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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 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: referenceKEK BPM variable (6D):
Position: x:32 y:19 z:2 nmAngle: x:0.01 y:0.01 z:0.1 rad
~1m 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!
• 100-0.01Hz (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.