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Radiation shield vibration measurement at KAGRA site

Radiation shield vibration measurement at KAGRA site. Kazuhiro Yamamoto on behalf of the KAGRA colloaboration Department of physics, Faculty of Science, University of Toyama Gravitational Wave Advanced Detector Workshop @Reef view hotel, Hamilton island , Queendland, Australia

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Radiation shield vibration measurement at KAGRA site

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  1. Radiation shield vibration measurement at KAGRA site Kazuhiro Yamamoto on behalf of the KAGRA colloaboration Department of physics, Faculty of Science, University of Toyama Gravitational Wave Advanced Detector Workshop @Reef view hotel, Hamilton island, Queendland, Australia 10 May 2017 1 1 1 1

  2. Abstract Radiation shield vibration in cryostat could contaminate detector output. We have already measured this vibration before cryostats were installed at KAGRA site. Here, I will introduce current status of radiation shield vibration measurement at KAGRA site.

  3. Contents • Outlines • Measurement at Toshiba • Measurement at KAGRA site • Calculation • Summary

  4. 1. Outlines Two unique key features of KAGRA Cooled mirror to reduce thermal noise Underground site with small seismic motion 3km Y end 3km X front X end Y front Kamioka mine (Underground site) Atotsu Center Laser Cooling system can never bring vibration ! 4 4 4 4 4 4 4 4 4

  5. Outlines Main mirror parts 14m Beam duct

  6. Outlines Main mirror parts Vibration isolation system at room temperature Cryo duct in order to terminate 300K radiation 14m Beam duct Cryostatwith four cryocoolers

  7. 1. Outlines Stainless steel t=20mm Diameter 2.4 m Height ~4.3 m M ~ 12 ton Cold Mass: 8K shield ~455 kg 80 K shield ~590 kg Seismic Attenuation System (SAS) Cryogenic Payload 4.3 m Sapphire Mirror (-alumina crystal) View Ports Radiation Shields Duct Shield Main Laser Beam Cryocoolers Pulse tube, 60Hz 0.9 W at 4K (2nd) 36 W at 50K (1st) Four Cryocooler Units 2.6m S.Koike Heat links (soft aluminum) are necessary to cool down cryo payload

  8. 1. Outlines KAGRA adopts pulse tube cryocooler (developed by us) with small vibration. T. Tomaru et al., Classical and Quantum Gravity 21 (2004) S1005. Pulse tube cryocooler (Sumitomo Heavy Industries) Vibration reduction system 8 8 8 8 8 8 8 8 8

  9. 1. Outlines • Shield vibration could contaminate detector output. • Vibration via heat links could shake mirror. • Phase of (main beam) light could be fluctuated by scattered light in vibrating shield

  10. 2. Measurement at Toshiba What did we do so far ? Shield vibration measurement at Toshiba Keihin Product Operations (Yokohama) before cryostats were installed at KAGRA site. D Chen, L Naticchioni et al., Classical and Quantum Gravity 31 (2014) 224001. Frasconi F, Majorana E, Naticchioni L, Paoletti F and Perciballi M Meas. Sci. Technol. 25 (2014) 015103 Dan Chen (ICRR at that time) and Luca Naticchioni (Rome) developed and installed horizontal and vertical cryogenic accelerometers, respectively, and measured.

  11. 2. Measurement at Toshiba Dan Chen (ICRR at that time) and Luca Naticchioni (Rome) developed and installed horizontal and vertical cryogenic accelerometers, respectively, and measured. Dan Chen (horizontal) Luca Naticchioni (vertical) 11 11 11 11 11 11 11 11 11

  12. 2. Measurement at Toshiba How accelerometer works? We observed motion of mechanical oscillator. Thanks for servo system, this oscillator follows motion of ground. Feedback signal must be proportional to acceleration of ground. Sensors Luca (vertical) : LVDT Dan (horizontal) : Michelson interferometer 12 12 12 12 12 12 12 12 12

  13. 2. Measurement at Toshiba Result at Toshiba • Shield vibration could contaminate detector output. • Vibration via heat links could shake mirror. • Phase of light could be fluctuated by scattered light in vibrating shield • Dan considered (1) and concluded extra pendulum is necessary. D. Chen et al., Classical and Quantum Gravity 31(2014) 224001, 13 13 13 13 13 13 13 13 13

  14. 3. Measurement at KAGRA site All cryostats and cryo ducts were assembled at KAGRA site. What are differences measurement at KAGRA site from measurement at Toshiba ? (1)Seismic motion at site is much smaller. (2)We “derived” shield vibration “at KAGRA site” from measurement “at Toshiba”. Now we need not to do so, just measure ! (3)At Toshiba, cryostats were not connected anything, cryo ducts, vacuum pipe for vibration isolation system … (4)Cryostats were NOT fixed on ground in Toshiba. On the contrary, they are fixed.

