Structure formation, tearing and merging of relativistic electron beam propagating through a laser produced plasma

Hot electron transport in a high density plasmas has been studied using a two dimensional hybrid code. The results show that the initially cylindrical solid beam evolves into a hollow, annular beam due to the Weibel instability and generates strong magnetic fields on both sides of the annular ring. The annular structure subsequently breaks up into several beamlets due to a mechanism similar to a tearing instability. It is found that the magnetic fields parallel to the direction of beam propagation also grow during the tearing process. These beamlets are attract each other and finally they merged into a single beam which carries a net electric current. The tearing and merging processes have also been analyzed by the hybrid code for a uniform initial condition to determine an asymptotic behaviors of the total number of hot electron beams. We also have performed a three dimensional particle-in-cell (PIC) simulation to compare with the results of 2D hybrid code. It shows that the spatial variation of cold electron density is much more uniform than that obtained by 2D code.