Bremsstrahlung from thick targets and a diagnostic for electron energy distributions.

The bremsstrahlung from solid material caused by runaway electrons may blur severely the bremsstrahlung that is recorded from gases or plasmas in order to determine the energy distribution of their hot electrons. The expressions for these emissions are presented in order to compare their characteristics. Explanations are then given for an irregular feature observed at the tip of the spectrum for solid targets.

Qualitative modification of the high energy atomic photoionization cross section.

It is demonstrated that the nonrelativistic high energy omega-->infinity behavior of the photoionization cross section of an nl atomic subshell, sigma(nl)(omega), for l>0 is independent of l and is given by sigma(nl)(omega) approximately 1/omega(9/2), rather than the previously generally accepted sigma(nl)(omega) approximately 1/omega(l+7/2). Furthermore, for l = 1, although the exponent does not change, the coefficient is significantly altered. This modification of sigma(nl)(omega) is due to the interchannel interaction between ns photoionization channels and l not equal0 channels in the atom.