25/06/2015Robert King, Oxford University - Graduate Seminar Series 1 Electronic speckle pattern interferometry at the SLHC

25/06/2015Robert King, Oxford University - Graduate Seminar Series 2 Overview What is the SLHC? –How is Oxford involved? Electronic Speckle Pattern Interferometry (ESPI) –What is it? –How does it work? –How are we using it?

25/06/2015Robert King, Oxford University - Graduate Seminar Series 3 S uper LHC ATLAS upgrade required –Radiation damage ~10 years –Higher luminosity of SLHC ATLAS built for <700 fb -1 SLHC must cope with >3000fb -1 → New central tracker

25/06/2015Robert King, Oxford University - Graduate Seminar Series 4 The ‘stave’ Detectors mounted on carbon fiber staves –Low mass –Integrated cooling and services –Intrinsic mechanical stability Bus cable Hybrids Coolant tube structure Carbon honeycomb or foam Carbon fiber facing Readout IC’s Silicon sensors Staves inter-leaved

25/06/2015Robert King, Oxford University - Graduate Seminar Series 5 Where does ESPI come in? Accurate track resolution –Need thermo-mechanical stability to -25°C ESPI can verify this –Sub-micron precision –Large area –Frequent sampling –Non-invasive Oxford has experience

25/06/2015Robert King, Oxford University - Graduate Seminar Series 6 How ESPI Works (1) An expanded laser beam on rough surface gives laser speckle Interference caused by λ scale variations on surface

How ESPI Works (2) 1 Change in position O( λ) 2 Change in optical path length 3 Change in speckle pattern 25/06/2015Robert King, Oxford University - Graduate Seminar Series 7 Digitally subtract images Photograph final speckle pattern Photograph initial speckle pattern

25/06/2015Robert King, Oxford University - Graduate Seminar Series 8 How ESPI Works (3) Initial pixel value Final pixel value |Subtraction| Bright Dark Bright DarkBright → Intensity contours = displacement contours

25/06/2015Robert King, Oxford University - Graduate Seminar Series 9 How ESPI works (4) Silicone diaphragm under pressure Each ‘fringe’ ~ λ/2 displacement

25/06/2015Robert King, Oxford University - Graduate Seminar Series 10 The Oxford Setup Sensitive to in-plane and out of plane motion In-plane Out-of-plane

25/06/2015Robert King, Oxford University - Graduate Seminar Series 11 Laser Fiber coupling Camera Fibers Test Object

25/06/2015Robert King, Oxford University - Graduate Seminar Series 12 In-plane deformation example Video made by Sam Whitehead

25/06/2015Robert King, Oxford University - Graduate Seminar Series 13 Summary Integrated stave forms part of the SLHC upgrade Validate thermo-mechanical stability ESPI gives submicron accuracy over large areas Testing on prototype staves should begin soon Images sourced from Daniel Buria-Clark’s Thesis

25/06/2015Robert King, Oxford University - Graduate Seminar Series 14 Backup slides Out of plane measurement detail

25/06/2015Robert King, Oxford University - Graduate Seminar Series 15 In plane measurement detail

25/06/2015Robert King, Oxford University - Graduate Seminar Series 16 Speckle pattern formation