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