The 0.5-Mev gamma-ray and the low-energy gamma-ray spectrum to 6 grams per square centimeter over Minneapolis

Journal Article · Fri Feb 15 04:00:00 EST 1963 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/JZ068i004p00979· OSTI ID:4752737

Peterson, Laurence E.

The positron arnnihilation line at 0.5 Mev has been found to be a prominent feature of the low-energy gamma spectrum produced in the atmosphere by cosmic rays. The measurement, that covered the energy range between 37 kev and 3.5 Mev, is made with a phoswich scintillation counter carried on a balloon to a depth of 8 g/cm² over Minneapolis. The flux at 0.5 Mev is found to be 0.51 plus or minus 0.03 photon/cm/sup 2/ sec at 6 g/cm², and, when extrapolated to zero depth, gives a residual of 0.18 plus or minus 0.03 photon/ cm/sup 2/ sec. All components of the spectrum, including the line at 0.5 Mev, are observed to have a transition maximum at 90 g/cm² and a length for absorption of 180 g/cm². These indicate the origin of the low-energy gamma rays to be associated with the electronic component of secondary cosmic rays. Evaluation of the source function at 0.5 Mev over the entire atmospheric column gives 8.6 positrons per incident primary cosmic ray at lambda = 55 deg geomagnetic. Since no statistically significant time variations are observed during the seven hours of constant depth balloon flight, an upper limit on the flux of certain possible extraterrestrial point sources, that made high elevation meridian transits, can be obtained. The flux at 0.5 Mev from the quiet sun and from the Crab nebula must be less than about 0.1 photon/cm/sup 2/ sec at the earth.

• Research Organization: Univ. of Minnesota, Minneapolis
• Sponsoring Organization: USDOE
• NSA Number: NSA-17-013313
• OSTI ID: 4752737
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: 4 Vol. 68; ISSN 0148-0227
• Publisher: American Geophysical Union
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ABSORPTION
ANNIHILATION
ATMOSPHERE
BALLOONS
COSMIC RADIATION
DISTRIBUTION
EARTH
ELECTRONS
ENERGY
ENERGY RANGE
GAMMA RADIATION
GEOMAGNETIC COORDINATES
INTERACTIONS
KEV RANGE
LEVELS
MAGNETIC FIELDS
MEASURED VALUES
MEV RANGE
MINNESOTA
POSITRONS
PRODUCTION
SCINTILLATION COUNTERS
SECONDARY EMISSION
STRATOSPHERE
VARIATIONS