In a typical X-ray tube (which is also a cathode-ray tube), electrons (negative) are accelerated from the cathode (also negative) towards the anode (positive).

In a typical X-ray tube (which is also a cathode-ray tube), electrons (negative) are accelerated from the cathode (also negative) towards the anode (positive). A medical imaging X-ray operates at 150 kV, while a radiotherapy linear accelerator (LINAC) usually goes up to 22 MV. However, in these applications, the electrons are "pulled" by the anode as well as "pushed" by the cathode and RF cavities (RF only used in LINAC). In CRT televisions, the X-rays generated by the tube are shielded by a special glass screen containing strontium and barium. In this case, what is interesting is not the voltage per se, but the fact that the electron beam is polarized. A typical electron beam does not have aligned spins. In the Brookhaven setup, the electrons are spin-aligned. The full article subtitle is: >Scientists and engineers develop world's highest-voltage, highest-intensity polarized photocathode electron gun, a crucial component for the future Electron-Ion Collider COTS X-ray systems use mostly thermal emission tungsten filament cathodes or, rarely, field-emission carbon nanotube cathodes. The carbon nanotubes sound fancy but are mostly known for fancy sales pitches and frequent repair tickets. Photocathodes are a specialized technique.