Novel X-ray sources and systems using gated electron emitters

Novel X-ray sources and applications may be achieved with a combination of gateable electron micro-sources and tailored electron targets. A simple, broad area X-ray source can be constructed in a biplanar geometry, one side consisting of a low atomic number, X-ray transmissive substrate with an array of emitters, and the other side a simple metallic target. The simple metallic target can be replaced with a composite target in which different areas of the surface are coated with different X-ray emitting metals. The resulting X-ray spectrum will be the composite of spectra of all the irradiated metals. The spectrum is selected with sets of separately gated field emitter arrays, each registered to a respective anode metal. Low voltage electronics control the gate array selections. With the further addition of electron focusing within the tube and an external X-ray detector, the device becomes capable of imaging the composition of the electron target. By augmenting the device with a sample handling capability, whereby the sample is put in the location of the target, this instrument then becomes capable of X-ray compositional analysis in a manner analogous to an electron microprobe or SEM with EDX attachments. Such instruments can be miniaturized and used for automated analysis systems. The potential for low power, automated analysis by small, unmanned, distributed systems could augment the capabilities already present with high power laboratory instrumentation. An important technical issue on which the practicality of these developments depends, is the robustness of gated field emitter sources. Recent progress in this area is described.