hexabundles meet ozpoz hexabundle science workshop university of sydney 24 th november 2008 andrew...
TRANSCRIPT
Hexabundles meet OzPoz
Hexabundle science workshop
University of Sydney
24th November 2008
Andrew McGrath, AAO
Buttons
• Existing OzPoz has single-fibre buttons and mini-IFUs with 20 fibres each
• Mini-IFUs view 2x3 arcsec FoV• FACBs (acquisition bundles) with 19
fibres• Common button package
Bundles
• Single-fibre buttons fed with sleeved fibre
• 19- and 20-fibre bundles also carried in slightly larger diameter sleeve
Retractor
• Take up slack in fibre• Keep mild tension in fibre to button (~1 N)• Diameter of bundle• Bend radius ~24 mm• Flexibility
Magnetic attachment
• Buttons secured magnetically to field plate
• Strong enough – Static friction must hold button stable to ~1 N retractor tension, in arbitrary orientation wrt gravity
• Not too strong – Robot gripper limits to ~4 N
• Clamping force ~2.5 N
Bundle handling experience
• Works well for existing design• No evidence of effects of ‘tangling’ of
fibres against each other within 19- and 20-fibre sleeved bundles
• 2dF retractors carry unsleeved bundles of fibres for guide bundles
FLAMEing Hexabundles?• Can we use the existing arrangement to fit one or
more 61-core hexabundle fibre bundles to OzPoz?• Notionally, assemble a FACB or mini-IFU button with a
hexabundle feed
– Seems OK
FLAMEing Hexabundles?
• Can the existing OzPoz retractor accommodate a bundle of 61 fibres?
• Currently handles 20• Diameter of bundle will increase• Stiffness of sleeved bundle will increase
FLAMEing Hexabundles?
• Need to identify a suitable sleeve• Could increase retractor spring force to
accommodate increased stiffness• Flow-on effects to magnetic force and robot
force capacity could render unfeasible
FLAMEing Hexabundles?
• Could subdivide the bundle to manageable subsets
• Multiple adjacent retractors per button• Minor additional placement limitations• Probable requirement for increased
magnetic force to provide static friction• Robot flow-on effects may render
unfeasible
FLAMEing Hexabundles?
• Unsleeved bundle likely much more flexible• Similar arrangement to 2dF, fibres in a
loose plait• Tangling issues and fibre breakage are
important concerns
FLAMEing Hexabundles?
• Or… consider FLAMEing Hexabundles as a one-off type of test
• Don’t run the fibre bundle through a retractor at all
• Manually place the button on the field plate• Use the robot for metrology only• Tweak the button(s) into place by tapping
with a finger