Ryutaro Ishiwari

Elastic Scattering of Protons from B¹¹, Al, P, Co and Cu from 6 to 7.4 MeV

The energy dependence of the angular distributions of protons elastically scattered by the odd nuclei, B 11 , Al, P, Co and Cu, was measured in the energy range from 6 to 7.4 MeV by using the 105 cm Kyoto University Cyclotron. No remarkable energy dependence of the pattern of the angular distributions was found in all the energy and angular ranges studied. It may be concluded that a less energy dependence of the angular distributions of protons elastically scattered by the odd nuclei is due to a less contribution of the compound elastic scattering and moreover a less energy dependence of the compound elastic scattering.

Quasi-Free α-α Scattering in Be9 and C12 at 37 MeV

Energy and angular correlations between two alpha particles from the Be 9 (α, 2α)He 5 and C 12 (α, 2α)Be 8 reactions were investigated. The incident alpha particle energies were 32.3 MeV and 37.4 MeV for Be 9 and 37.4 MeV for C 12 . It is concluded that the quasi-free scattering of incident alpha particles from alpha clusters in Be 9 is the main process of the (α, 2α) reaction on Be 9 . It remains some ambiguity for the mechanism of the (α, 2α) reaction on C 12 to be explained as a simple quasi-free scattering process.

Search for Possible Geometrical Effect on Stopping Power Measurement

The possibility that the geometrical condition might affect the observed energy loss of heavy charged particles in matter has been considered. The energy losses of 8.78 MeV alpha particles in Al, Cu, Ag and Ta have been measured with good and poor geometries. It has been found that the energy losses observed with good geometry are slightly smaller than those observed with poor geometry. It appears that the geometrical effect may really exist, although the amount of the effect is small and comparable with the statistical uncertainties for the present experimental condition. It has been concluded that this effect is not the origin of the discrepancies between our stopping power data for 7.2 MeV protons and the data of Andersen et al. Some discussions have been made on the comparison of stopping powers for 8.2 MeV alpha particles with those for protons of the same velocity.

On the Ionization-energy Relation for Alpha-particles in Air

To investigate the effect of columnar recombination on the ionization measurement in air, the ratio of the specific ionizations at two fixed residual ranges for polonium alpha-particles was measured with a shallow ionization chamber under various field strengths and angles between the field and the alpha-track. It was found that the observed ratio varies appreciably with varying field strength and angle. It was shown that the observed variation of the ratio can be explained by the effect of columnar recombination and agrees qualitatively with Jaffes theory. The value of the parameter b in Jaffes formula, which gives the best agreement with the experiments, was newly determined as 9.5×10 -4 for alpha-particles in atmospheric air. The observed specific ionization curve was corrected for recombination by Jaffes theory. Then, the corrected curve was integrated and the true ionization-range relation free from recombination was determined. By comparing this relation with the fixed points of the range-energy ...

IONIZATION YIELD OF THE N

The ionization yield of the N 14 ( n , p )C 14 reaction produced by thermal neutrons in air was measured with a pulse ionization chamber. The uncorrected value of the reaction energy was obtained as 0.600±0.006 Mev. This value was corrected for columnar recombination and for the variation of W , the average energy to produce an ion pair, with particle energies. For the variation of W α , the empirical formula obtained in the previous work was used. Assuming that W p is equal to W α for the same velocity and that the relative value of W C with respect to Po alpha particles is 1.10, the corrected reaction energy was calculated as 0.621±0.006 Mev in good agreement with the established Q value. This result indicates that W p for about 600 kev is actually equal to W α for the same velocity in air. Some evidences, which suggest that the relative value of W C is about 1.10 and W α for the same velocity as C 14 is probably equal to this value, were also discussed.