I was reading up on electrostatic particle accelerators when I read a statistic stating the efficiency of converting wall electrical power (the electrical power from the outlet) into beam power in an accelerator. I tried finding out why this was the case and doing some first cut calculations. The most I could come up with was a lot of the power gets wasted by particles not being efficiently collimated, I.E. most of the accelerated particles hit the wall. Now, I'm pretty sure that is not the only reason, I assume depending on the quality of the vacuum, scattering by the leftover gas molecules would also contribute to the lost beam power, as well as losses via emitted radiation from focusing the charged particles with magnetic fields.
Am I getting this right? Or am I missing some huge power draw that sucks most of the power away from the beam? I know the efficiency depends somewhat on the beam maximum energy (since higher energy beams have higher brehmstrahlung and cyclotron radiation losses), I'm looking at the power efficiency of a 10 MeV electrostatic electron beam accelerator.
Why are 10 MeV electron electrostatic particle accelerators so inefficient?