The energy produced in this system is in the kinetic energy of particles. They would not bounce or refocus or reinforce the reaction.
The laser works off of light energy which, for the purpose of the laser, has a wavelength and a resonant cavity can be created, energy reflected, etc.
With kinetic matter particles, this would not work.
The cylindrical fusor has, indeed, been discussed, but no one has made one yet, since the farnsworth team did it in the 60's and found it wanting. But it does work, just not the way you envision.
Richard Hull
Created on Wednesday, April 04, 2001 1:25 AM EDT by Richard Hull