Deformation analysis of ATHENA test filters made of plastic thin films supported by a mesh under differential static pressure

Within ESA Cosmic Vision 2015-2025 Science Program, ATHENA was selected to be a Large-class high energy astrophysics space mission. The observatory will be equipped with two interchangeable focal plane detectors named X-Ray Integral Field Unit (X-IFU) and Wide Field Imager (WFI). In order to optimally exploit the detector sensitivity, X-ray transparent filters are required. Such filters need to be extremely thin to maximize the X-ray transparency, that is, no more than a few tens of nm, still they must be able to sustain the severe stresses experienced during launch. Partially representative test filters were made with a thin polypropylene film, coated with Ti, and supported by a thin highly transparent mesh either in stainless steel or niobium. Differential static pressure experiments were carried out on two filter samples. In addition, the roles of the mesh on the mechanical deformation is studied, adopting a finite element model (FEM). The numerical analysis is compared with experimental results and found in good agreement. The FEM is a promising tool that allows to characterize materials and thicknesses in order to optimize the design

X-IFU Filter Wheel Optical Blocking Filters Technology Demonstration Plan

The main purpose of the present plan is to provide a clear path to demonstrate the TRL5 by the Mission Adoption for the three OBFs on the X-IFU Filter Wheel (FW). An effort has been performed in trying to identify what shall be considered technology, for which the maturity has to be demonstrated, and what is design that can still contribute to improve the performances of the FW filters along phases B and C of development. The X-IFU FW filters conceptual design is similar to that defined (during phase A) and described in the "X-IFU Filter Wheel Mechanism and Electronics Design Description", and the "X-IFU Thermal Filters (THFs) Description" documents presented at the I-PRR. The preliminary design of the X-IFU FW Filters rely on heritage from previous missions and characterization tests performed in phase-A on breadboards manufactured by LUXEL Corporation (Friday Harbor, WA, USA). The adoption of a design similar to that of the X-IFU THFs for frame shape and materials, and to that of the WFI FW filters for film and coating thicknesses, as well as for overall dimensions, allow migrating part of the achievements reached by the X-IFU THFs and WFI FW filters to the X-IFU FW filters. For this reason, the TDP for the X-IFU FW filters will be mainly focused on the vibro-acoustic performances. With this respect, minor effort will be dedicated to the thick and very robust meshless filter (25 μm PI + 100 nm Al) designed to observe very bright x-ray sources. The goal of this activity is to demonstrate TRL5 before MAR for the baseline technology of filters manufactured by LUXEL (PI/Al on BeCu mesh). However, in parallel to verify also the maturity of other filter technologies and to mitigate the risks of having only one manufacturer, we will procure and test filter samples and bare meshes of other European manufacturers (OXFORD instruments, XRNanotech). The identified TECHNOLOGY development elements that we consider critical in the X-IFU FW OBFs are described in this document. In section 7 we list the breadboards (BBs) we have identified to perform the necessary characterization tests aimed at demonstrating their maturity

The Athena X-ray Integral Field Unit: a consolidated design for the system requirement review of the preliminary definition phase

The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer, studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory, a versatile observatory designed to address the Hot and Energetic Universe science theme, selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), it aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over an hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR, browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters. Finally we briefly discuss on the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, and touch on communication and outreach activities, the consortium organisation, and finally on the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. (abridged).Comment: 48 pages, 29 figures, Accepted for publication in Experimental Astronomy with minor editin

Thermal modelling of the ATHENA X-IFU filters

The X-IFU instrument of the ATHENA mission requires a set of thermal filters to reduce the photon shot noise onto its cryogenic detector and to protect it from molecular contamination. A set of five filters, operating at different nominal temperatures corresponding to the cryostat shield temperatures, is currently baselined. The knowledge of the actual filter temperature profiles is crucial to have a good estimation of the radiative load on the detector. Furthermore, a few filters may need to be warmed-up to remove contaminants and it is necessary to ensure that a threshold temperature is reached throughout the filters surface. For these reasons, it is fundamental to develop a thermal modeling of the full set of filters in a representative configuration. The baseline filter is a polyimide membrane 45 nm thick coated with 30 nm of highpurity aluminum, mechanically supported by a metallic honeycomb mesh. In this paper, we describe the implemented thermal modeling and report the results obtained in different studies: (i) a trade-off analysis on how to reach a minimum target temperature throughout the outer filter, (ii) a thermal analysis when varying the emissivity of the filter surfaces, and (iii) the effect of removing one of the filters

X-IFU Thermal Filter THF300 thermalization study

This document reports a parametric thermal study performed on different technical solutions to heat the X-IFU thermal filter TH300 to minimize molecular contamination during the lifetime of the mission. The thermal model retrieves the radial temperature profile on the THF300 filter of the X-IFU instrument and establishes the necessary conditions to keep all the filter area above the temperature of 320 K [AD1]. The outcomes of this study have guided the choice of the baseline heating strategy compliant with the stringent thermal specifications of the X-IFU instrument, the selection of the filter mesh and plating materials, and the required operating temperature of the 300 K carrier

Technical Note 9 – Athena filters: conclusion and programmatic

This document summarizes the main results of the activity. The most important aspects related to fabrication of target filters are presented together with their most important characterized properties. Based on the presented results we made few recommendations in the scheme of ATHENA filter planning

Technical Note 7 - Test plan for the Athena filters

This document contains the test plan for the characterization of a set of CNT filters manufactured according to the design of two of the thermal filters, namely THF2 and THF300, in the current Athena X-IFU design, that is undergoing the instrument system requirement review (I-SRR). In particular, a set of fully representative filters has been manufactured by Ametek/Canatu using the high density CNT pellicle, bare and coated with aluminum, attached to Au plated BeCu meshes, and mounted onto aluminum frames. This document provides a brief description of test procedure, test equipment, and schedule for each proposed characterization methodology to be performed within task 5 of the contract. For more technical details on the equipment and accuracy of the test methodology we sometimes address the previous technical notes TN2 and TN6

TN8 – Athena filters characterization and qualification report

This document is a report of filter characterization tests performed on a set of filter breadboards representative of two of the Athena X-IFU thermal filters, namely the THF2 mounted on the 2K aluminum shield, which is a Faraday cage, at 150 mm from the microcalorimeter focal plane array, and the THF300 the larger and outer thermal filter mounted on the main shield of the cryostat which is also a Faraday cage. Such filter breadboards have undergone the same tests performed on similar filter samples based on the polyimide/Al baseline technology