Mechanical Design Review February 25, 2008 Université de Montréal SCUBA-2 Polarimeter Mechanical Design Review February 25, 2008 Université de Montréal

Instrument Location Three (3) attachment points Nasmyth platform (no change of gravity vector during operation) Cannot be dismounted without removing SCUBA-2 from the antenna

Instrument Footprint Space in front of the cryo window shared with Calibration Source Fairly space limited on the front of the instrument particularly along the optical axis.

Motion Requirements Fixed chasis with movable plates in and out of the beam using rails and drive mechanism. Translation axis Waveplate and Polarizers plates slide in and out Limit switches and home switch Each axis has encoder for fine ajustement Rotation axis Waveplate rotational angle sensor Rotation speed control

Motion - Translation Translation mechanism uses Acme screw Anti-backlash nut Linear rails Home sensor. Limit Switches Permanent magnet brush DC motor Cable track

Motion – Rotation Precision thin section bearing (large aperture) Timing belt driven Low profile and high torque motor Electronically commutated, no mechanical brushes to wear out Ball bearings also add to the longevity of the motor. SiGNUM™ RESM angle encoder system angle encoder offers accuracy, resolution, and repeatability at high speed

Waveplate Mounting Designed by Cardiff Tested by UdM at Martin Houde's Lab Titanium lug to the Waveplates insitu to ensure correct alignment O-ring ensures that the waveplate is held in place

Polariser Holder Photolithographic polarisers Clear aperture diameter 300mm Aperture form circular Frame Outer Diameter 350mm Total assembly thickness: <16mm

Connectors Four (4) connectors Metal bayonet coupling quick and reliable connection Cable has straigth-type socket connector Extra connector location (spare) not populated

Instrument Handling Three (3) eye bolts 140kg workload limit One (1) Handle Rack with wheels to store instrument horizontal or vertical storage can be bolted on optical bench