1. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 1 Options for interferometric monitoring of CLIC test magnet M. S. Warden, P. A. Coe, D. Urner, A. Reichold

2. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 2 Outline Interferometers –Distance Meters –Compact Straightness Monitors Complementary to accelerometer readings Options for the CLIC test magnet –Sequence of instrumentation

3. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 3 Interferometer: Distance meter Absolute distance Displacement Operates in two modes –Absolute Distance (<  m resolution) –Displacement measurement (nm resolution) Two modes combined –Displacements referred to absolute distance –Tolerant to interruption of measurements

4. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 4 Instruments: CSM Compact Straightness Monitor Example from ATF2 –Measures plane to plane Internal displacements and rotations measured CSM always blind to 6 external DoF

5. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 5 Interferometers: Make relative measurements Distance Meters measure point to point –Range and displacements (  changes) Compact Straightness monitor –Combines distance meters to measure object to object 3 translational degrees of freedom 3 rotational degrees of freedom

6. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 6 Compare and contrast with accelerometer CSM measures internal DoF –network distances between lines of sight –blind to external rotations / translations Accelerometer measures local deviations from free fall –multiple axes of test mass(es) –blind to free fall (local 1g can be cancelled off)

7. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 7 Flexible range of options Interaction on CLIC is still in its infancy –No process yet for drawing up interferometer required specifications understanding conflicting uses of space Initial discussions lead to “bizarre” first ideas We envisage flexible programme –First: making simple studies –Later: Installing more sophisticated systems

8. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 8 Instrumentation could be staged Build up number of interferometers –First study with simple distance meters May increase number of distance meters –Upgrade later to simple CSM arrangement –Final stage complete suite of CSMs

9. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 9 First measure most important DoF Start with simplest interferometers –Distance meters (DMs) measuring the vertical coordinate wrt floor –Learn which issues are most important Suitable reference datum Structural Vibrations Vacuum / Protected air –Would compare with accelerometers one accelerometer at each end of line Reflector Launch Head

10. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 10 Monitor several points independently Floor Magnet Test several points along the magnet –at first independent DMs Compare readings with accelerometers –on the magnet –and on the floor

11. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 11 These might be cross linked DMs Subject to constraints –we don’t know these Only possible –if planned in advance We would like to understand –what is possible –what is impossible –with respect to using spaces under/around the magnet

12. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 12 Ultimately: Install cross linked CSMs With some form of enclosure –Although it need not take this form

13. Tue 31 Mar 2009 15:50 (CEST) 13:50 UTC CLIC stabilisation day 5 - LAPP OXFORD MONALISA 13 Summary We propose a staged build up of interferometer installation Many DoF can be measured with CSMs Can learn a lot with simple instruments (DMs) –These can be installed as soon as magnet is ready –Would like to compare with accelerometers We need to better understand the constraints