1. Internal CDR meeting December 20th, 2005
SCUBA-2 Polarimeter
Internal CDR meeting
December 20th, 2005

2. Meeting Agenda Beginning of the meeting at 10h30 am
Mechanical Design Overview
FEA
Discussion
Lunch at 12h00 am
Optical design
Model
Ghosting
Mirror Sample
Paper Publication
Planning
End of meeting at 3h00 pm

3. Mechanical Design Mechanical Design Overview FEA Discussion
Space envelope
Translation module
Rotation module
FEA
Discussion

4. Space envelope
New ICD
Connector positions

5. Translation Modules Miniature linear guide from THK
Cage ball
Lead screw with anti-backlash nut
Miniature Maxon servo motor, gearbox and encoder
15 seconds to go from store to operating position
Service life 1000 to 3000 hrs
Limit switch
Home and end position
Selection of limit switch to be confirm with electronic

6. Rotation Module Timing belt (8.5:1 ratio) Thin section bearing
5 mm pitch GT belt
Neoprene, fiberglass reinforced
Belt Useful life approx hrs
Custom made timing pulley PD mm
Efficiency 95%
Thin section bearing
Angular contact preloaded bearing pair
Solid lubricant
Friction torque max: 1 Nm at 20C, 1.6 Nm at –15C 2RPM
Lead time weeks

7. Rotation Module Maxon flat motor 90Watt Renishaw angle encoder
Biggest motor that could fit in the allowed space
Continuous operation: 2000 rpm, 557mNm
At 20C with SF = 2.2, Speed max : 5 hz
At -15C with SF = 1.5, Speed max : 5 hz
Service life hrs
Renishaw angle encoder
CA 280 mm

8. Rotation Module Cable management Cable tack has been pre-selected
Will hold encoder and motor cable
Size of motor cable needs to be confirm
Size of track : 9.9mm x 20 mm
Bend radius 37 mm

9. FEA Dynamics Statics in three orientation Modal analysis
First mode 52 hz > 12 hz
Statics in three orientation
Deformation of entire polorimeter
Deformation max 35 um
Deformation and constraint of sapphir plate
Tilt max in operation : deg

10. Discussion

11. Optical design of the SCUBA-2 polarimeter
CDR meeting
December 20th, 2005

12. Optical Design
Model
Image quality: remains the same with adjustment on M (p. 2)
Footprint & Vignetting:
for the 277 mm diameter half wave plate: no impact on the beam (p. 14)
For the 200 mm diameter sapphire half wave plate: affects the sensitivity but no vignetting (p )
Calibration source: covers the whole beam footprint (p. 23)

13. Optical Design
Mirror Sample needed or theoretical data sufficient? (p. 37)
Instrumental polarization:
Impact of the telescope and camera mirror surfaces (p. 39)
Impact of the polarizers (isolation) (p )
Camera window and filters: unknown (p )
Derivation of a Mueller matrix and a Jones matrix representing the sapphire half wave plate (p )

14. Optical Design Instrumental polarization simulated in Zemax
Telescope + Camera :
polarization of an unpolarized beam = 0.769% (p. 57)
Ellipticity (added phase) = 0.22° (p. 57)
Telescope + Camera + Polarimeter:
polarization of an unpolarized beam = 99.80% (p. 61)
Ellipticity (added phase) = 0.32° (p. 61)

15. Optical Design Ghosting:
Most important ghost: retro-reflection between analyzer polarizer and half wave plate.
Spot size = 127 mm dia. at detector plane (p )
Uncertainty on the phase of the retro-reflected beam
The beam retro-reflected from the half wave plate has a phase that varies with the wavelength (p. 66, 73-74)
There seems to be no big problem in the operation mode (p ). Ghosts in the calibration mode are more important (p ). The simulation results probably represents the worst case scenario.

16. Optical Design Paper publication
Waveplate simulation results / experimental results
Whole instrument simulation
Publication date:
After characterization of sapphire waveplate?
After commitionning?

17. Planning Optical elements delivery schedule Mechanical parts delivery
The temporary gear needs to be replaced by the final one. Need 1 week at INO to perform the replacement.
Final mechanism delivery: confirm the date of September 2006
Waveplate test setup:
INO to provide mechanical interface data for gear holder but not gear holder itself