Abstract :
The analysis and results given here show that boundary layer dynamics obeys very useful scaling laws which permit one solution of the basic equations to hold for many cases. In particular, during the time that the X-ray pulse is linearly rising, or when the pulse time history changes slowly after a rapid rise, (or when the pulse behaves as any power of time), the equations scale completely, and a single solution suffices for all pulse parameters for a given shape of the electron energy spectrum. Detailed solutions for the time-dependent structure of the boundary layer for two cases of interest were presented in the previous two sections. In both cases the emission electron spectrum was assumed to be exponential with an arbitrary average energy E, and the angular distribution was taken to be proportional proportional to cos ¿. The material yield Y is arbitrary. In the first case the incident X-ray flux is taken to rise linearly in time at an arbitrary rate, while in the second case the flux is taken to be a step function turned on at t = 0 and then held constant at an arbitrary value. Useful scaling laws are apparent from the equations in the previous two sections. For example, for a linearly rising pulse, the surface electric field varies only as the cube root of the yield, or the electron average energy, or the flux rise rate, Equation 43.
