I have found two main theories that would entail particle beams. The first I have found from several places, and the second is one I have come up with. Both of these theories would utilize light emitted from the hilt (a powerful LED would work well) to make the beam visible, ideally bouncing off of the individual particles and thus being diffused.

The first idea would use a beam of particles that is constantly circulating from the hilt. Imagine a fountain of particles (electrons, protons, or whole atoms) -- they are shot out, then arc back towards the hilt and shoot back out again. There actually are particle accelerators that can accelerate charged particles in an oval shape, but this requires that the whole beam be within the accelerator.

In addition, it would require an extremely strong magnet to get the electrons to arc back after being shot out of the hilt -- otherwise, it would just turn into a particle beam blaster. Perhaps some sort of "force field" could be produced that can have a magnetic charge at the top. This would also facilitate the vaccuum required for this to work.

The second idea, I think, gets around the massive magnetic field that would be required to arc electrons back. Instead of going all the way out and arcing back, they would rotate in a circle. Both protons and electrons would have to be utilized; they would attract each other obviously, and so would provide a more substantial blade. In addition, I think if there was enough of an attraction between the protons and electrons and they were both rotating fast enough, the blade would be able to conduct torque, which is what would make you able to hit objects with it and repel other blades.

The video below illustrates the second idea: