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SAM LGS Mechanical Design

SAM LGS Preliminary Design Review September 2007, La Serena. SAM LGS Mechanical Design. A. Montane, A. Tokovinin, H. Ochoa. Location at SOAR and components. Laser box (easy) Beam transfer (trivial) LLT (challenging) SOAR interfaces. LGS operation strategy.

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SAM LGS Mechanical Design

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  1. SAM PDR SAM LGS Preliminary Design Review September 2007, La Serena SAMLGS Mechanical Design A. Montane, A. Tokovinin, H. Ochoa

  2. SAM PDR Location at SOAR and components • Laser box (easy) • Beam transfer (trivial) • LLT (challenging) • SOAR interfaces

  3. SAM PDR LGS operation strategy • Easy acquisition of the LGS in SAM (+-10”) Reduce LLT de-pointing (thermal & flexure), compensate by M1 lateral actuators • Center Gaussian beam on the LLT pupil to ~1cm Compensate beam displacement at LLT-M2 caused by the projector’s flexure by controlled tilts of M4 • Diffraction spot (Strehl>0.8)  focus, flexure Compensate LLT focus changes (thermal & flexure) by M1 focusing (to 2.5 µm)

  4. SAM PDR Laser box (1): inside • UV laser: 813x127x86mm, 14.5kg, 15..35 C • Blue alignment laser • Optical elements (beam expander, compensator, mirrors, …) • Air-tight, thermal stabilization and insulation We know what’s inside, but no detailed design yet

  5. SAM PDR Laser box (2): interface Thermal insulation Tilt adjustment Box mass ~60kg

  6. SAM PDR Beam transfer and M4 Actuators M-230.1 M2 (2” diam.) on kinematic mount 1” aluminum beam duct tube, flexible joints

  7. SAM PDR Laser Launch Telescope (LLT) Requirements: • D=0.3m, F=0.5m primary mirror (M1): 1” = 2.5 µm • D=15mm, F=15mm secondary (M2) • Low total mass (<8kg initially), L<700mm • Blind pointing to SOAR axis within 10” (goal) • Actively correct pointing (slowly) to 0.2” ( 0.5 m) • Focus from 7km to infinity (in temp. range -5..+25 C), accuracy 2.5m • Protection from dust and wind • Alignment and control tools

  8. SAM PDR LLT overview

  9. SAM PDR LLT: primary mirror 11mm diameter in the center Back side • Material : Aluminum 6061 T6 • Weight : 1.315 Kg • Outer diameter : 300 mm • Central hole : 11mm diam. • Support with 3 points Front side 3 points support

  10. SAM PDR Primary mirror flexure Flexure map when looking at zenith. Mechanical flexure maximum : 0.046 µm After subtraction of focus and tilt, residual flexure is 8nm rms (req.: <25nm)

  11. SAM PDR Pointing assembly (1) M1 upper plate Range ± 500 µm Flexure post Lower plate LLT points by pivoting M1 around the focus (or curvature center) of M2 using 3 flexure posts M1

  12. SAM PDR Pointing assembly (2) M1 • Material: Aluminum 6061 T6 • Mass: 2.100 kg Motor M-230.10 Motor M-230.10 Flexure post Lower plate

  13. SAM PDR Pointing assembly (3) Motor M-230.10 PhysikInstrumente • 10 mm Travel Range • 0.05 µm Minimum Incremental Motion • Velocity to 2 mm/sec. • Integrated Limit Switches • Front Mount • Max Force 70 N • Weight 0.30 Kg • Backlash 2 µm =1” [tip-tilt servo??] loose star?

  14. SAM PDR upper plate Lower plate Pointing assembly (4) Spring 2 position Motor M-230.10 The x-y position of the upper plate is defined by the two actuators, with flat matching surfaces and spring loads. The actuators are oriented at 120° Motor support Flexure post 3 position 120° Range ± 500 µm

  15. SAM PDR LLT: Focus assembly Post connected to the base plate The pointing assembly is connected with focusing assembly in 4 points M1 Base plate M3 Motor M-230.10 M3 Post connected to base plate Spring Flexure leaf Lever Lever Flexure shaft The lever is pressed to the motor by a spring Focus range ± 0.5 mm Mass: 5.5 kg

  16. SAM PDR LLT: Secondary support Mass 0.8 kg Nut Invar piece Post Spacer for adjustment M2 , material BK7 Outer diameter 15 mm The mirror glued to an invar piece

  17. SAM PDR LLT: M1-M2 alignment Push M1 with pointing assy. by lateral screws, then fix it and retract the screws

  18. SAM PDR LLT: M3 support and ATP • M3 tilts aligned manually (accessible from outside LLT) • AM3 sends star light to lens+CCD (boresight camera, ATP) • ATP is used as auto-collimator for alignment

  19. SAM PDR LLT: Secondary supportflexure • Mechanical flexure maximum : 9 µm • Flexure analysis of the secondary support at zenith distance 60°, max. for SOAR operation

  20. SAM PDR Flexure analysis of the LLT structure at zenith distance 60° • Mount at 3 fixed points • Mechanical flexure of M2: 18 µm lateral, 27 µm axial • Relative displacement between M1 axis and M2 focus: 1.1 µm lateral (need <73 µm ) • Overall LLT tilt: 4.7”

  21. SAM PDR Thermal behavior of the LLT M1 made of Al  a-thermal design 0.39mm Temperature change 20 C  M1-M2 lateral shift 30 µm (12”) LLT base plate is de-coupled mechanically from the steel SOAR structure, but residual deformation is still present

  22. SAM PDR LLT: Protective cylinder and shutter Iris shutter LLT can be additionally protected by a plastic cap installed manually Shutter motor Mass: 5.0 kg

  23. SAM PDR LLT interface with the SOAR telescope 3 steel posts, reproducible mount

  24. SAM PDR Laser Launch Telescope mounted Mounted above the SOAR secondary M4 Total LLT mass: 18.7kg

  25. SAM PDR Laser cable and cooling lines To do: laser rack design Cable length 7m

  26. SAM PDR THE END

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