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 o C Fixed Temperature of -120 o C 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 Material Focal Plane Temp ( o C) ΔT Focal Plane to CCD (K)Max Stress (MPa) Max CCD Deformation (µm) Y-direction Deformation (µm) Al (-122.0)4.5 (2.0)102.5 (106.3)16.5 (14.4) ( ) Invar (-124.5)7.5 (4.5)14.5 (18.32)8.9 (8.7) ( ) SiC (-120.7)2.5 (0.7)8.8 (12.6)8.2 (8.2) ( ) Note: Values in () indicates Moly spacer instead of Invar AluminumInvar 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 o C where frame attaches to focal plane Radiation to 22 o C Radiation to -120 o C

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-LAH Invar36Fused Silica