Seismic sensors in PACMAN Peter Novotny 1 st PACMAN workshop 3 rd February 2015, CERN.
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Transcript of Seismic sensors in PACMAN Peter Novotny 1 st PACMAN workshop 3 rd February 2015, CERN.
Seismic sensors in PACMAN
Peter Novotny1st PACMAN workshop
3rd February 2015, CERN
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20152
Outline
• Why seismic sensors in PACMAN• How seismic sensors work• PACMAN requirements to sensors• State of the art seismic sensors• Current work• Conclusions
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20153
Why we need seismic sensor?
• Ground is shaking all the time even if we don’t see or feel it.
Power Spectral Density of ground motion for different sites
Micro seismicpeak
Cultural noise
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20154
Why we need seismic sensor?
• When measuring beam position with nm resolution we need to know how this ground motion propagate through the bench and influence our measurements.
• Therefore we want to measure ground motion at different positions of the bench.
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20155
How seismic sensors work?
Theoretical principle
Transducer
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20156
Transducers
Seismic sensor with electromagnetic transducer
Transducer
• Resistive• Capacitive• Piezoelectric• LVDT - Linear variable differential transformer• Optical (Interferometers, encoders)• Elmg. – coil + magnet• Eddy current• …
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20157
Types of transducers
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20158
Sensor parameters
• Bandwidth – fmin - fmax
• Sensitivity S – conversion factor from D,V,A to Volts• Self noise N – determine resolution• Resolution R = N/S – smallest measureable value• Dynamic range – Max/Min measureable value• Active/passive – need of power supply• Weight and dimensions• Robustness against magnetic stray field and radiation
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 20159
PACMAN requirements for sensor
• Bandwidth = 0.1Hz – ≈200 Hz• Resolution ≤ 0.1nm (rms@1Hz) which means high sensitivity and low self-noise• Stray magnetic fields resistance
different mg. field on the ground than on the magnets• Dynamic range ≥ 80dB
from 0.1nm to at least 1µm• Weight < few kg & compact size
to fit inside the bench
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201510
State of the art sensors
Different types of sensors for different use like:• Natural ground motion measurement (tides,
waves)• Earthquakes monitoring• Oil and gas exploration• Building, bridges structural monitoring • Nuclear test ban treaty monitoring • …
Geophones
Seismometers
Piezo-accelerometers MEMSaccelerometers
Force balanced optical accelerometers
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201511
Geophones
• Output voltage proportional to ground velocity
above natural frequency.• Simple and compact solution • Low noise but also low sensitivity
Our requirements: Low noise Weight and size Price× Sensitivity× Resolution× Bandwidth× Magnetic resistance
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201512
Seismometers
• Output voltage is proportional to ground velocity in certain frequency bandwidth.
• Utilise the feedback control of mass position to extend bandwidth to low frequencies.
Our requirements: Very low noise Resolution• Bandwidth• Weight and size
× Magnetic resistance
× Price
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201513
Piezo-accelerometers
• Output voltage is proportional to ground acceleration below natural frequency.
• High self noise at lower frequencies
Our requirements: Bandwidth Weight and size Magnetic resistance• Price× High self noise at
low freq.× Resolution
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201514
MEMS accelerometers
• Output voltage is proportional to ground acceleration below natural frequency. (similar freq. characteristic as piezo-acc.)• High self noise because of light mass.
Principle
MEMS realisation
Final product
Our requirements: Bandwidth Weight and size Magnetic resistance Price× High self noise× Resolution
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201515
Promising candidates
Force balanced optical accelerometers
Short period seismometer CP ZM500
Measurements and tests need to be done to check requirements fit.
Short period seismometer Guralp CMG-6T
PACMAN CP ZM500 CMG-6T Optical acc.
Bandwidth [Hz] 0.1 - 200 0.1 - 100 0.1 - 100 0.1 – 1k
Noise@1Hz [nm/s2/√Hz] 4 0.3 2.5 20
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201516
Noise in seismic sensors
Sources of noise:• Thermomechanical (Brownian) noise
• Molecular collisions with mass• Thermoelectrical (Johnson) noise
• Random thermal excitation of charge carriers• Other semiconductor electronic noise
• Schottky noise• Flicker 1/f noise
• Discretisation noise• ADC converters
!Noise is the most limiting parameter of sensor resolution!
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201517
Noise comparison
Acquisition hardware noise is also very important and should be below sensor noise.
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201518
Current work
• Characterization of the seismic sensors available on the market and those developed by Laboratories
• Comparison of their TF, S/N ratio and bandwidths • Investigation of alternative and innovative approaches:
– Optical transducers (Interferometers, Fibre Bragg grating)– Molecular Electronic Transducers (MET)– Tunnelling effect– Noise reduction in MEMS accelerometers– …
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201519
Current work
• Measurements and data processing
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201520
Next steps
• Development of the optimum sensor for PACMAN• Integration into the PACMAN bench.• Analysis of the performances and robustness.
Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 201521
Conclusions
• We need seismic sensors to know how GM has influence on the beam position measurement.
• Many state of the art sensors exist but were designed for different purposes (don’t match PACMAN requirements).
• Some of them seem promising.• Measurements needs to be done to test their performance.• Investigation of new technologies and possible improvements.• Development of optimum senor for PACMAN, integration to
bench and analysis of its performance.
Thank you for yourattention!
Backup slides
How does seismic sensor work?
𝒎�̈�+𝒄 �̇�+𝒌𝒚=−𝒎�̈�
𝝎𝟎=√ 𝒌𝒎
Laplacetransform
Naturalfrequency
𝑇𝑤𝑦=𝑌𝑊
=𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡
Transfer functions:
𝑇 �̇� �̇�=�̇��̇�
= 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
𝑇 �̈� 𝑦=𝑌�̈�
=𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛
!! Information about absolute motion is in relative motion!!𝝎 /𝝎𝟎
Few sensors and their producers
Producer type of sensorsGURALP Seismometersion geophonesSercel (Mark Products) geophonesKinemetrics (Streckeisen)
Seismometers + FBA
Nanometrics SeismometersREFTEK SeismometersLennartz electronic SeismometersMetrozet Seismometers + FBA
EentecFDBCK MET geophones
+ FBASINUS Piezo-velocity sensorGeoSIG geophones + FBAEndevco accelerometersWilcoxon accelerometersDYTRAN accelerometersDJB Instruments accelerometersMMF accelerometersBrüel & Kjær accelerometersPCB accelerometersCOLIBRYS accelerometersMETTECH METGEOTECH INSTRUMENTS Seismometers
Secondments
• Development of the seismic sensor for stabilisation of the Final Focus (of CLIC)
• Equivalent of 7 months (already started)• Their measuring and control system
• High precision mechanic manufacturer
• 3 months starting in April 2015• Project:
• Measurement and adjustment techniques for precision applications