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Stabilization of Final Focus with Nano-Meter Precision

Develop active feedback systems to monitor and stabilize final focus quadrupoles or beam position monitors in the energy chicane. Use laser interferometric methods to monitor relative position with nanometer-scale resolution. Implement algorithms for active stabilization.

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Stabilization of Final Focus with Nano-Meter Precision

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  1. StabilizationoftheFinalFocus: Stabilization with Nano-Meter Precision

  2. Goal: • Development of active feedback systems to monitor and stabilize for example final focus quadrupoles or the beam position monitors in the energy chicane. • Develop laser interferometric methods to monitor relative position of two objects at • Nanometer scale resolution. • For separations of order 10m. • Frequency range 100Hz – 0.01 Hz • Develop and implement algorithms for active stabilization. KEK: Integrated spectrum of vertical motion

  3. Measurement of Relative Motion • Typical situation: • Need straightness monitor to measure relative motion. (Leave for development later). • Need distance meter to project out. (Develop first). Reference Structure Straightness monitor to measure relative vertical movement between ref. structures Reference Structure Vertical & angular position measurement of ref. structure Quadrupole Quadrupole ~10m

  4. A Straightness Monitor Made from Distance Meters at ATF (KEK) • Accuracy few tens of nanometer for vertical displacement between KEK and SLAC BPM. SLAC BPM KEK BPM Floor node

  5. A Straightness Monitor Made from Distance Meters • Project 6-D coordinates from one BPM via middle triangle to the other BPM. SLAC BPM KEK BPM Floor node

  6. A Straightness Monitor Made from Distance Meters • Red lines: Michelson interferometer displacement meter nm resolution. • Multilateration requires absolute distance meter with mm resolution: FSI. • Both systems with same setup! SLAC BPM KEK BPM Floor node

  7. Spider web Design with Opto-Geometrical Simulation: Simulgeo • Resolution of distancemeter: 1nm • Mount precision of distancemeter: 1nm • Angle precision of distancemeter holder: 10 mrad. SLAC BPM: reference KEK BPM variable (6D): Position: x:32 y:19 z:2 nm Angle: x:0.01 y:0.01 z:0.1 mrad ~1mm absolute distance resolution needed to determine constants required to solve geometry.

  8. Vacuum system considerations • Develop small force vacuum mount using double bellow system. • Allows small motion (~0.5 mm) of BPM-system • Test stand to measure remaining force on BPM frame. Long vacuum tube for interferometer Attached to BPM. Holds retro reflector. Firm connection

  9. Stabilization • Actively stabilize setup using input from interferometers: • Both Nano-BPM setups are mounted on actuators. • Use movers on SLAC setup for coarse angle adjustment. • Use piezo movers on KEK setup for small adjustments. • We measure the relative motion of the two reference frames of the SLAC and KEK BPM’s • Closed loop feedback system relates the KEK reference bar to the KEK nano-BPM’s. • Closed loop feedback system relates the SLAC carbon fibre frame to the SLAC nano-BPM’s. • Overall feedback loop has to integrate 3 measurements!

  10. Snowmass • Work out what upstream energy chicane demands. • List of systems which would benefit from accurate position knowledge. • Final focus quadrupole vibrations

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