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Leibniz Institute for Plasma Science and Technology
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17489 Greifswald
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The Leibniz Institute for Plasma Science and Technology (INP) is the largest non-university institute in the field of low temperature plasmas, their basics and technical applications in Europe. The institute carries out research and development from idea to prototype. The topics focus on the needs of the market. At present, plasmas for materials and energy as well as for environment and health are the focus of interest.

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Modelling microdischarges in metal vapour of cadmium in comparison with electrical measurements - Dataset

Thermal Plasma Technology

The dataset provides the data related to the modelling of microdischarges in metal vapour of cadmium. Such microdischarges occur in a testing equipment for the safety assessment of electric devices for explosion protection. A one-dimensional unified non-equilibrium model that resolves the entire discharge gap is employed and simulations are conducted for a constant current of 60mA with gap lengths varying between 20 μm and 160 μm. These conditions match the experiment and enable a comparison with measured data. The predicted discharge voltage obtained as a function of the discharge length is compared to the measurements and shows a good agreement. The model provides the heat generation relevant to the prediction of a gas mixture ignition.

microdischarge
fluid model
cadmium
FieldValue
Group
INP
PTB Berlin
Authors
Baeva, Margarita
Jovanović, Aleksandar
Methling, Ralf
Bratek, Dominik
Schüler, Niklas"
Carsten
Uhrlandt, Dirk
Release Date
2025-09-12
Identifier
154919d7-75ef-4b51-a86a-0c653b06fb79
Permanent Identifier (DOI)
10.34711/inptdat.943
Permanent Identifier (URI)
https://www.inptdat.de/node/943
Is supplementing
10.14311/ppt.2025.2.112
Plasma Source Name
Cadmium microdischarge
Plasma Source Application
safety assessment
Plasma Source Specification
DC
atmospheric pressure
non-thermal
Plasma Source Properties

The electrode configuration includes a cathode made of cadmium (Cd) and an anode made of tungsten (W) with lengths of 10mm and a diameter of 100 μm each. The length of the plasma region varies from 20 μm up to 160 μm during the contact separation.
Plasma Source 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 μm and ∼ 200 μm (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.
Plasma Medium Name
air-H2_Cd
air
H2
Cd vapour
Plasma Medium Properties

The plasma is assumed to contain electrons and heavy particles of Cd atoms and singly charged Cd+ ions in their ground states. Admixture of air/H2 appears after the main microdischarge.
Plasma Medium 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. Later on the gas characterising the explosive atmopshere (a mixture air/H2) is supposed to mix with the metal vapour.
Plasma Target Name
Cd cathode
W anode
Plasma Target Properties
Melting and evaporation of the cathode made of Cd. Thermo-field emission from the Cd cathode with precomputed values of the electric current density as a function of the electric field and the temperature on the cathode
Plasma Diagnostics Name
fluid model
voltage measurement
OES
electrical measurements
Plasma Diagnostics Properties

A unified non-equilibrium fluid in one dimension is used to obtain the plasma parameters in Cd metal vapour. It considers the ground state atoms and singly charged ions of Cd. The model solves the equations for conservation of species, energy of electrons and heavy particles (atoms, molecules, ions), the Poison equations for the electric potential, the heat transfer in the electrodes for a current level controlled by an external circuit. A collisional-radiative model for the population of the excited states of Cd atoms can be considered in a second step.

The 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 μs, long distance microscope, image intensifier, and a high-speed camera.
Plasma Diagnostics Procedure

The model equations are solved using a fully coupled approach. The plasma domain is resolved in 1600 mesh elements and 300 elements are used for the electrodes. The electric current in the model has a constant value of 60mA. A steady-state solution is sought for a gap length of 20 μm 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
140 from 20 μm up to 160 μm with a speed of 0.14m/s.
The discharge length is measured along the line connecting the strongly emitting anode and cathode areas. The length is defined as the distance between the endpoints, which represent the half of the maximum emission intensity. The discharge width is taken along lines that are perpendicular to the central line. Here again, the value at the half-maximum of the emission intensity is considered. Over 600 measurements for 15 discharges were carried out with a current of 60 mA.
Language
English
License
Creative Commons Attribution 4.0 International (CC BY 4.0)
Public Access Level
Public
Contact Name
Baeva, Margarita
Contact Email
baeva@inp-greifswald.de
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Modelling microdischarges in metal vapour of cadmium in comparison with electrical measurements

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