![Table 2 Characteristic properties of a microdischarge channel in air at atmospheric pressure [1]](/figures/table-2-characteristic-properties-of-a-microdischarge-bxed6860.webp)
![Fig. 9. Lichtenberg figures for the BD in (a) Xe [1] and (b) air (single +15kV pulse [36]).](/figures/fig-9-lichtenberg-figures-for-the-bd-in-a-xe-1-and-b-air-35anzciy.webp)
Q2. What future works have the authors mentioned in the paper "The barrier discharge: basic properties and applications to surface treatment" ?
The possibility to treat or coat surfaces at low gas temperature and pressures close to 1 atm is an important advantage of their application. There is a great potential for BD plasma processing in future.
Q3. What is the optical system shown in the left upper part of the figure?
Spatial resolution and scanning over the microdischarge axis was provided by the optical system shown in the left upper part of the figure.
Q4. Why do microdischarges change their positions randomly?
At high amplitude of the applied voltage (and low operation frequency), the microdischarges change their positions randomly on the surface because of the nearly homogeneous distribution of residual charge on dielectric [19].
Q5. What is the main reason for the formation of diffuse BDs at atmospheric pressure?
The generation of stable diffuse BDs at atmospheric pressure requires special operation conditions, that are mainly determined by the propertiesof feeding gas.
Q6. What are the conditions of non-thermal plasmas?
The conditions of non-thermal plasmas are mainly characterized by a relatively low temperature of the neutral gas in contrast to a significantly higher kinetic temperature of the electrons.
Q7. What is the frequency of the feeding voltage?
Thedensities of residual species from the previous halfperiod that can initiate the diffuse discharge generation in the next half-cycle, are dependent on the repetition frequency.
Q8. What are the advantages of dielectric barrier discharges?
These discharges demonstrate a great flexibility with respect to their geometrical shape, working gas mixture composition and operation parameters (e.g. power input, frequency of feeding voltage, pressure, gas flow) [1,2].
Q9. How is the discharge of a plasma maintained?
Thenon-equilibrium between these main components is permanently maintained by applying DC or AC electric fields to the discharge electrodes.
Q10. What is the ns range of the microdischarge channel?
The development of microdischarge channels, which is characterized by the production of high-energy plasma electrons, takes place in the ns range.
Q11. What is the quantity of the light pulse intensity?
The measured quantity is actually a time delay between these two signals, and the recorded quantity is a probability density function for the light pulse intensity evolution.
Q12. What is the typical shape of a microdischarge channel?
At the dielectric surface the microdischarge channels continue as surface discharges covering a much larger area than the diameter of the filament.
Q13. Why do the microdischarge channels emerge at fixed positions?
The microdischarge channels have the tendency to emerge always at fixed positions (‘‘spot formation’’) because of a memory effect.
Q14. What is the ms scale of the BDs in helium?
In helium effective ionization and excitation processes occur in the electric field of the cathode region by direct collisions of atoms with energetic electrons and by three body processes, generating He+ and He2 + ions (glow mode) [18,31,52].
Q15. What is the main reason for the transition to the filamentary BD?
The properties of the microdischarges of filamentary BDs do not depend on the external driving circuit (e.g. the frequency, feeding voltage wave form) over a wide range of operationconditions.
Q16. What is the phase of the microdischarges in the plasma?
the phase of plasma chemical reactions by atoms, radicals, excited species and short waved radiation typically starts within the ms scale.
Q17. What is the total current in the outer circuit?
There are two components forming the total current in the outer circuit: the displacement current driven through the dielectric material and the net discharge current (compare the details in Fig. 15a).
Q18. What is the dominant method of ionization of nitrogen molecules in the ground state?
in dry air (already in nitrogen with an admixture of about 500 ppm oxygen [49]), the direct ionization of nitrogen molecules in the ground state by electrons is dominant.