X-ray Component
Thin metal layers deposited on a beryllium or diamond window generate photons when struck by a high energy electron beam. The tungsten transmission target allows the resulting x rays to pass through the substrate and reach the sample, which is positioned very close to the focal spot. This geometry is essential for achieving high magnification in microfocus inspection systems.
Photon Emission
Electrons from the cathode are accelerated toward the tungsten layer, where they interact with the atoms to produce bremstrahlung and characteristic x rays. Tungsten is chosen for its high atomic number and high melting point, which makes it an efficient and durable material for photon production. The thickness of the layer is a trade off between the number of x rays generated and the amount of self-absorption that occurs within the metal.
Cooling the back of the target window is necessary to prevent the tungsten from evaporating or cracking under the thermal load.
Device Lifespan
Gradual degradation of the metal surface eventually leads to a decrease in x ray flux and a change in the spot size. Replacing the target assembly is a standard maintenance task that restores the imaging performance of the system to its original specifications.
