MONALISA David Urner, Armin Reichold , Paul Coe, Matthew Warden, Geoff Rayner Monitoring Alignment and Stabilisation with high Accuracy (Previously known as StaFF) WP 3
Dec 22, 2015
MONALISA
David Urner, Armin Reichold , Paul Coe, Matthew Warden, Geoff Rayner
Monitoring Alignment and Stabilisation with high Accuracy
(Previously known as StaFF)
WP 3
12 April 2007 MONALISA - M. Warden 2
Contents
• Motivation
• Overview of system
• The distance meter– Design– Construction– Data analysis
• Future developments
12 April 2007 MONALISA - M. Warden 3
Motivation
• A critical requirement for achieving and maintaining luminosity in ILC is:
• Stability of Beam Delivery System– This is true for BDS as a whole– And particularly so for the final focussing
quadrupoles
• Achieving stability requires accurate monitoring of magnet positions
12 April 2007 MONALISA - M. Warden 5
The Challenge:
• Develop an optical system to accurately determine relative position and orientation in 6D
• Direct line of sight may not be available
• In general, such a system needs:– Distance meters– Straightness monitors
12 April 2007 MONALISA - M. Warden 6
The Distance Meter
• Components:– Reference interferometer– Measurement interferometers
• Two modes:– Absolute distance measurement, using
frequency scanning interferometry– Small displacement measurement, using
fixed frequency interferometry
12 April 2007 MONALISA - M. Warden 7
The importance of absolute distance measurement
• Take two fixed points:
• Measure distances to a third point:
• Triangulate this point:
• Calculate axes for displacement measurements:
12 April 2007 MONALISA - M. Warden 8
Compact Measurement Interferometer
• Simple, compact design
• Gold-coated beam-splitter cube acts as one interferometer arm
• Will replace far mirror with corner cube– Allows for easy alignment– Can simultaneously measure
distances to many points
measurement distance
launchfibre
receivingfibres
12 April 2007 MONALISA - M. Warden 9
Reference Interferometer
• Both interferometers share the same phase step from piezo mounted mirror
• Taking two measurements gives a measure of accuracy
• Can keep one interferometer as a benchmark, and test alternatives with the other
Parallel s
12 April 2007 MONALISA - M. Warden 10
From design to reality
• Have constructed both reference and measurement interferometers
• Testing them now
12 April 2007 MONALISA - M. Warden 11
Preliminary Data Analysis
• Start with raw photodiode voltages
• Extract reference phase
• Fit sinusoids to measurement interferometer voltages
Mea
sure
men
t I
nter
fero
met
erR
efer
ence
Int
erfe
rom
eter
12 April 2007 MONALISA - M. Warden 12
Future Development
• Move ahead with distance meter development– Hardware design– Analysis methods
• Change to evacuated interferometers