Electron Acceleration for X-ray Production Using Paired Pyroelectric Crystals

The exposure of pyroelectric crystals to a heating cycle in near-vacuum conditions has been shown to be a viable method of producing x-rays. The z-negative face of the crystal forms a positive charge as the crystal heats, and a negative charge as it cools. The opposite is true for the z-positive face. Literature has shown that this charge is great enough to accelerate electrons to energies of up to 170 keV. This phenomenon can be used to create small X-ray, electron and charged particle sources. X-rays are produced when the electrons in the ambient gas are accelerated by this field toward a target (when the exposed face of the crystal is negatively charged) or toward the crystal itself (when the exposed face is positively charged). In this experiment, z-cut lithium tantalate crystals with 5 mm x 5 mm surface area and thicknesses of 1, 2, 4, and 10 mm were placed in a vacuum and subjected to a thermal cycle. A 10 x10 x 0.5 mm crystal was also tested. The counts per thermal cycle and maximum energy of the x-ray spectra were shown to increase with crystal thickness. In addition, a system was explored in which two 10 mm crystals were arranged in series. This system was shown to double the maximum x-ray energy. Additional crystal thicknesses and system geometries that may further increase maximum x-ray energy and yield are currently under investigation.