The characterisation of a secondary fluorescence X-ray tube for medical imaging, security screening and analytical applications

Describes the characterisation of a new prototype secondary fluorescence X-ray tube. This tube allows the user to interchange the secondary target, and thus select the X-ray tube spectrum. Measurements of the focal spot size, intensity the Kα fluorescence lines and the spectral purity of the source are presented for a range of secondary targets including tantalum, tungsten, silver, copper and a rhodium layer on tungsten. Measurements with the tantalum target confirmed that the intensity from the new Fluorex tube was of the same order as measured previously (8.5×10⁵ photons/s/mm² source area into 1×10^-4 sr) at 160 kV and 3.75 kW. This was found to be approximately 30-40 times less than the flux into a comparable energy window containing the Kα emission lines of a conventional tungsten anode X-ray tube operating at 140 kV and 3.75 kW