Abstract: The present invention provides an apparatus and process for depositing a thin layer on the surface of a transparent substrate by the known process of cathodic sputtering. Atoms for forming the thin layer are produced from four cathodic plates arranged so as to form a rectangular parallelepiped. An anode covers one open end of the parallelepiped, and the substrate receving the thin layer is placed at the other open end of the parallelepiped. A magnetic field is produced by a permanent magnet, and the entire apparatus is supported by a metal support. A cooling channel surrounds the parallelepiped to enable the cooling of the cathodic plates.