Multilayer (ML) thin film coatings have shown promise in achieving hard x-ray nanofocusing with high reflectivity and high resolution. The chemical, structural, and long-term stability of Ir/B4C MLs, which are of great interest to the synchrotron and astrophysics communities, are not yet fully understood. The evolution of the x-ray performance of Ir/B4C ML mirrors was monitored over 5 years, and the chemical and structural properties were investigated in depth. Reflectivity scans reveal significant alteration in the energy range of 3.4 to 10 keV over this period. Furthermore, thickness and density degradation of B4C layers were observed in scanning electron transmission microscopy results. The oxidation of B4C occurs only for the top layers, whereas the buried B4C layers go through various complex chemical modifications. The x-ray reflectivity model of Ir/B4C structure was modified, based on the experimental findings, and resulted in good understanding of the long-term reflectivity performance of the x-ray mirror coatings.
We present the latest progress on the industrial scale coating facility for the Advanced Telescope for High-ENergy Astrophysics (ATHENA) mission. The facility has been successfully commissioned and tested, completing an important milestone in preparation of the Silicon Pore Optics (SPO) production capability. We qualified the coating facility by depositing iridium and boron carbide thin films in different configurations under various process conditions including pre-coating in-system plasma cleaning. The thin films were characterized with X-Ray Reectometry (XRR) using laboratory X-ray sources Cu K-α at 8.048 keV and PTB's four-crystal monochromator beamline at the synchrotron radiation facility BESSY II in the energy range from 3.6 keV to 10.0 keV. Additional X-ray Photoelectron Spectroscopy (XPS) measurements were performed with Al K-α radiation to analyze the composition of the deposited thin films.
X-ray reflectivity (XRR) characterization of X-ray mirrors is an essential step for designing space telescopes and instruments. We report on production and characterization of platinum thin films coated onto a at thick glass substrate for evaluating measurement results obtained using several XRR systems. The main objective of this study is to compare the XRR results measured using facilities at the Technical University of Denmark, DTU Space, and BESSY II for the Advanced Telescope for High-ENergy Astrophysics (ATHENA) mission funded by the European Space Agency, ESA. This sample will be used as a reference sample for testing and calibrating similar measurements at relevant X-ray facilities. This information demonstrates the stable performance of the platinum mirror as a reference sample. Also, the overlayer effect on mirror performance is investigated.
Qualification of coating performance at the low-energy range of the Advanced Telescope for High Energy Astrophysics (ATHENA) is important to ensure that the mirror coatings satisfy the performance criteria required to meet ATHENA's science objectives. We report on the design, implementation, and expected performance of a state-of-the-art Low-Energy X-ray Reflectometer (LEXR) acquired with the purpose of qualifying the soft energy X-ray performance of mirror coatings for ATHENA. The reflectometer components are housed in a vacuum chamber and utilizes a microfocus Al source with custom made Kirkpatrick-Baez mirrors and W/Si monochromator to produce a collimated beam of 1.487 keV photons. The system has been designed with source interchangeability, allowing reconfiguration to an 8.048 keV reflectometer using a Cu source or other energies with sources such as Fe, Mg, etc. Several mirror samples can be mounted on a motorized stage, and a 2D CCD camera is used to obtain spatially resolved detection.
Excellent X-ray reflective mirror coatings are key in order to meet the performance requirements of the ATHENA telescope. The baseline coating design of ATHENA was initially formed by Ir/B4C but extensive studies have identified critical issues with the stability of the B4C top layer which shows strong evolution over time and appears incompatible with the industrialization processes required for the production of mirror modules. Motivated by the need for a compatible top layer material to improve the telescope performance at low energies and based on simulated performance, a SiC top layer has been selected as the best substitute to B4C. We report the latest development of Ir/SiC bilayer coatings optimized for ATHENA and the characterization of coating performance and stability.
We present the expected coating performance based on design and simulations, tested coating performance evaluated by means of X-ray reflectometry and short and long term stability of several materials considered as coating options for the X-ray mirrors of the ATHENA mission. As part of this study we also report on the compatibility of the X-ray reflecting coatings to the industrial processes involved in the assembly of mirror modules using Silicon Pore Optics technology.
Thin film coated mirrors enable pioneering observations of X-rays and soft gamma rays. The performance of the reflective mirrors is key in expanding knowledge of the hot and energetic Universe. A critical part of maturing the optics technology is firstly, to establish a smooth surface and interface of the selected materials and, secondly, to obtain an in-depth understanding of the contamination in the thin films and ultimately, to ensure long-term stability. The aim of this study is to investigate the chemical composition, roughness and stability of boron carbide and iridium thin films and the effects of nitrogen incorporation.