Graphenic Carbon X-Ray Transmission Windows: Design and Properties

X-ray transmission windows made of graphenic carbon (GC) are a replacement for currently used beryllium windows, offering an increased transmission while avoiding the health concerns of beryllium [1]. Here, we demonstrate improved low energy x-ray transmission windows, suited for the energy range between 0.1 keV and 1 keV based on the same window material. The direct deposition of the graphenic carbon onto a silicon substrate leads to strong silicon carbide bonds and results in a gas tight configuration with helium leak rates of the final window below 1 × 10-12 mbar l / s. Utilizing a support structure with a bar grid design, a window thickness of 140 nm, a window diameter of 7 mm, and a nominal fill factor of 85%, the low energy graphenic carbon window offers an increased transmission compared to currently used polymer windows, while offering a higher rejection of optical radiation [2]. The high stability of graphenic carbon towards high temperatures allows the vacuum encapsulation of low energy detector modules utilizing graphenic carbon transmission windows, which has previously not been possible. The high mechanical strength of graphenic carbon is validated by dynamic pressure loading tests of the window. No visible degradation nor an increased helium leak rate was observed after 10 million pressure cycles with a differential pressure of greater 1200 mbar applied across the transmission window having an open diameter of 7 mm and a GC thickness of 1 µm. Pressure bulge tests evaluated the Young`s modulus of GC to approximately 130 GPa. Raman and FE simulation studies show that the material is deposited with a high compressive stress of approximately 500 MPa and that the stress of a pressure loaded window is not distributed uniformly, but has a high peak at the edge. In addition, the high resilience of graphenic carbon is corroborated by x-ray radiation and ozone exposure tests. References: [1] S. Huebner, N. Miyakawa, S. Kapser, A. Pahlke, and F. Kreupl, IEEE Trans. Nucl. Sci. 62, 588 (2015). [2] S. Huebner et al., accepted for publication in Phys. Status Solidi B, 1-10 (2015) / DOI 10.1002/pssb.201552216     «

X-ray transmission windows made of graphenic carbon (GC) are a replacement for currently used beryllium windows, offering an increased transmission while avoiding the health concerns of beryllium [1]. Here, we demonstrate improved low energy x-ray transmission windows, suited for the energy range between 0.1 keV and 1 keV based on the same window material. The direct deposition of the graphenic carbon onto a silicon substrate leads to strong silicon carbide bonds and results in a gas tight confi...     »