Large Shell Hard X-Ray Multilayer Development

Project Objective

A project to develop a multilayer deposition chamber to directly coat MSFC’s full shell x-ray optics, significantly increasing the optics energy bandpass.

Project Description

X-ray observatories with conventional single layer coatings such as iridium have limited hard-x-ray response. Depth graded multilayers consisting of W/Si and Pt/C can be used to greatly extend the reflectivity of grazing incident mirrors into the hard-x-ray regime. The state-of-the-art hard x-ray telescope, Nuclear Spectroscopic Telescope Array (NuSTAR), is limited with an angular resolution of 60 arcseconds. The current capabilities of MSFC’s full shell optics offer an order-of-magnitude improvement in angular resolution performance and have been demonstrated at 5-7 arcseconds. By developing direct multilayer coating technology and pairing it with MSFC’s high-angular resolution x-ray optics, unprecedented sensitivity can be achieved in the hard x-ray bandpass. Direct multilayer coating of full shell optics will be a unique capability to MSFC, and development of this technology can be implemented for a broad range of observatories. Additionally, this technology would greatly benefit the proposal efforts of a hard-x-ray space telescope Explorer mission.

Project Results and Conclusions

The ST-12 X-ray group received funds to purchase a Dual Direct-Cooled Linear DC Magnetron Assembly manufactured by Angstrom Sciences, Inc., which will be used to apply the coatings. The lead time for this item was several months, and the group did not receive the magnetron until early Fall 2024. Prior to delivery, a spare coating chamber was identified and retrofitted for the magnetron. Upon delivery of the magnetron, additional fixturing hardware was designed and manufactured to safely install the magnetron into the chamber with the item being mounted in the chamber in early December 2024.

Separate funding, provided by ST12, allowed for the purchase of high-purity silicon, carbon, tungsten, and nickel DC magnetron targets. The targets will be integrated with the DC Magnetron and will act as the source material for the multilayers. The targets were also delivered in the Fall of 2024. Currently, the now complete multilayer deposition chamber is being commissioned through component integration and coating of test samples. A pre-existing x-ray optic mandrel developed for the Imaging X-ray Polarimetry Explorer (IXPE) mission is being refurbished. Supplemented by the ST12 directed work package, new optics replicated from this mandrel will be multilayer coated using the new chamber in the Summer of 2025. The effective area and optical performance of these optics will be measured at Marshall-100 Meter X-ray Beamline both before and after coating with results presented afterwards.

Over the last year, the Super–High Energy Replicated Optics (SuperHERO) balloon telescope mission was awarded funding from Astrophysics Research and Analysis (APRA). SuperHERO plans to use single-layer Iridium coating for its first mission which is set for the Fall of 2028. For all future science flights, SuperHERO will implement multilayer coatings utilizing this system to increase the effective area and bandpass of the observatory.

MSFC Priority: This effort lies directly in the Center priority area of Optics Support for Astrophysics

NASA Technology Taxonomy: TX08 (Sensors & Instruments)

• The development of a large multilayer coating chamber will allow for the in-house coating of MSFC’s replicated shell optics and builds upon our current coating capabilities that were successfully employed to single layer Ir coat MSFC's missions including the Astronomical Roentgen Telescope X-ray Concentrator (ART-XC) and other suborbital missions.
• The capability to multilayer coat full shell x-ray optics at MSFC is key to facilitating an end-to-end fabrication program and will grow current skill sets.
• The Astrophysics Division of NASA’s Science Mission Directorate recognizes that technological development of low stress reflective coatings is of Tier 1 priority for future arcsecond resolution, thin-substrate, grazing-incidence X-ray optics for Probe and Great Observatory missions in the coming decade.

The continued developmen of the direct multilayer deposition of full shell optics will benefit the selected SuperHERO suborbital APRA mission and will support the proposal efforts of a future Explorer Class, hard-x-ray mission.

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