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Ambient Noise Measurements At Different Synchrotron Light Facilities

Wilhelm Bialowons Ambient Noise Measurements Diamond, Didcot, UK August 13, 2013

Wilhelm Bialowons | Ambient Noise Measurements | August 13, 2013 |

Outlook

>  Introduction §  Motivation and Webpage vibration.desy.de

§  Effect of Ground Vibration on the Orbit Stability of Storage Rings

§  Seismic Sensor with Feedback Circuit

§  Ground Vibration Classification and Definitions

§  Ground Vibration Amplification and Transfer Function

§  Design Rules for Machine and Beam Line Supports

>  Ambient Noise and Floor Motion Measurements at Diamond from September 1, 13:30 h to October 18, 2010, 14:00 h §  Root Mean Square values over the whole period and Comparison with PETRA III

§  Selected Power Spectral Densities

§  Comparison of Power Spectral Densities and RMS-Values at Diamond with other sites

>  Summary

>  References


Motivation etc.

>  Ambient noise (from human activities), floor motion (from infrastructure), transfer function of supports (and temperature stability) have an influence on the position stability of machine and beam line elements and ultimately on the beam quality

>  Requirements of of current and next generation machines approach a region where ground motion may decrease performance

>  Vibration measurements could help to asses these influences

>  Originally data were collected for the comparison of potential International Linear Collider sites

>  Data taking at the different sites always with identical instruments

>  Data analysis always with identical software tools

>  Presentation of the results for everyone

>  With time extension of the measurements to Synchrotron Light Facilities

>  Webpage: http://vibration.desy.de


vibration.desy.de


Effect of Ground Vibration on the Orbit Stability of SRs

If all N quadrupoles in a storage ring are vibrating randomly with the RMS value a then the distortion can be estimated by: q

hy2j i ⇠=a�y

2p2f sin⇡qy

pN

The beam oscillation should not exceed 10 % of the beam size �yj =q

�y"y

R =ap

�y

2p2f sin⇡qy

p"y

pN < 10%

At Diamond the vertical RMS quadrupole vibration should be lower than approximately 100 nm an the horizontal value below 1µm. Under these conditions the orbit is inherent stable.


Seismic Sensor with Feedback Circuit

Opened seismometer CMG-3T from Guralp with a built-in DM24 digitizer.


Seismic Sensor with Feedback Circuit(cont‘d)

>  Used instrument: CMG-3ESPD from Guralp

>  Principle: The acceleration is physically measured. The signal will be internally integrated and then digitized with a 24-bit digitizer.

>  Frequency range: 1/60 to 50 Hz

>  Sensitivity: 400 pm/s per bit

! F = mxixi+

!

k!

!!

F!

C Ui

m

k

Equivalent feedback circuit for one channel of a velocity broadband seismic sensor.


Ground Vibration Classification and Definitions

Ocean Waves

Ambient Noise Floor Motion and Resonances

Coherent

Incoherent

Power Spectral Density py :

Z ⌫2

⌫1

py(⌫)d⌫ :=

⌦y2↵⌫2

⌫1

“White” Background Noise


Cross Correlation K and Coherence C

K(⌫) =hx(⌫)y⇤(⌫)ip

hx(⌫)x⇤(⌫)ihy(⌫)y⇤(⌫)i

C(⌫) = mod [K(⌫)]

Vertical Coherence between HERA WL350 and 745 (July 3, 2013 2:00 h)


Ground Vibration Amplification and Transfer Function

Transfer Function Ty(⌫) :=

spyMagnet

(⌫)

py Floor

(⌫)


Transfer Function


Design Rules for Machine and Beam Line Supports

“Simple” support design rules for keeping the ground stability also for the machine and beam line elements are:

>  No resonances below 50 Hz (i.e. low beam position, single, very short, less than 5 mm and stable adjustment element and non-positive connections, as at a vacuum flange, beside the adjustment element)

>  Typically the adjustment element are three screws forming a tripod. The area centre of this tripod is below the element centre of mass

>  Quadrupoles (together with Beam Position Monitors and the respective end of the vacuum chamber) are the fix points of the construction

>  The supports in the LCLS undulator section at SLAC in Menlo Park, CA are a good example


Measurements at Diamond in September 2010


Measurements at Diamond in September 2010 (cont’d)


Measurements at Diamond in October 2010


Measurements at Diamond in October 2010 (different Scale)


Measurements at PETRA III in September 2012


Comparison between PETRA III Slab and HERA Tunnel


Vertical Power Spectral Density on September 23, 2010


Power Spectral Density on September 23, 2010 2:00 h


Power Spectral Density on September 23, 2010 12:00 h


Power Spectral Density at Diamond and PETRA III


Selected vertical Power Spectral Densities at different Sites*

*Siting Study for European ILC Sites ILC-HiGrade-Report-2010-004


Assessment of Ground Vibration (PSD) at Diamond


Vertical RMS-Values at different Institutes and Sites

Site Minimal RMS-Value / nm Moxa (Seismic Station 0.6 Asse (Salt Mine NDL -900 m) 0.8 PETRA III 40 HERA WL 745 40 CERN Campus 5.0 LHC 2.0 ESRF 40 SLAC 5.0 FNAL Campus 7.0 FNAL NuMI Target Hall 3.0 APS 15 Minimal Noise < 0.5 Diamond 10


Summary

>  Measured ambient noise at Diamond: Vertical Root Mean Square above 1 Hz between 10 nm and 20 nm (50 nm).

>  Much lower than at PETRA III in Hamburg: Vertical Root Mean Square above 1 Hz between 40 nm and 120 nm.

>  At Diamond the ambient noise is comparable with APS and approximately in the mid range between ESRF and ALBA on the upper end of the scale and CERN and SLAC on the lower end.

>  For further investigations the stability of the machine and beam line elements must also be taken into account.

>  But even then it is the assumed that the effect of the ground vibration on the stability is still marginal compared to other effects.


References

>  Measurements of Ground Vibration and Orbit Motion at HERA, V. Shiltsev, B. Baklakov, P. Lebedev and C. Montag, J. Roßbach, DESY HERA 95-06, June, 1995.

>  Ground Vibration Measurements at the Proposed ALBA Site in Barcelona, W. Bialowons and H. Ehrlichmann, EUROTeV-Report-2005-007, March 10, 2005.

>  Site Selection Criteria for European ILC Sites, W. Bialowons and J. A. Osborne, ILC-HiGrade-Report-2010-003, March 31, 2012.

>  Siting Study for European ILC Sites, W. Bialowons, J. A. Osborne and G. Shirkov, ILC-HiGrade-Report-2010-004, March 31, 2010.

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