SAM LGS Mechanical Design

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Transcript SAM LGS Mechanical Design

SAM LGS Preliminary Design Review
September 2007, La Serena
SAM LGS
Mechanical
Design
A. Montane, A. Tokovinin, H. Ochoa
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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
Thermal insulation
Tilt adjustment
Box mass ~60kg
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Beam transfer and M4
M2 (2” diam.) on kinematic mount
Actuators M-230.1
1” aluminum beam
duct tube,
flexible joints
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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
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LLT overview
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LLT: primary mirror
11mm
diameter
in the
center
Back side
Front side
Material : Aluminum 6061 T6
Weight : 1.315 Kg
Outer diameter : 300 mm
Central hole : 11mm diam.
3 points support
Support with 3 points
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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
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
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Pointing assembly (2)
M1
Motor M-230.10
Motor M-230.10
Flexure post
Lower plate
Material: Aluminum 6061 T6
Mass: 2.100 kg
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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??]
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loose star?
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Pointing assembly
(4)
upper plate
Lower plate
Spring
2 position
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 M-230.10
Motor support
Flexure post
3 position 120°
Range ± 500 µm
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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
Spring
Lever
Flexure leaf
Lever
Post connected
to base plate
Flexure shaft
Focus range ± 0.5 mm
The lever is pressed
to the motor by a
spring
Mass: 5.5 kg
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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
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LLT: M1-M2 alignment
Push M1 with
pointing assy. by
lateral screws,
then fix it and
retract 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
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
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LLT: Protective cylinder and shutter
Iris shutter
LLT can be
additionally
protected by a
plastic cap installed
manually
Shutter
motor
Mass: 5.0 kg
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LLT interface with the SOAR telescope
3 steel posts,
reproducible mount
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Laser Launch Telescope mounted
M4
Total LLT mass: 18.7kg
Mounted above the SOAR secondary
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Laser cable and cooling lines
To do: laser rack design
Cable length 7m
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THE END
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