Absorber tube

The invention relates to an absorber tube, in particular for solar collectors (10) in solar thermal power plants, having at least one collector mirror (12), comprising a metal tube (22) for carrying and heating a heat transfer medium, a sleeve tube (24) enclosing the metal tube (22) for forming an annular space (26) that can be evacuated, a first container (40) disposed in the annular space (26) and filled with protective gas, wherein the first container (40) comprises an outlet opening (52) closed by a closure material (54), which releases the outlet opening (52) under external actuation for introducing the protective gas into the annular space (26), wherein the external actuation can be applied by an opening unit (67) that can be activated for releasing the outlet openings (52), and an outer ring (37) and a transition element (36) enclosing the metal tube (22) for sealing off the annular space (26). The first container (40) is fixed in the annular space (26) by means of a retaining device (50), wherein the retaining device is disposed on the outer ring (37) and/or on the transition element (36).