1. Recent progress of KAGRA cryogenic system
Kazuhiro Yamamoto
Institute for Cosmic Ray Research (ICRR)
the University of Tokyo
6th Einstein Telescope Symposium　　　
Laboratorie des Materiaux Avances CNRS, Lyon, France
20 November 2014 1 1 1 1

2. Contribution
E. Hirose, A. Khalaidovski, T. Miyamoto, Y. Sakakibara, T. Sekiguchi,
H. Tanaka, C. Tokoku, T. Uchiyama, T. AkutsuA, H. IshizakiA,
F. E. Peña ArellanoA, R. TakahashiA, A. HagiwaraB, N. KimuraB, R. KumarB, T. KumeB, S. KoikeB, I. MurakamiB, T. SuzukiB, S. TerashimaB, T. TomaruB,
K. ToyodaB, D. ChenC, R. DeSalvoD, E. MajoranaE, L. NaticchioniE,
W. JohnsonF, K. CraigG, A. CummingG, R. DouglasG, G. HammondG ,
K. HaughianG, I. MartinG, P. MurrayG, S. RowanG , D. HeinertH, G. HofmannH,
J. KommaH, S. KrokerH, R. NawrodtH, C. SchwarzH, S. GotoI, M. TanakaI,
S. IokaJ, K. NakamotoJ, H. NezukaJ, KAGRA collaboration
ICRR.UT, NAOJA, KEKB, Astro.S.UTC, Sannio Univ.D, INFNE,
Louisiana State Univ.F , University of GlasgowG,
Friedrich-Schiller-Universitaet JenaH, Jecc TorishaI,
Toshiba Keihin Product OperationsJ, KAGRA collaboration

3. 0. Abstract Although there are many topics, here, I will explain
(1)Cryostat
(2)Monolithic sapphire suspension
(3)ELiTES activity

4. Contents
Introduction
Cryostat
Sapphire suspension
ELiTES activity
Summary

5. 1. Introduction Schematic view of KAGRA interferometer
Four mirrors of arm cavity will be cooled.
3km
3km
Mozumi
Y-end
Sakonishi
X-end
Kamioka mine
(Underground site)
Atotsu
Center
Vibration isolation system, Cryocooler unit, Cryostat, Cryogenic payload 5 5 5 5

6. 1. Introduction
Outline of vibration isolation and cryostat
14 m 6

7. 1. Introduction Outline of vibration isolation and cryostat 14 m
Cryogenic mirror 7

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

9. Outline of vibration isolation and cryostat
Heat link (pure Al or Cu)
Heat link (pure Al or Cu)
Pulse tube cryocoolers
Pulse tube cryocoolers
Sapphire fiber
Sapphire mirror (About 20K)
Pulse tube cryocoolers 9 9 9 9

10. 1. Introduction Cryo duct Pulse tube cryocoolers
Baffles
Cryo duct
2 Pulse tube cryocoolers 10 10 10 10 10 10

11. 2. Cryostat KAGRA cryostats have already been assembled !
at Toshiba Keihin Product Operations
Review paper about KAGRA cryogenics:
Y. Sakakibara et al.,
Classical and Quantum Gravity 31(2014) 11

12. 2. Cryostat
One year ago, the cryostats were moved to the warehouse near Kamioka. 12 12

13. 2. Cryostat KAGRA tunnel excavation was finished on March 2014.
Review paper about KAGRA tunnels:
T. Uchiyama et al.,
Classical and Quantum Gravity 31(2014) 13 13

14. 2. Cryostat Next step : Installation of cryostats in KAGRA site
Last cryostat was installed at the day before yesterday (18 Nov. 2014) !
(T. Suzuki, N. Kimura, T. Tomaru, T. Kume)
What are the next missions today ?
Topological measurement around cryostat
Assembly (cryocoolers,
vacuum duct for vibration isolation system, …)
Cooling test
Construction of clean booth … 14 14

