An electrical radiation heater arrangement for a vacuum enclosure comprises at least two sets of linear heating sources, arranged in a corresponding number of concentric heating zones, being arranged directly on the vacuum side of the vacuum enclosure and electrically connected to current rails arranged on the vacuum side with each of the current rails being connected to one electrical feedthrough from vacuum to ambient. Preferably, the heating sources are arranged in a polygon approaching a circle, essentially radially or a combination of both.