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PhFPU Design for PACS Instrument: Thermal and Grounding Scheme Validation

This document provides an overview of the design and requirements of the PhFPU (Photoron Focal Plane Unit) for the PACS (Photodetector Array Camera and Spectrometer) instrument. It includes information on the design, thermal considerations, grounding scheme, and validation and qualification tests.

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PhFPU Design for PACS Instrument: Thermal and Grounding Scheme Validation

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  1. PACS – IHDRPhFPU Design J. Martignac CEA/DSM/DAPNIA Service d’Astrophysique

  2. INTRODUCTION • PhFPU Requirements • BFP & PhFPU : - Design -Thermal & Grounding Scheme - Validation & Qualification • Critical Items

  3. PhFPU Requirements • Mass around 7 kg. • External Envelope & Mechanical I/F according to the Doc. : PACS-KT-ID-005-iss.4 • Admissible Load according to the Doc : PACS-KT-AN-005-iss.2 • Thermal Consumption : • -  to 12µW at 300mK • -  to 4,3mW at 2K without the Cooler

  4. BFP : Design • The BFP is mainly composed by 5 Sub-assemblies: • the mechanical structure, • the focal plane at 300 mK, • the 300mK thermal strap • the 2K circuit buffer, • the envelope.

  5. BFP : Design Review

  6. Cooler Harness Holder Connector Panel 4K Structure PhFPU : Design • The PhFPU is mainly composed of 8 Sub-assemblies: • the 4K Structure,

  7. R & B BFPs Holder Stainless Steel Insulating Tubes Voltalef Insulating Spacers PhFPU : Design • the 2K Structure,

  8. R BFP R&B BFP Filters Boxes R&B 2K/4K Ribbon Cables B BFP PhFPU : Design • the two BFPs Red & Blue ,

  9. 3He Cooler Harness 3He Cooler L0 Straps Baffling Shield Covers PhFPU : Design • the 3He sorption Cooler

  10. R&B Copper Braid R&B BFPs Thermall I/F 300mK Thermal Strap Kevlar wires suspension to the 2K Stray light Baffling Copper Braid Kevlar wires suspension to the 4K 3He Cooler Thermal Interface PhFPU : Design • the PhFPU 300mK Thermal Strap from the cooler to the BFPs

  11. R&B BFP L0 I/F 2K Feedthrough (by KT) Copper Braids Stray Light Baffle L0 Strap I/F PhFPU : Design • the 2K Thermal Strap,

  12. 2K Baffle 4K Baffle PhFPU : Design • & the Baffles.

  13. PhFPU : Design PhFPU assembly • Status: • Mechanical I/F: OK • Optical I/F: SOAM (KT) • Parts Manufacturing: OK • Integration Tools: OK • Black Paint: in progress • Full Assembly: First Time • Thermal: to be validated

  14. élec=2,8mW (B&R BFP) PhFPU 2K I/F struct=0,8mW flex=0,5mW R6 Rc4 PhFPU 4K Structure PhFPU R3 Feedth.=0,5mW TBC by KT Rc3 R1 Evap. Switch I/F T  2K Evap. Rc1 h0,12W.K-1 R2 Pump Switch I/F Pump. Rc2 h0,075W.K-1 PhFPU Thermal Equivalent Scheme Global Thermal budget on the L0 level: - 4,1mW + 0,5mW* *:(TBC by KT) L0 Straps manufacturing is under responsibility of Astrium

  15. PhFPU Structure @ 4K BFP Housing @ 2K Evap. Pump Cooler Structure @ 4K Optical Bench Space Scraft L0 Thermal Straps He Tank PhFPU Grounding scheme • The PhFPU grounding configuration is like represented: • one shield @ 2K close to the bolometers and signal • one shield @ 4K performed by the outer PhFPU and Cooler Structure • the electrical insulation between the two shields are performed by: • Voltalef parts at the Structure level • 0,1mm layer of STYCAST 1266 between copper foils at the Thermal Strap level (300mK & 2K)

  16. Validation & Qualification • Succesful Warm vibrations have been done : • on a BFP Structure alone • at the PhFPU level • & at the Instrument level A new PhFPU SM has been build for the Cold vibration campaign at CSL. The BFP Kevlar suspensions only survived to the first two axis (Y & Z), and a breakage occured at the beginning of the third run (X). But higher input levels than specified in the IIDA was applied.

  17. BFP : Validation & Qualification – Future Tests New stiffness measurements at 4K will be done on a BFP Structure in two directions : - axial (applied load  to the focal plane) - transverse ( // to the focal plane) These tests should be repeated 2 or 3 times on the same Structure to study the thermal cycling influence on the Kevlar wire suspensions. • Cold vibrations are planed : • on a BFP Structure alone • on a BFP equiped with detectors and its complete readout circuit to validate all the interconnections from the detectors to the end of the 2K/4K Ribbon Cable.

  18. PhFPU : Validation & Qualification – Future Tests • A complete PhFPU FEM is complete now with the Cooler & the BFP Kevlar suspensions • Warm vibrations will be done at the PhFPU level to investigate potential coupling between the PhFPU 4K Structure and 3He Cooler: • Cooler SM refurbished with a Titanium core and a functionnal switch linked to a representative L0 Strap: TBC!). • New cold vibrations campaign under negociation (ESA/Inst).

  19. PhFPU Critical Items • Critical: • Qualification at Cold temperature • BFP Kevlar wire suspension • Mechanical load on the Cooler thermal switches I/F • To be validated: • 0,3K Strap thermal behaviour (without & with electrical insulating parts. • Cooler behaviour mounted on the PhFPU (thermal environment)

  20. Progress since IBDR • 3 models of the PhFPU have been built: SMKT, SMKT2 & SOAM • Warm vibrations done succesfully passed at sub-assembly and at instrument level • BFP assembly & integration is now completely stabilised • 2K/4K ribbon cables manufacturing is now under control • PhFPU design is complete, all the parts for the QM are manufactured

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