x - ray diagnostic system . the system includes a source of x - rays which communicates with an x - ray beam concentrator spaced apart from the x - ray source and disposed for receiving x - rays from the x - ray source . an x - ray spectrometer is disposed for receiving x - rays from the concentrator . in a preferred embodiment , the concentrator is formed of a cylindrical spiral of a metal - coated plastic material having a surface for reflecting x - rays . in another embodiment , the concentrator includes a plurality of concentric nested cylinders of a metal - coated plastic material for reflecting x - rays . in yet another embodiment , the concentrator is a glass capillary bundle . the concentrator allows the spectrometer to be spaced away from the source of x - rays such as scanning electron microscope .