Design and properties of low-energy X-ray transmission windows based on graphenic carbon

Abstract

X-ray transmission windows for the low energy range, especially between 0.1 and 1 keV have been designed and fabricated based on graphenic carbon (GC) with an integrated silicon frame. A hexagonal and a bar grid support structure design have been evaluated. The bar grid design offers higher X-ray transmission and better visible light rejection than polymer-based windows, and allows vacuum encapsulation of silicon drift detectors (SDD). The high mechanical resilience of graphenic carbon is demonstrated by pressure cycle tests, yielding over 10 million cycles without damage. The data are complemented by bulge tests to determine a Young's modulus for graphenic carbon of approximately 130 GPa. Additional finite-element simulation and Raman studies reveal that the mechanical stress is not homogeneously distributed, but reaches a maximum near the anchoring points of the free standing graphenic carbon membrane. The cross-section of a vacuum encapsulated silicon drift detector (SDD) in (a) shows the highly transparent X-ray transmission window that is integrated into the top of a TO8 housing. The photograph (b) shows a prototype TO8 detector module with a graphenic carbon low-energy transmission window with an hexagonal support grid structure.