Floor Tilt and Vibration
Measurements for the ATF2
Mika Masuzawa ,KEK
IWAA06
29 September, 2006
Contents
1. Introduction
•
•
ATF
ATF2
2. Measurements:
Comparison between ATF and ATF2
Tilt measurements

•
•
ATF
ATF2
Vibration measurements

•
•
Comparison
Variation at ATF2 (day to day)
3. Summary
1. Introduction : ATF
ATF (The Accelerator Test Facility)
Built for R&D work for a future electron-positron linear
collider.
Produce, measure and control a very low emittance beam.
Construction
started in 1993
– by adding the damping ring to the pre-existing injection
linac in the assembly building.
– Reinforcement of the floor was needed.
– A special foundation with more than 200 piles, 1 m in
diameter and 14 m in length, was used.
– Many expansion joints were introduced to prevent the floor
from cracking due to thermal expansion and contraction.
The expansion joints also play an important role in
damping the floor motion and vibration.
1. Introduction : ATF
Lowest among the same type
accelerators
Beam energy :
1.28 GeV
ex
1.0x10-9rad.m
ex
1.0x10-11 rad.m
sx
70 mm
sy
7 mm
Multi bunch
0.7x1010 /bunch x 20
Circumfrence 138m
1. Introduction : ATF2
The ATF2 project will extend the existing ATF extraction line with
an ILC-type final focus system.
– Although the ATF2 beam energy is two orders of magnitude
smaller than the ILC beam energy, many features of the ATF2
are common to the ILC final focus system.
– The ATF2 optics design is identical to that for the ILC, and the
natural chromaticity and the relative beam energy spread are
similar.
– The beam will be focused down to about 40 nm in the vertical
direction at the IP, which is only a factor of ~5 larger than at the
ILC.
– Most of the tolerances, such as the tolerances on magnetic field,
jitter vibration and power supply stability, are common between
the ATF2 and the ILC.
– The beam center has to be controlled to within a few
nanometers at the IP.
1. Introduction : ATF2
With all the similarities between the ATF2 and the ILC ,
ATF2 will be a very good model for the
ILC final focus system and a successful
commissioning of the ATF2 project will
assist in the design of the ILC.
Do we need to re-do the floor outside of the ATF area?
How large is the floor motion (tilt/vibrataion) there ??
Let’s measure them.
1. Introduction : ATF2
Assembly building
ATF measurements
(tilt & vibration)
ATF2 measurements
(tilt & vibration)
2a. Measurements
Tilt measurements
• Leica Nivel 20 digital tiltmeter
Vibration measurements
• Servo type velocity sensor VSE355G2
(Tokyo Sokushin Co. ,LTD.)
For sensor resolution and huddle test results,
→http://acfahep.kek.jp/subg/ir/nanoBPM/
• Servo acceleration sensor MG-102S
(Tokkyo-kiki Co., LTD.)
For sensor resolution and huddle test results,
→ R.Sugahara et.al., “Performance of an active vibration system for GLC”,
IWAA2004.
2a. Measurements : Floor tilt at ATF
October 2004
S M T W Th F Sa
At ATF beam line
10/25(Mon)-11/1(Mon)
Access time to the beam area was
limited.
X: perpendicular to the beam line (NS)
Y: parallel to the beam line (EW)
X
Y
Sensors on the floor
2a. Measurements : Floor tilt at ATF
50mrad
An earthquake
occurred.
Big spikes
in both x/y
at 10:40 am
No clear daily motion is seen.
The earthquake turned out to be one of the large
aftershocks of the 2004 Mid-Niigata earthquake.
The aftershock was reported as being magnitude6.1
(and an intensity level 6- on the 7-grade Japanese
intensity scale at its origin in Niigata prefecture).
The intensity level at the KEK area was 2~3.
The 1st one (M 6.8)
occurred on 24th.
KEK
2a. Measurements : Floor tilt at ATF
• No clear diurnal motion was seen.
– No clear dependence on outside air temperature.
