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G. Balik , B. Caron, L. Brunetti (LAViSta Team)

Optimization of the final focus stabilization for CLIC. G. Balik , B. Caron, L. Brunetti (LAViSta Team) LAPP-IN2P3-CNRS, Université de Savoie, Annecy, France & SYMME-POLYTECH Annecy-Chambéry, Université de Savoie, Annecy, France. The 21 st October 2010. Final focus stabilization.

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G. Balik , B. Caron, L. Brunetti (LAViSta Team)

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  1. Optimization of the final focus stabilization for CLIC G. Balik , B. Caron, L. Brunetti (LAViSta Team) LAPP-IN2P3-CNRS, Université de Savoie,Annecy, France& SYMME-POLYTECH Annecy-Chambéry, Université de Savoie, Annecy, France The 21st October 2010

  2. Final focus stabilization Direct disturbances : Acoustic noise, cooling... Final focus Final focus Detector Position at the interaction point Magnetic axis of the focalisation magnet FOCUSING MAGNET Desiredbeam Beam (e+) Beam (e-) ΔY≠0 (if no trajectory control) position KICKER ACTIVE/PASSIVE ISOLATION RIGID GIRDER Indirect disturbances : Seismic motion Repetition rate of the beam: 50 Hz Specification: Displacement of the beam at the IP < 0.1nm integrated RMS @ 0Hz IWLC 2010 - CERN - 2010-10-21

  3. Typical ground motion measured at CMS CERN (K.Artoos, M.Guinchard…) PSD [m²/Hz] Frequency [Hz] Beam trajectory control • Active/passive isolation Beam trajectory control limited by the repetition rate of the beam Ground motion integrated RMS already between a few nm to dozens of nm at 5 Hz IWLC 2010 - CERN - 2010-10-21

  4. Mechanicalschemeandcontrol pointofview + + Seismic motion Active/passive isolation Direct disturbances + + Desired beam position: Y=0 Actuator (Kicker) Position at the IP: ∆Y IWLC 2010 - CERN - 2010-10-21

  5. Feedbackscheme Active/passive isolation Seismic motion + + + - Desired beam position: Y=0 Actuator (Kicker) Controller Position at the IP: ∆Y BPM noise Sensor (BPM) + Controlleroptimized to minimize the PSD of displacement of the beam(∆Y) in function of the disturbance seismic motion + The results of the optimization depend on the considered seismic motion and on the active passive isolation. Direct disturbances + + Efficiency of the feedback scheme: 0 Hz to [4 – 5]Hz (limited by the repetition rate of the beam: 50Hz) It is needed to improve the efficiency of the control IWLC 2010 - CERN - 2010-10-21

  6. Feedback + Adaptive scheme Seismic motion Active/passive isolation - + + + + - Adaptive filter BPMnoise Y=0 Actuator (Kicker) Controller Position at the IP: ∆Y Sensor (BPM) + + Adaptive filter reconstruct and cancel the disturbance Direct disturbances Efficiency of the control greatly increased (in the same range: 0 Hz to [4 – 5]Hz) + + Beam motion still at a detrimental level at 5Hz Specification of the future active/passive isolation IWLC 2010 - CERN - 2010-10-21

  7. Pattern of a global active/passive isolation Determination of the pattern of the global Active/passive isolation (Kg) Active/passive isolation (Kg) Seismic motion + - + + + - Adaptive filter BPMnoise Y=0 Actuator (Kicker) Controller ∆Y(q) Sensor (BPM) Example if we consider Kg as a second order low pass filter: + + Static gain Go Independent from ξ in the range [0.01 – 0.7] Resonant frequency f0 [Hz] Direct disturbances + + IWLC 2010 - CERN - 2010-10-21

  8. Feasibility demonstration with industrial products - + + + + - = + f0 = 2Hz ξ = 0.01 TMC table (K1) Mechanical support (K2) BPMnoise Seismic motion (CMS data) Active/passive isolation + Adaptive filter + Y=0 Actuator (Kicker) Controller Direct disturbances Position at the IP: ∆Y + + MAGNET Sensor (BPM) ACTIVE/PASSIVE TMC Table (K1) Mechanical support (K2) ISOLATION IWLC 2010 - CERN - 2010-10-21

  9. Results PSD [m²/Hz] Frequency [Hz] Integrated RMS displacement [m] Frequency [Hz] IWLC 2010 - CERN - 2010-10-21

  10. Robustness (Mechanical support) Integrated RMS displacement = f(ξ, f0) • Controller optimized for the PSD of the ground motion filtered by the TMC table + Mechanical support K2 ξ= 0.01 f0 = 2 Hz Integrated RMS [m] f0 = f0 ± 10% ξ = ξ ± 50% • The worst case: f0 = 2.2 Hz ξ = 0.005 Integrated RMS displacement of the beam 0.1nm @ 0.1Hz Damping ratio: ξ [ ] Resonant frequency: f0 [Hz] IWLC 2010 - CERN - 2010-10-21

  11. Robustness (BPM noise) Integrated RMS displacement = f(W) Active/Passive isolation Seismic motion - + + + + - Adaptive filter • W: white noise added to the measured displacement BPM noise W(q) Y=0 Actuator (Kicker) Controller ∆Y(q) Sensor (BPM) + BPM’s noise has to be < 13 pm integrated RMS @ 0.1 Hz + Integrated RMS at 0.1 Hz [m] Direct disturbances + + The BPM is a post collision BPM: Amplification of 105 BPM noise W [m] IWLC 2010 - CERN - 2010-10-21

  12. Example with the solution being developed at LAPP Mid-lower magnet Lower electrode of the capacitive sensor V-support for the magnet 1355mm Elastomeric strips for guidance Fine adjustments for capacitive sensor (tilt and distance) Piezoelectricactuator below its micrometric screw Mechanical support for magnet (A. Badel, J-P. Baud, R. Le Breton, G. Deleglise, A. Jérémie, J. Lottin, L. Pacquet) IWLC 2010 - CERN - 2010-10-21

  13. Conclusions • Feedback + Adaptive control: • Feasibility demonstration of the beam stabilization proposed • New specification of the active/passive isolation • Future prospects : • Implementation of the controller under placet IWLC 2010 - CERN - 2010-10-21

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