It is possible to use graphene as an arctube material of HPS and MH lamps?
No, arctube shuold be an insulator, but graphene is a conductor, it will short out the arc...
Plus graphene is a 2D structure, just an atom thick carbon layer, so just alone not possible to be used for any structural component.
It's use is, where youneed some very thin film with reasonable conductivity (for it's thickness the conductivity is very high, but as you can not make it so thick, it can not replace tradditional bulk conductors), so applications are e.g. the current distribution over the LED junction surface, a conductive layer for top of some flexible materials (flexible OLED screens,...; electrically conductive, transparent, tough for that thin surface),...