1. The stabilisation of the final focus (StaFF) system Sun 12 th March 2006 MDI – LCWS06 at I I Sc Bangalore David Urner, Paul Coe, Armin Reichold

2. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Linear Collider : $ into Luminosity LC physics output ~ Collision precision Collisions rely on bunches : –Bunch “quality” approaching collision –Transverse positions approaching collision and magnet stability : –stability of final focci producing the collision where StaFF comes in

3. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Aims of StaFF To monitor relative stability of vital components down to the nm scale To use interferometers in a grid around the vital components To use established interferometry techniques with novel design interferometers To measure positions at least at 100 Hz

4. Detector Quadrupole 10 m Detector Detector Detector Project Out Reference Objects Direct line of sight Machine – Detector Interface No Direct line of sight Reference Objects

5. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Other uses e.g. Beam - delivery ~1 km Same system can be deployed for beam – delivery magnets, BPMs etc energy chicane

6. Example nano-BPMs at KEK / ATF Convenient Ceiling Floor Convenient ceiling object Beamline axis Optical Grid (Vacuum lines) Measure relative vertical motion of object A versus object B. (measure 6D coordinates) A B NANO BPMs At A & B

7. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Example nano-BPMs at KEK / ATF Triangle across girder down to Floor node Floor node

8. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Triangle Nodes Distance meter heads located in triangle nodes. Floor node –Overall resolution improves if firmly anchored. –Dome anchored separately from interferometers. Ceiling nodes: position stability rel. unimportant. All triangle nodes –Angular stability of node needed to about 10  rad. FLOOR NODE

9. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Allows objects to be placed (6D) in hierarchal structure –Reference positions. –Fixed positions (with error). –Variable placements (the objects to be measured). Objects can be points, mirrors, distance meters… –e.g. Distance meter assumes measurement between points with error. Matrix inversion accounts for errors and attempts to constrain 6D position of all points. ATF at KEK Written by Laurent Brunel : for CMS alignment c.1999 Spider web Design with Opto-Geometrical Simulation: Simulgeo

10. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Resolution of distancemeter: 1nm Mounting precision of distancemeter: 1nm Angular precision of distancemeter holder: 10  rad. SLAC BPM: reference KEK BPM variable (6D): Position/nm x 32 y 19 z 2 Angle/  rad x 0.01 y 0.01 z 0.1 ~1  m absolute distance resolution needed to determine constants required to solve geometry. Spider web Design with Opto-Geometrical Simulation: Simulgeo

11. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Timescale: 0.01-100 Hz –Laser interferometers ideal. Typical motion amplitudes: –On the order of a micron KEK ground motion 1m1m 1 Hz

12. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Interferometer Studies A number of designs are being studied Currently setting up lab space in Oxford Plan to test interferometers at ATF Final interferometers MUST be in vacuuo Combine fixed and swept wavelengths Nanometre resolution is routine in interferometry – The devil is in the details

13. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore

14. Initial interferometer tests Anti-reflection coated Lens

15. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Ideally this would produce... when the signals from neighbouring fibres are read out

16. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore 3 channels recorded in same scan

17. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore These signals can be analysed... Or by fitting to a sinusoid Length Either by calculating a periodogram using FFT N.B. These are only generic examples!! They do not correspond to signals shown earlier – but similar

18. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Work in progress... Setting up a new test area (lab corner) - Highly sensitive thermometer system - New optical table Testing a zero-force bellows for vacuum connections Designing, constructing and testing new interferometer designs

19. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore StaFF summary Proposed experiment conducted within framework of StaFF (Stabilization of Final Focus for ILC). Funded by EuroTEV. Development of active feedback systems to monitor and stabilise, for example, final focus quadrupoles or beam position monitors in the energy chicane. –Develop laser interferometric methods to monitor relative position of two objects at nanometer scale when ~10m apart. –Develop and implement algorithms for active stabilization. StaFF at KEK: Stabilize Nano-BPM systems relative to each other.

20. The StaFF project P Coe et alLCWS06 I I Sc. Bangalore Thank you for listening