This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

The mechanisms responsible for memory effect in nitrogen at 6.6 mbars have been analysed based on experimental data of electrical breakdown time delay as a function of afterglow period. The analysis has shown that positive ions remaining from previous discharge, as well as metastable and highly vibrationally excited molecules, are responsible for memory effect in the early afterglow. These molecules lead to the formation of positive ions in mutual collisions in the afterglow. Positive ions initiate secondary electron emission from the cathode of a nitrogen-filled tube when voltage higher than static breakdown voltage is applied on the electrodes. On the other hand, N(S4) atoms have a large influence on memory effect in late afterglow. They recombine on the cathode surface forming N2(AΣ3u+) metastable molecules, which release secondary electrons in collision with the cathode. The higher values of electrical breakdown time delay in the case of the tube with borosilicate glass walls than in the case of the tube with copper walls are a consequence of faster de-excitation of neutral active particles on the glass. Indirect confirmation of this assumption has been obtained when the tubes were irradiated with gamma radiation.

Experimentally measured electrical breakdown time delay data versus the afterglow period (representing ‘memory curves’) for nitrogen-filled tubes at pressures of 6.6 and 13.3 mbar have been shown. The influence of N(4S) nitrogen atoms on secondary electron emission from the cathode (the SEE process) in late afterglow has been discussed. N(4S) atom concentration decay over relaxation time τ, N(4S)(τ), has been analysed by a numerical model and two analytical models. N(4S) decay analytical models are combined with different yield models that describe the SEE process by N(4S) and these combinations are employed to fit the experimental data. It has been shown that in late afterglow solving of very simple analytical equations instead of numerical solving of partial differential equations for N(4S)(τ) fitting can be used and that the combination of the first and the second order of the SEE process by N(4S) in yield modelling should be used in the case of 13.3 mbar pressure.

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The processes which are a consequence of neutral active particles presence in post-discharge nitrogen-filled tube at 13.3 mbar pressure have been analyzed. The analysis has been performed based on the experimental data of electrical breakdown time delay as a function of afterglow period τ. The most significant parameters such as applied voltage, discharge current, time, and exposure to radiation have been varied. It has been shown that the increase in applied voltage and discharge time, as well as exposure to UV radiation, leads to the decrease of the mean value of electrical breakdown time delay t¯d. This decrease occurs for τ>70 ms, when N(S4) atoms play a dominant role in breakdown initiation. The increase in discharge current leads to the decrease of t¯d values for τ≤70 ms, when positive ions dominantly induce breakdown. The most important reactions which lead to formation of positive ions and neutral active particles are also presented in the paper.