Emulsion chamber observations of primary cosmic-ray electrons in the energy range 30-1000 GeV

A series of emulsion exposures, beginning in Japan in 1968 and continued in the U.S. since 1975, has yielded a total balloon-altitude exposure of 98,700 m/sup 2/ sr s, nearly 10 times the exposure factor obtained by other experiments. The electron spectrum derived by combined data from all our chambers exposed from 1968 to 1976 is well represented by J/sub e/(E)=1.6 x 10/sup -4/(100 GeV/E)/sup 3.3plus-or-minus0.2/ /m/sup 2/ sr s GeV in the energy range 30--1000 GeV. This result is in good agreement with our earlier results and with those of several other groups. We discuss our data in terms of several models of cosmic-ray propagation. Interpreted in terms of the energy-dependent leaky-box model, our electron spectrum results suggest a galactic electron residence time of 1.0(+2.0, -0.5) x 10/sup 7/ yr, which is consistent with the result from /sup 10/Be observations. Additional chambers current under analysis will allow us reliably to extend the spectrum beyond 1 TeV. We discuss the possibly that departures from smooth power-law behavior in the spectrum due to individual nearby sources will be observable in this energy range.