Structure and Composition of Air Shower Cores

Extensive air showers were observed with an arrangement in which details of their structure and composition could be studied with the help of a large cloud chamber and a 102-counter hodoscope, while extension trays permitted a classification of the showers in three groups according to their initial energy, and a selection favoring events with cores striking near the central cloud chamber-hodoscope set. The electron density distribution is found to be flatter than the Molière structure function, and despite the different shower ages in the three energy groups, to be nearly the same for all the showers recorded. A structure function $\phi \mathrm{}\left(r\right)\mathrm{}\propto r^{-0.76\mathrm{}} \mathrm{to} r^{-0.85\mathrm{}}$ in the immediate neighborhood of the core fits the data best. An attempt to correlate the very dense local cascades started by high-energy electrons or photons with the expected multiple cores representing the high multiplicity of the nuclear interaction initiating the shower failed; the structure of the groups of local cascades observed does not appear to vary with the shower energy. The penetrating component contains $N$ particles interacting in the lead plates of the chamber with a mean free path of approximately 165 g/${\mathrm{cm}}^2$, and consisting of neutrons (41±8 percent) and charged particles. The total abundance of penetrating particles near the core does not differ appreciably from that found by various authors in experiments not as strongly biased in favor of the detection of shower cores. The abundance ratios of $N$ particles to $\mu$ mesons, and of penetrating particles to electrons, show only slight variations with the shower age and demonstrate that the nucleonic cascade reaches its maximum somewhat later than the electron cascade.