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A novel single dielectric pellet DBD that is designed to facilitate studying the interaction between plasmas and catalysts is presented. The influence of material dielectric constant on plasma dynamics across a range of applied voltages is determined through the use of electrical characterisation combined with videos of the discharge. Different discharge modes in nitrogen are observed and their behaviour is characterised. A particular focus is given to the phenomenon known as 'partial discharging'. This is where incomplete plasma formation occurs between the electrodes of the reactor, which may have implications for the fair testing of catalysts in packed bed reactors. Additionally, the occurrence of an 'almond shaped' QV plot in the event of pointto-point discharging in PBRs is explained. This work provides easily implemented analytical techniques that can be applied to understand the behaviour of plasmas within packed bed DBD reactors.

Plasma is gaining increasing interest for N2 fixation, being a flexible, electricity-driven alternative for the current conventional fossil fuel-based N2 fixation processes. As the vibrational-induced dissociation of N2 is found to be an energy-efficient pathway to acquire atomic N for the fixation processes, plasmas that are in vibrational non-equilibrium seem promising for this application. However an important challenge in using non-equilibrium plasmas lies in preventing vibrational-translational (VT) relaxation processes, in which vibrational energy crucial for N2 dissociation is lost to gas heating. We present here both experimental and modeling results for the vibrational and gas temperature in a µs pulsed microwave (MW) N2 plasma, showing how power pulsing can suppress this unfavorable VT relaxation and achieve a maximal vibrational non-equilibrium. By means of our kinetic model, we demonstrate that pulsed plasmas take advantage of the long time scale on which VT processes occur, yielding a very pronounced non-equilibrium over the whole N2 vibrational ladder. Additionally, the effect of pulse parameters like the pulse frequency and pulse width are investigated, demonstrating that the advantage of pulsing to inhibit VT relaxation diminishes for high pulse frequencies (around 7000 kHz) and long power pulses (above 400 µs). Nevertheless, all regimes studied here demonstrate a clear vibrational non-equilibrium while only requiring a limited power-on time, and thus we may conclude that a pulsed plasma seems very interesting for energy-efficient vibrational excitation.

Atmospheric pressure dielectric barrier discharges (DBD) has many industrial applications and remains a focus of academic research. This chapter provides a thorough overview of electrical diagnostics for DBD, with a specific focus on charge-voltage measurement techniques. These methods are often underutilised in the existing scientific literature, despite the fact that they can provide useful insights into plasma behaviour. Both optimization of the electrical measurement setup and the interpretation of results are treated in-depth. The diagnostic techniques are discussed for a range of applications, from classic planar DBDs, to catalyst packed beds, plasma actuators, as well as techniques for measuring single microdischarges.