Homoclinic chaos is sho~n to occur in the electric current measured on an electrical discharge in argon. We report a clear sequence of four hesitations followed by a reverse period doubling. The experimental signals are used io construct return time-and time of fl-igh-t
We report that dc-excited discharges in gases display current oscillations which develop into deterministically chaotic behavior. A period-doubling Oscillatory phenomena on dc current applied to a glow discharge has a long history, being first reported more than forty years ago. " These oscillations can be followed by monitoring the voltage, the light emitted, or the current, as we have done here. The main characteristic of the oscillations depends on the particular gas, total pressure, tube diameter, and so on. In spite of being known for more than forty years, no quantitative, nor even a unique qualitative, explanation of these phenomena has been given.Our experiment is schematically shown in Fig. 1. It consists of measuring the current through sealed electrical discharge tubes of spectral lamps (Pliicker's tubes) of the type commonly used to calibrate low-resolution spectra. The nonlinear element in the circuit is the lamp operating in the glow regime, excited by a dc 0-5-kV continuously adjustable high-voltage source. The discharge tube was placed in a water heat bath to stabilize its temperature. R~and R2 constitute a 100-kA ballast resistor with R2 a 10-kA wire-wound potentiometer used for fine tuning the current. Variations of the current through the lamp were measured from the voltage drop across R3 and displayed on the screen of an oscilloscope after conveniently decoupling the dc component by a capacitor C~(see Fig. 1). These variations (typically 0-0.3 mA in amplitude) were further processed to obtain the trajectory in the phase space dl/dt X1 The dc component of th. e current was measured by a 3 -, ' -digit multimeter shunted by a capacitor C2 as indicated in Fig. 1. The oscillatory phenomena to 19&7 The American Physical Society 613
We show that homoclinic chaos in the current of a DC electrical discharge is easily characterized through return maps. We derive the same information from a Poincaré section map, a time-of-flight map, and a next maximal amplitude map. The presence of a homoclinic orbit in the phase space of our system is responsible for the equivalence of the three kinds of return maps.
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