Sta FF Motion Stabilization with NanoMeter Precision Proposed

Sta. FF: Motion Stabilization with Nano-Meter Precision • Proposed experiment conducted within framework of Sta. FF (Stabilization of Final Focus for ILC). • Funded by Euro. TEV. • Development of active feedback systems to monitor and stabilize 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 resolution. • For separations of order 10 m. • Frequency range 100 Hz – 0. 01 Hz – Develop and implement algorithms for active stabilization. • Sta. FF at KEK: Stabilize Nano-BPM systems relative to each other. KEK: Integrated spectrum of vertical motion

Why Sta. FF at KEK • Benefits for Sta. FF – Test of distance meters in accelerator environment. – Measurement of 6 -D coordinates trough intermediate object (triangle), similar method is needed to project out position and orientation of accelerator component at ILC. – Related objects are BPMs: Allows cross check of achieved resolutions. • Benefits for nano-BPM – Unfold nano-BPM resolution and broadening caused by mechanical relative motion between the two BPM setups. – Each setup uses 3 BPM’s also establishing beam angles. Two sets can in principle measure relative displacements • Each beam bunch differs in position and angle → over-constrained system needed. • 2 -platform stability important for energy chicane – BPMs measure beam position, proposed experiment measure relative position motion.

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

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

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

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

Spider web Design with Opto. Geometrical Simulation: Simulgeo • Resolution of distancemeter: 1 nm • Mount precision of distancemeter: 1 nm • Angle precision of distancemeter holder: 10 mrad. SLAC BPM: reference KEK BPM variable (6 D): Position: x: 32 y: 19 z: 2 nm Angle: x: 0. 01 y: 0. 01 z: 0. 1 mrad ~1 mm absolute distance resolution needed to determine constants required to solve geometry.

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! • 100 -0. 01 Hz (or preferably even slower) is unusual frequency range for feedback system and might require some fundamental study. • Collaboration with Euro. TEV partners developing closed loop feedback circuits expected.