How can you create an electric current in a vacuum?

Under normal conditions, the vacuum does not conduct an electric current, since there are no charged particles in it. To create a current in the vacuum, it is necessary to introduce free charge carriers. Let’s see how this can be done. At room temperature, electrons are trapped inside the metal, despite the fact that they undergo thermal motion. The reason for this is that the surface layer of metal ions has a positive charge and, attracting escaping electrons, returns them back to the crystal lattice. However, some electrons can acquire kinetic energy sufficient to overcome the forces of Coulomb attraction. At room temperature, the number of such electrons is negligible. However, as the temperature rises, their number increases.