Report from sub-groups Cryogenic Cryogenic payload Kazuhiro Yamamoto Institute for Cosmic Ray Research (ICRR) the University of Tokyo KAGRA face to face meeting　　　 Institute for Cosmic Ray Research, Kashiwa, Japan 15 February 2013 I will explain cryogenic payload.

Contribution R. Takahashi, T. Sekiguchi, Y. Sakakibara, C. Tokoku, M. Kamiizumi, U. Iwasaki, E. Hirose, T. Uchiyama, S. Miyoki, M. Ohashi, K. Kuroda, T. AkutsuA, H. IshizakiA, T. SuzukiB, N. KimuraB, S. KoikeB, T. KumeB, K. TsubonoC, Y. AsoC, T. UshibaC, K. ShibataC, D. ChenD, N. OhmaeE, K. SomiyaF, R. DeSalvoG, E. MajoranaH, L. NaticchioniH, W. JohnsonI, A. CummingJ, R. DouglasJ, K. HaughianJ, I. MartinJ, P. MurrayJ, S. RowanJ , G. HofmannK, C. SchwarzK, D. HeinertK, R. NawrodtK, S. GotoL, KAGRA collaboration ICRR.UT, NAOJA, KEKB, Phys.S.UTC, Astro.S.UTD, E.UTE,S.TITF, Sannio Univ.G, INFNH, Louisiana State Univ.I , University of GlasgowJ, Friedrich-Schiller-Universitaet JenaK, Jecc TorishaL, KAGRA collaboration I will explain cryogenic payload.

0. Abstract Although there are many topics, but here, I will explain (1)1/4 cryostat (2)Experiments in Toshiba cooling test (3)Sapphire fibers I will explain cryogenic payload.

Experiments in Toshiba cooling test Sapphire fibers Summary Contents Introduction 1/4 cryostat Experiments in Toshiba cooling test Sapphire fibers Summary I will explain cryogenic payload.

1. Introduction Schematic view of KAGRA interferometer Four mirrors of arm cavity will be cooled. 3km 3km Mozumi Y-end Sakonishi X-end OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector. 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 OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector. Cryostat Cryogenic mirror 6

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 OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector. Cryo-coolers Pulse tube, 60Hz 0.9 W at 4K (2nd) 36 W at 50K (1st) Main LASER beam Remote valve unit S. Koike

1. Introduction Outline of cryogenic payload Outer shield (80K) Vacuum chamber (300K) Inner shield (8K) Sapphire fiber Heat links (pure Al) Sapphire mirror (About 20K) OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector. Y. Sakakibara et al., Classical and Quantum Gravity 29 (2012) 205019. 8 8

2. 1/4 cryostat Cryogenic payload is not a simple system. We need cryostat to test cryogenic payload performance. KAGRA cryostat is not appropriate for test. Difficult access in mine Cleanness must be kept 1/4 cryostat will be prepared in Kashiwa campus. OK, I would like to explain what happened in the last half year. Design and discussion for ¼ cryostat to check payload is in progress. This is the latest design.

2. 1/4 cryostat Bid (for parts of 1/4 cryostat) was opened ! (Jecc Torisha) Discussion for final design is in progress. Preliminary and not latest version. OK, I would like to explain what happened in the last half year. Design and discussion for ¼ cryostat to check payload is in progress. This is the latest design.

3. Experiments in Toshiba cooling test KAGRA cryostat is being assembled ! OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector. at Toshiba Keihin Product Operations

3. Experiments in Toshiba cooling test Cooling test of KAGRA cryostat is in progress. We have plans of experiments in Toshiba cooling test of KAGRA cryostat. Experiment 1 : Initial cooling time Sample 1 : Metal hollow spheres Sample 2 : Dummy payload Experiment 2 : Measurement of shield vibration Accelerometers developed by Luca Naticchioni (Rome) and Dan Chen (ICRR) OK, what is cryogenic payload ? This is the cross section of tunnel of LCGT. This tall tower is vibration isolation system. There is cryogenic payload under this vibration isolation. Cryogenic payload is in cryostat. Payload includes mirror, which is the most important part of gravitational wave detector.

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Initial cooling time of KAGRA cryostat and cryogenic payload is about 2 months (if no tricks). At beginning of initial cooling, heat transfer is dominated by radiation. Diamond Like Carbon (DLC) coating (High emissivity, Large radiation) on shields and payload (except for mirror) The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. 13

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Initial cooling time with DLC (shield and mass) Calculation by Y. Sakakibara This is result of his calculation. The horizontal axis is time. The vertical axis is the temperature. These thin lines are the result without DLC coating. These thick lines are temperature with DLC coating. So, initial cooling time with is almost half ! OK fine. But this calculation should be checked experimentally. Almost half ! 14

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Experimental test of effect of high emissivity coating (DLC) Inner sphere (copper) is suspended inside outer sphere (aluminum) at 77 K Cooling time is examined with and without DLC coating This is result of his calculation. The horizontal axis is time. The vertical axis is the temperature. These thin lines are the result without DLC coating. These thick lines are temperature with DLC coating. So, initial cooling time with is almost half ! OK fine. But this calculation should be checked experimentally. 15

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time This is result of his calculation. The horizontal axis is time. The vertical axis is the temperature. These thin lines are the result without DLC coating. These thick lines are temperature with DLC coating. So, initial cooling time with is almost half ! OK fine. But this calculation should be checked experimentally. We can observe DLC effect. 16

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Sample 1 : Metal hollow spheres (100 mm in diameter) to check scaling law Y. Sakakibara’s small experiment: 30 mm in diameter Without DLC The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. With DLC Both spheres were suspended in the shields. The sphere without DLC is being cooled now !

