Study of current sheath dynamics in dense plasma focus in the presence of axial magnetic field using laser shadowgraphic technique

摘要

The study of plasma sheath structure and its dynamics in the presence of external axial magnetic field (B/sub z/) in dense plasma focus has been made with the help of N/sub 2/-laser shadowgraphic technique. The shadowgraphs of axial phase show that in the presence of external B/sub z/ the current sheath gets diffused near the end attached to the central electrode when it reaches to the top of the central electrode. The shadowgraphs of radial collapse phase show clearly distinct hump formation above central electrode under the influence of B/sub z/. Moreover, during the radial collapse phase a part of the current sheath lying close to central electrode gets highly diffused in comparison to the rest of the current sheath. Diffused bubble formation on the ionization wave front and dominantly visible remnant of plasma sheath above central electrode have also been observed during the quiescent phase (the expansion phase after the peak compression).