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

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

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

Contents Introduction Cryostat Sapphire suspension ELiTES activity Summary

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

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

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

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

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

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

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) 224003. 11

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

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) 224005. 13 13

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

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

2. Cryostat Cryostat in warehouse 16 16

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

2. Cryostat In front of warehouse … 18 18

2. Cryostat Mission on the midnight … 19 19

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

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

2. Cryostat In tunnel 22 22

2. Cryostat In tunnel … 23 23

2. Cryostat Y end 24 24

2. Cryostat Y end 25 25

2. Cryostat Y end 26 26

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

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

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

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

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.

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

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

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

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

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). https://events.ego-gw.it/indico/conferenceOtherViews.py?view=standard&confId=7 Safety factor derived from measurement : 3 - 16 Broken jointed end

3. Sapphire suspension HCB shear strength test at cryogenic temperature (Strength vs crystal direction) Rebecca Douglas and Karen Haughian Requirement : 1 MPa Preliminary https://events.ego-gw.it/indico/conferenceOtherViews.py?view=standard&confId=7 37

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

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

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

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 !

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

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

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

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

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

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 (http://www.gravity.ircs.titech.ac.jp/GWADW2014/slide/Rahul_Kumar.pdf) Dummy Cu wire nail head Sapphire blade spring

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

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. 2012 - Feb. 2016) European people can visit Japan for KAGRA. 49

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

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

4. ELiTES activity ELiTES stimulates stay in Europe of researcher in Japan. D.Chen For sapphire suspension (around 4 months in total) 16 Sep. 2013 - 1 Nov. 2013 : Rome 4 Jun. 2014 - 25 Jun. 2014 : Rome 25 Jun. 2014 - 31 Jul. 2014 : Jena 27 Jun. 2014 - 15 Nov. 2014 : Jena 52

4. ELiTES activity Refereed Journal papers by ELiTES (so far) Sapphire fiber thermal conductivity A. Khalaidovski et al., Classical and Quantum Gravity 31 (2014) 105004. Investigation about vibration of radiation shield D. Chen et al., Classical and Quantum Gravity 31(2014) 224001. Mechanical loss of coating at cryogenic temperature E. Hirose et al., Physical Review D 90(2014) 102004. 53

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

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.

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

Thank you for your attention !

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

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 107 1*106 5*106 at 20K -6*106 Thermal Conductivity 3000 5000 5000 at 20K [W/m/K] -6000 IMPEX fibers satisfy the KAGRA requirement.

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

3. Sapphire suspension Bonding between sapphire fibers and sapphire mirror Hydroxide Catalysis Bonding Rebecca reported in ELiTES meeting (Dec. 2013). https://events.ego-gw.it/indico/conferenceOtherViews.py?view=standard&confId=7 61

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)045010. Rebecca Douglas and Karen Haughian stayed in Japan in the last autumn. Rebecca reported in ELiTES meeting (Dec. 2013). https://events.ego-gw.it/indico/conferenceOtherViews.py?view=standard&confId=7 62

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

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.

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.

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.

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

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.

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.

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.

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

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

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

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.

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. 2014.9.20 日本物理学会2014年秋季大会 榊原裕介　Yusuke Sakakibara 75

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 2014.9.20 日本物理学会2014年秋季大会 榊原裕介　Yusuke Sakakibara 76

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 2014.9.20 日本物理学会2014年秋季大会 榊原裕介　Yusuke Sakakibara 77

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. 2014.9.20 日本物理学会2014年秋季大会 榊原裕介　Yusuke Sakakibara 78

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) 062003 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. 2014.9.20 日本物理学会2014年秋季大会 榊原裕介　Yusuke Sakakibara 79

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)045010. Rebecca Douglas and Karen Haughian stayed in Japan in the last autumn. Rebecca reported in ELiTES meeting (Dec. 2013). https://events.ego-gw.it/indico/conferenceOtherViews.py?view=standard&confId=7 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

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

3. Sapphire suspension

3. Sapphire suspension

3. Sapphire suspension

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

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

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

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

3. Sapphire suspension

3. Sapphire suspension