SAM PDR 1

SAMSAM LGSLGSMechanical Mechanical

DesignDesign

A. Montane, A. Tokovinin, H. Ochoa

SAM LGS Preliminary Design Review September 2007, La Serena

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Location at SOAR and components

Laser box (easy)

Beam transfer (trivial)

LLT (challenging)

SOAR interfaces

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LGS operation strategy

1. Easy acquisition of the LGS in SAM (+-10”)

Reduce LLT de-pointing (thermal & flexure),

compensate by M1 lateral actuators

2. 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

3. Diffraction spot (Strehl>0.8) focus, flexure

Compensate LLT focus changes (thermal & flexure)

by M1 focusing (to 2.5 µm)

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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

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Laser box (2): interface

Box mass ~60kg

Thermal insulation

Tilt adjustment

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Beam transfer and M4

M2 (2” diam.) on kinematic mount

1” aluminum beam

duct tube,

flexible joints

Actuators M-230.1

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Laser Launch Telescope (LLT)

D=0.3m, F=0.5m primary mirror (M1): 1” = 2.5 µmD=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

Requirements:

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LLT overview

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LLT: primary mirror

Material : Aluminum 6061 T6

Weight : 1.315 Kg

Outer diameter : 300 mm

Central hole : 11mm diam.

Support with 3 points

11mm diameter in the center

3 points support

Back side

Front side

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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)

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Pointing assembly (1)

M1

Range ± 500 µmFlexure post

Lower plate

upper plate

M1

LLT points by pivoting M1around the focus (or curvature center) of M2 using 3 flexure posts

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Pointing assembly (2)

Material: Aluminum 6061 T6

Mass: 2.100 kg

Motor M-230.10 Motor M-230.10

Flexure post

Lower plate

M1

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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??]

Motor M-230.10

PhysikInstrumente

Pointing assembly (3)

loose star?

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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°

Range ± 500 µm

upper plate Lower plate

Motor M-230.10

Motor support

Spring

2 position

Flexure post3 position 120°

Pointing assembly (4)

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The pointing assembly is connected with focusing assembly in 4 points

Lever

Spring

The lever is pressed to the motor by a spring

LeverFlexure leaf

Base plateM1

Flexure shaft

Motor M-230.10

M3 Post connected to base plate

Post connected to the base plate

M3

LLT: Focus assembly

Focus range ± 0.5 mm

Mass: 5.5 kg

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LLT: Secondary support

Invar piece

M2 , material BK7

Outer diameter 15 mm

The mirror glued to an invar piece

Spacer for adjustment

Nut

Post

Mass 0.8 kg

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LLT: M1-M2 alignment

Push M1 withpointing assy. bylateral screws,then fix it andretract the screws

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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

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LLT: Secondary support flexure

Mechanical flexure

maximum : 9 µm

Flexure analysis of the

secondary support at

zenith distance 60°,

max. for SOAR

operation

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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”

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Thermal behavior of the LLT

Temperature change

20 C

M1-M2 lateral shift

30 µm (12”)

LLT base plate is de-coupled mechanically from the steel SOAR structure, but residualdeformation is still present

0.39mmM1 made of Al a-thermal design

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LLT: Protective cylinder and shutter

Iris shutter

Mass: 5.0 kg

LLT can be additionally protected by a plastic cap installed manually

Shutter motor

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LLT interface with the SOAR telescope

3 steel posts,reproducible mount

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Laser Launch Telescope mounted

Mounted above the SOAR secondary

M4

Total LLT mass: 18.7kg

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Laser cable and cooling lines

Cable length 7mTo do: laser rack design

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THE END