1. Vibration measurements at KAGRA site
Kazuhiro Yamamoto
Institute for Cosmic Ray Research (ICRR)
the University of Tokyo
ELiTES: 5th general meeting　　　
University of Toyama, Toyama, Toyama, Japan
10 February 2017 1 1 1 1

2. 0. Abstract
We measured vibration of radiation shield (at Toshiba) before we installed KAGRA cryostat at KAGRA site.
Now we are measuring shield vibration at site. Progress in last one year is reported here.

3. Contents
Introduction
Toshiba
KAGRA site
Summary

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

5. Outlines of cryostat 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

6. 1. Introduction
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
Is vibration enough small ? 6 6 6 6 6 6 6 6 6

7. 2. Toshiba
Toshiba Keihin Product Operations (Yokohama) fabricated four KAGRA cryostats. Before delivery, they conducted cooling test at their factory (2013).
In this cooling test,
we measured vibration
of radiation shield. 7 7 7 7 7 7 7 7 7

8. 2. Toshiba
Dan Chen (ICRR at that time) and Luca Naticchioni (Rome) developed and installed horizontal and vertical cryogenic accelerometers, respectively.
Dan Chen (horizontal)
Luca Naticchioni (vertical) 8 8 8 8 8 8 8 8 8

9. 2. 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 9 9 9 9 9 9 9 9 9

10. 2. 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) , 10 10 10 10 10 10 10 10 10

11. 2. Toshiba
They measure near Yokohama (second largest city in Japan !). How did they derive vibration at KAGRA site ? 11 11 11 11 11 11 11 11 11

12. 2. Toshiba
They also measured vibration of ground. They 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) , 12 12 12 12 12 12 12 12 12

13. 2. Toshiba
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. 13 13 13 13 13 13 13 13 13

14. 3. KAGRA site
In fact, all four cryostat have already been installed at KAGRA site (by Feb 2015) !
We repeat same measurement at KAGRA site ! 14 14 14 14 14 14 14 14 14

15. 3. KAGRA site
Mission for measurement at KAGRA site started on spring 2016.
Calibration at Rome on May 2016
Kazuhiro visited Rome to ask Luca join again (vertical accelerometer). 15 15 15 15 15 15 15 15 15

16. 3. KAGRA site
Mission for measurement at KAGRA site started on spring 2016.
Kazuhiro asked Toshiro Ochi (Fresh graduate student in ICRR) to recover Dan’s horizontal accelerometer. 16 16 16 16 16 16 16 16 16

17. 3. KAGRA site
Mission for measurement at KAGRA site started on spring 2016.
Measurement at Kashiwa (ICRR)
Red : RION
Blue : Toshiro’s
Kazuhiro asked Toshiro Ochi (Fresh graduate student in ICRR) to recover Dan’s horizontal accelerometer. 17 17 17 17 17 17 17 17 17

18. 3. KAGRA site
On November 2016, both accelerometers were installed at KAGRA site. 18 18 18 18 18 18 18 18 18

19. 3. KAGRA site
On November 2016, both accelerometers were installed at KAGRA site.
Kazuhiro
Yamamoto
Toshiro
Ochi
Luca
Naticchioni
Maurizio
Perciballi
Ettore
Majorana
also came.
We did it ! 19 19 19 19 19 19 19 19 19

20. 3. KAGRA site
On 22nd of December 2016, cryostat was closed and vacuum pump started to work. 20 20 20 20 20 20 20 20 20

21. 3. KAGRA site
We measured vibration in vacuum at room temperature. Analysis is in progress.
Cryocoolers will start to work on 27th of February (two weeks later !). It takes 2 weeks to cool down. 21 21 21 21 21 21 21 21 21

22. 3. KAGRA site What must we check ?
(1)Vibration via heat links could shake mirror.
First of all, we compared measured vibration at KAGRA site with Dan’s “calculated” vibration at site.
If we find large discrepancy, we must reconsider Dan’s idea; extra pendulum for vibration isolation. 22 22 22 22 22 22 22 22 22

23. 3. KAGRA site What must we check ?
(2)Phase of light could be fluctuated by scattered light in vibrating shield
We never evaluated.
Now Simon Zeidler is investigating this noise. We have already pass our data at room temperature in vacuum. 23 23 23 23 23 23 23 23 23

24. 4. Summary
Shield vibration measurement is crucial to evaluate noise in KAGRA (heat link, scattered light).
We are going to measure shield vibration at KAGRA site. We have already installed accelerometers and cooling will start on 27th of February.
We will also evaluate noise (heat link, scattered light) based on this measurement. 24 24 24 24 24 24 24 24 24

25. ELiTES strongly supported Rome group activity for this mission.
Kazuhiro demonstrates these accelerometer in KAGRA site tour on this afternoon. 25 25 25 25 25 25 25 25 25

26. Kazuhiro’s new office is in this building.
Kazuhiro Yamamoto moves to University of Toyama on 1st of March as an associate professor.
Kazuhiro’s new office is in this building.
Kazuhiro must not only give lecture to undergraduate students, but also contribute KAGRA.
Kazuhiro leads this vibration measurement at site and supports sapphire mirror HCB mission in clean booth of University of Toyama.
Kazuhiro’s assistant professor age is almost overlapped by ELiTES. Kazuhiro appreciates ELiTES. 26 26 26 26 26 26 26 26 26