Stabilization of

theFinalFocus:Stabilization with Nano-Meter

Precision

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

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 at ATF (KEK)

• 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.

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 interferometerAttached to BPM.

Holds retro reflector.Firm connection

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!

Snowmass

• Work out what upstream energy chicane demands.

• List of systems which would benefit from accurate position knowledge.

• Final focus quadrupole vibrations