A diffusion-type cloud chamber eight feet long, four feet wide, and five inches deep has been used to study the lateral structure of cosmic-ray air showers in a region near the core. Three showers were recorded in which the core lay within sixty to ninety centimeters from some point on the periphery of the chamber. The results show that the lateral distribution of the shower particles in all but one photograph follow exceedingly well the Moliere distribution. The deviations from the Moliere distribution are almost all within the expected Gaussian fluctuations. In those pictures exhibiting little or no gradient, the deviations from the average density were normal.

No abstract

A diffusion cloud chamber 8 ft long, 4 ft wide, and 5 in. deep has been built and operated successfully for 540 hrs out of a continuous 720-hr run. Though the actual area is 32 sq ft, the area photographed was 21 sq ft or approximately 2 sq m. A sensitive layer of good quality extending 2½ to 3 in. above the floor was easily maintained. The coolant temperature was held near −67°C and the air above the glass sheet forming the top was held at 30°C. A clearing field of 30 v (top negative) was found desirable to keep the chamber free from general rain. The chamber contained an air and methyl-alcohol mixture operated at 1 atmos pressure. Tracks in the sensitive region were photographed through the top with the aid of several mirrors. The chamber was used to study the structure of the cores of cosmic-ray air showers. It is now being used for studies with the bevatron.