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Preliminary ANSYS Results:CCD Fixture and Lens Frame
Andrew Lambert
Outline
• CCD Results– Temperatures– Deformations– Conclusions
• Lens Frame Results– Vertical Orientation Deformation– Horizontal Orientation Deformation– Deformation due to Thermal Expansion– Conclusions
Thermal BC’s
• Radiation to 22 oC • Fixed Temperature of -120 oC on Focal Plane• Heat Flow of 110 mW at each corner• Heat Flow of 20 mW where Flex Strips attach
Temperatures
Aluminum Invar
SiC
Deformation of CCD
Base MaterialFocal Plane Temp
(oC)ΔT Focal Plane to
CCD (K) Max Stress (MPa)Max CCD Deformation
(µm)Y-direction Deformation
(µm)Al -124.5 (-122.0) 4.5 (2.0) 102.5 (106.3) 16.5 (14.4) 14.5-14.7 (12.1-12.3)Invar36 -127.5 (-124.5) 7.5 (4.5) 14.5 (18.32) 8.9 (8.7) 5.2-5.3 (4.9-5.0)SiC -122.5 (-120.7) 2.5 (0.7) 8.8 (12.6) 8.2 (8.2) 4.0-4.2 (4.1-4.2)
Note: Values in () indicates Moly spacer instead of Invar
Aluminum Invar
SiC
CCD Simulation Conclusions
• Aluminum performs the worst in terms of stress and deformation
• Invar and SiC have similar mechanical performance, however SiC has better thermal conduction and hence is better suited for cooling.– A ΔT of 20 K was the worst case scenario, and both Invar and SiC are
better than this• Note: thermal contact points are modeled perfectly, which will not be the case
in reality.
• Overall, the best material for use is SiC, however; using Moly spacers with Invar greatly improves thermal conduction from the base to the CCD – makes it competitive with SiC
• The best combination was a SiC focal plane with Moly spacers
Structural BC’s
• Fixed supports where frame attaches to focal plane• Standard Earth gravity
Lens Frame - Vertical
Note: The deformed lens shape is exaggerated!
Invar
Titanium
Lens Frame - Horizontal
Note: The deformed lens shape is exaggerated!
Invar
Titanium
Thermal BC’s
• Fixed Temperature of -120 oC where frame attaches to focal plane
• Radiation to 22 oC • Radiation to -120 oC
Thermal Expansion
Invar
Titanium
Lens Frame Simulation Conclusions
• The Titanium and S-LAH59 combination does not perform well structurally– If this combination is used, we need to “beef up” the lens frame
considerably– S-LAH59 is much heavier than the Fused Silica
• Invar36 and Fused Silica perform much better• Neither model has high stress – no failure modes• Invar36 and Fused Silica seem to be the best option going
forward.• No matter which combination is used, I would recommend
reinforcing the lens frame structure
Frame Material
Lens Material
Vertical Deformation (µm)
Horizontal Deformation (µm)
Max. Thermal Deformation (µm)
Titanium S-LAH59 1.3 31.3 545.6Invar36 Fused Silica 0.6 16.7 94.9