A variety of medical diagnostic, laboratory, security screening, and industrial quality control imaging systems, along with certain other types of systems (e.g., radiation-based treatment systems), utilize X-ray tubes as a source of radiation during operation. Typically, the X-ray tube includes a cathode and an anode. An electron beam emitter within the cathode emits a stream of electrons toward an anode that includes a target that is impacted by the electrons.
A large portion of the energy deposited into the target by the electron beam produces heat within the target, with another portion of the energy resulting in the production of X-ray radiation. Indeed, only about 1% of the energy from the electron beam X-ray target interaction is responsible for X-ray generation, with the remaining 99% resulting in heating of the target. The X-ray flux is, therefore, highly dependent upon the amount of energy that can be deposited into the source target by the electron beam within a given period of time. However, the relatively large amount of heat produced during operation, if not mitigated, can damage the X-ray source (e.g., melt the target). Accordingly, conventional X-ray sources are typically cooled by either rotating or actively cooling the target. However, when rotation is the means of avoiding overheating, the amount of deposited heat along with the associated X-ray flux is limited by the rotation speed (RPM), target heat storage capacity, radiation and conduction cooling capability, and the thermal limit of the supporting bearings. Tubes with rotating targets also tend to be larger and heavier than stationary target tubes. When the target is actively cooled, such cooling generally occurs relatively far from the electron beam impact area, which in turn significantly limits the electron beam power that can be applied to the target. In both situations, the restricted heat removal ability of the cooling methods markedly lowers the overall flux of X-rays that are generated by the X-ray tube.
Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of possible embodiments. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below.
In one implementation, an X-ray source is provided. In such an implementation, the X-ray source includes: an emitter configured to emit an electron beam and a target configured to generate X-rays when impacted by the electron beam. The target includes a thermally-conductive substrate; two or more X-ray generating layers, wherein X-ray generating layers are separated by at least one intervening thermally-conductive layer; and one or more interface layers formed between a respective X-ray generating layer and one or both of the first thermally conductive layer or a respective intervening thermally-conductive layer.