Possible Indirect Method for the Detection of γ-Ray Flashes from Supernovae

摘要: THE electron-photon cascade calculations of Messel and Crawford1 contain a remarkable feature which has not attracted widespread attention. Although the secondary electrons reach maximum numbers die away in fashion broadly consistent with previous calculations, very low energy γ rays persist relatively large to great depths absorber. For primary photon 500 MeV air, for example (Table K756 ref. 1), photons total ≥1 MeV, mean electron number falls 0.78 at 10 radiation lengths (r.1.), 0.009 16 r.1.; but photons, reaching 11.1 5 r.1., is attenuated slowly, 5.48 are still predicted 30 r.1. The carried 10.46 so average about 2 MeV. Similarly higher energies: 50 GeV produces 577 2.04 In general, it seems that primaries more than 2% reaches form 1 rays; air corresponds 1,100 g cm−2, or sea level.