Visible micron-sized particles in an electropositive gas

We present micron-sized particles existing in a central plasma space. The particles were taken in an electropositive N2 discharge using a digital in-line holography (DIH) system. Apart from the crystalline particles, DIH images showed a variety of filaments as well as closed loops formed by dark particles and streams of gray particles. The electric current characteristic of filaments and loops indicates that the dark and gray particles are negative in charge. As real-time monitored, the particles showed fluctuations in shape, spatial location and gray scale level. On average, the shifts in the lateral and vertical directions of particles were within one pixel distance, which is advantageous in diagnosing plasma.