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

2. 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

3. 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.

4. 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

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

6. 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

7. 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

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

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

10. 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