I think the energy deposited is almost all just from the kinetic energy of the particles. The U-70 Synchrotron from the article produced 76 GeV protons. Electr

I think the energy deposited is almost all just from the kinetic energy of the particles. The U-70 Synchrotron from the article produced 76 GeV protons. Electron-volts (eV) are a unit of kinetic energy. That works out to 0.012 microjoules per proton. This was a pulsed machine, with a repetition rate of 0.11 Hz (9 seconds between pulses). In one pulse there were 1.7×10^13 protons. That adds up to about 200 kJ per pulse: About the same kinetic energy as a Toyota Corolla (1200kg) travelling at 65km/h. As for exactly how the interaction would happen: The particles would have bounced around the atoms in Mr Bugorski's head. They would lose energy I think mostly via interactions with atomic electrons. As they decelerated, they would also throw off Bremsstrahlung photons which would create a pencil-beam of x-rays. At that energy there would also be plenty of nuclear interactions which would tend to produce neutrons and prompt gamma rays. Not all of the kinetic energy in the pulse would have been absorbed by Mr Bugorski's head. The energy deposited into a medium by a proton beam is described by the Bragg Peak. If you look it up, protons of ~200MeV would be almost entirely stopped by a human head (~20cm). But at almost 400 times that energy, I think a large fraction of the kinetic energy would just come out the other side in the form of neutrons, gammas, x-rays, and slightly slowed protons.