15. 2. Cryostat
Y end
X end
Y arm
X arm
Center room
New Atotsu 15 15

16. 2. Cryostat
Cryostat in warehouse 16 16

17. 2. Cryostat
In front of the warehouse …. 17 17

18. 2. Cryostat
In front of warehouse … 18 18

19. 2. Cryostat
Mission on the midnight … 19 19

20. 2. Cryostat
Cart in front of entrance of KAGRA site 20 20

21. 2. Cryostat
Cryostat on the cart at KAGRA site entrance ! 21 21

22. 2. Cryostat
In tunnel 22 22

23. 2. Cryostat
In tunnel … 23 23

24. 2. Cryostat
Y end 24 24

25. 2. Cryostat
Y end 25 25

26. 2. Cryostat
Y end 26 26

27. 2. Cryostat Cryo duct Pulse tube cryocoolers 2 Pulse tube cryocoolers
Baffles
Cryo duct
2 Pulse tube cryocoolers 27 27 27 27 27 27

28. 2. Cryostat Cryo duct Baffle Duct
Scattered light
Baffle
Mirror
Baffle
Duct
Y. Sakakibara proceeds with investigation about 300 K radiation through duct, evaluation of scattered light noise. 28 28 28 28 28 28

29. 2. Cryostat Cryo duct : Measurement of radiation through duct
300K radiation into cryo duct
Measured 300K radiation
transmitted by cryo duct
Calculated 300K radiation
transmitted by cryo duct
KAGRA requirement is satisfied. 29 29 29 29 29 29

30. 2. Cryostat Cryo duct : Evaluation of scattered light noise
KAGRA requirement is satisfied. 30 30 30 30 30 30

31. 3. Sapphire suspension “Sapphire monolithic lop-eared suspension”
One of the most important
parts of KAGRA :
Main sapphire mirrors
are included.
All parts are made
from sapphire.
Mainly, D. Chen proceeds with investigation.

32. 3. Sapphire suspension Blade spring Fiber Flat cut Nail head of fiber
(compensation of fiber length difference)
Fiber
Flat cut
Nail head of fiber
Ear
Mirror
A. Hagiwara

33. 3. Sapphire suspension
fiber break
Hydroxide Catalysis Bonding
D. Chen

34. 3. Sapphire suspension Current status R&D for components
(fiber, bonding technique …)
Strength, thermal resistance, mechanical loss …
Largest concern : Mechanical loss, especially,
Hydroxide Catalysis Bonding
It will be measure soon !
2. Prototype
One fiber prototype
Full size prototype 34

35. 3. Sapphire suspension
Strength test of sapphire fibers with nail heads
in Glasgow (G. Hammond, E. Majorana)
Fiber suspended weight. Moreover, weight was swung or pulled.
Broken jointed end
Broken jointed end
15kg test hang

36. 3. Sapphire suspension
Strength test of sapphire fibers with nail heads
in Glasgow (G. Hammond, E. Majorana)
Fiber suspend weight. Moreover, weight was swung or pulled.
G. Hammond reported in ELiTES meeting
(December 2013).
Safety factor derived from measurement :
Broken jointed end

37. 3. Sapphire suspension
HCB shear strength test at cryogenic temperature
(Strength vs crystal direction)
Rebecca Douglas and Karen Haughian
Requirement : 1 MPa
Preliminary 37

38. 3. Sapphire suspension Strength of HCB after thermal cycle (D. Chen)38 38

39. 3. Sapphire suspension Strength of HCB after thermal cycle (D. Chen)39 39

40. 3. Sapphire suspension Thermal resistance
Paper about thermal conductivity measurement sapphire fibers with nail heads was accepted !
Thermal conductivity is enough high for KAGRA.

41. 3. Sapphire suspension Thermal resistance (HCB and indium bonding,
C. Schwarz, D. Chen)
C. Schwarz’s poster
Further investigation is necessary,
but, thermal resistance looks enough small !

42. 3. Sapphire suspension Mechanical dissipation
Sapphire fiber with nail head (D. Chen, E. Majorana)
Rome
100mm length fiber
Long (300 mm) fiber, reproducibility …

43. 3. Sapphire suspension Mechanical dissipation
Mechanical loss of indium (Jena) : D. Chen
f = 3*10-3
Mechanical loss of HCB will be measured soon.

