Halo doesn't fire plasma, and if it did, tuning it to not damage structures and planets of any kind would make it worthless. Halo propels super-massive neutrinos that target neural networks at extreme superluminal speeds.

Ok. I wasn't exactly clear on the difference in firing mechanisms and functionality between Halo and the Composer beyond the obvious difference of one kills everything and the other just removes them from a physical plain of existence.