1. Development & validation of an absolute FSI network STATUS & NEXT STEPS SU internal meeting 16 July 2015 Solomon William KAMUGASA

2. 1.N ≈ 2 glass retroreflectors 2.First FSI prototype 3.Calibration alternatives 4.Proposal for next generation prototype 5.FSI multilateration redundancy study 6.Some simulations results based on 8 channel FSI Content

3. N≈2 retroreflector Pros Wide viewing angle Allows good geometry Can be machined accurately Sphericity λ/10 Cons Limited return intensity N varies with λ Difficult to get in ‘standard’ sizes

4. Understanding N≈2 Beam lost Path followed by returned beam Reflected Transmitted 0.8889 0.1111 * * = Return intensity = 8.78% of emitted light

5. N≈2 reflector constant Reflector constant

6. N≈2 return intensities 10mm S-LAH79 30mm Etalon Gain 8 average intensity [%] Distance [mm] F=18.75mm collimator F=37.13mm collimator

7. S-LAH79 lateral tolerance Horizontal displacement [mm] Vertical displacement [mm]

8. N≈2 Market study Ready for order S-LAH79 (max diameter =10mm) Etalon (current diameter =30mm) Awaiting info TaFD55 can be done in diameter = 0.5”(12.7mm) P-SF68 – awaiting slab dimensions

9. Aluminium spherical support Proof of concept Existing 1.5” supports Distances in different directions from same point First prototype enabling centring of optical fibre end

10. True distance [m] Distance error [nm] Error caused by 0.1mm y-offset at various distances Offset definition Two possible offsets 1.Along the beam (x-offset) Effect: significant - a constant 2.Perpendicular to beam (y-offset) Effect: negligible - decreases with distance Offset definition

11. ItemValue X-offset [mm]21.987 1σ Standard deviation [µm]21 Residual [µm] Number of samples X-offset residuals X-offset calibration

12. 1 st FSI network

13. Alternative calibration strategy 1.Improvement of existing strategy More stable supports More data Consider more than 3 points Cheaper (existing components) 2.LSA solution based on CMM and FSI measurements Both x & y offsets determined Based on accurate CMM measurements More costly (CMM time)

14. XY stage Ceramic sphere FSI collimator Ball bearings Support frame 3 ball bearing support Articulation arm Proposal for motorised FSI prototype Advantages: Easy calibration Possible to measure distances in various directions from same point Can be measured by QDaedalus & CMM y x

15. FSI redundancy study Observations from all FSI stations to all targets Number of targets Global relative redundancy [%] Multilateration in general = low redundancy = low reliability Reliability can be tremendously increased by: Using more stations &/or targets making multiple observations along a given line of sight

16. x y x z Optimal geometry for 4 channel FSI 4 channel system, 1 target Short tetrahedron with equilateral triangle base 4 th station – same x, z as target but extruded y 4 stations minimum for LSA solution 4 is half the number of existing channels (4 on each side of magnet) Semi major axis sigma [µm] Semi minor axis sigma [µm] xy error ellipse based on 10µm a priori sigma y z A priori sigma = 10µm Sx=Sy=Sz=9µm

17. Fiducialisation Simulation Object: 300×400×300mm 8 stations, 16 targets 6 targets on each side ‘seen’ by 4 stations each 2 targets on top of object & 2 to the extremes ‘seen’ by all 8 stations x y z

18. Input: A priori stdev: 10µm Observations between most stations One entry per line of sight Total observations: 94 Unknowns: 72 6 constraints not included in calculation of precision PointSX [mm]SY [mm]SZ [mm] T1A0.010.0120.009 T2A0.010.0110.008 T3A0.010.0120.009 T4A0.0080.01 T5A0.0080.01 T6A0.0080.01 T1B0.010.0120.009 T2B0.010.0110.008 T3B0.010.0120.009 T4B0.0080.01 T5B0.0080.01 T6B0.0080.01 T1C0.006 0.007 T2C0.006 0.008 T3C0.0060.0050.008 T4C0.0070.0050.008 Simulation results

19. PointSx[mm]Sy[mm]Sz[mm] T1A0.0070.0090.006 T2A0.0070.0080.006 T3A0.0070.0090.006 T4A0.0060.007 T5A0.0060.007 T6A0.0060.007 T1B0.0070.0090.006 T2B0.0070.0080.006 T3B0.0070.0090.006 T4B0.0060.007 T5B0.0060.007 T6B0.0060.007 T1C0.004 0.005 T2C0.004 0.006 T3C0.004 0.006 T4C0.0050.0040.005 Input: 2 entries per line of sight Number of observations:188 Number of unknowns:72 Simulation results

20. Input: 1 entry per line of sight No observations between stations Number of observations:80 Number of unknowns:72 PointSx[mm]Sy[mm]Sz[mm] T1A0.0250.0260.014 T2A0.0270.0170.01 T3A0.0290.0260.012 T4A0.0090.0120.018 T5A0.0080.0130.014 T6A0.0090.014 T1B0.0250.0260.014 T2B0.0270.0170.01 T3B0.0290.0260.012 T4B0.0090.0120.018 T5B0.0080.0130.014 T6B0.0090.014 T1C0.0150.0110.039 T2C0.0070.0090.032 T3C0.0160.0060.014 T4C0.007 0.014 Simulation results

21. PointSx[mm]Sy[mm]Sz[mm] T1A0.0170.0180.01 T2A0.0190.0120.007 T3A0.0210.0190.009 T4A0.0060.0080.013 T5A0.0060.0090.01 T6A0.0070.01 T1B0.0170.0180.01 T2B0.0190.0120.007 T3B0.0210.0190.009 T4B0.0060.0080.013 T5B0.0060.0090.01 T6B0.0070.01 T1C0.0110.0080.027 T2C0.0050.0070.023 T3C0.0120.0040.01 T4C0.005 0.01 Input: 2 entries per line of sight No observations between stations Number of observations:160 Number of unknowns:72 Simulation results

22. 1.Better understanding of N=2 2.Prototype development 3.Further simulations 4.Measurements & inter-comparisons Next steps

23. http://pacman.web.cern.ch/ Thank you for your attention