X-ray Fluorescence in Member States: Austria. A Low Power Mo Tube TXRF Spectrometer with Electrically Cooled Silicon Drift Detector

The design of a compact TXRF spectrometer yielding detection limits in the range of 10 pg for the medium Z elements like Rb is described. An air cooled Mo anode X ray tube (Oxford XTG), focus size approximately 100 x 120 μm2 and 50 W power, thus operational with 50 kV and 1 mA from a compact small light weighted X ray generator (Matsusada, JAPAN) forms a compact source for TXRF. High voltage and tube current of the generator is computer controlled and allows remote adjustment according to dead time depending on the sample. The beam is emitted from a point like focus and is collimated by a slit of 50 μm. Next in the beam path is the multilayer monochromator of 25 mm diameter on a quartz substrate (Mo-Si with a 2d spacing of d=4 nm, AXO Dresden), which delivers an intensive monoenergetic beam due to the high reflectivity offered. The multilayer is seated in an Al holder and can be adjusted by means of a combination of rotator and translator stages to easily find the Bragg condition for the high intensive Mo-Ka which is then the excitation energy.