Sukeaki Yamashita

Augular Distributions of the Alpha Particles from the ( p , α) Reactions on Na 23 and K 39 at 6.9∼7.3 MeV

The angular distributions of the reactions Na 23 ( p , α)Ne 20 and K 39 ( p , α)A 36 leading to the ground and first excited states of the residual nuclei have been measured at 6.9, 7.1 and 7.3 MeV of the incident proton energy, respectively, by the use of a semiconductor detector. For the reaction Na 23 ( p , α)Ne 20 the angular distributions of these alpha particles are almost 90° symmetrical at 7.1 MeV of the incident proton energy, and they are slightly unsymmetrical about 90° at 7.3 and 6.9 MeV. For the reaction K 39 ( p , α)A 36 , the angular distributions are almost 90° symmetrical at all energies of the incident protons. It is considered that the reactions Na 23 ( p , α)Ne 20 and K 39 ( p , α)A 36 leading to the ground and first excited states of the residual nuclei, at around 7 MeV of incident proton energy, occur through a compound nucleus process and in the former reaction the number of the compound states excited by the about 7 MeV protons are probably not so many as to justify the statistical...

Elastic and Inelastic Scattering of 14.7 MeV Deuterons and of 29.4 MeV Alpha-Particles by Li 6 and Li 7

The angular distributions of alpha-particles and deuterons scattered elastically and inelastically by Li 6 and Li 7 were measured. The 2.18 MeV state of Li 6 , the 0.478 MeV and the 4.63 MeV states of Li 7 were appreciably excited. The experimental angular distributions were analysed with the DWBA theory, and the deformation parameters of the above mentioned states were determined. Experimental results and the DWBA analysis show the existence of some difference between the inelastic scattering of alpha-particles by Li 6 and by Li 7 , while no appreciable difference was observed in the case of the deuteron scattering. The DWBA calculation predicts larger quadrupole deformations of the excited states of Li 6 and Li 7 as compared with rotational model calculations of the energy levels.

Angular Distributions of Alpha-particles from F 19 , Al 27 and P 31 bombarded with Protons

The angular distributions of the alpha-particles were obtained for the reactions F 19 ( p , α) O 16 leaving the residual nucleus in the ground state, Al 27 ( p , α) Mg 24 and P 31 ( p , α) Si 28 leaving the residual nuclei in the ground and first excited states at four bombarding energies between 6.0 MeV and 7.4 MeV. The angular distribution for the reaction F 19 ( p , α) O 16 shows the backward peak at each energy, but at small angles it depends on the bombarding energy. The angular distributions for the reactions Al 27 ( p , α) Mg 24 and P 31 ( p , α) Si 28 are also energy-dependent, but contain a larger isotropic part than those for the reaction F 19 ( p , α) O 16 . The integrated cross sections for the reactions Al 27 ( p , α) Mg 24 and P 31 ( p , α) Si 28 leaving the residual nuclei in the first excited states are several times as large as those for the reactions leaving the residual nuclei in the ground states. It appears unlikely that these reactions can be accounted for by the formation of compoun...

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.

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 ...

Al

The angular distributions have been measured for the eight groups of alpha particles leading to the ground state and the excited states of Mg 25 from the reaction Al 27 ( d , α)Mg 25 with 14.7 MeV deuterons, by using a semiconductor detector of p - n junction. The differential cross-sections of the reactions leading to the single levels of Mg 25 are compared with a formula obtained from the two-nucleon pick-up theory. The experimental angular distribution for each alpha group with a comparatively large cross-section is in agreement, at least in forward angle, with the theoretical curve. The alpha group leading to the 3.40 MeV level of Mg 25 is considered to come from the transition to the 9/2+ state rather than to the 3/2- state. The total cross-sections for the levels of Mg 25 corresponding to the same K -band 5/2+ as that of the ground state of Al 27 are larger than the others.

sup 27

Slow beam extraction from the INS-AG electron synchrotron was done by using a one-third resonance of the betatron oscillation. A current strip was used to change the number of the radial betatron oscillation per revolution from 2.25 to 7/3 and to enlarge the amplitude of the oscillation. The extracting beam orbit was analysed using an approximate Hamiltonian which has a separatrix represented by three straight lines and the result was in good agreement with that pursued by a computer. The properties of the extracted beam were as follows; The efficiency was 50% for electrons of 300 MeV up to 1 GeV. The maximum beam intensity was 4×1011 electrons per second. The maximum duty cycle was 3%. Phase volumes for the horizontal and the vertical motions were 10-3 rad cm and 0.75×10-3 rad cm, respectively. The beam transport system and the radiation shielding system are also described.

(d,/cap alpha/)Mg

Angular distributions and total cross sections of the C 12 ( d , α)B 10 and O 16 ( d , α)N 14 reactions were obtained in the deuteron energy range from 15 MeV to 20 MeV. Deuteron energies were 15.1, 15.9, 16.7, 17.5, 18.2, 19.0 and 19.7 MeV in the C 12 ( d , α)B 10 reaction, and were 14.9, 15.4, 15.7, 16.0, 16.5, 16.9, 17.3, 18.1, 18.8 and 19.6 MeV in the O 16 ( d , α)N 14 reaction. Alpha particle groups leaving the residual nuclei in their low-lying states showed pronounced forward and backward peaks simultaneously in the whole energy range. Total cross sections decreased gradually with increasing deuteron energies, but some anomalies were found. Reaction mechanism is discussed under the assumptions of knock-out and heavy-particle stripping processes, and it is indicated that the clustering of nucleons at the surface of the target and or the residual nuclei seems to play an important role in these reactions.

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Abstract A simple method for preparing thin, uniform films of deuterated polyethylene is described.

REACTION AT 14.7 Mev

Angular distributions of alpha particles from the O/sup 16/(d, alpha )N/ sup 14/ reaction were measured. Results from the ground-state and second-excited- state reactions are presented in graphical form. The absolute cross section calculated from C/sub 8/H/sub 4/O/sub 2/ agreed reasonably with that from the O/ gas target. The principle of isotopic spin conservation was violated in this reaction. Comparison is made with previous experiments (T. Yanabu, J. Phys. Soc. Japan 16, 2118(1961); NSA, 15i 2l556; NSA, 15: 26972). (L.N.N.)