The Diffuse X-Ray Spectrum from 14 TO 200 keV as Measured on OSO-5

The measurement of the energy spectrum of the diffuse component of the cosmic X-ray flux made on the OSO-5 spacecraft is described. The contributions to the total counting rate of the actively shielded X-ray detector are considered in some detail, and the techniques used to eliminate the noncosmic components are described. Positive values for the cosmic flux are obtained in seven energy channels between 14 and 200 keV, and two upper limits are obtained between 200 and 254 keV. The results can be fitted by a power4aw spectrum of the form Flux = (46 + 10)E- photons (cm2 5 sterad keV)-1. A critical comparison is made with the OS 0-3 results, with the conclusion being that the reported break in the energy spectrum at 40 keV is possibly produced by an erroneous correction for the radioactivity induced in the detector on each passage through the intense charged-particle fluxes in the South Atlantic Anomaly. If such a break in the spectrum exists at all, it cannot be as sharp or as great a change as that reported by Schwartz et al. Subject headings: spectra, X-ray - X-rays