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Seismic motion analysis of the SuperB site of Frascati

Detailed overview of seismic motion analysis at the SuperB site in Frascati, including data acquisition, analysis techniques, and comparison of ground motion. Results and implications discussed.

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Seismic motion analysis of the SuperB site of Frascati

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  1. Seismic motion analysis of the SuperB site of Frascati L. Brunetti1, B. Bolzon1, A. Jeremie1, S. Tomassini2, M. Esposito2 1 : LAPP Laboratory of Particules physics at Annecy-le-Vieux, IN2P3 – CNRS – University of Savoy - France2 : LFN INFN Laboratory of Nuclear Physics at Frascati - Italia SuperB meeting at CaltechDecember 2010

  2. Overview • Brief summary of the 1st campaign (October 2009, 2.5 days) with additional analysis • Results of the 2nd campaign (October 2010, 4 days) • Link to the stabilization and the current developments dedicated to CLIC CalTech - SuperB 2010

  3. Brief reminder of the 1st campaign • Summary of the first campaign status (October 2009) : • Point 1 : future detector (near a main road where there is much traffic and near a power plant) • Point 2 : near the DAFNE damping ring and the main pumping station of the DAFNE cooling plant. • Point 3 : near a main road as point 1 • N.B.1: no measurements done in the holes at points 3, 4 (3: stone, 4: water) • N.B.2: all points not far from the high way and the rail-way CalTech - SuperB 2010

  4. Instrumentation set-up • Sensors : • Data acquisition: • Acquisition system: PULSE from Brüel & Kjaer (amplifiers included) • Noise of the measurement chain, including PULSE, Guralp used from 0.2Hz to 50Hz and Endevco used from 50 to 100Hz, measured at LAPP: • allow very accurate measurements of ground motion even for a quiet site CalTech - SuperB 2010

  5. Data analysis • FFT parameters used for the analysis of the long term measurements: • Window: Hanning • Frequency resolution: 0.016Hz • Time resolution: 20 min (54 spectra averaged for 20min each  18 hours) • Spectra average: 55 (data set of 64 s),exponential (2τ:1195s), 66.67% overlap • FFT parameters used for the other measurements: • Window: Hanning • Frequency resolution: 0.016Hz • Average : 50 (data set of 64 s), exponential (2τ:1195s), 66.67% overlap • Measurement time: 20 minutes  Average of the amplitude of GM (single event noise smoothed out)  Accurate measurements of transfer function and coherence • GM measured in various sites in the world by Desy team • PSDs also measured during 60s and averaged for 15 min or longe • Almost same analysis: amplitude of GM measured at NFL by us can be compared to the ones of various sites in the world CalTech - SuperB 2010

  6. 1st campaign : On surface at different pts • Comparison of ground motion for different locations : PSD of the vertical displacement • Distribution of motion versus frequency quite the same for the four locations • Amplitude almost the same (low frequency) for the four locations • → [0.2;100]Hz: ~70-80nm • → [1;100]Hz: ~30-35nm RMS of the 3 directions displacement • Nominal horizontal beam size: 160 times larger than the vertical one • Horizontal tolerances should be much less strict than vertical one • Horizontal GM not so much higher than vertical one Pt 1 • Measurement focused on the vertical direction CalTech - SuperB 2010

  7. 1st campaign : On surface and in underground (50m) • Comparison of GM between vertical / horizontal axes : • At point 1, GM measured simultaneously on the surface and on the hole of 50m depth with Endevco accelerometers (vertical direction) • (Guralp geophone diameter to large to be put inside the hole (d=70mm) ) • Results shown above 1.3Hz, frequency from where data are reliable (high signal to noise ratio) PSD Transfer Function • Above 2.4Hz (beginning of cultural noise): vibrations of surface damped in the hole • Above 20Hz: factor of damping goes up to 20 (transfer function) CalTech - SuperB 2010

  8. 1st campaign : long term measurement • PSD of ground motion versus time and frequency : Quite same spectra with time except for one area from 8h to 9h40: high increase of amplitude in the range [3; 30]Hz corresponds exactly to traffic Point 3 :New basement(rigid floor) Analysis versus time : Analysis versus frequency : Cultural noise(human activities) Microsismic peak(ex : waves of ocean) CalTech - SuperB 2010

