Window member for an x-ray device

Abstract

A window member for separating an internal environment of an x-ray device from an environment external to the x-ray device is provided. The window member comprises a substrate and a coating layer disposed upon a surface of the substrate. The substrate is formed from a polycrystalline material and is substantially transparent to low-energy x-rays. The coating layer is non-porous, covers the crystal grains at the surface of the substrate and extends into the grain boundaries therebetween, such that the coating layer forms an impermeable barrier between the substrate and the external environment.

1 . A window member for separating an internal environment of an x-ray device from an environment external to the x-ray device, the window member comprising a substrate and a coating layer disposed upon a surface of the substrate, wherein:
 the substrate is formed from a polycrystalline material and is substantially transparent to low-energy x-rays; and   the coating layer is non-porous, covers the crystal grains at the surface of the substrate and extends into the grain boundaries therebetween, such that the coating layer forms an impermeable barrier between the substrate and the external environment.   
     
     
         2 . A window member according to  claim 1 , wherein the coating layer extends into the grain boundaries to a depth of at least 100 nm below the surface. 
     
     
         3 . A window member according to  claim 1 , wherein the coating layer extends into each grain of the boundaries to a depth at which the spacing between the grains at the boundary is the atomic scale. 
     
     
         4 . A window member according to  claim 1 , wherein the coating layer forms a continuous film having a uniform thickness and covering the surface of the substrate. 
     
     
         5 . A window member according to  claim 1 , wherein the thickness of the coating layer is less than 200 nm. 
     
     
         6 . A window member according to  claim 1 , wherein the coating layer conforms to the surface profile of the substrate as defined by the crystal grains and grain boundaries. 
     
     
         7 . A window member according to  claim 1 , wherein the porosity of the coating layer is less than or equal to 1%. 
     
     
         8 . A window member according to  claim 1 , wherein the pinhole density of the coating layer is less than 10 cm −1 . 
     
     
         9 . A window member according to  claim 1 , wherein the attenuation of low-energy x-rays caused by the coating layer is less than or equal to 5% of the attenuation of low-energy x-rays caused by the substrate. 
     
     
         10 . A window member according to  claim 1 , wherein the thickness and the constituent material of the coating layer are selected in combination such that the attenuation of low-energy x-rays caused by the coating layer is less than or equal to 5% of the attenuation of low-energy x-rays caused by the substrate. 
     
     
         11 . A window member according to  claim 1 , wherein the coating layer is formed only from materials comprising elements having atomic number between 8 and 80. 
     
     
         12 . A window member according to  claim 1 , wherein the coating layer comprises an adhesion layer and a protection layer, wherein the adhesion layer affixes the protection layer to the surface of the substrate, and wherein the protection layer is non-porous. 
     
     
         13 . A window member according to  claim 12 , wherein the porosity of the protection layer is sufficiently low to prevent the surface of the substrate being exposed to atmospheric gas or liquid. 
     
     
         14 . A window member according to  claim 12 , wherein the adhesion layer comprises Al 2 O 3 , and the protection layer comprises TiO 2 . 
     
     
         15 . A window member according to  claim 12 , wherein the thickness of each of the adhesion layer and the protection layer is less than 200 nm. 
     
     
         16 . A window member according to  claim 1 , wherein the coating layer is disposed on the substrate by way of atomic layer deposition. 
     
     
         17 . A window member according to  claim 1 , wherein the coating layer comprises an electrically conductive material. 
     
     
         18 . A window member according to  claim 1 , wherein the coating layer comprises TiO 2  doped with Nb. 
     
     
         19 . A window member according to  claim 1 , wherein the coating layer has a conductivity greater than 10 −6  Sm −1 . 
     
     
         20 . A window member according to  claim 1 , wherein the substrate is substantially transparent to x-rays in the 0.5-10.0 keV energy band. 
     
     
         21 . A window member according to  claim 1 , wherein the substrate has a transmissivity greater than 90% for x-rays in the 0.5-10.0 keV energy band. 
     
     
         22 . A window member according to  claim 1 , wherein the transmissivity of the substrate and the coating layer in combination is greater than 85% for x-rays in the 0.5-10.0 keV energy band. 
     
     
         23 . A window member according to  claim 1 , wherein the transmittance of the substrate and the coating layer in combination is greater than 95% of the transmissivity of the substrate alone. 
     
     
         24 . A window member according to  claim 1 , wherein the substrate is formed from beryllium.