphire fibers with nail heads

20. 20 4. Current status Ettore Majorana asked IMPEX HighTech GmbH (German company). They can make similar fibers (nail heads on the both ends). Shorter fibers (about 100 mm in length) are coming soon. (c) Sapphire fibers with nail heads

21. 21 4. Current status Quality check Thermal conductivity : T. Ushiba His talk (today). Q-value : K. Shibata (KEK) and Y. Sakakibara (Jena) ELiTES stimulates measurement by Japanese in Jena ! (c) Sapphire fibers with nail heads

22. 22 4. Current status E. Hirose’s talk in afternoon WP2 session. Mechanical coating loss : Discrepancy between Tokyo and Glasgow E. Hirose is measuring mechanical loss in ICRR and K. Craig and P. Murray (supported by ELiTES) will join on this month. Y. Sakakibara also will measure in Glasgow. ELiTES stimulates measurement ! Parametric instability : K. Shibata His talk in afternoon WP2 session. Although this instability is not so serious in KAGRA and ET-LF, it matters in ET-HF. (d) Sapphire mirror and coating

23. 23 4. Current status Vibration of shield could be problems. Vibration via heat links, Scattered light This measurement is at cryogenic temperature and in vacuum. Luca Naticchioni (supported by ELiTES) and Dan Chen will measure vertical and horizontal vibration of radiation shield of KAGRA in cooling test (this autumn and winter), respectively. D. Chen and Luca Naticchioni’s talk in this WP1 session. (e) Vibration of shield

24. 24 4. Current status (e) Vibration of shield 24 Improvement is necessary… Measurement on radiation shield is necessary. Measurement of vibration of cryocooler unit (not radiation shield !) are in progress.

25. 25 4. Current status T. Sekiguchi is developing (His talk after this talk!). (1) Vibration via heat links (above 1 Hz) (2) Thermal noise (above 10Hz) (3) Control scheme (Investigation started recently) M. Nakano proceeds with the research for (3). (f) Mechanical simulation

26. 26 4. Current status 26 (g) Baffle for large angle scattering in cryostat Optimal shape : T. Akutsu’s talk (yesterday) Reflection Transmission Mirror side With DLC coating Preliminary result Suspension with heat links (5W!) must be designed !

27. 27 4. Current status Metal wire and sapphire ribbon W. Johnson : JGW-G1201127, G1201271 Composite mirror suspension silicon blades, sapphire ribbon, silicon hinge R. DeSalvo : JGW- G1201101, T1201126 A. Bertolini and A.Conte’s talk in this WP1 session. ELiTES initiative (h) Other ideas for suspension

28. 28 5. KAGRA payload in ELiTES ELiTES has already started and supports the development of KAGRA cryogenic payload. I expect that these investigations will also be useful for ET.

29. 29 5. KAGRA payload in ELiTES Some items for future research (not perfect list) Investigation material properties (Q, thermal conductivity, strength etc.) of coating, fiber and so on. Sapphire bonding, Sapphire fiber clamp Control and damping scheme Actuators and sensors at cryogenic temperature Reduction of initial cooling time Thermal resistance of clamp.... and so on. Please give us your opnions and suggestions !

30. 30 6. Summary 1/4 cryostat for test of cryopayload : Design and discussion are in progress. Current R&D topics Inital cooling time Sapphire fiber with nail head Sapphire mirror and coating Vibration of shield Mechanical simulation Baffle for large angle scattering in cryostat Other ideas for mirror suspension Some future research items for ELiTES

31. 31 6. Summary ELiTES has already started and supports the development of KAGRA cryogenic payload. I expect that these investigations will also be useful for ET.

32. 32 Thank you for your attention !

33. 33 2. Cryocooler unit 33 1.Outline Pulse tube cryocooler (Sumitomo Heavy Industries) Vibration reduction system

34. 34 2. Cryocooler unit 4. Vibration measurement Pulse tube cryocooler Heat conductor Cryostat Vibration of this part was measured.

35. 35 2. Cryocooler unit 4. Vibration measurement Institute for Cosmic Ray Research, the University of Tokyo T. Kume also proceeds with vibration measurement.

36. 36 2. Cryocooler unit 4. Vibration measurement Displacement sensor

37. 37 S. Koike

38. 38 S. Koike

39. 39 Sample 1 for Toshiba experiment: Sapphire and metal hollow sphere Evaluation of emissivity Scaling law (Y. Sakakibara’s small experiment: 30 mm in diameter) His talk (100 mm in diameter) 4. Current status (b)Initial cooling time

40. 40 Sample 2 for Toshiba experiment : Dummy payload (hollow masses) Half size Hollow masses (~5 kg) DLC coating Sapphire bulk as dummy mirror Preparation is in progress. 4. Current status (b)Initial cooling time S. Koike