Modelling fast electron transport in solids and with application to Rayleigh-Taylor instability studies

This thesis presents numerical investigations of the fast electron transport and discusses the fast electron heating of solid targets. Three areas have been investi- gated in this context: The first area introduces the concept of an ideal fast electron transverse confine- ment which is obtained when the transverse dimensions of the target are comparable to the laser spot size. This facilitates the heating of thick targets. This investigation also explores the angular dispersion phenomenon in the context of the fast electrons. This dispersion results in a longitudinal velocity spread of the fast electrons which adversely affects their penetration of the target, and this in turn impairs the heating. The work here shows that angular dispersion can not be avoided even when ideal fast electron transverse confinement is achieved. Moreover, this dispersion impedes fast electron penetration more significantly than does electric field inhibition. The results indicate the importance of taking the angular dispersion into account in fast electron transport calculations. The second area investigates the effect of grading the atomic number at the in- terface between the guide element and the solid substrate on resistive guide heating. The numerical results imply that this graded interface configuration improves the heating in large radius guide resembling that obtained in smaller guide. The larger radius guide with the graded interface configuration is more tolerant to laser point- ing stability than smaller radius. Further, this configuration increases the magnetic collimation of fast electrons since more powerful confining magnetic field is obtained. The last area studies numerically a Rayleigh-Taylor (RT) instability experiment driven in a fast-electron-heated solid target. It was found that it is possible to drive the RT instability in dense plasma isochoric heated by the fast electrons. The RT instability growth occurs in few picoseconds, after establishing strong radiative cooling. The curve growth rates depends on the type of atomic model used. Practi- calities of extracting RT instability data due to structure in the heating profile are described.