A measurement of neutron flux in the range 30 -130 Mev at altitudes of 10, 670 feet and 100,000 feet was performed with a directionally sensitive proton recoil detector. The detector consisted of two counters of scintillator plastic which measured dE/dx and energy of proton recoils originating in a third plastic scintillator. Charged particles were eliminated by a guard counter. Energy calibration was performed with charged cosmic ray particles; efficiency and angular sensitivity were calculated. The angular response was checked at 10,670 feet, where a reasonable angular distribution of cosmic ray neutrons could be assumed.
Four balloon flights to 100,000 feet were undertaken in two of which the instrument was programmed to point in various directions with respect to the zenith. Data from the counters were digitized, displayed on a bank of lamp indicators and photographed on continuously moving film. Event rate at altitude was 5 per minute. The angular distribution at balloon altitude showed a maximum at approximately 90° with respect to the zenith in contrast to the downward flux observed at 10,670 feet. The data were consistent with an energy spectrum behaving as l/E1.3with omnidirectional intensity at 100,000 feet of 1.2 10-2 /cm2 -sec-Mev over the energy range detected.
The directly observed recoil angular dependence and energy spectra were converted to the corresponding functions for incident neutrons by folding in calculated response functions for the detector.
Level of Degree
Physics & Astronomy
First Committee Member (Chair)
Christoper Pratt Levitt
Second Committee Member
John R. Green
Third Committee Member
Victor H. Regener
Sydor, Michael. "The Atmospheric neutron spectrum at high altitudes." (1964). https://digitalrepository.unm.edu/phyc_etds/222