Synopsis
Counter measurements on extensive air showers were performed at an atmospheric depth of 600 g cm -2 and 700 g cm-2 in the Peruvian Andes, corresponding to respectively 4540 meter and 3250 meter altitude. Three and sixfold coincidences obtained from counter arrays with different sensitive area were compared. The coefficient g of the inverse power law differential spectrum relating the relative occurrence of a shower to its density was determined. A deviation from the generally accepted theory is found, the constant g varying from 2,27 4-0,04 to 2,48 ~. 0,03 depending on its method of determination. The extension of the set-up used for obtaining these values of g varied from 1,6 to 3 m. Results obtained with a different set-up (distances up to 100 m) are also given, g increasing from 2,5 ยฑ 0,1 to 3,2 4-0,2 when the extension of the set-up was increased from 5 to 98 m. The absorption lengths obtained from these experiments show a decrease from 138 4-5 g cm -2 to 45 4-3 gcm -2 ~dth increasing shower size. in cooperation with Professor Dr. C. Monge of the University San Marcos in Lima, was part of the research program of the Foundation for fundamental Research of Matter (F.O.M.) supported by the Institution for pure scientific Research (Z.W.O.). *) There remains an indication that this explanation does not entirely account for the more rapid absorption of tile large showers (40, 100 m) in comparison with the N-component. Fourfold coincidences obtained with the set-up shown in figure 3, but after placing 1.5 cm of lead between each of the trays A and A" yielded an absorption length of 61 4-5gcm -2 and 66 4-5gcm -~ for b = 40 and b ~ 100 m respectively.