• The floor tilt recovered smoothly after the earthquake.
2a. Measurements : Floor tilt at ATF2
50mrad
Not as flat as ATF
Outside air temp. dependence
in x/y.
X (north-south) drifts
Atmospheric pressure??
2a. Measurements : Floor tilt at ATF2
• A clear day and night effect, about 10 mrad peak-topeak, is seen in both x- and y- directions.
• There seems to be a drift in the x-direction, which
shows a weak correlation with the atmospheric
pressure.
2b. Measurements : Floor vibration
Chiller &pump
Green floor
Concrete shield
~2 m
Yellow floor
Floor paint removed
For tilt measurements
2b. Measurements : Floor vibration
amplitude comparison between ATF and ATF2
X
V
Y
ATF2 (red) vibrates more than ATF(blue),
especially in vertical.
could be a problem…
2b. Measurements : Floor vibration
comparison between ATF and ATF2
vertical
ATF2
ATF
Both measrured by acceleration sensors @14:00 April 1, 2004.
Amplitude of
ground motion
M.Masuzawa
Presented at LCPAC at KEK，March 2006 by Andrei Seryi
2b. Measurements : Floor vibration
comparison between ATF and ATF2
• We should try to damp the ATF2 floor vibration, to
the level of the ATF area, by reinforcing the structure.
• Especially since the amplitude of a girder is larger
than that of a floor.see the next slide for an
example.
• We recommended that the ATF2 floor should be
reinforced.
Vibration amplitude
10
The amplitude ratio of the vibration of the girder at the ATF beam line
to the floor nearby. The present ATF girder vibrates more,
by an order of magnitude than the floor!
What we will do …
• The position of the final doublet quadrupoles (FD)
must be stabilized to a few nm vertically and 50 nm
horizontally.
• Motion of FD with respect to the IP is most critical.
– FD and IP will be installed on a common rigid support at
ATF2 to reduce their relative motion.
• IF FD were to be mounted independently from the IP
(ILC), an active stabilization system will be needed.
– High speed (> 10 Hz) and high resolution ( sub-nano level).
– Such system might be tested at ATF2 (yesterday’s talk by
Morita)
2b. Measurement : ATF2 floor vibration (~5 days)
day to day variation
December 2004
S M T W Th F Sa
Weekend effect?
Quieter
Sunday
Date
2b. Measurement : ATF2 floor vibration ,day to day variation
“Anti-weekend” effect
for low-frequency ( f > 0.3Hz) floor vibration
“Anti-weekend” effect is significant
(several times larger) in X and Y.
Not much effect in V.
Why?
Sunday
Exceeds 1 mm
It was a very windy weekend
Wave height and wave period at Port of Onahama
Sunday
ATF2 floor (yellow)
2nd peak appears when the wave height was big.
ATF2 floor (Green)
ATF2 floor vibration, wind speed and wave height
0.3Hz component follows wind speed??
0.1Hz component follows wave height??
Floor vibrates on windy days. Unfortunately no data taken over this
weekend at the current ATF beam line.
Summary
• The diurnal effect in the floor tilt is a few
times larger in the ATF2 beam extraction area
than in the ATF beam line area.
– The peak-to-peak daily tilt was measured to be 10
mrad in the ATF2 area when the outside air
temperature varied by ~15 degrees. There was no
such daily tilt in the ATF area.
– An earthquake occurred during the measurement at
the ATF area, but the floor tilt recovered smoothly.
Summary
• The floor vibration is also larger in the ATF2, especially in the
vertical direction. The vibration amplitude at 10 Hz is 50-60
nm in vertical, which is larger than the vertical beam spot size
expected by the ATF2.
• The ATF2 floor motion is significantly affected by strong
wind and/or waves. This could be a result of the beam line
being on the surface of the ground.
Reinforcement is needed in the ATF2 area.
Will be done as part of the ATF2 construction.
Stay tuned and see how well we can stabilize the beam at the ATF2.
(with reinforced floor, good girder/mover, active stabilization system(?))