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
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.
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Contents
1.
2.
3.
4.
Introduction
Toshiba
KAGRA site
Summary
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1. Introduction
Two unique key features of KAGRA
Cooled mirror to reduce thermal noise
Underground site with small seismic motion
Mozumi
Y-end
Sakonishi
X-end
Atotsu
Center
Kamioka mine
(Underground site)
Cooling system can never bring vibration !
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Outlines of cryostat
Seismic Attenuation System (SAS)
View Ports
Four Cryocooler Units
Radiation Shields
Cryogenic Payload
4.3 m
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
Sapphire Mirror
(-alumina crystal)
Duct Shield
2.6m
Cryocoolers
Pulse tube, 60Hz
0.9 W at 4K (2nd)
36 W at 50K (1st)
S.Koike
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 ?
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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.
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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
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
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2. Toshiba
Shield vibration could contaminate detector output.
(1) Vibration via heat links could shake mirror.
(2) 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,
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2. Toshiba
They measure near Yokohama (second largest city
in Japan !). How did they derive vibration at KAGRA
site ?
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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) 224001,
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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.
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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 !
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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).
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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.
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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.
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3. KAGRA site
On November 2016, both accelerometers were
installed at KAGRA site.
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3. 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 !
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3. KAGRA site
On 22nd of December 2016, cryostat was closed and
vacuum pump started to work.
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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.
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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.
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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.
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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.
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ELiTES strongly supported
Rome group activity for this
mission.
Kazuhiro demonstrates these
accelerometer in KAGRA site
tour on this afternoon.
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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.
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