It doesn't exactly state the temperature AT ALL. Though it is a large highly power super heated Plasma Cannon with special parts that increases it's power and heat to highly extreme levels.
Some of it's current parts that are in it are the:
Crystal Ball which focuses the beam as much as possible.
Energy Cart which provides more power to the cannon
Laser Device MK II (The first part which is something I made. In X5 It was only a standard Laser Device) Allows it to restore it's power as much as possible.
Then the Liquid Nitrogen Tanks: (Another part I made, in X5 it was just Hydrogen) The only thing that can keep it cool.
I'd say at max power the center of the blast would be almost as hot as the earth's core. That's only at Max Power.