  15. 3. Measurement at KAGRA site We also measured vibration of ground at Toshiba. We calculated product of Kamioka mine seismic motion and the ratio of shield vibration to ground vibration. D. Chen et al., Classical and Quantum Gravity 31(2014) 224001, 15 15 15 15 15 15 15 15 15

  16. 3. Measurement at KAGRA site All cryostats and cryo ducts were assembled at KAGRA site. What are differences measurement at KAGRA site from measurement at Toshiba ? (1)Seismic motion at site is much smaller. (2)We “derived” shield vibration “at KAGRA site” from measurement “at Toshiba”. Now we need not to do so, just measure ! (3)At Toshiba, cryostats were not connected anything, cryo ducts, vacuum pipe for vibration isolation system … (4)Cryostats were NOT fixed on ground in Toshiba. On the contrary, they are fixed.

  17. 3. Measurement at KAGRA site (2)At Toshiba, cryostats were not connected anything, cryo ducts, vacuum pipe for vibration isolation system … Duct for vibration Isolation System has been NOT attached yet 3 km duct has been NOT attached yet Toshiba

  18. 3. Measurement at KAGRA site Now, vacuum ducts are connected to cryostat. 3 km duct has been NOT attached yet At KAGRA site

  19. 3. Measurement at KAGRA site All cryostats and cryo ducts were assembled at KAGRA site. What are differences measurement at KAGRA site from measurement at Toshiba ? (1)Seismic motion at site is much smaller. (2)We “derived” shield vibration “at KAGRA site” from measurement “at Toshiba”. Now we need not to do so, just measure ! (3)At Toshiba, cryostats were not connected anything, cryo ducts, vacuum pipe for vibration isolation system … (4)Cryostats were NOT fixed on ground in Toshiba. On the contrary, they are fixed at site.

  20. 3. Measurement at KAGRA site Mission for measurement at KAGRA site started on spring 2016. Kazuhiro visited Rome to ask Luca join again (vertical accelerometer). He kindly accepted. Kazuhiro asked Toshiro Ochi (Fresh graduate student in ICRR) to recover Dan’s horizontal accelerometer.

  21. 3. Measurement at KAGRA site On November 2016, both accelerometers were installed at KAGRA site. 21 21 21 21 21 21 21 21 21

  22. 3. Measurement at KAGRA site On November 2016, both accelerometers were installed at KAGRA site. Toshiro Ochi Kazuhiro Yamamoto Luca Naticchioni Maurizio Perciballi Ettore Majorana also came. We did it ! 22 22 22 22 22 22 22 22 22

  23. 3. Measurement at KAGRA site First cooling test was over (April 2017). We found some issues and have to fix by second cooling test (summer or autumn 2017). And calculation and analysis are still in progress … Here, I show only result from horizontal motion at room temperature (in vacuum). 23 23 23 23 23 23 23 23 23

  24. 3. Measurement at KAGRA site Comparison with measurement at Toshiba Kamioka_cryocooler on Toshiba_cryocooler on Comparison with measurement at Toshiba The vibration level in the cryostat of Kamioka is about 100 times smaller than the measurement by Toshiba below 10 Hz. It was lower than the vibration at Toshiba in all frequency bands. 24 24 24 24 24 24 24 24 24

  25. 3. Measurement at KAGRA site Measurement result at site 2 Hz Vibration of cryocooler and harmonics Cryocooler off Cryocooler on

  26. 3. Measurement at KAGRA site Vibration analysis of vacuum chamber and radiation shield S. Koike investigated vibration modes of radiation shield and vacuum chamber of cryostat using ANSYS, application software of Finite Element Method.