  9. 1st campaign : coherence measurement • Setup of the measurement : • Exemple of results : rigid floor of the new basement Soft floor Rigid floor • Comparison : • Goal: confirmation of the importance of a rigid floor for stability and evaluation of the NFL floor • Comparison done with coherence measured on the ATF2 where a special floor was built for stability (same data analysis performed) • Value : frequency where the coherence highly falls (under 0.8) for each distance • Basement (and parking) floor really better than ATF2 floor although ATF2 floor was built for stability whereas basement floor was not • LNF ground: very promising for good coherence properties CalTech - SuperB 2010

  10. Summary of the 1st campaign • Vertical ground motion measurements during 18 hours • [0.2; 1]Hz: vary from 65nm to 76nm  low compared to many other sites in the world (Desy team study) but may be higher in a longer time • [1; 100]Hz: vary from 12 to 65nm (quite low) except from 8h to 9h40 Max (transient): 700 nm Max (average): 240 nm → Due to traffic observed in the range [3; 30]Hz, it increases up to :- 240nm (Average of 20’)- 700 nm (Transient of 6s) • GM measured simultaneously on surface and in a 50m depth hole • Cultural noise well attenuated in depth on its entire frequency range • →huge vibrations due to traffic should be well attenuated in depth • Very better if Super B is in underground !! CalTech - SuperB 2010

  11. Summary of the 1st campaign • GM measured at 4 locations on surface (various vibration sources) • Almost the same (vertical GM) for the 4 pts (non rush hours the day) →GM measured for 18 hours (pt 3) well representative of LNF GM • Horiz. GM not much higher than vertical GM compared to tolerances • Coherence for different distances at 2 pts (soft and rigid floor) • Rigid floor keeps the coherence at higher frequencies than a soft floor • NFL concrete floor better than ATF2 floor (built for stability) • Very important analysis for the vibrations control strategy → More details in a INFN report and an IPAC article. CalTech - SuperB 2010

  12. 2nd campaign : objectives • To repeat and to increase the quantity of data • Short term measurement at different points • Long term measurement • Comparison of underground and surface measurement in the news holes • Coherence measurement in function of the concrete and of the location : Daɸne experiment 1 5 4 3 2 CalTech - SuperB 2010

  13. Comparison of the 4 points on surface • Short term measurement : vertical direction • The objective was to check if the amplitudes of the cultural noise (on surface) are the same before the measurements in the 4 holes Cultural noise (vertical) on surface for the four points (vertical direction) • Amplitudes are not very important.  The amplitudes reveals variations from one measurement to the other (mainly above a few herz) CalTech - SuperB 2010

  14. Comparison between the three directions for each point • Short term measurement : RMS • Same remarks concerning the amplitudes. • → The study is focused on the Z direction, considering the tolerances (Nominal horizontal beam size: 160 times larger than the vertical one). CalTech - SuperB 2010

  15. Instrumentation • Waterproof accelerometer support Sensor • No influence on the measurement CalTech - SuperB 2010

  16. Magnitude of transfer function between holes and surface • Short term measurement : • Well damped in underground • The damping is various in function of the frequency • The correlation is not evident in fonction of the deepth of the holes - Nature of the ground ? - Level of the cultural noise ? - Hours of the measurement ?... → Long term measurements CalTech - SuperB 2010

  17. Long term measurement • Point 1 (future detector) : on surface and in a 50m depthhole • FFT parameters : comparison with 2 approaches • Averages: • Window: Hanning • Overlap: 66.67% • Frequency resolution: 0.016Hz • Time resolution: 1195s (~20 minutes) (trigger of the multibuffer, whose size is of 52) • Averaging: Exponential (2*Tau=1195s) with 54 averages (data sets of 64s averaged) • Transient: • Window: Hanning • Frequency resolution: 0.1563Hz • Time resolution: 6s (trigger of the multibuffer, whose size is of 52) • Averaging: Exponential (2*Tau=6.4s) with 1 average CalTech - SuperB 2010

  18. Long term measurement • Integrated RMS from 1.3Hz to 100Hz : Point 1 • Evolution of the amplitude with cultural noise (day and night) • Sigma very important on surface (→ real time vibration control) • Sigma and mean well damped in the hole • Seems that the ratio is higher when cultural noise is higher (see next slide) CalTech - SuperB 2010

