I'm not sure either, but looks like some kind of time delyed NEON lighting.
If it's neon, then it would not make a good FX lightsaber because Neon needs to be incased in Glass and glass shatter upon impact.
It could also be Plasma. Which would explain the large distance between the lighting shell and blade shell.
I would bet that is some kind of low votage plasma saber. Which is dangrous in a larger 1:1 scale.