StaFF: Motion Stabilization with Nano-Meter Precision Proposed experiment conducted within framework of StaFF (Stabilization of Final Focus for ILC). Funded by EuroTEV. 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 10m. Frequency range 100Hz – 0.01 Hz –Develop and implement algorithms for active stabilization. StaFF at KEK: Stabilize Nano-BPM systems relative to each other. KEK: Integrated spectrum of vertical motion

Why StaFF at KEK Benefits for StaFF –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: –Need straightness monitor to measure relative motion. (Leave for development later). –Need distance meter to project out. (Develop first). Quadrupole ~10m Reference Structure Reference Structure Vertical & angular position measurement of ref. structure Straightness monitor to measure relative vertical movement between ref. structures

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

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

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

Spider web Design with Opto- Geometrical Simulation: Simulgeo Resolution of distancemeter: 1nm Mount precision of distancemeter: 1nm Angle precision of distancemeter holder: 10  rad. 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  rad ~1  m 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! Hz (or preferably even slower) is unusual frequency range for feedback system and might require some fundamental study. Collaboration with EuroTEV partners developing closed loop feedback circuits expected.