Measurements of the Effect of Paraffin and Lead on the Rate of Production of Very Large Cosmic-Ray Bursts

Observations have been made at sea level of burst frequency and magnitude for bursts larger than 15×${10}^6$ ion pairs, using a Model C cosmic-ray intensity meter. The effects of the following on the rate of production of bursts of different magnitudes have been investigated: ($a$) degree of shielding of the ionization chamber; ($b$) heavy building structure above the instrument; ($c$) lead placed immediately above the ionization chamber; ($d$) paraffin placed immediately above the ionization chamber. The results on the enhancement of burst production by lead agree with, and extend the range of, those already reported. Paraffin has a much smaller effect than lead on the rate of production of large bursts.