preliminary ansys results: ccd fixture and lens frame

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