[benman94]

Also note that WeekendHacker's analysis of ion deflection/ion burn size is incorrect. An ion is NOT deflected by 10% of the deflection angle the electron beam undergoes. He's completely missing the fact that the ions in a magnetic focus tube are NOT being focused before undergoing the minute degree of deflection they experience. Well, they are being focused, but again, the magnetic field has such a minute effect on the ions, that they are essentially unfocused in comparison with the electron beam. If you had a 'static focus tube like a 12AP4 or a 9AP4, you should see a MUCH smaller ion burn because the ions are focused along with the electron beam, and then deflected to a marginal degree by the magnetic field. The ion burn on a 12JP4 is comparatively large because the ions are essentially unfocused. The large burn is NOT a product of deflection; his assertion that the ions are undergoing 10% of the deflection experienced by an electron is absolute hogwash.

Does anyone have a photo of a 12AP4 or 9AP4 with a really bad ion burn?

Edit again:

The issue of focus is actually what has prevented fast neutron beam therapy from taking off. For certain tumors, especially tumors that are extremely hypoxic, neutron beams do more damage to the rogue DNA than proton beams, X-ray photons, etc. There's a problem with a neutron though: they are both relatively massive, and chargeless (well it may have a charge around 10^-22 e, so essentially chargeless). Because they are changeless, we can't focus them electro-statically or magnetically, so we must resort to collimating a "beam" from the neutrons produced. This is incredibly inefficient, and shaping the beam can be a bit of a challenge. The ion beam in a magnetic focus, magnetic deflection tube is analogous in some respects to a neutron beam: you'd better produce it with the direction you prefer, because you can't do anything to deflect/focus it later.