The Rate of Production of Very Large Cosmic-Ray Bursts as a Function of Lead Shielding Thickness

Experiments have been performed at Chicago with two Compton-Bennett cosmic-ray meters to determine the frequency of occurrence of very large bursts (120 to more than 1000 particles) as a function of lead shielding thickness. The thickness of lead for optimum burst rate was found on both meters to be in the neighborhood of 3 centimeters. This is larger than the optimum for showers and small bursts, a fact which is in qualitative agreement with the theory of Carlson and Oppenheimer. Quantitatively, the maximum determined experimentally is of the same order of magnitude as that predicted by the theory though lower.