An apparatus and a process for generating, accelerating and propagating beams of electrons and plasma at high density, the apparatus comprising: a first dielectric tube, which contains gas; a hollow cathode, which is connected to said first dielectric tube; a second dielectric tube, which is connected to said hollow cathode and protrudes inside, and is connected to, a deposition chamber; an anode, which is arranged around said second dielectric tube, in an intermediate position; means for applying voltage to said cathode and said anode; means for evacuating the gas from the chamber; and means for spontaneous conversion of gas in the first dielectric tube into plasma.