The electrode configuration includes a cathode made of cadmium (Cd) and zinc (Zn) and an anode made of tungsten (W) with lengths of 10mm and a diameter of 100 \u03bcm each. The length of the plasma region varies from 20 \u03bcm up to 160 \u03bcm during the contact separation.
\n", "procedure": "An electric contact of a wire (anode) is established on the rough surface of a metal block (cathode). The wire is pulled away from the surface which initiates an electric discharge. The main discharge develops in metal vapour at distances between 20 \u03bcm and \u223c 200 \u03bcm (the so-called microdischarges). The wire moves further away from the surface, the released heat causes a thermochemical reaction, which can lead to the formation and the development of a flame front.
\n" }, "medium": { "name": "Cd, Zn", "properties": "The plasma is assumed to contain electrons and heavy particles of Cd or Zn atoms and singly charged Cd+ or Zn+ ions in their ground states. Admixture of air/H2 appears after the main microdischarge.
\n", "procedure": "Spark ignition occurs during the contact separation at a constant current of 60 mA. Initially, the spark is ignited in the metal vapour of Cd or Zn. Later on the gas characterising the explosive atmopshere (a mixture air/H2) is supposed to mix with the metal vapour.
\n" }, "target": { "name": "Cd cathode, Zn cathode, W anode", "properties": "Melting and evaporation of the cathode made of Cd or Zn. Thermo-field emission from the Cd/Zn cathode with precomputed values of the electric current density as a function of the electric field and the temperature on the cathode " }, "diagnostics": { "name": "fluid model, voltage measurement, OES, electrical measurements, collisional-radiative model", "properties": "A framework that combines a unified nonequilibrium plasma model and a collisional-radiative model is employed. The plasma model provides the basic plasma parameters (number densities of ground state neutral and singly charged species and their energies, electric field, discharge voltage). Number densities of excited atomic states were obtained on a second stage employing a collisional-radiative model and the already known plasma parameters. This modelling framework allowed one to obtain spatially and temporally resolved plasma parameters and the population of the excited atomic states in the entire discharge gap during the separation of the electric contacts.
\nThe electrical characteristics of the discharge have been studied and quasi-stationary current-voltage characteristics have been obtained by using a setup that includes a DC control system, oscilloscope, providing the electrical parameters with a time step of 1.6 \u03bcs, long distance microscope, image intensifier, and a high-speed camera.
The model equations are solved using a fully coupled approach. The electric current in the model has a constant value of 60mA. A steady-state solution is sought for a gap length of 20 \u03bcm to mimic the initial two phases of contact opening. Then, a deforming mesh approach is applied to simulate the moving electrode. The discharge gap was increased from 20 \u03bcm up to 160 \u03bcm with a speed of 0.14m/s.
\nA full discharge image was recorded for each wavelength with significant emission. 2D spectral images for Cd and Zn are provided.