Positive Excess and Electron Component in the Cosmic-Ray Spectrum

The sea-level cosmic-ray energy spectrum has been determined, using a 30-cm counter controlled cloud chamber in a 12,400-oersted magnetic field. The spectrum of mesotrons alone is obtained by inserting a 10-cm lead filter in the counter train, the total spectrum is obtained with no filtering, and the spectrum of the soft (electron) component is then the difference between these two spectra. An excess of positive particles exists both with and without the lead, the ratio of positives to negatives being 1.21±0.08 (standard error) in the former, and 1.18±0.08 in the latter case. Comparison of the spectra with and without lead shows the presence of an absorbable component (electrons) in the energy region 2 to 8×${10}^8$ ev but no absorbable particles of higher energy. The spectra have been corrected for the distortion at low energies caused by the magnetic field. The corrected mesotron spectrum possesses a maximum and a rapid decrease below the maximum while the total spectrum shows no maximum but a continuous increase in number with decreasing energy.