Development of High Power X-Ray Generator with LaB₆ Cathode and its Application to Fluorescence XAFS Measurement

Abstract
The NRIM super XAFS is a high-power X-ray generator equipped with a compact rotating anode and a lanthanum hexaboride (LaBs) cathode, specially developed for XAFS experiments. The design is different from the conventional source for X-ray diffraction, and the electron gun has enabled an extremely high tube-current (-1,100 mA) even at low tube-voltage (14.5 ~ 19.0 kV) when the beam is focused (around 0.07 mm at 6 deg. take off). The generator has an excellent stability and the filament life has been significantly prolonged by the unusual high vacuum specification of the tube. When a Johansson-type spectrometer is combined, intense monochromatic X-rays (5 x 10⁶ ~ 10⁷ counts/(sec-mm²) at the sample position), which are completely free from higher order harmonics and tungsten contamination lines, are available. The present system has been applied to the fluorescence XAFS measurement, and it has been found that the spectrum with good quality can be obtained for thin films vrithin 0 . 3 ~ 1 day, and as for a transmission technique, the measuring time is quite short, 30 min ~ 2 h.