SummaryNeutrons obtained by bombarding a thick beryllium target with 600 keY. deuterons were studied by the photographic plate technique at angles of emission of 0, 90, and 150°. Five previously reported neutron groups were confirmed giving energy lev"els of B'O at 0'73,1'75,2·20, and 3·64 MeV. An additional group corresponding to an energy level of 2·85 MeV. was observed and the evidence for regarding these as genuine beryllium neutrons is discussed. The Q-value for the ground state transition is found to be 4·35±0·02MeV. which agrees with the value 4·36±0·04 deduced from the most recent masses.
The stopping power of Ilford C2 nuclear emulsion under fixed water content conditions has been determined for protons in the energy range 1.73-5.26 MeV. with an accuracy of 1 per cent. The variation of stopping power with water content has been calculated and an appropriate correction applied. It has been found that the values obtained in this experiment are in substantial agreement with those of Lattes, Fowler, and Cuer, and of Rotblat, A consistency in stopping power of better than 0.3 per cent. has been observed between several batches. Some data on the straggling of protons in nuclear emulsion are presented.
SummaryThe differential and integral range spectra of the hard component of cosmic rays in water have been measured down to a depth of 18·3 m. of water, and the integral results confirm the work of Ehmert (1937) and Wilson (1938) in this region. A lack of statistical accuracy in the differential measurements prevents the possible observation of an anomaly corresponding to 2·5 BeV./c. momentum. A comparison of the range and momentum spectra on the basis of the energy loss data of Halpern and Hall shows satisfactory agreement. The absolute value of the differential intensity is found to be 20 per cent. higher than that given by Rossi (1948) but agrees with the more recent result of York (1952).
SummaryThe differential and integral range spectra of the hard component of cosmic rays in water and lead have been determined up to a thickness of 1500 g cm-2 of water, and 2800 g cm-2 of lead. The differential results indicate that there is no anomaly with an intensity greater than 5 per cent. in the differential momentum spectrum in the region below 4 Be VIc. A comparison of the integral range and momentum spectra supports the energy loss data of Halpern and Hall in preference to those of Bethe and Bloch in the case of water. No such distinction of the theories is possible in the case of lead and, although the integral absorption curve in lead agrees with that obtained by Heyland and Duncanson (1953b), there is an unexplained discrepancy between experiment and theory. The intensity of knock-on showers as a function of thickness of water absorber has also been determined.
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