Another Modular Focal Plane: Part 2 – FP assembly Bruce C. Bigelow University of Michigan Department of Physics 5/17/04

Modular focal plane assembly 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

Focal Plane Baseplate Requirements: final focal plane flatness: +/- 25 microns detector temperature stability +/- 1K high stiffness – high first resonance This talk: sample base-plate designs two materials examined base-plate FEA

FP Baseplate design and FEA Design of baseplate consider Al 7075 and Moly MZT materials three mounting points to optics bench via bipods bipods not included in design or FEA cut-outs for detector access

Focal plane base-plate - front Note webs in access holes – not in FEA models

Focal plane base-plate - back Base-plate rib structure – simpler than FEA model

Focal plane fully populated

FP Baseplate design and FEA consider Al 7075 and Moly MZT materials Moly plate is 50 mm thick: 31 Kg Al. plate is 75 mm thick: 13 Kg sub-array loads modeled with point masses static and dynamic analyses completed

FP Baseplate FEA rib thickness: red - 6 mm purple - 5 mm cyan - 6 mm blue - 10 mm

FP Baseplate FEA sub-modules as point masses 1.0 kg 0.5 kg 16 Kg total sub- module mass

FP Baseplate FEA – Al 7075 (meters) Gy, Y deflections – 1.8 microns max

FP Baseplate FEA – Al 7075 (meters) Gy, Z deflections – 2.1 microns PV

FP Baseplate FEA – Al 7075 (meters) Gz, Z deflections – 4.8 microns

FP Baseplate FEA – Al 7075 Mode/Freq. 227 Hz 238 Hz 261 Hz 325 Hz Dynamic analysis – first mode

FP Baseplate FEA – MZT (meters) Gy, Y deflections – 0.8 microns PV

FP Baseplate FEA – MZT (meters) Gy, Z deflections – 1.1 microns PV

FP Baseplate FEA – MZT (meters) Gz, Z deflections – 4.2 microns PV

FP Baseplate FEA – MZT Mode/Freq. 249 Hz 258 Hz 290 Hz 491 Hz 654 Hz Dynamic analysis – first mode

Baseplate FEA Summary Mat. Mass Thick Gy-Uy Gy-Uz Gz-Uz Fn Al 7075 227 Hz MZT 31 Kg 50 mm 0.8um 1.1um 4.2um 249 Hz

FP Modular Baseplate Conclusions: sample designs stiff, high resonances flatness specs met in two orientations (and probably all) consider other substrate materials (Ti, CF)? refine interfaces spectrograph, BITE sources, cryostat mounts thermal links, detect. wiring, baffles, shields optimize design for loads and material (ribs, thicknesses, etc)