Abstract: An ozone generator (10) has a helical spring anode (12) located within a sealed glass dielectric tube (14) and a metal tube cathode (15) spaced across an annular gap (16) from glass tube (14). The dielectric/electrode subassembly (12, 14, 15, 16) is contained within a hollow cylindrical housing (25) made up of a tubular sleeve (26) centered between left and right porting collars (27, 28) and left and right end caps (30, 31). Gas inlet and outlet fittings (43, 44) connected through collars (27, 28) to flow oxygen axially along gap (16) through a varying intensity corona discharge, having maximums at centers of coils and minimums between coils of spring (12), and frequency determined by flow speed and coil twin separation. Fluid inlet and outlet fittings (50, 51) connect through sleeve (26) to pass cooling fluid along an annular conduit (47) formed between the inside of sleeve (26) and the outside of cathode (15).