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

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

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

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

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

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

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