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A dielectric barrier discharge in a 2 mm air gap was studied. The experiments show that the mesh electrode and PET film really make the discharge looking homogeneous. The breakdown onset voltage in the case of a mesh electrode and PET film is 6.4 kV, considerably lower than 8 kV, the breakdown voltage in the usual case using two spherical electrodes. The field calculations show that even with this much lower voltage the gap field in the region very close to the PET film is enhanced to a value near the breakdown field in the usual case. It may be this field enhancement that initiates a corona discharge which provides seed electrons, leading to the breakdown of the whole air gap at a lower voltage. A lower voltage applied to the gap means a lower averaged field over the gap. Because the development of an electron avalanche is very sensitive to the electric field, a small decrease in the field will depress the avalanche significantly, preventing a homogeneous discharge from transiting to filament discharge. This may be the reason why a mesh electrode and PET film make the discharge look homogeneous.

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The stable homogeneous dielectric barrier discharge (DBD) is obtained in atmospheric 2–3 mm air gap. It is generated using center frequency 1 kHz high voltage power supply between two plane parallel electrodes with specific alumina ceramic plates as the dielectric barriers. The discharge characteristics are studied by a measurement of its electrical discharge parameters and observation of its light emission phenomena. The results show that a large single current pulse of about 200 μs duration appearing in each voltage pulse, and its light emission is radially homogeneous and covers the entire surface of the two electrodes. The homogeneous discharge generated is a Townsend discharge during discharge. The influences of applied barrier, its thickness, and surface roughness on the transition of discharge modes are studied. The results show that it is difficult to produce a homogeneous discharge using smooth plates or alumina plate surface roughness Ra < 100 nm even at a 1 mm air gap. If the alumina plate is too thin, the discharge also transits to filamentary discharge. If it is too thick, the discharge is too weak to observe. With the increase of air gap distance and applied voltage, the discharge can also transit from a homogeneous mode to a filamentary mode. In order to generate stable and homogeneous DBD at a larger air gap, proper dielectric material, dielectric thickness, and dielectric surface roughness should be used, and proper applied voltage amplitude and frequency should also be used.

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