44. 3. Sapphire suspension Mechanical dissipation
Thermal noise calculation (D. Chen, R. Kumar)
Preliminary
D. Chen

45. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)
Sapphire blade spring
Indium Bonding
Hydroxide Catalysis Bonding
Shinkosha
Sapphire mass
6kg in weight (1/4 of KAGRA mirror)
Design : D. Chen

46. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)
Sapphire blade spring
Dummy Cu wire
Sapphire mass
D. Chen, J. Komma, H. Tanaka, Y. Liu

47. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)
Resonant frequency of vertical mode
Measurement : 14.3 Hz, Calculation : 14.4 Hz
R. Kumar, GWADW2014 (
Dummy Cu wire
nail head
Sapphire blade spring

48. 3. Sapphire suspension Full size prototype
Preparation for (similar size) prototype of
lop-eared is in progress.
Dummy mirror bulk was sent to IMPEX for flat cut on barrel surface for Hydroxide Catalysis Bonding.
Dummy mirror (Shinkosha)
Delivery : March 2015

49. 4. ELiTES activity ELiTES: ET-LCGT interferometric Telescope
Exchange of Scientists
Grant for collaboration
between KAGRA and ET
European 7th Framework Programme
Marie Curie action (Mar Feb. 2016)
European people can visit Japan
for KAGRA. 49

50. 4. ELiTES activity
Guests supported by ELiTES in 2014
11 persons 50

51. 4. ELiTES activity
Guests supported by ELiTES in 2014
15 persons 51

52. 4. ELiTES activity ELiTES stimulates stay in Europe
of researcher in Japan.
D.Chen
For sapphire suspension
(around 4 months in total)
16 Sep Nov : Rome
4 Jun Jun : Rome
25 Jun Jul : Jena
27 Jun Nov : Jena 52

53. 4. ELiTES activity Refereed Journal papers by ELiTES (so far)
Sapphire fiber thermal conductivity
A. Khalaidovski et al.,
Classical and Quantum Gravity 31 (2014)
Investigation about vibration of radiation shield
D. Chen et al.,
Classical and Quantum Gravity 31(2014)
Mechanical loss of coating at cryogenic temperature
E. Hirose et al.,
Physical Review D 90(2014) 53

54. 4. ELiTES activity Next ELiTES meeting at Tokyo : Feb. 2015
Conference site in The University of Tokyo :
Yayoi auditorium, Ichijou Hall/Annex 54

55. 5. Summary Cryostat All four cryostats were installed at KAGRA site !
We must proceed with
assembly, measurement, and so on ...
Cryo duct : Y. Sakakibara
Measurement of 300K radiation transmittance
Evaluation of scattered light noise
KAGRA requirements are satisfied.

56. 5. Summary Sapphire lop-eared monolithic suspension : D. Chen
R&D for components
Mechanical loss is a remaining concern.
Prototype (one fiber, full size)
Assembly or preparation is in progress.
ELiTES activity
11 long stay guests, 15 short stay guest in 2014
D. Chen stayed in Europe for 4 months
(sapphire suspension).
3 refereed journal papers, so far

57. Thank you for your attention !

58. 3. Sapphire suspension Sapphire fibers with nail heads
Quality check under collaboration with ET (ELiTES)
Q-value
Measurement in Glasgow, Jena, Rome and Tokyo
Thermal conductivity
Measurement in Jena, Rome and Tokyo
Strength
Measurement in Glasgow

59. 3. Sapphire suspension IMPEX fibers satisfy the KAGRA requirement.
Sapphire fibers with nail heads
Latest summary of Q and thermal conductivity
Moltech IMPEX KAGRA
requirement
Q-value * *106
at 20K *106
Thermal
Conductivity
at 20K [W/m/K]
IMPEX fibers satisfy the KAGRA requirement.

