Arradiance (United States)

The X-ray reflectance of Pt-based coatings deposited by atomic layer deposition (ALD) has been measured in support of assessing the feasibility of using this deposition method for the production of X-ray mirror coatings that can achieve high X-ray reflectance without causing unacceptably large degradation of mirror figure as a result of coating stress-driven substrate deformation. Specifically, reflectance measurements of single-layer Pt, Al 2 O 3 /Pt bilayer, and Al 2 O 3 /Ni/Pt trilayer coatings grown by ALD on flat Si substrates were made using synchrotron radiation at X-ray energies in the range from 0.35 to 10 keV, revealing that the reflectance of the bilayers and trilayers is superior to that of single-layer sputtered Ir below 3.5 keV. Single-layer Pt and Al 2 O 3 /Pt bilayer coatings produced using thermal ALD were also deposited onto both the front and back surfaces of thin, figured, sub-arcsecond-quality X-ray telescope mirror segments made of polished, single-crystal Si, without discernible degradation of surface figure. These results, along with the successful implementation of batch-coating of two such mirrors simultaneously with high-reflectance coatings grown by thermal ALD, demonstrate the viability of employing stress-balanced, double-sided ALD coatings to mitigate substrate deformation resulting from film stress in high-reflectance coatings. This approach may thus enable the mass production of high-performance, sub-arcsecond X-ray telescope mirrors.

Atomic layer deposition (ALD) technology is used to nanoengineer functional films inside the pores of microchannel plate (MCP) electron multipliers, enabling a novel MCP manufacturing technology that substantially improves performance and opens novel applications. The authors have developed custom tools and recipes for the growth of conformal films, with optimized conductance and secondary electron emission inside very long channels (∼6–20 μm diameter and >600 μm length, with tens of millions of channels per single MCP) by ALD. The unique ability to tune the characteristics of these ALD films enables their optimization to applications where time-resolved single particle imaging can be performed in extreme conditions, such as high counting rates at cryogenic temperatures. Adhesion of the conductive and emissive nanofilms to the 20 μm pore MCP glass substrates and their mechanical stability over a very wide range of temperatures (10–700 K) were confirmed experimentally. Resistance of ALD MCPs was reproducible during multiple cool-down cycles with no film degradation observed. Optimizing resistance of novel MCPs for operation at cryogenic temperature should enable high count rate event detection at temperatures below 20 K.