Master thesis and internship[BR]- Master's thesis : Conceptual Design of the ATHENA X-IFU Dewar Entrance Assembly Hold-down and Release Mechanism[BR]- Integration internship

Abstract

This master thesis presents the conceptual design of the Hold-Down and Release Mechanism (HDRM) of the Dewar Entrance Assembly (DEA) door cryo-mechanism of the X-ray Integral Field Unit (X-IFU) aboard the ATHENA space observatory. The HDRM plays a critical role in ensuring the integrity of the cryostat during launch by maintaining vacuum tightness and thus protecting the ultra-thin filter that interfaces with the DEA.

A comprehensive design methodology combining analytical modeling in MATLAB and numerical simulation using SolidWorks was implemented to assess the static equilibrium, actuation forces, and kinematic behavior of the HDRM. The Chebyshev four-bar linkage mechanism was selected based on heritage designs from the Herschel observatory, with adaptations to meet the specific kinematic and dimensional constraints. A parametric optimization process has been discussed and implemented to refine the HDRM configuration towards an optimal solution. Thermo-mechanical aspects were considered, and the main actuation requirements were established.

Preliminary finite element analysis and motion simulations were performed to confirm that the kinematic and dimensional requirements were met. Furthermore, experimental campaigns on candidate joint materials were conducted to evaluate compression forces, leak tightness, and thermal behavior at cryogenic conditions using different gasket samples from two suppliers.

The results demonstrate the feasibility of the proposed HDRM concept in meeting the mission’s operational requirements. However, a discussion of the weaknesses and limitations of the conceptual design is also provided. This includes the need for further work on detailed actuator integration, the cryostat cover assembly design, structural integration, and alternative concepts that could be better suited for this application.