60. 3. Sapphire suspension Bonding between sapphire fibers
and sapphire mirror
Diffusion bonding
Hydroxide Catalysis Bonding (AdLIGO and Virgo)
If fibers are broken, bonding parts must be taken apart …
Candidates : Indium, Optical contact, Screws
Test (in progress or near future plan)
Strength test (tensile and shear) : KEK
Thermal resistance : ICRR
Mechanical dissipation : Jena and Glasgow
(ELiTES) 60

61. 3. Sapphire suspension Bonding between sapphire fibers
and sapphire mirror
Hydroxide Catalysis Bonding
Rebecca reported in ELiTES meeting (Dec. 2013). 61

62. 3. Sapphire suspension Bonding between sapphire fibers
and sapphire mirror
Hydroxide Catalysis Bonding
(Rebecca Douglas[Glasgow],
GWADW2013).
Strength (about 60 MPa)
measured by her is 10 times larger
than those of previous papers.
T. Suzuki et al., Journal of Physics; Conference Series 32(2006)309.
A. Dari et al., Classical and Quantum Gravity 27(2010)
Rebecca Douglas and Karen Haughian stayed in Japan in the last autumn.
Rebecca reported in ELiTES meeting (Dec. 2013). 62

63. 7. For future Some items for future research (not perfect list)
(a)Investigation material properties
(Q, thermal conductivity, strength etc.)
of coating, fiber and so on.
(b)Sapphire bonding, Sapphire fiber clamp
(c)Control and damping scheme
Actuators and sensors at cryogenic temperature
(d) Mechanical and thermal simulation for payload
(e) Vertical spring in cryostat
(f) Reduction of initial cooling time
Thermal resistance of clamp ....
(g) Baffles for scattered light in radiation shield
(h) Assembly procedure
The next topic is the vibration of shield. Takanori Sekiguchi calculated the vibration via heat links. Takanori assumed that vibration of heat link anchor in the radiation shield is the same as that of CLIO. But, this vibration depends on the structure of shield. So, Luca from Rome and Chen Dan will measure vibration of radiation shield of KAGRA cryostat on this autumn. Luca and Chen will measure the vertical and horizontal motion. Here, I would like to introduce Chen Dan’s activity for horizontal motion. 63

64. 8. Summary Cryostat : Assembly is in progress.
Cooling test is coming soon.
Cryogenic duct : Optimum position of 5 buffles
Future work : scattered light
Cryocooler unit :
Cooling test and vibration measurement : OK
Cryogenic payload
Preparation for 1/4 cryostat to check
payload performance is in progress.
Current main R&D topics
Inital cooling time, Sapphire fiber with nail head,
Coating mechanical loss, Vibration of shield
This is the summary. Design and discussion for ¼ cryostat is in progress. Sapphire fibers with nail head can be provided by Moltech and IMPEX. These R&D items are investigated. Other ideas for mirror suspension were proposed. Collaboration with ELiTES in progress and I hope the collaboration with university of Toyama will established near future.

65. 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
This is the issues for development of cryogenic payload; how to assemble and install, strength, control and damping system to reduce fluctuation and instability, cooling and noise.

66. 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 …
This is the issues for development of cryogenic payload; how to assemble and install, strength, control and damping system to reduce fluctuation and instability, cooling and noise.

67. 5. Other topics Metal blade spring for vertical vibration isolation
Cryogenic test is in progress in Kashiwa.
Q measurement of wires to suspend masses (except for mirror) is in progress (tungsten, CuBe, …)
Measurement of magnetism
of mass and black coating
Control system
Cryogenic tests are in progress.
Stepping motor to adjust angle of masses : KEK
Optical sensor (a candidate
to monitor mass motion) : ICRR 67 67 67 67 67 67

68. 4. Sapphire fibers After Yusuke left …. Clamp for IMPEX fibers in Jena
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.

69. 4. Sapphire fibers Profile measurement in Glasgow
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.

70. 5. Sapphire suspension Sapphire fibers with nail heads
Q measurement in Jena
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.

71. 2. Cryostat
In November 2014, the last two cryostats were installed at center room ! Mission was over yesterday !
Y end
X end
Y arm
Center room
X arm
New Atotsu 71 71

72. 2. Cryostat
In October 2014, the second cryostat was installed at X end !
Y end
X end
Y arm
X arm
New Atotsu 72 72

73. Installation of cryostats to X and Y ends
T. Suzuki, N. Kimura,
T. Tomaru, T. Kume 73

74. 使用した反射率 (Al + Solblack)
熱放射の計算
使用した反射率 (Al + Solblack)
熱放射はダクトシールドによって多数回反射され、パワーを減らす
熱放射は、商用光線追跡ソフトZEMAXを用いて計算
熱放射の光線をランダムな角度で放出
光線がシールドに反射させる際に、光線のパワーに反射率をかけていく
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.

