Energy determination of the cascade shower by means of a new type of emulsion chamber with diffuser module

Abstract An account is given of a new type of emulsion chambers which have been in our use since 1997 in our RUNJOB program (RUssia–Nippon JOint Balloon-program). Each chamber is equipped with an additional “diffuser module” placed under the usual set of modules. We have made the experiments using 4 cm thick diffuser modules composed of several photo-sensitive layers (X-ray films and/or nuclear emulsion plates) sandwiched with spacers. The result is as follows. Even in the case where the path length of only 6 radiation lengths is available within the calorimeter module placed above, the visible energy sum is determined with an accuracy better than σ ∼0.2 for a group of electromagnetic cascade showers induced by a proton of energy up to several tens of TeV, or by an iron nucleus of energy up to one hundred TeV. If the available path length in the calorimeter module is 9 radiation lengths, we can estimate the energy sum up to ∼100 TeV within an accuracy of σ ∼0.2 for a proton-induced cascade shower group. It means that the use of our new-type emulsion chamber can reduce the detector payload dramatically, which is essentially important for the high-energy cosmic-ray observations made on board the vehicles such as balloons, satellites and so on.