I don't see a problem with NegaBlaster. You've explained what it stands for and it'll only be the odd person who construes it the wrong way. Even then, any publicity is good publicity.
It's supposed to be shortened for Negative Blaster. But I suppose there is the odd person who would think that, I guess I can consider giving it a different name as RPGFan suggested then.
Negablaster actually sounds like a good name, but if it's still pending and you're open to suggestions... how about Psi-blaster or Psion Pulser or something like that.