ABSTRACT
INTRODUCTION This work deals with the operation of neon-xenon and neon-helium-xenon filled signs powered by a pulsed electronic driver. In previous publications [1,2] we report on the selection of xenon based rare gas filling for the operation of new environmentally friendly signs used in publicity lighting. A strong trade off between the light output, expressed in Lux, and the lifetime, up to 20 000 hours, was demonstrated. This paper presents experiments on the performance of these xenon based discharges excited by a compact lab-developed driver. This driver delivers short duration current pulses in the microsecond range with a pulse repetition rate ranging from a few hertz up to 40 kHz. After a short description of the experimental set up, the efficiency of pulsed mercury free signs, the effect of the pulse duration on the positive column kinetics and on the chromatic coordinates are presented. EXPERIMENTAL RESULTS Experimental set up
The experimental set up allows the production of cold cathode high voltage glow discharges in mixtures of high purity rare gases. A neon tube bombarder, glass tubes equipped with conventional cylindrical electrodes and coated with various phosphors, spectroscopic (110-900 nm) and electrical (voltage and current probes) diagnostics tools are used. In this paper, a sealed sign filled with a He, Ne, Xe mixture at a pressure of 5 mbar was powered either by conventional AC transformer (3,5 kV, 50 mA, 50 Hz) or electronic ballast (4,5 kV, 50 mA, 25 kHz) or the lab developed pulsed driver. This latter delivers pulses of microsecond duration with a rise time of the voltage as short as 200 ns. The pulse shape, amplitude and repetition rate are measured across the tube connected with a resistive shunt. Typical input powers are of a few tens of watts for repetition rate in the kilohertz range.
