Status of the Ir and Ir/SiC coating development for the Athena optics

Abstract

The mirror coatings for the Athena X-ray telescope assumes Ir/SiC bilayer thin films as a baseline design.Adding the soft overcoat to the Ir X-ray mirror coatings for the Athena optics is used to improve the low energy performance necessary to achieve the telescope effective area requirements. The Athena mirror is based on silicon pore optics technology, for which the manufacturing process involves a sequence of wet chemical and thermal post-coating treatments of the mirror plates. Establishing compatibility of the thin film material candidates following exposure to these processes is critical for the Athena mission since the specific coating quality will influence the performance of the X-ray telescope. We present an investigation of Ir and Ir/SiC thin films exposed to post-coating treatments based on coatings produced at DTU Space. The current status of the chemical procedures is presented with representative coatings from the Athena-dedicated coating facility.

Impact of annealing on performance of X-ray mirror coatings for Athena

“…11822 118220D-4 DTU Space. 15 The Ir/B 4 C bilayer annealed under atmospheric conditions underwent drastic changes, similar to previous observations. 16 The XRR measurements post-annealing resembles those of an Ir single layer without an overcoat and the best-fit parameters indicate a B 4 C layer with significantly reduced thickness and density.…”

Design, performance, and utilization of the Low-Energy X-ray Reflectometer at DTU space

“…The reflectometer has proven to be a useful resource for fast characterization of low-density coating behavior and mirror sample performance and is already being utilized to provide valuable data. 26,27…”

Compatibility of iridium thin films with the silicon pore optics technology for Athena

“…The iridium thin films were deposited onto photoresist patterned SPO plates, representative of the Athena middle-radius mirror plates. The plates were exposed to in-situ plasma cleaning prior to thin film deposition in order to remove surface contamination, ensuring a smooth surface and compatibility with the wet-chemical cleaning procedure 14,22 .…”

“…As the optics development is scaling up for the industrialized mirror plate production and assembly [2][3][4] , the development of X-ray mirror coatings for Athena is progressing alongside, [5][6][7][8][9][10][11][12][13][14] with several aspects of material stability [14][15][16] and optimization of performance 17 being investigated. The thin film designs under study for the Athena X-ray mirrors at present include iridium single-layers, and bilayers of iridium with a low-Z overcoat of either boron carbide, silicon carbide, or carbon.…”

“…One of the critical aspects in adopting a coating design is addressing the compatibility of the candidate materials with the wet-chemical, mechanical and thermal post-processing required for the SPO technology. Previous studies based on preliminary wet-chemical treatment have indicated compatibility of iridium thin films 14,18 . Since then, further refinement of the wet-chemical processes has been enabled with the installation of a fully automated wet bench at cosine Research BV 19 .…”