Modern ion guns can produce beam energies from 10eV to more than 10keV.
What is the highest beam energy Fermilab can achieve?
The dependence of surface dose and penetration depth on beam energy is clearly visible.
The allure of beam energy is illustrated by the inefficiencies of the space shuttle.
This solution was proposed for maximum flexibility in beam energy.
As the beam energy of the electrons is increased, the total escaping electrons can be seen to increase.
Each ingot is heated with a different beam energy so that their evaporation rate can be controlled.
Historically, as radiation machines were improved in the 1930s-1940s, the beam energy (and so its penetration) were increased.
The beam energy of electrons is 1.28 GeV in normal operation.
This means that its effects diminish with increasing beam energy.