  19. Long term measurement • Ratio of the integrated RMS between the hole and surface : Highestdamping Lowestdamping Medium damping Medium damping 2 • Check of the transfer function versus frequency for these 4 different damping factors • Compare also with the data of last year CalTech - SuperB 2010

  20. Long term measurement • Transfer function magnitude between surface and hole : Siesmic Steady Variable • 1,3 – ~8 Hz : about the same damping • >8 Hz (traffic…) : various damping in function of the hours and the date. • Efficient damping in underground. • Possible to have a good evaluation of the ground motion damping of a site in underground only on a certain bandwidth. CalTech - SuperB 2010

  21. Long term measurement : Daɸne • 2 objectives : • GM measurement experiment ON • Support of QD0 experiment ON CalTech - SuperB 2010

  22. Long term measurement : Daɸne • RMS of the ground motion and QDO support, experiment ON Peaks • 21 hours of measurements • → First 7 hours: very high peaks of vibrations • → Then: mean very stable versus time and sigma very small : vibrations quite small on the floor and QD0 CalTech - SuperB 2010

  23. Long term measurement : Daɸne • Comparison GM and QDO : • After 7 hours: only a factor 2 in average and only up to a factor 3 in transient !! → Very good supports from the ground to QD0 • First 7 hours: up to a factor 70 in average and to a factor 600 in transient !! CalTech - SuperB 2010

  24. Long term measurement : Daɸne • RMS in function of the frequencies : • Above 5Hz: high peaks of vibrations during the first 7 hours disappear • < 5hz : has to be correlated with the activities of the experiment at this period CalTech - SuperB 2010

  25. Long term measurement : Daɸne • Transfer in function of the time : • From 12h00 to 18h20: • Huge peaks of vibrations up to 5Hz • Globally, decrease with time CalTech - SuperB 2010

  26. Long term measurement : Daɸne • Transfer in function of the time : • From 18h40 to 8h20 : • Peaks of vibrations below 5Hz diseapear • Resonances not very big on QD0 support • → Very good mechanical supports between QD0 and the floor!! • 8h20-8h40: • - Peaks of vibrations below 5Hz appears one more time • Conclusion: huge peaks of vibrations below 5Hz appears the day and diseapear the night • Something off the night in the machine? CalTech - SuperB 2010

  27. Long term measurement : Daɸne • Comparison of ground motion between vertical and horizontal directions • Vertical and horizontal direction: not big difference of amplitude • The two directions seem correlated above 1Hz CalTech - SuperB 2010

  28. Coherence measurement : Daɸne • Setup of measurement: Wall in front of the KLOE detector • Measurements in the 3 directions CalTech - SuperB 2010

  29. Coherence measurement : Daɸne • Vertical direction : Fall of coherence due to low signal to noise ratio • Value : frequency where the coherence highly falls (under 0.8) for each distance 7,7 6 20 30 21 7,3 CalTech - SuperB 2010

  30. Coherence measurement • Comparison beetween different types of concrete of the LNF and ATF2 : • DAɸNE floor less good than the basement (and parking), but better than ATF2 floor although ATF2 floor was built for stability • Can be due to the discontinuity of the concrete. • However, LNF ground seems promising for good coherence properties • One have to take care on the quality of the concrete CalTech - SuperB 2010

  31. Summary of the 2nd campaign • GM measured simultaneously on surface (various vibrations sources) and in different depth holes • Cultural noise well attenuated in depth on its entire frequency range. • Difficulties to correlate the attenuation between the different points with short term measurements. • The damping is function of the cultural noise level. • Horizontal GM not much higher than vertical GM compared to tolerances. • Coherence for different distances at 2 pts in the Daɸne • The type of the concrete is very important (comparision basement and Daɸne) • Daɸne QDO motion and experiment influence • The structure is quite rigid even if it was not made for vibrations • The influence of the process can be very important • A lot of datas which are very important for the stabilization strategy • It still some analysis but LNF seems to be a good site for vibrations • Other sites comparison (Tor Vergata, LHC, Desy data…) → a INFN report is under progress. CalTech - SuperB 2010

  32. Stabilization CalTech - SuperB 2010

  33. Stabilization • Link between the measurement and the strategy of stabilization (final focus) • The target is to have a differential motion between the 2 beams lower than the tolerances • The approach will be selected in function of : • The specifications • The distance between the 2 last QD0 • The coherence of the ground motion • The level of the ground motion • The mechanical properties of the QD0 et its support • The influence of the internal system • The beam repetition rate • … • The simulation of the whole system can be started thanks to the measurements. • Ex of applications : ATF2 and the current developments dedicated to CLIC CalTech - SuperB 2010

