Surface Modification of Thin Rods by Theta-Pinching Metallic Plasmas

Metallic-ion deposition on the surface of a thin dielectric rod is successfully demonstrated by using a small theta-pinch device. This method needs no application of a negative potential and has few limits on the surface irregularities of the treatment objects. A single-turn coil surrounding a glass tube of 16.6 mm in inner diameter is excited by a capacitor discharge circuit. Nitrogen gas is filled up to 10 Pa and pre-ionized before triggering the capacitor discharge. The plasma is concentrated and expanded repeatedly with the coil current of 15-kA peak and 1.54-mus periods. Through the interaction between the expanding plasma and a metalized film placed at the inner wall of the tube, the metallic ions are generated and introduced into the pinching plasma and utilized for deposition. The pinching time of the plasma is around 0.25 mus obtained from a streak photograph. Polytetrafluoroethylene rods of 3 mm in diameter are placed at the center of the tube and exposed to the pinching plasma. An electron-probe microanalyzer analysis shows that the thickness of a deposited gold is around 10 mum after 400 shots of the discharges