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Ground Motion Measurements at ESA

M. Albrecht (Notre Dame)

F. Gournaris (UCL)

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Why ? Energy Spectrometry ILC test beam experiments T474 and T475 will test concepts for incident beam

energy monitoring at the ILC Upstream spectrometer uses a 4 magnet chicane with microwave BPMs before, in

the middle, and after the chicane. In order to get the best possible measurement, we need accurate knowledge of B*dl

and position of the beam ground motion can limit the precision of the chicane !!

3 concrete blocks on which the chicane will sit..

Motion of interest is the relative motion of the concrete blocks!

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Geophone measurements I3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+23E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

1.0

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

6E+23E-2 1E-1 1E+0 1E+1 1E+2

real

imaginary

coherence

Coherence & Cross Correlation of ch0 & ch1

Calibration measurements (side by side)

Only vertical motion !

Freq. range 1 to ~20 Hz (i.e. mostly fast motion)

30sec measurements @ 400Hz sampling rate

x30 amplification (with possible problems!!)20nm relative motion ?

Freq HZ

Freq HZ

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Ch0

Geophone measurements II

3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+21E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

Ch1

1E+3

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

1E+23E-2 1E-1 1E+0 1E+1

ch0

ch1

ch0-ch1

1-rho

power[(micronsRMS 2̂/Hz)*f 4̂]

Relative vertical ‘fast’ motion between the two ends of the chicane ~50nm

Similar for other arrangements along the chicane..

Freq HZ Freq HZ

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STS-2 SeismometersLow noise broadband (0.01 – 50 Hz) feedback seismographs (‘Very sensitive’)

Can get to 100sec measurements (0.01Hz) ~ calibration cycle of spectrometer!

x,y,z differential signals

Usual measurement setup includes covering the STS-2’s with styrofoam boxes for thermal and air current insulation…

After movement, the seismometers were let to settle for ~2hours

In NLC 0th Order Rep. measurements, seismometers were let to settle for 1 day, and usually movement cycle was 2-3 days..

Due to time restrictions, this was not possible in our case…

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Seismometers I 3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+21E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

Calibration measurement:

4kHz sampling rate, 30 sec sample

Relative motion: 3nm

3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+21E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

Freq HZ

Freq HZ

Other configurations give similar signals in the 30 – 50 nm range.

But only valid for ‘fast’ motion (>0.1Hz) due to 30sec sample

x signal

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Seismometers II 400 sec samples @ 1kHz sampling rate

Which means we can get to 100sec timescales

3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+21E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

x signal

3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+21E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

x signal3E+0

1E-4

1E-3

1E-2

1E-1

1E+0

2E+21E-2 1E-1 1E+0 1E+1 1E+2

ch0

ch1

ch0 - ch1

1-rho

Integrated amplitude[micronsRMS]

y signal

On the floor at the two ends of the chicane

On the concrete blocks

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Comments

Data give 50 – 100nm relative motion between girders at frequencies <0.5 Hz, about 30nm for > 0.5 Hz.

Noise sources (water cooling, cultural noise) exist in ESA.. Need more STS-2 long timescale measurements (400+ sec samples) Need to determine amount of noise introduced by short settling period for the

seismometers… Do we need to follow the long settling strategy? Very time consuming..

Suggestions for improvement…

Data still ‘preliminary’ Need to better understand seismometer behavior