Introduction

Abstract

The most widespread light sources that provide a line spectrum are different gaseous discharge devices. In high-frequency (hf) electrodeless spectral lamps (ELs) the discharge is excited by a hf field, created within the lamp with the help of electrodes or inductors located outside. The hf voltage, applied to initiate and sustain the discharge, is supplied to the inductor from a hf generator or a self-excited oscillator. The lamps, usually bulbs of spherical or cylindrical form, are filled with an inert gas or with an inert gas with additives of those elements which produce the desired radiation. The pressure of the gas is usually chosen between 0.7 and 20 mbar. The frequency of the exciting field is variable, depends on the size and shape of the glass bulb, and can be chosen within a range from several up to hundreds of MHz. The exciting electrodes are usually built as either an inducing coil (inductor) or a capacitor incorporated into the electric circuit of the hf field generator. When a proper discharge mode is chosen by setting the gas pressure (in case of vapors, via temperature), the power of the exciting field, as well as taking care of the design of the lamp, the emission of intense narrow spectral lines is observed.