Isao Kumabe

Alpha Particles from the Interaction of 14.8-MeV Neutrons with Medium Weight Nuclei

The angular and energy distributions of alpha particles resulting from V 51 ( n , α)Si 48 and S 32 ( n , α)Si 29 reactions induced by 14.8-Mev neutrons were measured with Ilford C2 nuclear plates. It was found that the angular distributions for the entire energy regions in the center-of-mass system are concave upward and approximately 90° symmetrical, and the energy distributions show that the alpha particles with energies below the Coulomb barrier are more emitted than expected. Also the curve on a semilog plot of the relative level density calculated from the energy distributions of the alpha particles fits a straight line which would correspond to Maxwellian distributions with the temperatures of about 0.9 Mev for Sc and about 1.5 Mev for Si. The total cross sections of V and S are 126 mb±15% and 109 mb±15% respectively. Experimental data on ( n , α) reaction so far obtained by us are summarized and discussed in detail.

Ionization chamber system to eliminate the memory effect of tritium

Abstract The memory effect due to the adsorption of tritium onto the electrodes of an ionization chamber sometimes reduces the accuracy of the results. Ionization chambers are generally used to monitor the tritium level in a gas stream because of their reliability, flexibility and wide range of measurement. In this paper we shown that the memory effect is mainly brought about by the transfer of tritium from the gas stream to surface water on the electrode wall by adsorption or isotope exchange reactions. A way to simulate the extent of the memory effect is proposed. An ionization chamber system which can eliminate the memory effect by applying an isotope exchange reaction is also proposed.

Scattering of 34.4-MeV Alpha Particles by the Tin Isotopes

The angular distributions of alpha particles elastically and inelastically scattered by 116 Sn, 117 Sn, 118 Sn, 119 Sn and 120 Sn have been measured at 34.4 MeV. The angular distributions of the prominent groups corresponding to the quadrupole and octupole excitations were fitted with the results of DWBA predictions. In these calculations Coulomb excitation was found to be important for these nuclei. The extracted deformation parameters β 2 and β 3 for the even tin isotopes are in good agreement with those obtained by other workers. Both the shapes and magnitudes of the angular distributions of the groups corresponding to the quadrupole and octupole excitations for the odd-mass tin isotopes were found to be very similar to those for the even tin isotopes. Possible hexadecapole excitations are discussed.

Elastic and Inelastic Scattering of 28.5 MeV Alpha Particles by Medium-Weight Nuclei

Elastic and inelastic scattering of 28.5 MeV alpha particles by Ni 60 , Ni 58 , Ti 48 , Co 59 and Al 27 has been studied. The angular distributions of the prominent group from the 2 + first excited state and the 3 - “anomalous” group for even nuclei were fitted by calculations based on Blair model. The angular distributions of the 4 + groups near 2.5 MeV in Ni 60 , near 2.5 MeV in Ni 58 and near 3.3 MeV in Ti 48 were found to have intermediate phase between the corresponding elastic distribution and the corresponding first 2 + inelastic distribution. On the other hand, the angular distributions of the 2 + groups near 3.1 MeV in Ni 60 , near 3.0 MeV in Ni 58 and near 2.4 MeV in Ti 48 were found to be almost exactly out of phase with the corresponding elastic distributions. Large cross sections of the inelastic alpha scattering to the 2.21– and 3.0–MeV states in Al 27 suggest that these states are the members of a K π =5/2 + rotational band based on the ground state.

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.

Energy Dependence of Angular Distributions of the Reaction Al27(p, α)Mg24 in the Energy Region between 10.5 and 14.5 Mev

The angular distributions of the reactions Al 27 ( p , α)Mg 24 resulting in the ground and first excited states of Mg 24 were measured at 37 energies between 10.5 and 14.5 Mev, making use of proportional counters. Similar behaviour was obtained for both reactions. The variation of the shape of the angular distributions with the bombarding energy is rather smooth in the higher energy region, but becomes rapid with decreasing the bombarding energy. There appear some resonance-like peaks and valleys in the excitation curves at laboratory angles of 50°, 90° and 130° but their positions are not coincident with one another and in the higher energy region these peaks disappear in the excitation curves for the total cross sections. The variations of the excitation curves for the total cross sections and of the shape of the angular distributions with energy in the lower energy region may be due to the fluctuations in the number or properties of the compound nucleus levels and to the interference between the compou...

