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Solomon William KAMUGASA

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Presentation on theme: "Solomon William KAMUGASA"— Presentation transcript:

1 Development and validation of an absolute Frequency Scanning Interferometry (FSI) network
Solomon William KAMUGASA 1st PACMAN workshop, CERN, Geneva, Switzerland 3rd February 2015

2 PACMAN metrology 1. Fiducialisation of components
25/01/2015 1. Fiducialisation of components Integrate these 2 steps 2. Alignment of components on a common support CMM preferred (0.3µm + 1ppm) However… Measurement volume is limited It’s immobile Pre-alignment in tunnel 11-14 µm over 200m Goal: Develop portable alternatives Cable of comparable accuracies Able to cope with larger measurement volumes One such alternative is FSI multilateration

3 Multilateration 𝑅 𝐹 𝑣 𝑖𝑗 𝑙 𝑖𝑗
25/01/2015 Coordinate determination using distances only Z Y X Distance-coordinate relationship is well known Requires distances from at least 3 known points Self-calibration possible by increasing stations and targets Coordinate uncertainty dependent on distance uncertainty 𝑙 𝑖𝑗 𝑣 𝑖𝑗 𝑅 𝐹 𝑙 𝑖𝑗 + 𝑣 𝑖𝑗 = 𝑥 𝐹 − 𝑥 𝑅 𝑦 𝐹 − 𝑦 𝑅 𝑧 𝐹 − 𝑧 𝑅 2

4 Distance measurement system
25/01/2015 Absolute Multiline by Etalon Absolute distance (FSI) Uncertainty 0.5µm/metre Traceable to SI metre Up to 100 distance measurements simultaneously

5 System adaptation Hardware
Modification of fibre end to enable absolute distance measurement between two points. Design of suitable housing Development of calibration strategy to determine any offsets Software Current software provides distance information Some upgrades have been done linking approximate coordinates with distances Prototype MATLAB application to convert AML output file to form readable by LGC++

6 Retroreflector options
25/01/2015 SMR Limited viewing angle Greater return intensity N=2 glass sphere Unlimited viewing angle Lower return intensity 30 0 Advantages of wide viewing angle Better geometry hence better precision Provides more options for system configuration Requirements High precision machining of 0.5” and 1.5” spheres Potentially compatible with Micro-triangulation

7 Lateral tolerance test
Why important? Greater tolerance = easier channel alignment Ability to continue measuring even with slight misalignment ±1mm (3cm sphere)

8 Impact of misalignment on distance
Do we measure the same distance if slightly misaligned? 1mm 1mm We conducted simulations in MATLAB to find out. Assumptions: uniform refractive index of air = 1 uniform refractive index of glass = 2

9 Impact of misalignment on distance
Effect of lateral misalignment on distance measured using a 0.5 inch sphere

10 Impact of misalignment on distance
25/01/2015 Effect of lateral misalignment on distance measured using a 1.5 inch sphere

11 Multilateration strategy
Motorised rotating head Need to measure distances to several points from a single point Several channels on one mount Divergent beam

12 Several channels one mount
Several distances from one point Divergent beam Single beam to several targets Limited measurement volume (diverging lens) Limited measurement range (laser power) Technical know-how (software and hardware) Motorised mount Single beam to several targets Careful calibration strategy Method to ‘teach’ instrument position of targets Maximum measurement range (20m) and volume Several channels one mount Several beams in one mount to several targets Strategy used in ATLAS Design of suitable mount and support frame Careful calibration strategy Divergent beam for easy alignment

13 Stretched wire measurement
Attempt to measure 0.1mm Cu-Be wire directly with FSI Noticeable increase in intensity Insufficient for measurement Maybe possible with thicker wire Or different lens Alternatives: 1. Mount tiny reflectors on wire 2. Include reflector in wire tensioning system (Both options likely to have an impact on other measurements) 3. Detect wire using WPS

14 Network simulations CERN’s LGC++ will be used to conduct simulations & to solve the 3D network Simulations will: Compare various network configurations to help choose the best Take into account existing constraints Determine the optimum number of channels Provide post adjustment statistics and outlier detection.

15 Inter-comparison and validation
FSI multilateration Accuracy Reliability Robustness Micro-triangulation Inter-comparison Leitz CMM Validation

16 Integration on FPAB

17 Extrapolation & summary
Ultimate aim: To develop a portable coordinate measuring system based on FSI multilateration for CLIC that can be extrapolated to other projects Summary: System modification Stretched wire measurement Multilateration strategy Tests, validation & extrapolation

18 Thank you for your attention!

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