The present invention pertains to RF (radio frequency) inductive coupling plasma (ICP) sources exciting and maintaining plasma within a closed and vacuum sealed discharge chamber filled with a gaseous medium at a controllable pressure in the range from 1 mTorr to atmospheric pressure. The inductively couple plasma source of the present invention includes a radio frequency source, a quasi-closed O-type solenoidal inductor comprised of two equal section U-shaped solenoid coil halves separated from one another to form two operating gaps between aligned spaced ends of the solenoid coil halves. Each of the U-shaped halves of the solenoid coil is sectioned to have an electrical midpoint connected to the radio frequency source and the distal outer ends of the solenoid coils, which correspond to the aforesaid aligned spaced ends of the quasi-closed solenoidal inductor, are connected to ground. A metallic housing having a discharge chamber therein is provided with two opposed walls having symmetrically opposed bone shaped ports. The ports are closed and vacuum sealed with insulating material and the ports each include two through side openings dimensionally respectively fitted to and engaging with the spaced ends of the quasi-closed solenoidal inductor. The bone shaped ports further include a through slot connecting the side openings along their center line for inductive excitation and maintenance of plasma in the operating gaps situated within the discharge chamber.