In the present experiment, the three-dimensional distribution of energy deposition was measured for 1-GeV electron-induced showers in water and aluminum. For the water target, two different detectors were employed: CsI(Tl) and anthracene. The measured longitudinal distribution of energy in water was found to be essentially independent of the detector employed in the measurement, while the radial distribution of energy deposition shows a strong detector dependence. Data were measured for the aluminum target with a Ca${\mathrm{F}}_2$(Eu) detector. All of these data support the description that the primary energy-deposition mechanism at the initiation of the shower is ionization of the target material, and that the principle energy-transport mechanism after shower maximum is the propagation of minimum-attenuation $\gamma$ rays. The radial distributions of energy deposition show that the apparent dependence on the atomic number of the target observed in an earlier experiment was in part a detector-dependent result. The radial distributions nevertheless show significant differences from the prediction based on the Monte Carlo calculations of Nagel.

• Received 30 January 1969

DOI:https://doi.org/10.1103/PhysRev.184.426