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The Quiet Time Flux of 0.16-1.6 MeV Cosmic Ray Positrons

Mewaldt, R. A. and Stone, E. C. and Vogt, R. E. (1975) The Quiet Time Flux of 0.16-1.6 MeV Cosmic Ray Positrons. In: Proceedings of the 14th International Cosmic Rays Conference. Vol.1. Max Planck Gesellschaft , p. 401.

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Measurements of the cosmic ray positron flux near ~ 1 MeV are of interest because of possible contributions in this energy region from β-decay sources. Previously we reported (Hurford et al.,1973) an upper limit for the quiet time positron flux at ~1 MeV of ~2x10^(-3) cm^(-2)•sec^(-1)•sr^(-1)•Mev^(-1), based on a preliminary analysis of data from the Caltech Electron/Isotope Spectrometer on IMP-7. The method of positron detection is discussed in Mewaldt et. al. (1975). Our IMP-8 instrument has somewhat improved positron detection efficiency and includes an analysis mode that allows a determination of the rate of background events with positron- like signatures. Subtraction of this background contribution and the accumulation of additional data with improved statistical accuracy from both instruments shows that less than 30% of the positron-like events are due to positrons. This results in the new upper limits to the 0.16 to 1.6 MeV positron flux shown in Figure 1. These new upper limits are a factor of ~ 2 lower than those we reported previously. Thus we find no evidence for ~ 1 MeV positrons which might result from the β-decay of radioactive interstellar secondaries or the decay of ^(56)Co in supernovae.

Item Type:Book Section
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URLURL TypeDescription
Mewaldt, R. A.0000-0003-2178-9111
Stone, E. C.0000-0002-2010-5462
Additional Information:© 1975 MPE. Provided by the NASA Astrophysics Data System. This work was supported in part by the National Aeronautics and Space Administration under Contract NAS5-11066 and Grant NGR 05-002-160.
Group:Space Radiation Laboratory
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NASANGR 05-002-160
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Space Radiation Laboratory1975-08
Record Number:CaltechAUTHORS:20140410-133715368
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ID Code:44864
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Deposited On:10 Apr 2014 21:56
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