  34. 2 possible approaches • Rigid support : ATF2 approach (transfer function of 1 and no influence of the cooling) • Easiest approach but limited • Use of beeswax and a honeycomb table in order to obtain a very good transmission of the floor vibrations. • Small influence of the cooling Transfer function of ~1 between the floor and the support Beeswax • The differential motion between QD0 and the Target is under the specifications. No beeswax (fixed on the floor) • Active isolation : CLIC approach : • More complex CalTech - SuperB 2010 34

  35. CLIC beam trajectory control strategy • Association of different actions: • [0 (fb/~10)] : beam trajectory correction until 3 - 4 Hz F1 • [(fb/~10) 100+] : mechanical correction - Active / passive isolation M1 - Active compensation M2 (fb = 50 Hz) • The beam control states the specifications of the mecanical control : RMS @ 3 Hz • Mechanical scheme: Action F1 Action M2 Action M1 CalTech - SuperB 2010

  36. Stabilization strategy • Feedback setup: • Parametric linear Controlleroptimized to minimize the PSD of displacement of the beam (∆Y) in function of the disturbance seismicmotion • Adaptive filter based on the recursive least square (RLS) algorithm, designed to minimize the prediction error Static gain Go • Determination of the pattern of the global Active/passive isolation Resonant frequency f0 [Hz] Example if we consider Active isolation as a second order low pass filter: Independent from ξ in the range [0.01 – 0.7] CalTech - SuperB 2010

  37. Active passive isolation • Industrial solution : TMC table • Composed of one rigid bloc and 4 active feet - Passive isolation: High frequency attenuation but amplification of very low frequency (resonant filter) - Active isolation: Attenuation of the previous amplified disturbances -Attenuation down to 0.2nm at 4Hz -Already over the specifications (0.1nm) -Expensive system CalTech - SuperB 2010

  38. Feasibility demonstration • Simulation done with the CMS detector data measurement • With industrial products - + + + + - = + BPMnoise f0 = 2Hz ξ = 0.01 TMC table (K1) Mechanical damper (K2) Seismic motion (CMS data) TMC Table (K1) Mechanical damper(K2) + + Adaptive filter Direct disturbances + + Y=0 Actuator (Kicker) Controller Position at the IP: ∆Y MAGNET Sensor (BPM) ACTIVE/PASSIVE ISOLATION CalTech - SuperB 2010

  39. Feasibility demonstration • Results : • Robustness is ok • Specifications are respected • Tests under progress in PLACET with CERN CalTech - SuperB 2010

  40. Feasibility demonstration Mid-lower magnet • Solution under progress : Lower electrode of the capacitive sensor V-support for the magnet 1355mm Elastomeric strips for guidance Fine adjustments for capacitive sensor (tilt and distance) Piezoelectric actuator 2mV=0.1nm CalTech - SuperB 2010

  41. Active compensation • Feasibility demonstration on a prototype: • Demonstration of a mecanical control at a sub-nanometer scale • Can be used like an additionnal control if the there are disturbances due to the experiment itself CalTech - SuperB 2010 41

  42. Summary of our activities dedicated to the control part • Methodology of the stabilization of the future Compact Linear Collider • - Dedicated instrumentation (Sensors, actuators, filters, acquisition system etc…) • - Association of controls : active / passive isolation, active compensation, beam trajectory • control • - Feasibility demonstration of the beam stabilization and active compensation • - New specification of the active/passive isolation • Current activities : • Implementation of the control of the home made mechanical isolation and tests • Implementation of the beam control strategy in a beam accelerator simulation (PLACET) and test on a prototype. • Future prospects : • The limitation is the sensor : future study in order to use the mass of the magnet CalTech - SuperB 2010

  43. Spares CalTech - SuperB 2010

  44. X direction Fall of coherence due to low signal to noise ratio CalTech - SuperB 2010

  45. Y direction Fall of coherence due to low signal to noise ratio CalTech - SuperB 2010

  46. Long term measurement • Integrated RMS from 10Hz to 100Hz : • Integrated RMS from 50Hz to 100Hz : CalTech - SuperB 2010

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