It's maybe worth mentioning that the beams at CERN are made of quite a few particles and there was as much energy in the beam as in a high speed train (and same

It's maybe worth mentioning that the beams at CERN are made of quite a few particles and there was as much energy in the beam as in a high speed train (and same in the magnets), before the high luminosity upgrade. The beam dumps are massive pieces of graphite and concrete with water cooling. Also at these energies the wavelength is very small so the energy can be quite concentrated in a small region of space-time.