1. MONALISA David Urner, Armin Reichold, Paul Coe, Matthew Warden, Geoff Rayner Monitoring Alignment and Stabilisation with high Accuracy (Previously known as StaFF) WP 3

2. 12 April 2007MONALISA - M. Warden2 Contents Motivation Overview of system The distance meter –Design –Construction –Data analysis Future developments

3. 12 April 2007MONALISA - M. Warden3 Motivation A critical requirement for achieving and maintaining luminosity in ILC is: Stability of Beam Delivery System –This is true for BDS as a whole –And particularly so for the final focussing quadrupoles Achieving stability requires accurate monitoring of magnet positions

4. 12 April 2007MONALISA - M. Warden4 Motivation

5. 12 April 2007MONALISA - M. Warden5 The Challenge: Develop an optical system to accurately determine relative position and orientation in 6D Direct line of sight may not be available In general, such a system needs: –Distance meters –Straightness monitors

6. 12 April 2007MONALISA - M. Warden6 The Distance Meter Components: –Reference interferometer –Measurement interferometers Two modes: –Absolute distance measurement, using frequency scanning interferometry –Small displacement measurement, using fixed frequency interferometry

7. 12 April 2007MONALISA - M. Warden7 The importance of absolute distance measurement Take two fixed points: Measure distances to a third point: Triangulate this point: Calculate axes for displacement measurements:

8. 12 April 2007MONALISA - M. Warden8 Compact Measurement Interferometer Simple, compact design Gold-coated beam-splitter cube acts as one interferometer arm Will replace far mirror with corner cube –Allows for easy alignment –Can simultaneously measure distances to many points measurement distance launch fibre receiving fibres

9. 12 April 2007MONALISA - M. Warden9 Reference Interferometer Both interferometers share the same phase step from piezo mounted mirror Taking two measurements gives a measure of accuracy Can keep one interferometer as a benchmark, and test alternatives with the other Parallels

10. 12 April 2007MONALISA - M. Warden10 From design to reality Have constructed both reference and measurement interferometers Testing them now

11. 12 April 2007MONALISA - M. Warden11 Preliminary Data Analysis Start with raw photodiode voltages Extract reference phase Fit sinusoids to measurement interferometer voltages Measurement Interferometer Reference Interferometer

12. 12 April 2007MONALISA - M. Warden12 Future Development Move ahead with distance meter development –Hardware design –Analysis methods Change to evacuated interferometers

13. Thank you for listening …time for lunch?