Highly sensitive x-ray films to detect electron showers in the 100 GeV region

Nonscreen type x-ray films were used in emulsion chamber experiments to detect high energy showers in cosmic rays. The range of the detection threshold is from about 1 to 2 TeV depending on the exposure conditions. Different types of x-ray films and sheets, i.e., highly sensitive screen type x-ray films and luminescence sheets were tested. The threshold of the shower detection is found to be about 200 GeV, which is much lower than that of nonscreen type X-ray films. These films are useful to detect showers in the medium energy range, a few hundred GeV, of cosmic ray electrons