Accession Number : AD0625714


Title :   THE LOW-ENERGY COMPONENT OF THE TOTAL DOSE FOR DEEP GAMMA PENETRATIONS IN AIR AND WATER.


Descriptive Note : Technical note.,


Corporate Author : ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD


Personal Author(s) : Garrett,C. W.


Report Date : NOV 1965


Pagination or Media Count : 17


Abstract : A difference of a factor of two in the buildup factors for infinite water and infinite air at deep penetration distances (e.g., 10 mean free paths) for point isotropic cobalt-60 sources is noted. One possible cause for the discrepancy is the improper accounting of the dose delivered by low-energy photons (energies less than 100 keV) in the infinite air case, which was treated by a Monte Carlo analysis. The possible effects of this cause are presented, showing that lack of present knowledge of the differential number flux density for low-energy photons diffusing in low-Z materials leads to great uncertainty in the fraction of the total dose delivered by the low-energy component. Experimental data indicate that essentially all of the discrepancy between the water and air buildup factors could be attributed to a neglect of the low-energy dose. On the other hand, recent Monte Carlo calculation of the low-energy flux suggests that the cause for the discrepancy must be accounted for by other, at present undetermined, factors. (Author)


Descriptors :   , AIR, WATER.


Subject Categories : RADIOBIOLOGY
      NUCLEAR PHYSICS & ELEMENTARY PARTICLE PHYSICS


Distribution Statement : APPROVED FOR PUBLIC RELEASE