IN2P3Les deux infinis

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

Optimization of the final focus stabilization for CLIC

The 21st October 2010

Final focus stabilization

Repetition rate of the beam: 50 Hz

Position at the interaction point

Indirect disturbances : Seismic motion

Beam (e-)ΔY≠0

(if no trajectory control)

Final focusDetector

Final focusDirect disturbances :

Acoustic noise, cooling...Magnetic axis of the

focalisation magnet

Desired beam Beam (e+) ACTIVE/PASSIVE

ISOLATION

FOCUSING MAGNET

RIGID GIRDER

KICKERposition

Specification:Displacement of the beam at the IP < 0.1nm integrated RMS @ 0Hz

2Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Typical ground motion measured at CMS

PS

D [

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

CERN (K.Artoos, M.Guinchard…)

3Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Position at the IP: ∆Y

Seismic motion

Desired beam position: Y=0

++

Active/passive isolation

Actuator(Kicker)

Mechanical scheme and control point of view

+ + Direct disturbances

4Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Position at the IP: ∆Y

Seismic motion

Desired beam position: Y=0

++ ++

BPM noise

Active/passive isolation

Actuator(Kicker)+

-Controller

Sensor(BPM)

Feedback scheme

Controller optimized 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

5Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Feedback + Adaptive scheme

Position at the IP: ∆Y

Seismic motion

Y=0 ++ +

+

BPM noise

Active/passive isolation

Actuator(Kicker)+

-Controller

Sensor(BPM)

+ + Direct disturbances

Adaptive filter

+-

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

Adaptive filter reconstruct and cancel the disturbance

6Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Pattern of a global active/passive isolation

∆Y(q)

Seismic motion

Y=0 ++ ++

BPM noise

Active/passive isolation (Kg)

Actuator(Kicker)+- Controller

Sensor(BPM)

+ + Direct disturbances

Adaptive filter

+-

Resonant frequency f0 [Hz]

Sta

tic g

ain

Go

Determination of the pattern of the global Active/passive isolation (Kg)

Example if we consider Kg as a second order low pass filter:

Independent from ξ in the range [0.01 – 0.7]

7Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Active/passive isolation

Position at the IP: ∆Y

Seismic motion(CMS data)

Y=0 ++ +

+

BPM noise

Actuator(Kicker)+

-Controller

Sensor(BPM)

+ + Direct disturbances

Adaptive filter

+-

TMC Table (K1)

Mechanical support (K2)

ACTIVE/PASSIVEISOLATION

MAGNET

= +

TMC table (K1) Mechanical support (K2)

Feasibility demonstration with industrial products

f0 = 2Hzξ = 0.01

8Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Inte

gra

ted

RM

S d

isp

lace

me

nt

[m]

Frequency [Hz]

PS

D [

m²/

Hz]

Frequency [Hz]

Results

9Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

ξ= 0.01f0 = 2 Hz

• Controller optimized for the PSD of the ground motion filtered by the

TMC table + Mechanical support K2

f0 = f0 ± 10%ξ = ξ ± 50%

• The worst case:f0 = 2.2 Hzξ = 0.005

Integrated RMS displacement of the beam 0.1nm @ 0.1Hz

Integrated RMS displacement = f(ξ, f0)

Integrated RMS [m]

Damping ratio: ξ [ ] Resonant

frequency: f0 [Hz]

Robustness (Mechanical support)

10Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

• W: white noise added to the measured displacement

BPM’s noise has to be < 13 pm integrated

RMS @ 0.1 Hz

Integrated RMS displacement = f(W)

Robustness (BPM noise)

∆Y(q)

Seismic motion

Y=0 ++ ++

BPM noise W(q)

Active/Passive isolation

Actuator(Kicker)+- Controller

Sensor(BPM)

+ + Direct disturbances

Adaptive filter

+-

BPM noise W [m]

Inte

grat

ed R

MS

at

0.1

Hz

[m]

The BPM is a post collision BPM:

Amplification of 105

11Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

Mid-lower magnet

1355mm

Elastomeric strips for guidance

Piezoelectric actuator below its micrometric screw

Lower electrode of the capacitive

sensor

Fine adjustments for capacitive sensor (tilt and

distance)

V-support for the magnet

Mechanical support for magnet (A. Badel, J-P. Baud, R. Le Breton, G. Deleglise, A. Jérémie, J. Lottin, L. Pacquet)

Example with the solution being developed at LAPP

12Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21

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

Conclusions

13Gaël Balik - LAPP IWLC 2010 - CERN - 2010-10-21