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Another Modular Focal Plane:Another Modular Focal Plane:Part 1 – Sub-modulesPart 1 – Sub-modules
Bruce C. Bigelow
University of Michigan
Department of Physics
5/17/04
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Focal Plane Sub-modulesFocal Plane Sub-modules
Motivations: install/remove single detectors from “front” of FP assemble detectors in modules of 3 x 3
simplify assembly, integration, and test reduce part counts, simplify part design simplify part fabrication individual module thermal control (Vis vs. IR) optimize materials for detector packages (CTE)
local, discrete control of focal plane surface height minimize mechanical mass minimize thermal time constants minimize gravity deflections for ground testing maximize resonant frequencies
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Focal Plane Sub-modulesFocal Plane Sub-modules
Requirements: final focal plane flatness: +/- 25 microns support different optimal temperatures for Vis and IR detector temperature stability +/- 1K high stiffness – high first resonance
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Focal Plane Sub-modulesFocal Plane Sub-modules
This talk: sub-module designs sub-module FEA
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IR sub-moduleIR sub-module
Rockwell H2RG package
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IR sub-moduleIR sub-module
Rockwell H2RG package with filter and frame
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IR sub-moduleIR sub-module
Rockwell H2RG package on moly MZT sub-plate
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IR sub-moduleIR sub-module
Rockwell H2RG 3 x 3 sub array
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IR sub-moduleIR sub-module
3 x 3 sub array with flexure mounts
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IR sub-moduleIR sub-module
Sub-array with CRICs, flex circuits, connectors, local IR electronics (cold), sub-plate heater
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IR sub-moduleIR sub-module
Finished IR module with aperture mask
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CCD sub-moduleCCD sub-module
Finished CCD module with aperture mask
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Sub-module FEASub-module FEA
FE Analyses: Static analysis – gravity deflections
package mass modeled by doubling sub-plate density moly packages and sub-plate, invar flexures omit package cutouts, mounting holes, etc. focal plane axis vertical and horizontal
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Sub-module static FEASub-module static FEA
(meters)
Sub-module, Gy, Y deflection = 1.1 microns
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Sub-module static FEASub-module static FEA
(meters)
Sub-module, Gy, Z deflection = +/- 0.3 microns
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Sub-module static FEASub-module static FEA
(meters)
Sub-module, Gz, max. Z deflection = 0.8 microns
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Sub-module FEASub-module FEA
FE Analyses: Dynamic analysis - vibration modes and frequencies
package mass modeled by doubling sub-plate density omit package cutouts, mounting holes, etc.
First resonance = 528 Hz for Invar/Invar case First resonance = 630 Hz for Moly/Invar case
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Sub-module dynamic FEASub-module dynamic FEA
Moly sub-plate and Invar flexures – first mode
Mode/Freq.
1. 630
2. 630
3. 654
4. 1289
5. 1376
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Sub-module dynamic FEASub-module dynamic FEA
Moly MZT sub-plate and flexures – third mode
Mode/Freq.
1. 630
2. 630
3. 654
4. 1289
5. 1376
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Sub-module thermal FEASub-module thermal FEA
Thermal analysis – stress and distortion omit package cutouts, mounting holes, etc. omit package mass, stiffness -160 K temperature shift static, isothermal analysis no effort yet to optimize flexure design no effort yet to optimize stiffness of sub-plate
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Sub-module thermal FEASub-module thermal FEA
Elements:
Purple = Invar
Red = Moly
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Sub-module thermal FEASub-module thermal FEA
Purple = invar
Red = molyMax stress at Invar/Moly joint (not realistic), 86.8 MPa (12,557 Psi), (Invar yield ~ 250 MPa)
(Pascals)
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Sub-module thermal FEASub-module thermal FEA
Purple = invar
Red = molyShrinkage of Invar vs. Moly in X direction, +/- 50 microns
(meters)
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Sub-module thermal FEASub-module thermal FEA
Purple = invar
Red = molyShrinkage of Invar vs. Moly in X directionSub-plate displacement in Z direction – 15 microns
(meters)
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Sub-module thermal FEASub-module thermal FEA
Purple = invar
Red = molyShrinkage of Invar vs. Moly in X directionSub-plate displacement in Z direction – 15 microns
(meters)
Distortion of mounting surface ~2 micron
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FP sub-modulesFP sub-modules
Conclusions: sub-module designs for Vis and IR developed
• detector packages
• filters with mounts
• sub-plates
• sub-plate mounting flexures
• electrical connectors, junction boxes FEA demonstrates stiffness, high resonant freq. FEA demonstrates acceptable thermal performance