[en] The dynamic response of a planar target irradiated by a tightly pinched intense relativistic electron beam is found to be very sensitive to in-depth heating by the beam due to x-ray deposition and to diode voltage fluctuations. We find that voltage fluctuations are primarily responsible for the observed wave structure preceding the large-amplitude shock wave while x-ray deposition affects the response to a lesser extent. The implications of these results for electron-beam fusion target and accelerator designs are noted