Traditionally users of x-ray spectrometers have been forced to optimize their instrument for light element analysis and heavy element analysis through the choice of either a light or heavy element anode. The advent of the rhodium tube brought some relief to this situation, but some compromise was still required. The recent addition of the scandium side-window tube to the range has provided twice the excitation efficiency of the chromium tube, whilst providing an equivalent heavy element performance.

In the past there have been attempts to produce x-ray tubes combining the properties of both light and heavy element tubes. An example of this is the dual-target tube which has two preferentially excited targets (anodes) of different materials constructed side-by-side.