Vibra&on measurements
H. Yamaoka, R. Sugahara
and M. Masuzawa

Purpose of the measurements• To characterize the vibra&ons.
• Where is it that vibrates?
– Magnets– Suppor&ng table– ﬂoor• At which frequency?
– Characteris&c frequencies• With what amplitude?
– Will it cause a serious degrada&on in the machine
performance?

KEK environment

Measured by R.Sugahara et.al (KEK Report 2003‐12)

D9~11mbelow GL

D3

Higashi-odoriroad~11m
below GL

KEK environment

Measured by R.Sugahara et.al (KEK Report 2003‐12)

KEK site is muchworse
than SPring‐8…

D9

D3 is worse
than D9.

D9

D3 is closer toHigashi‐Odori.
A clear day&nighteﬀect around
3Hz（↓）,
caused byhuman ac&vi&es
such as traﬃc,is seen as
predicted.

Sensors
We use six accelera&on sensors (MG‐102S, Tokkyo‐kiki Corpora&on).
Each sensor measures one direc&on, 3 sensors to measure (X,Y,Z).
2 sets of sensors, one set usually on the ﬂoor and the other on the magnet for
example.
Servo Accelerometer
ＭＧ‐１０２Size

40×40×50mm

Max. input±２G

Resolu&on

１／106G
Acc. 0.1〜400Hz
Acc. 60dB = 1gal/V

Measurements
KEKB IR*Power Spectrum Density (PSD) plots*Integrated amplitude (vs frequency) plots
Data taken in June. 2009
when Belle solenoid, QCS and the ring magnets wereturned off.

PSD

~8Hz peak

Tunnel ﬂoor
H.Yamaoka

~3Hz : characteris&c frequency of the soil
called “Kanto loam” around KEK.
Induced by human ac&vi&es,
mainly ver&cal vibra&on.
Day & night eﬀects and weekend eﬀects
have been observed.

0.2~0.3 Hz: Ocean waves & wind.
Depends on the weather, mainly in horizontal vibra&on.

Amplitude~110 nm @ 1Hz~8Hz peak~50 nm @ 10Hz

Tunnel ﬂoor
H.Yamaoka

Comparison with some old data
WE have been measuring the mo&onof the tunnel ﬂoor, magnets,
supports in many places since 2003.

For how long has this
8Hz peak been around?
⇒ Since we started measuring

Belle End-yoke open

So I will show you some old data set, with includes QCS cryostat data.

IR magnet vibra&on (2003 data)
VerticalFrom 2009 data
@10Hz
~30 nm (QCS boat)~50 nm(QC1RE)@1Hz~120 nm(QCS boat)~110 nm(QC1RE)

SuperKEKB
σy＊QCS
cryostat

Consistent !
This photo was taken when
QCS was retracted (not while the vibra&on
data were taken),(Near the) IP vibrates more than the vibration
measurement locations indicated by
We can not place the vibration sensors
anymore near IP but can get some
information fromthe displacement sensors,which measure the relative
distance between QCS and BELLE CDC.

Note:The displacement sensors were originally installed
for measuring larger displacement (several hundred microns)
Sub-micron calibration ??

LXRXLVRV± 1µm

1 second

The ~4 Hz motion is in phase.
⇒ BELLE is vibrating, not QCS.

1 secondIn phase

LX
RX

Out of phase± 15µm± 1µm

1 second

Sometimes 8Hz becomes more
dominant than 4Hz.
The ~8 Hz motion is NOT in phase.
⇒ QCS L/R are vibrating
independently.

“1” in Japanese seismic
Intensity scale.
Did not feel anything.

A good collision condition maintained by“iBump” system was lost, resulted in a beamloss (not beam abort).

SuperKEKB
will be much more sensitive.
“1” in Japanese seismic
Intensity scale.
Tiny earth quake.

Measurements
on BELLE

Data taken on Dec. 26 , 2009

Measurement loca&ons(12/28/2009)

1300 tonnes

18H.Yamaoka

BELLE
PSD

4 Hz peakgrows
towardthe top
19

H.Yamaoka

BELLE
Amplitude

196nm
301nm
93nm

248nm
354nm
80nm
25nm
17nm
20nm

9nm
12nm
18nm

204nm
254nm
121nm
14nm
27nm
19nm

67nm
52nm
82nm

102nm
68nm
72nm

3nm
2nm
8nm

10nm
12nm
9nm

4 Hz peakgrows
towardthe top20

H.Yamaoka

Measurement results‐ First resonance is around ~3‐4Hz.
‐ Amplitude on the barrel is bigger than on the table.
‐ Amplitude on the End‐Yoke increases toward the top.

‐ The Belle detector is not ﬁxed to the ﬂoor.
‐ The barrel yoke is just placed on the table.
‐ Top of the end‐yoke is not ﬁxed.

150tonnes

Improvements/modification arebeing discussed.
21
H.Yamaoka

Summary
QC1RE
QCS‐boat

KEKB tunnel at the IP vibrates at
Movable table

KEKB tunnel
ﬂoor
Belle‐standB4 ﬂoor~ 0.3 Hz in the horizontal direc&on (micro‐seismic)~3 Hz in the ver&cal direc&on & horizontal
direc&on (resonance of the “Kanto loam”
soil around KEK)
In addi&on, magnets, QCS boat and thetable vibrate at ~ 8Hz.

SummaryBELLE detector vibra&on
First resonance is measured around~3‐4Hz, mainly in horizontal direc&ons.
‐Amplitude on the barrel is bigger than atthe table.
‐ Amplitude on the End‐Yoke increases
going towards the top.

Summary ( 2009 data)

Summary table by H.Yamaoka

The vibra&on amplitude of the IR magnets are much smaller
than the size of the colliding beams (~2µm ver&cally & ~100µmhorizontally) for KEKB but comparable for SuperKEKB.

Summary• Progress in understanding the characteris&c of the IR vibra&on
are being made.
• We understand where the 8 Hz (IR) and 4Hz (BELLE) come from.
• How to reduce the vibra&on IR components & BELLE?
⇒ being discussed/inves&gated.
• Faster orbital (collision) feedback system will help (is a must).
⇒But what do we monitor?
⇒A faster corrector magnet (“iBump”) system needs to bedeveloped. Some study with the beam is planned.
• The eﬀect of the helium ﬂow will be studied in May
when we turn on the cryogenic system for QCS.
⇒ as the data shown were taking while no helium ﬂow.

spare