Observation of plasma bullet with a charge-coupled device camera and a photo-sensor amplifier

Summary form only given. Plasma plume of atmospheric pressure discharge has been observed as `plasma bullet´ whose speed is about 10⁴~10⁵ m/s. To explain the high velocity of bullet propagation, Lu and Laroussi have suggested a photo-ionization based model. However, the fundamentals of propagation mechanism are not yet well understood. In this report, more precise observations of plasma plume are conducted with the equipments as ICCD (intensified charge coupled device) camera and a photo sensor amplifier combined with optical fiber. In the experiments, the transient behaviors of plasma are observed at a pencil type plasma jet as well as a long discharge tube (glass or flexible Teflon) extended from the muzzle of plasma jet device. The movement of plasma bullet is taken with the time deviation of 10 ns by ICCD camera. However, the photographing area is very small so that a picture of long plasma column about a several 10 cm in length cannot be taken. The photo sensor is installed at the point of plasma column. The optical intensity from the measuring point is amplified and the amplified optical signal is transferred to the oscilloscope through the optical fiber. On the oscilloscope display, the optical signals as well as the signals of voltage and current are observed to be compared between them. The measuring points are selected at some point without restriction of plasma column length. The behavior of plasma is taken to the profiles of applied voltage including the polarity of positive and negative. The data obtained in this measurement with two observation systems, are provided to the verification of plasma propagation mechanism.