1. David Urner Oxford University/JAI
MONALISA
David Urner
Oxford University/JAI
Clic stabilization day #4

2. What can laser interferometry do for you?
Nanometre level relative distance measurements
Micrometre level absolute distances
Large range of frequencies: from hours to 100kHz
Large motion range (mm)
Clic stabilization day #4

3. Clic stabilization day #4
Recent Results
In Air
Distance 40cm
Offset: 0.001nm
Sigma: 0.29nm
Clic stabilization day #4

4. Good results in protected air
Experiment done with our new prototype launch head:
1sec: RMS 0.4nm
1min: RMS 1nm
Reason to believe that
increase is caused by
laser frequency shifts
Air protection: simple cardboard box
Clic stabilization day #4

5. Work at standard pressure
Advantage: No vacuum systems needed
Cheaper
Flexible
Disadvantage: Long-term stability compromised by pressure and gas temperature changes
Can be measured and corrected to a certain degree
R&D needed
Further improvements possible
Frequency stabilization of laser to Rb87 line
Proper enclosure
Usage of light gas such as he instead of air
Lose some of cheap/flexible advantage
Clic stabilization day #4

6. Clic stabilization day #4
Mockup
Short distances:
Vertical ~50cm
Horzontal~1m
Resolutions in air sufficient.
Vacuum vessel:
Influences magnet support
Isolation with bellows possible
but requires fancy force cancelation
Clic stabilization day #4

7. Start with protected air measurements for Mockup
Simple plastic pipe tubes sufficent
Allows in situ adaptation of observation network
Prior simulations would suggest a triangle with cross-braces should give good results
Requires proper simulations
Possible measurements of magnet:
Vertical motion
Horizontal motion
Flexing 1st and higher modes
Expansion (compare quadrants)
Comparison with seismic measurements
Long term behaviour
Temperature dependence
Typical beam tube dia: 5cm
Get a view
At pole tips
Possible way to compare to
seismic measurements
Clic stabilization day #4

8. Clic stabilization day #4
Summary
Protected air – gas at normal pressure likely to be sufficient
Start with simple system but leave room for possible upgrade to helium or vacuum
Determine best configuration of interferometers
Specify and prioritize overall goals to be measured with mock-up
Need input from beam dynamics group to understand what the specifications for beamline quadrupoles really mean:
Stabilize one quad with respect to next?
What is limit for other than 1 second
How far can quadrupoles move at a beam interruption before full beam based alignment is required
Ho far can quadrupoles move before mechanical alignment is required
Clic stabilization day #4