Sta bilization of the F inal F ocus : 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 ~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: 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.

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

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