<p>A non-radioactive source for Atmospheric Pressure Ionization is described. The electron-beam sealed tube uses a pyroelectric crystal (s). One end of the crystal is grounded while the other end has a metallic cap with sharp feature to generate an electron beam of a given energy. The rate of heating and/or cooling of the crystal is used to control the current generated from a tube. A heating and/or cooling element such as a Peltier element is useful for controlling the rate of cooling of the crystal. A thin window that is transparent to electrons but impervious to gases is needed in order to prolong the life of the tube and allow the extraction of the electrons. If needed, multiple crystals with independent heaters can be used to provide continuous operation of the device.</p>
