Using Coincidences to Investigate Zenith Angle Dependence of Stratospheric Cosmic Rays

Abstract

Cosmic ray air showers result when high-energy particles from outer space strike atmospheric nuclei and produce downward sprays of secondary rays including electrons, positrons, muons and neutrinos. The charged particles in such cosmic ray showers can trigger Geiger counters as they pass through the detectors. Hence monitoring coincidences between two or more Geiger counters can provide insight into the direction of travel and/or the physical spatial extent of a cosmic ray shower. We present a preliminary report on a stratospheric ballooning payload designed to make coincidence measurements of charged particles traveling at zenith angles of 0 degrees (vertical) and 90 degrees (horizontal). This was a follow-on to an earlier experiment in which we used a stepper motor to repeatedly change the angle (with respect to zenith) of a pair of coincidence-counting Geiger counters during a stratospheric balloon flight. The new payload contains four fixed pancake-shaped RM-80 Geiger counters -two stacked vertically (aligned with zenith) and two stacked horizontally (aligned perpendicular to zenith). Each pair of detectors is separated by 18 cm, so as to narrow the opening angle of the coincidence detector. This configuration can sample both vertical and horizontal coincidences simultaneously, with no moving parts as was done with the stepper motor. Although the new configuration cannot study coincidences at intermediate angles, it also allows us to study triple and quadruple coincidences.