A Noisy Hollow-Cathode Tube in Pulsed and Continuous Excitation Regimes

Abstract

The noise characteristics of the optoelectronic channel in an atomic-absorption spectrometer were studied. The spectrometer may be used with spiral and graphite electrothermal atomizers. The noise was measured during the development of a glow discharge in a hollow-cathode tube (HCT) at current-pulse lengths of 50 and 500 μs and a filling factor of 2–20. It was found that the rms noise level in the optoelectronic channel decreased with increasing duration of the current pulses in the HCT. The results are compared to the rms noise level in the optoelectronic channel under conditions of continuous HCT feeding. The noise component of the relative measurement error is shown to be 5–10%, depending on the material of the HCT cathode and the measurement time (with reference to the beginning of the current pulse). It is demonstrated that the HCT is suitable for atomic-absorption spectrometers with the pulsed and continuous excitation.