Development of a Palm-size Electron Probe X-ray Analyzer

An electron probe microanalyzer (EPMA) with a palm-size chamber including the electron source and the sample stage was developed using a pyroelectric crystal. Energy of obtained continuous X-rays and lower limits of detection of transition metals (titanium, iron, and nickel) were evaluated. End point energy (Duane-Hunt limit) of obtained continuous X-rays was about 40 keV, but the palm-size EPMA can analyze characteristic X-rays with energies less than 20 keV due to the small amounts of electrons with energies above 20 keV. It is possible to measure thin metal wires of titanium, iron, and nickel with the palm-size EPMA. Their lower limits of detection were 0.081 mm for titanium, 0.051 mm for iron, and 0.057 mm for nickel as surface areas, respectively. INTRODUCTION Brownridge (1992) first reported that it is possible to generate X-rays using pyroelectric crystals. After that, Brownridge and his co-workers developed the X-ray generator (Brownridge, 2004; Tornow et al., 2008), and then Amptek Inc. commercialized a portable X-ray generator using a pyroelectric crystal. The X-ray generator can produce X-rays with the Duane-Hunt limit of 35 keV. Geuther et al. (2005) reported that they fabricated an X-ray generator using a paired-crystal of lithium tantalate (LiTaO3) and that X-rays with the Duane-Hunt limit of 215 keV were generated. Hiro et al. (2010) reported that they developed a portable X-ray tube which consisted of a paired-crystal of LiTaO3 and that characteristic X-rays of copper and zinc were obtained by putting a brass plate on a LiTaO3 crystal in the portable X-ray tube. This result implies that it is possible to develop a small size electron probe microanalyzer (EPMA) using a pyroelectric crystal if samples were placed instead of the brass plate. In the present study, we developed the small size EPMA with a palm-size chamber including the electron source and the sample stage based on Hiro’s idea and evaluated the performance of the palm-size EPMA. EXPERIMENTAL The apparatus we developed in the present study is shown in Figure 1 (a). As for an electron source of the apparatus, single crystal of LiTaO3 (Shin-Etsu Chemical) was attached on a Peltier device with silver paste. The size of the LiTaO3 crystal was 3 mm × 3 mm in the x-y plane and 5 mm in the z-axis, and the top face of the LiTaO3 crystal was the –z plane. The other face of the Peltier device was attached on a copper rod with silver paste, and a copper wire was connected between silver electrode on the top surface of the Peltier device and the copper rod (Figure 1 (b)). The center of the bottom of the copper rod was drilled in order to insert a wire of the Peltier device, and the exit of the hole was closed with low vapor pressure resin. The sample stage was attached on another copper rod, whose bottom had a hole in the center, with silver paste (Figure 1 (c)). The copper rod was connected to an oil-sealed rotary pump through a vacuum joint. The sample stage had 45 gradients and consisted of brass. Samples were placed on the sample stage Copyright ©JCPDS-International Centre for Diffraction Data 2012 ISSN 1097-0002 252