We should not assign great significance a priori to the fact that our sensitivities are between others' values for £0 = 25 MeV and E0 = 30 MeV. Our distance sample-converter is greater (15 cm), and our electron beam intensity double (~210 µ ) theirs. However, these features result in opposite effects. Moreover, the general agreement of sensitivity ratios is quite important, because it implies activation trends for our system, parallel with those of thintarget, low-Eo facilities, for the whole range of giant resonance energies (k = 10 to 30 MeV). That is, it suggests reasonably similar bremsstrahlung spectrum shapeswithin said range-for the ORELA and conventional facilities (2, 4, 6), as we had expected from Figure 1.Table II shows, finally, that our sensitivities agree best with Lutz's results. The latter were obtained from a comprehensive table (2,4) which lists calculated sensitivities for 76 photon reactions on 59 elements for electron beam energies £0 = 25, 30, and 35 MeV. With reasonable approximation, the average ratios of Table II can be used to estimate sensitivities for our PAA system, from Lutz's table, for elements and reactions not included in our work.
ACKNOWLEDGMENTWe thank J. A. Harvey and . A. Todd for their continuous interest in our work, and ORELA's operators for smooth scheduling and conduction of our bombardments.