Hexabundles meet OzPoz

Hexabundle science workshop

University of Sydney

24th November 2008

Andrew McGrath, AAO

OzPoz – the FLAMES positioner

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

Buttons

Retractor

• Take up slack in fibre• Keep mild tension in fibre to button (~1 N)• Diameter of bundle• Bend radius ~24 mm• Flexibility

Retractor

• Take up slack in fibre• Keep mild tension in fibre to button

(~0.1N)

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