CATALYTIC OXIDATION OF TRITIUM IN WET GAS.

Use of precious metal catalyst is recommended in the tritium recovery system because it can oxidize tritium at ambient temperature. The ability to operate at the ambient temperature without preheating and past cooling is a large advantage in the ease of system operation. It is observed in this study, however, that the catalytic oxidation characteristics of the precious metal catalysts are largely affected by the water vapor to such extent that almost no oxidation rate of tritium is expected in the wet gas. Effect of the water vapor on the oxidation rate is quantitatively discussed based on data obtained in this study and an emergency cleanup system from the room air with pre-adsorption bed is proposed.

EXCITATION FUNCTIONS AND ANGULAR DISTRIBUTIONS OF THE REACTIONS Al*SUP 27/ (p,*alpha/)Mg*SUP 24/ AT 12.7 *approximately/ 14.1 Mev AND Cr*SUP 52/(p,*alpha/)V*SUP 49/ AT 9.0 *approximately/ 14.2 Mev

Making use of a proportional counter, alpha particles have been observed from the reactions Al 27 ( p , α)Mg 24 resulting in the ground and first excited states of Mg 24 and Cr 52 ( p , α)V 49 resulting in the lowest three and a few higher states. Excitation curves have been measured at a laboratory angle of 50° with respect to the bombarding beam, from 12.7 to 14.1 Mev for Al 27 ( p , α)Mg 24 and from 9.0 to 14.8 Mev for Cr 52 ( p , α)V 49 . The former shows a sharp energy dependence, while the latter shows a fairly smooth structure. Angular distributions have been measured at 14.1, 13.0 and 12.8 Mev for Al 27 ( p , α)Mg 24 and at 14.2, 13.0, 12.0, 11.0, 10.0, 9.5 and 9.0 Mev for Cr 52 ( p , α)V 49 . Although the Al 27 ( p , α 0 )Mg 24 data can be partially fitted by [ j 2 ( Q γ 0 ] 2 of Butlers theory, some angular distributions show strong backward peaking. Either interference between various direct interaction processes or between direct interaction and compound nuclear processes, or both are respons...

Angular Distributions of the Reactions Co59(p, α)Fe56 at 7.7∼14.1 Mev and Mn55(p, α)Cr52 at 7.6∼12.9 Mev

The angular distributions of the reactions Co 59 ( p , α)Fe 56 and Mn 55 ( p , α)Cr 52 resulting in the ground and first excited states of the residual nuclei have been measured at 7.7, 8.7, 9.8, 10.85, 11.9, 13.1 and 14.1 Mev and at 7.65, 8.85, 9.65, 10.7, 11.8 and 12.9 Mev of the incident proton energy, respectively, making use of proportional counters. Similar behaviour was obtained for these four reactions. For the reaction Co 59 ( p , α)Fe 56 the forward peak in the angular distribution is prominent at 14.1 and 13.1 Mev and disappears gradually with decreasing proton energy, and the angular distribution is approximately 90° symmetrical below about 11 Mev. For the reaction Mn 55 ( p , α)Cr 52 the angular distribution is considerably forward peaked at 12.9 and 11.8 Mev and it approximately 90° symmetrical below about 10 Mev. It was found that the total cross section integrated from the angular distributions for both reactions decrease smoothly with increasing proton energy. It is considered that the re...

Systematics and parameterization of continuum angular distributions for application to reactions induced by 14-MeV neutrons

Systematics are improved for application to reactions induced by 14-MeV neutrons. On the basis of this approach, new parameters for nucleon emission reactions are derived from Legendre polynomials fit 18- 25-MeV (p,n) and 18-MeV (p,p{prime}) data. For alpha-particle emissions, separate parameterizations are performed for equilibrium and preequilibrium components: Legendre coefficients obtained from calculations are parameterized for the former and the procedure used for nucleon emissions is applied to the latter. The angular distributions calculated using the present parameters show good agreement with those for 14-MeV (n,n{prime}), (n,p), and (n,{alpha}) reactions.