Modern physics lab experiments using crystal X-ray generators

Crystal X-ray generators can be made using small pyroelectric crystals such as LiTaO{sub 3} surrounded by gas at pressures of typically 15 mT. When heat is applied to one surface a strong electric field is produced at the opposite side of the crystal and electrons are accelerated toward it, giving rise to Ta L and M x-rays. On cooling the direction of the electric field reverses and a target x-ray spectrum is obtained. Two x-ray generators are described: The first is a sealed battery-powered, portable device, which can be used in routine lab experiments, such as the study of characteristic x-rays, x-ray absorption edges and x-ray fluorescence. The second is more sophisticated and is used for more advanced students. The object is to gain a better understanding of crystal x-ray generators by varying parameters such as the temperature range through which the crystal is cycled or the gas pressure or gas-type or the crystal to target distance. For both generators the decay time of the x-ray intensity can be studied as well as the x-ray spectra.