Exotic plasma bullets induced by residual electron control

Summary form only given. Atmospheric-pressure non-equilibrium plasma jets have recently received a major attention due to their widespread applications in surface and materials processing, biomedical engineering, and medicine. The discovery of fast-propagating plasma bullets opens an exciting possibility to control small bits of plasma solver sub-microsecond and possibly even nanosecond time scales. However, this fascinating phenomenon is still challenging to control and is far from being understood despite of a few mechanisms proposed.To control the dynamics of the residual electrons and the plasma channel structure and the plasma bullet propagation, we customized the DC voltage to vary it over the timescales comparable with the expected lifetime of the residual electrons. Consequently plasma plumes with exotically segmented channel structure and plasma bullet propagation are produced in atmospheric plasma jets, as shown in Fig. 1. These phenomena are explained by studying the plasma dynamics using nanosecond-precision imaging. One of the plumes is produced using 2 - 10 μs interruptions in the 8 kV DC voltage and features a still bright channel from which a propagating bullet detaches. A shorter interruption of 900 ns produces a sophisticated plume with the additional long conducting dark channel between the jet nozzle and the bright area. In this way, the bullet size, formation dynamics, and propagation speed and distance can be controlled. This may lead to the as yet elusive micrometer- and nanosecond-precision delivery of quantized plasma bits, warranted for next-generation health, materials, and device technologies.