james: That sounds like a reasonable explanation – most (some?) of the input is recovered from the ion beam and the X-rays are gravy.
Ivy: I guess if Learner says heavy ions are more compressible, b-B11 might work better – I hope he’s right.
A thought on ion beam conversion efficiency:
It occurs to me that ions traveling through a coil to generate electricity might be analogous to wind passing through a wind turbine. Thing is though, the maximum possible efficiency for a wind turbine is about 59% ie. no more than 59% of the kinetic energy of the wind passing through the turbine’s swept area can be recovered (sometimes referred to as the “Betz law”).
http://en.wikipedia.org/wiki/Betz’_law
What is going on is that the wind must slow when it reacts with the turbine blades but cannot slow beyond a certain velocity as it must keep moving to get out of the way of the incoming wind behind it. It seems to me that a similar situation might exist for a stream of ions traveling down the annulus of a coil or past a coil for that matter. Maybe then the efficiency of ion to electrical energy conversion is similarly limited for the same reason??