# Would a charged particle moving through a carbon nanotube experience no or negligible bremsstrahlung?

The context here is for beam-target fusion. The supposition is that it would actually possible to achieve breakeven with an accelerator-based system and cold targets based solely on a modest electrical acceleration (~10 keV) and the D-D fusion cross section (see here, page ~70 and surrounding discussion). What kills the efficiency of this system is the bremsstrahlung losses between the particles and the "cold" (i.e. <<1 million K) electrons of the target.

However, if one derives the Bethe-Block formulation for stopping power, there is a symmetric cancellation of the parallel force between the moving charge and the stationary electrons. The entire interaction is mediated through perpendicular force between the charged particle and the cold electron. (can't cite more than 2 links, but you can Google to find what I'm talking about).

So the question is, could these forces be suppressed to zero or near-zero for particles travelling down the axis of a 2D electron system like, say, a carbon nanotube? Such a system would have very little polarizability out-of-plane (perpendicular to the particle's velocity vector).

More broadly, is there research on how to manipulate bremsstrahlung interactions based on electron dynamics in confined (i.e. nanotube/nanowire/2D sheet) electronic systems?

• My unverified thought: D-D reactions will overwhelmingly not occur due to Coulomb repulsion, even in a nanotube (it does not change the problem). The issue is not only the target "spectator" atoms causing losses, but the bremsstrahlung between "fuel" atoms. – fffred Dec 13 '16 at 22:57
• At 10keV the D-D cross section is well below $10^{-4}$ barns. By 100keV it is well over 1 barn. You really don't want to be down at 10keV. But, what is the point of the nanotube? Accelerate D in to a gas of deuterium... – Jon Custer Dec 13 '16 at 23:23