Saturable Inductor Based Controlled Waveform Excitation Source for Exploding Thin Film Atomic Spectroscopy

Abstract

An adjustable waveform excitation source for exploding thin film atomic spectroscopy is described. Waveform control is achieved through a saturable inductor having control windings and placed in series with the underdamped discharge tank circuit. This results in a high-current pulse for efficient sample atomization followed by a low-current measurement interval. When this is combined with gated integration, ∼15-fold increases in analysis line/background intensity ratios are observed for V and Mn. With additional inductance added to the circuit, the current and duration of both the atomization pulse and measurement interval can be adjusted independently. Other features of the excitation source include a plasma shunt capacitor, which results in more reproducible dielectric breakdown of the plasma support gas, and a variety of high-current series switches for initiating the discharge. Triggered spark gap, gravity operated spark gap, silicon-controlled rectifier, and ignitron switches are compared with respect to resistance and switching time jitter. Examples of discharge current and voltage waveforms and preliminary analytical data are presented.