  27. 3. Measurement at KAGRA site Comparison with structural analysis results (radiation shield) 1~4 6 10~11 5 19 12 7~8 KEK Koike-san Many large peaks of the measurement result are consistent with analysis results of the radiation shield.

  28. 3. Measurement at KAGRA site Comparison with structural analysis results (radiation shield) Kamioka_cryocooler off Toshiba_cryocooler off 6 1~4 5 Dan Chen also mentions eigenmode of radiation shield was observed at Toshiba. (Number of observed is from 1th to 6th modes)

  29. Comparison with results in Toshiba(vacuum chamber) 1 Kamioka Toshiba A large peak of 16 to 18 Hz We didn’t observe large peak around 11 Hz at KAGRA site, butobserved large peak between 16 Hz and 18 Hz. It could be due to connection of 3 km ducts and cryostat is fixed on ground.

  30. 4. Calculation How vibration contaminates output of interferometer ? (1)Vibration via heat links. (2)Scattered light (1)Vibration via heat links After D. Chen’s evaluation, design of cryo payload was drastically changed. We have to take into account and proceed with calculation.

  31. 4. Calculation (2) Scattered light Recently, Simon Zeidler is investigating. http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=6422 We need baffle to absorb scattered light from mirror surface in order to decrease scattered light noise drastically. Simon evaluates how much scattered light noise with baffles. Baffle

  32. 5. Calculation (2)Scattered light. Recently, Simon Zeidler is investigating. http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=6422 Preliminary

  33. 4. Calculation • Scattered light noise strongly depends on baffle shape. • Vibration isolation system can decrease this noise but it is not taken into account in this graph. Investigation is in progress…

  34. 5. Summary We measured radiation shield vibration at Toshiba. Now, we are measuring at KAGRA site. We observed vibration peaks by cryocoolers, resonant modes of shield and vacuum chambers. We have plan for second cooling in next half year. We must fix issues. Noise by heat links and scattered light are being evaluated based on measurement result.

  35. ELiTES strongly supported Rome group activity for this mission.

  36. Thank you for your attention !

  37. 1. Outlines Result at Toshiba Measured vibration of shield

  38. 1. Outlines Result at Toshiba They derived noise spectrum by vibration via heat links from measured shield vibration Horizontal Vertical We need extra pendulum for heat link vibration isolation.

  39. 3. Measurement at KAGRA site They also measured vibration of ground. They calculated product of Kamioka mine seismic motion and the ratio of shield vibration to ground vibration. It is crucial that this evaluated spectrum is correct ! Vibration which can not be observed at Toshiba could be an issue at KAGRA site.

  40. 3. Shield vibration Measurement of radiation shield vibration at site to evaluate noise (1)Heat links transmit vibration (2)Scattered light reflected by shield Toshiro Ochi reports.

  41. 3. Shield vibration Toshiro installed accelerometers in X front cryostat without cross pipe. We would like to repeat measurement after cross pipe connection because resonant modes of vacuum chamber could be changed by this connection. Probably, next measurement around summer 2017, in other words, before laser beam passes through this cryostat. 2F Cross pipe vacuum chamber

  42. 6. Near future plan What must CRY do before next f2f meeting (end of August) ? At KAGRA site Cooling test of Y front cryostat Vibration measurement at X front cryostat Full hanging test of cryogenic payload (with “blank” sapphire bulk without coating) at Y end At KEK Cryogenic test of cryo payload and sapphire suspension part At University of Toyama HCB for “blank” bulk without coating and ETM

  43. Plan for re-measurement with cross pipe Currently no cross pipe is installed on the cryostat cryo-accelerometer installed . 2F Eigenmodes of cryostat with cross pipe could be different from that without the duct. Vibration measurement and hamming test to invstigate eigenmodes are necessary after cross pipe is connected to cryostat. We would like to perform the cooling test again. cross pipe duct vacuum chamber KEKHagiwara-san

  44. Measurement result at site 2 Hz Vibration of cryocooler and harmonics large peaks at 16 Hz, 23 Hz Cryocooler off Cryocooler on

  45. Temperature distribution2016 Nov.28 4K bar for Shield 4K side 80K side 80K bottom 4K bar for Pay 45 45 45 45 45 45 45 45 45

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