Abstract: An effusion source for epitaxial deposition plants wherein molecular vapor beams are directed towards a substrate to be grown in ultrahigh vacuum environment, which has a first tube, which is airtightly closed at one end by flanges allowing the passage of vapor inlet tubes and is equipped at the the other end with baffle plates and a nozzle for mixing vapors and shaping the molecular beam. A second tube, coaxially joined to the first tube, allows an interstice at ambient pressure and temperature to be obtained in the zone of the vapor mixing and molecular beam shaping, wherein a heating can be located.