Patent Number: 
Section: abstract

A source of electrons (10) generates a beam of free electrons which are accelerated through a vacuum chamber and collide with a target (34). The target has multiple layers of a high Z material such as tungsten or tantalum or for producing x-ray radiation when bombarded with high energy electrons. The target layers are located in sequence such that electrons that are not terminated in the first layer will pass to the second layer, and so on. This provides more efficient use of the generated electrons. The target layers are sandwiched between layers of a thermally conductive, low Z metal substrate (40), such as aluminum or copper or other material with a high thermal conductivity. Hollow passages (42) are bored in the substrate (40) to allow water or some other coolant to flow within them. As electrons strike the target (34), unwanted heat is generated along with the x-rays. The water carries the heat away from the target. As the passages are within the substrate, the water never comes into contact with the target material, and therefore, the life of the target is extended because oxidation and corrosion due to water exposure is inhibited.