EFFECT OF LIMITING ORIFICE (ANODE) GEOMETRY IN RADIO-FREQUENCY GLOW-DISCHARGE EMISSION-SPECTROMETRY

Studies are described that are focused on the evaluation of the role that limiting orifice (anode) geometry plays in the characteristics of an rf powered glow discharge (GD) atomic emission (AES) source. In particular, the role of orifice diameter on the parametric response of resonant and non-resonant state emission is investigated with regard to increasing the sputter efficiency and sensitivity of the device. Use of an extended, cylindrical anode is investigated with regard to reducing previously observed self-absorption characteristics. The roles of orifice diameter and discharge parameters on d.c. bias potential are studied and found to behave similarly to d.c. powered GD devices. Finally, the role of orifice diameter on plasma stabilization times is investigated. In all of the above investigations, use of a small (e.g. 2 mm) limiting orifice diameter is suggested for further development and analytical applications of the rf-GD-AES technique.