I'm afraid it is as Art says, you've got to get the energy back into the ions so they keep on goin' until they fuse. This is why thermal plasmas are so popular, because it is in the nature of plasmas/gases that they just keep on bouncing around (excepting for all the radiation losses).
If you try to recover energy from a scattered particle then all of a sudden you are at Q=1.0000000001. You've got to actually put the lost energy back into the particle that lost the energy for a half-chance at being anywhere near the minimum Q=3 you could possibly get away with to turn heat back into "premium" electrical power to put that energy back into another ion.