Optimization of the final focus stabilization for CLIC
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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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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 21st October 2010


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

Results

PSD [m²/Hz]

Frequency [Hz]

Integrated RMS displacement [m]

Frequency [Hz]

IWLC 2010 - CERN - 2010-10-21


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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


G balik b caron l brunetti lavista team

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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