Radiation transfer in low-density foam is influenced by the external radiation field which impacts on the foam when the size of plasma created in laboratory is not large to be opatical thick. The radiation transfers of different photon groups are sensitive probes of the conditions of the medium through which they propagate. The temporal behavior of photon groups to which the plasma is optical thin is quite different from that of photon groups to which the plasma is optical thick. The breakout times of different photon groups through the foam are distinguishable different in experiment when we measures them at the end of foam. The multi-group supersonic radiation transfer behavior in low-density foam is studied both by multi-group transfer numerical simulation and experiments. Two characteristic photon groups are chosen to do experimental research on the multi-group transfer behavior in low-density CH foam. A time-resolved chromatic streaked X-ray spectrometer measure the breakout of the two photon group from the far end of the foam cylinder. The distinguishable transfer time delay between two groups is observed.

A PIC (particle-in-cell)-MC (Monte Carlo) code to model electron beam transport into dense matter is developed. The background target is treated as a cold, stationary fluid and the fast electrons as particles with the relativistic motions. The process is described by a particle-in-cell method with consideration of the influence of both the self-generated electric and magnetic fields as well as collisions between the fast electrons and the target. The collisional part of the code is solved by the Monte Carlo-type method. Furthermore by assuming that the background current balances with the fast electron current, the electric field is given by the Ohm's law and the magnetic field is calculated from the Faraday's law. Both are solved in a two-dimensional cylindrical geometry. The algorithms implemented in the code are demonstrated and the numerical experiments are performed for monoenergy homogeneous fast electron beam transport in an aluminum target when the fields, collision and angular scattering are switched on and off independently.

We have developed a three dimensional (3D) PIC (particle-in-cell)-MC (Monte Carlo) code in order to simulate an electron beam transported into the dense matter based on our previous two dimensional code. The relativistic motion of fast electrons is treated by the particle-in-cell method under the influence of both a self-generated transverse magnetic field and an axial electric field, as well as collisions. The electric field generated by return current is expressed by Ohm's law and the magnetic field is calculated from Faraday's law. The slowing down of monoenergy electrons in DT plasma is calculated and discussed.

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