Patent Number: 
Section: claims

1. An x-ray window comprising:a support-frame encircling an aperture and having a top-side and a bottom-side, the top-side and the bottom-side parallel with respect to each other;a boron-film and an aluminum-film spanning the aperture of the support-frame;the boron-film having ≥90 weight percent boron throughout the entire boron-film, and having a near-side and a far-side opposite of each other;a hermetic-seal between and adjoining an outer-ring of the near-side of the boron-film and the top-side of the support-frame, the hermetic-seal is a direct bond between the boron-film and the support-frame and is free of the aluminum-film;the aluminum-film adjoins the near-side of the boron-film inside of the outer-ring;ThF≤1.25*(Th12+Th52), where ThF is a minimum thickness of all thin films spanning the aperture, Th12 is a minimum thickness of the boron-film in the aperture, and Th52 is a minimum thickness of the aluminum-film in the aperture; andan annular-film adjoining the bottom-side of the support-frame, having an aperture aligned with the aperture of the support-frame, and including ≥90 weight percent boron throughout the entire annular-film. 2. The x-ray window of claim 1, wherein the aperture of the support-frame is free of support ribs and 300 nm≤Th12≤1200 nm. 3. The x-ray window of claim 1, wherein the aperture of the support-frame is free of material of the support-frame. 4. The x-ray window of claim 1, wherein solid material in the aperture consists of thin films spanning the entire aperture. 5. The x-ray window of claim 1, wherein a maximum total thickness of all thin films in the aperture is ≤4000 nm. 6. The x-ray window of claim 1, wherein a percent thickness difference between the boron-film and the annular-film is ≤20%, where the percent thickness difference equals a difference in minimum thickness between the boron-film and the annular-film divided by a minimum thickness of the boron-film. 7. The x-ray window of claim 1, further comprising ≥0.05 weight percent hydrogen throughout the entire boron-film and the entire annular-film. 8. The x-ray window of claim 1, wherein the boron-film and the annular-film have an identical material composition. 9. An x-ray window comprising:a support-frame encircling an aperture and having a top-side and a bottom-side, the top-side and the bottom-side parallel with respect to each other;a boron-film hermetically-sealed to the top-side, spanning the aperture of the support-frame, the boron-film having ≥90 weight percent boron throughout the entire boron-film; andan annular-film hermetically-sealed to the bottom-side, having an aperture aligned with the aperture of the support-frame, and including ≥90 weight percent boron throughout the entire annular-film. 10. The x-ray window of claim 9, wherein ThF≤1.5*Th12, where ThF is a minimum thickness of all thin films spanning the aperture, and Th12 is a minimum thickness of the boron-film in the aperture. 11. The x-ray window of claim 9, further comprising an aluminum-film spanning the aperture of the support-frame; the aluminum-film having ≥50 weight percent aluminum throughout the entire aluminum-film; and the aluminum-film and the boron-film are the only solid structures spanning the aperture of the support-frame. 12. The x-ray window of claim 9, further comprising an aluminum-film spanning the aperture of the support-frame, the boron-film faces atmospheric pressure, and the aluminum-film faces a vacuum. 13. The x-ray window of claim 9, wherein a percent thickness difference between the boron-film and the annular-film is ≤20%, where the percent thickness difference equals a difference in minimum thickness between the boron-film and the annular-film divided by a minimum thickness of the boron-film. 14. The x-ray window of claim 9, further comprising ≥0.05 weight percent hydrogen throughout the entire boron-film and the entire annular-film. 15. The x-ray window of claim 9, wherein the boron-film and the annular-film have an identical material composition. 16. An x-ray window comprising:a support-frame encircling an aperture;a boron-film spanning the aperture and hermetically-sealed to the support-frame;the boron-film having ≥97 weight percent boron, ≥0.3 weight percent hydrogen, and a density of ≥2.04 g/cm3 and ≤2.24 g/cm3; andThF≤1.5*Th12, where ThF is a minimum thickness of all solid structures spanning the aperture and Th12 is a minimum thickness of the boron-film in the aperture. 17. The x-ray window of claim 16, further comprising:the support-frame has a top-side and a bottom-side opposite of each other;the boron-film is hermetically-sealed to the top-side; andan annular-film hermetically-sealed to the bottom-side, having ≥97 weight percent boron, ≥0.3 weight percent hydrogen, and a density of ≥2.04 g/cm3 and ≤2.24 g/cm3. 18. The x-ray window of claim 16, further comprising an aluminum-film adjoining an inner-side and a bottom-side of the support-frame. 19. The x-ray window of claim 17, wherein the boron-film faces atmospheric pressure and the aluminum-film faces a vacuum. 20. The x-ray window of claim 16, wherein the aperture is free of support ribs and 300 nm≤Th12≤1200 nm.