75. 榊原裕介 Yusuke Sakakibara
ダクトシールドの設計
クライオスタット
真空チェンバー
ダクトシールド
散乱光
バッフル 鏡
Length in mm
バッフル
ダクト
5 m
5 m
ダクト、バッフルは熱放射、散乱光を吸収するよう黒化処理（ソルブラック）
熱放射の計算値：最大0.38 W　(< KAGRA要求値: 0.5 W)
バッフルは、鏡からの散乱光をとらえるよう傾ける
観測時は冷凍機ユニットによって冷却
今回は性能試験のため、冷凍機を直接接続
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.
日本物理学会2014年秋季大会
榊原裕介　Yusuke Sakakibara 75

76. 榊原裕介 Yusuke Sakakibara
熱放射の測定
円板製作：工藤氏 (KEK)
冷凍機
コールドヘッド
温度計
ヒーター
熱放射
円板1
円板2
264 mm
320 mm
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.
2枚のアルミ円板を吊るす
両円板は、熱放射率、吸収率を上げるため黒化処理（ソルブラック）
円板1を300 Kまで昇温、円板1が熱放射を放出
円板2は、熱放射を吸収し、温度が上昇
円板2に取り付けたヒーターを用いて校正
日本物理学会2014年秋季大会
榊原裕介　Yusuke Sakakibara 76

77. 榊原裕介 Yusuke Sakakibara
振動測定（ダクトシールド2号機）
レーザー変位計
加速度計によって地面振動を測定
埼玉県川越市、ジェック東理社
レーザー変位計によってダクトシールド振動を測定（地面・シールドの相対変位）
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.
26 Hz
日本物理学会2014年秋季大会
榊原裕介　Yusuke Sakakibara 77

78. 榊原裕介 Yusuke Sakakibara
神岡でのダクトシールド振動
神岡での地面振動×測定した伝達関数：冷凍機OFFの場合を計算
今後ダクトシールド用冷凍機ユニットの振動の評価が必要
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.
日本物理学会2014年秋季大会
榊原裕介　Yusuke Sakakibara 78

79. 榊原裕介 Yusuke Sakakibara
散乱光雑音の評価
ソルブラック反射率・散乱特性の測定値を使用
KAGRAの要求を満たす
ソルブラック反射・散乱特性測定：ジェネシア+阿久津
鏡表面PSD: E. Hirose et al. Phys. Lett. D 89 (2014)
計算方法: D. J. Ottaway et al. OPTICS EXPRESS 20 (8) (2012) 8329
共振1 Hz 質量
23 kg
キャビティー内パワー
400 kW
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively.
日本物理学会2014年秋季大会
榊原裕介　Yusuke Sakakibara 79

80. 3. Sapphire suspension Bonding between sapphire fibers
and sapphire mirror
Hydroxide Catalysis Bonding
(Rebecca Douglas[Glasgow],
GWADW2013).
Strength (about 60 MPa)
measured by her is 10 times larger
than those of previous papers.
T. Suzuki et al., Journal of Physics; Conference Series 32(2006)309.
A. Dari et al., Classical and Quantum Gravity 27(2010)
Rebecca Douglas and Karen Haughian stayed in Japan in the last autumn.
Rebecca reported in ELiTES meeting (Dec. 2013).
Ok, we must check the quality of these fibers. Now, Takafumi Ushiba and Kazunori Shibata proceed with measurement of thermal conductivity and Q-values of sapphire fibers, respectively. 80

82. 3. Sapphire suspension Thermal resistance (HCB and indium bonding,
D. Chen)
Preliminary
Further investigation is necessary,
but, this result does not look bad …

83. 3. Sapphire suspension

84. 3. Sapphire suspension

85. 3. Sapphire suspension

86. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)
Shinkosha
(D. Chen, H. Tanaka)
September 2014

87. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)
Sapphire blade spring
Shinkosha

88. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)

89. 3. Sapphire suspension One fiber prototype (Shorter cooling time,
for smaller risk of full size prototype)

90. 3. Sapphire suspension

91. 3. Sapphire suspension