It is also possible to use X-rays to excite the core electrons to the point of ionization. The detector is cooled to liquid nitrogen temperatures to reduce electronic noise from thermal excitations. This promotes electrons in the plate into the conduction band, inducing a voltage proportional to the energy of the impacting X-ray which generally falls between about 1 and 10 keV. The beam is produced by an electron gun, in which electrons emitted thermionically from a hot cathode are guided down the column by an electric field and focused by a series of negatively charged “lenses.” X-rays emitted by the sample strike a lithium-drifted silicon p-i-n junction plate. The first is to use a high-energy electron beam like the one in a scanning electron microscope (SEM). There are two common methods for exciting the core electrons off the surface atoms. Adapted from Introduction to Energy Dispersive X-ray Spectroscopy (EDS), /public/manuals/EDS-intro.pdf. The arrows show the direction the vacancy moves when the higher energy electrons move down to refill the core. \) A diagram of the energy transitions after the excitation of a gold atom.
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