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Sample 1 : Metal hollow spheres The sphere without DLC is being cooled now ! Latest result The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. Calculation of Yusuke is quite correct !

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Sample 2 : Dummy payload (hollow masses) (100 mm in diameter) Half size Hollow masses (~5 kg) DLC coating Sapphire bulk as dummy mirror Evaluation of emissivity The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. Preparation is in progress. S. Koike

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Sample 2 : Dummy payload The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. We assembled before the cleaning and DLC coating deposition !

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Sample 2 : Dummy payload We assembled before the cleaning and DLC coating deposition ! Cleaning and DLC coating deposition is in progress. They will arrive at ICRR on 20th of February. The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. 21 21

3. Experiments in Toshiba cooling test Experiment 1 : Initial cooling time Sample 2 : Dummy payload Yusuke calculated the cooling time of 1/2 dummy payload. The next item is the initial cooling time. If we do not adopt any tricks, the initial cooking time is about 2 months. This is not so short. But, we found that heat transfer is dominated by radiation at beginning of initial cooling. So, we can expect that initial cooling time could be shorter if we adopt DLC coating on the shield and payload except for the mirror. DLC coating is the black one. I mean the high emissivity and large radiation. The details are described in Yusuke Sakakibaras’s master thesis in English. 22 22 22 22

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration Vibration of shield could be problems. Vibration via heat links, Scattered light We must measure the vibration of shield. This measurement is at cryogenic temperature and in vacuum. Luca Naticchioni (Rome) and Dan Chen (ICRR) will measure vertical and horizontal vibration of radiation shield of KAGRA in cooling test of Toshiba, respectively. ELiTES supports Luca’s visit. 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.

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration Dan Chen’s accelerometer 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. His accelerometer is consistent with commercial one (in air). 24

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration Dan Chen’s accelerometer He is proceeding with cryogenic test before measurement in Toshiba. 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. 25

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration Luca Naticchioni’s accelerometer 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. 26

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration 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. Luca’s accelerometer was installed in the shield (13th of Feb). 27

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration 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. Luca’s accelerometer was installed (13th of Feb). 28

3. Experiments in Toshiba cooling test Experiment 2 : Measurement of shield vibration 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. Luca’s accelerometer was installed (13th of Feb). 29

4. Sapphire fibers Sapphire fibers with nail heads are necessary to suspend mirrors. Test sample (T. Uchiyama) The next item is the sapphire fiber. We need fibers with nail heads, which is similar to this design drawn by Takashi Uchiyama. 30

4. Sapphire fibers T. Uchiyama asked MolTech GmbH (Germany). Sapphire fibers have already come ! Takashi sent his drawing to companies and asked whether they can make it or not. Only one company said yes, Moltech GmbH in Germany. And they have already sent them ! This is the photo. I would like to emphasis that length and diameter are similar to those of bKAGRA. But we must check quality as I will explain later. Length = 350 mm diameter = 1.8 mm Almost as needed in bKAGRA. Need to check the quality and improvement . 31 31

4. Sapphire fibers Ettore Majorana asked IMPEX HighTech GmbH (German company). They made similar fibers (nail heads on the both ends). Ettore Majorana remember the other German company IMPEX Hightech GmbH sell the sapphire. He asked them. They can make similar fibers which has nail heads on the both end. We ordered shorter fibers and they will arrive at this institute on beginning of September.

4. Sapphire fibers Quality check Q-value and profile of Moltech fibers: Y. Sakakibara at Glasgow and Jena. His stay is stimulated by ELiTES. Thermal conductivity measurement of Moltech fibers in Jena Discussion for strength test with 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.

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.

4. Sapphire fibers Preliminary result Q measurement in Jena (cool) and Glasgow (300K) It is comparable with KAGRA requirement ! 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. Preliminary result

4. Sapphire fibers Preliminary result Q measurement in Jena After Yusuke left …. Q measurement in Jena Preliminary result It is comparable with KAGRA requirement ! 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 Preliminary result Thermal conductivity measurement in Jena After Yusuke left …. It is same as KAGRA requirement (size effect) Preliminary result 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 Preliminary result Thermal conductivity measurement in Jena After Yusuke left …. Preliminary result It is smaller than KAGRA requirement, but same order of magnitude. 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 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 Strength test Kick off meeting with Glasgow (23rd Jan) (Thanks for E. Hirose) http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=1494 Glasgow group has (1)apparatus for tensile, bending, shear tests. (2)very high motivation. Kazuhiro should summarize strength requirement (He wrote memo, but it should be revised). 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 Next plan Measurement in Jena and Rome Discussion for strength test with Glasgow We are discussing other plan within ELiTES framework. 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. Summary 1/4 cryostat : Bid for parts was opened and discussion for final design is in progress. Experiments in Toshiba cooling test : Initial cooling time Metal sphere with and without DLC Both of them are installed in shield. Result without DLC is same as our expectation (up to now). 1/2 dummy payload Preparation is in progress. Measurement of shield vibration Intallation and preparation are in progress. 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.

5. Summary Sapphire fibers Moltech and IMPEX provided fibers with nail heads. Measurement of Q-values and thermal conductivity : Result is preliminary, but promising. Discussion for strength test was started. ELiTES strongly supports and stimulates research for KAGRA cryogenic payload. 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.

Thank you for your attention ! That’s all. Thank you for your attention.

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. 45

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.

8. Summary ELiTES has already started and supports the development of KAGRA cryogenic system. If you want to join our mission, let us know. 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.