Seismic sensors in PACMAN Peter Novotny 1st PACMAN workshop 3rd February 2015, CERN

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 2015

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 Cultural noise Micro seismic peak Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

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 2015

How seismic sensors work? Theoretical principle Transducer Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Transducers Seismic sensor with electromagnetic transducer Transducer Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 Types of transducers Resistive Capacitive Piezoelectric LVDT - Linear variable differential transformer Optical (Interferometers, encoders) Elmg. – coil + magnet Eddy current … Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 2015

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 2015

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 Force balanced optical accelerometers Seismometers MEMS accelerometers Piezo-accelerometers Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 2015

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 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 Our requirements: Bandwidth Weight and size Magnetic resistance Price High self noise Resolution MEMS realisation Final product Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Promising candidates Short period seismometer CP ZM500 Short period seismometer Guralp CMG-6T Force balanced optical accelerometers PACMAN CP ZM500 CMG-6T Optical acc. Bandwidth [Hz] 0.1 - 200 0.1 - 100 0.1 – 1k Noise@1Hz [nm/s2/√Hz] 4 0.3 2.5 20 Measurements and tests need to be done to check requirements fit. Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Noise in seismic sensors !Noise is the most limiting parameter of sensor resolution! 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 Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Noise comparison Acquisition hardware noise is also very important and should be below sensor noise. Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 Current work Measurements and data processing Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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 2015

Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015 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. Seismic sensors in PACMAN - Peter NOVOTNY - 3rd February 2015

Thank you for your attention!

Backup slides

How does seismic sensor work? Transfer functions: 𝑇 𝑤𝑦 = 𝑌 𝑊 = 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 Laplace transform 𝑇 𝑤 𝑦 = 𝑌 𝑊 = 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 𝒎 𝒚 +𝒄 𝒚 +𝒌𝒚=−𝒎 𝒘 Natural frequency Two important things coming out from this equation Natural frequency of oscillator which is one of important limiting factors for sensors Transfer functions which describe frequency dependant relation between absolute and relative motion From TF it’s obvious which relations are interesting for us (and those are three with flat characteristic) !! – what doeas it mean for us? we know TF but we also need to measure this relative motion 𝝎 𝟎 = 𝒌 𝒎 𝑇 𝑤 𝑦 = 𝑌 𝑊 = 𝑟𝑒𝑙𝑎𝑡𝑖𝑣𝑒 𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡 𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝝎/𝝎 𝟎 !! Information about absolute motion is in relative motion!!

Few sensors and their producers type of sensors GURALP Seismometers ion geophones Sercel (Mark Products) Kinemetrics (Streckeisen) Seismometers + FBA Nanometrics REFTEK Lennartz electronic Metrozet Eentec FDBCK MET geophones + FBA SINUS Piezo-velocity sensor GeoSIG geophones + FBA Endevco accelerometers Wilcoxon DYTRAN DJB Instruments MMF Brüel & Kjær PCB COLIBRYS METTECH MET GEOTECH INSTRUMENTS To give you idea how the sensors looks like Not exhaustive list

Secondments High precision mechanic manufacturer 3 months starting in April 2015 Project: Measurement and adjustment techniques for precision applications Development of the seismic sensor for stabilisation of the Final Focus (of CLIC) Equivalent of 7 months (already started) Their measuring and control system In regards to secondments LAPP – one of the things they are working on is a .1.odsek DMP produce high presicion