Transcript Slides - Indico

The stabilisation of the final
focus (StaFF) system
David Urner, Paul Coe, Armin Reichold
Sun 12th March 2006 MDI – LCWS06 at I I Sc Bangalore
Linear Collider : $ into Luminosity
• LC physics output ~ Collision precision
• Collisions rely on bunches :
– Bunch “quality” approaching collision
– Transverse positions approaching collision
• and magnet stability :
where StaFF comes in
– stability of final focci producing the collision
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Aims of StaFF
• To monitor relative stability of vital components
down to the nm scale
• To use interferometers in a grid around the vital
components
• To use established interferometry techniques with
novel design interferometers
• To measure positions at least at 100 Hz
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Machine – Detector Interface
Reference
Objects
Direct line of sight
Reference
Objects
Detector
Detector
10 m
Detector
Quadrupole
Detector
Project
Out
No Direct line of sight
Quadrupole
Other uses e.g. Beam - delivery
energy
chicane
~1 km
Same system can be deployed for
beam – delivery magnets, BPMs etc
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Example nano-BPMs at KEK / ATF
Convenient Ceiling
Convenient ceiling object
Beamline
axis
NANO BPMs
At A & B
A
Optical Grid
(Vacuum lines)
B
Floor
• Measure relative vertical motion of object A versus
object B. (measure 6D coordinates)
Example nano-BPMs at KEK / ATF
Triangle across girder
down to Floor node
Floor node
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Triangle Nodes
• Distance meter heads
located in triangle nodes.
• Floor node
– Overall resolution improves if
firmly anchored.
– Dome anchored separately
from interferometers.
• Ceiling nodes: position
stability rel. unimportant.
• All triangle nodes
– Angular stability of node
needed to about 10 mrad.
The StaFF project
P Coe et al
FLOOR NODE
LCWS06 I I Sc. Bangalore
Spider web Design with Opto-Geometrical
Simulation: Simulgeo
Written by Laurent Brunel :
for CMS alignment c.1999
• Allows objects to be placed
(6D) in hierarchal structure
– Reference positions.
– Fixed positions (with error).
– Variable placements (the
objects to be measured).
• Objects can be points, mirrors,
distance meters…
– e.g. Distance meter assumes
measurement between points
with error.
• Matrix inversion accounts for
errors and attempts to
constrain 6D position of all
points.
The StaFF project
ATF at KEK
P Coe et al
LCWS06 I I Sc. Bangalore
Spider web Design with Opto-Geometrical
Simulation: Simulgeo
• Resolution of distancemeter: 1nm
• Mounting precision of
distancemeter: 1nm
• Angular precision of
distancemeter holder: 10 mrad.
SLAC BPM: reference
KEK BPM variable (6D):
Position/nm x 32 y 19 z 2
Angle/mrad x 0.01 y 0.01 z 0.1
The StaFF project
~1mm absolute distance resolution
needed to determine constants
required to solve geometry.
P Coe et al
LCWS06 I I Sc. Bangalore
KEK ground motion
• Timescale: 0.01-100 Hz
1mm
– Laser interferometers ideal.
• Typical motion
amplitudes:
1 Hz
– On the order of a micron
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Interferometer Studies
• A number of designs are being studied
• Currently setting up lab space in Oxford
• Plan to test interferometers at ATF
• Final interferometers MUST be in vacuuo
• Combine fixed and swept wavelengths
• Nanometre resolution is routine in
interferometry – The devil is in the details
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Initial interferometer tests
Short arm
Retroreflector
Anti-reflection coated Lens
Fibre
MT connector
0.25
300 - 6000
Long arm
Intensity / a.u.
Ideally this would produce...
3
2
1
0
2
4
Laser Frequency change / GHz
when the signals from neighbouring fibres are read out
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
3 channels recorded in same scan
Intensity / a.u.
Intensity / a.u.
Intensity / a.u.
0.4
0.2
0.0
-0.2
-0.4
2
0
-2
0.5
0.0
-0.5
0
10
20
30
40
50
Change in Laser frequency / GHz
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
These signals can be analysed...
Amplitude / Arb units
• Either by calculating a
periodogram using FFT
• Or by fitting to a sinusoid
15
10
5
0
0.3
0.4
Length
0.5
Length / m
N.B. These are only generic examples!!
They do not correspond to signals shown earlier – but similar
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
Work in progress...
Setting up a new test area (lab corner)
- Highly sensitive thermometer system
- New optical table
Testing a zero-force bellows
for vacuum connections
Designing, constructing and testing new
interferometer designs
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
StaFF summary
• Proposed experiment conducted within framework of StaFF
(Stabilization of Final Focus for ILC).
• Funded by EuroTEV.
• Development of active feedback systems to monitor and stabilise,
for example, final focus quadrupoles or beam position monitors in
the energy chicane.
– Develop laser interferometric methods to monitor relative position of two
objects at nanometer scale when ~10m apart.
– Develop and implement algorithms for active stabilization.
• StaFF at KEK: Stabilize Nano-BPM systems relative to each other.
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore
The StaFF project
P Coe et al
LCWS06 I I Sc. Bangalore