Motoharu Kimura

Energy Spectra of Photoprotons from p 31 and Ca 40

Photoproton spectra from P31 and Ca40 irradiated by 19 and 20.5-Mev bremsstrahlung, respectively, were observed using nuclear emulsions and previous methods (K. Shoda, et al., J. Phys. Soc. Japan, 16: 1807(1961)). Results were compared with the statistical model using the Weisskopf level density (V. F. Wofeisskopf and J. M. Blatt, Theoretical Nuclear Physics (John Wiley and Sons), 311(1954)). Data are presented in graphical form.

Photoprotons from S 32

The energy spectrum of 24-Mev bremsstrahlung photoprotons from S32 was studied using nuclear emulsions. The target thickness was 11.1 mg/cm2, which determined mainly the resolution of the result (about 2.5% for proton energy of 9 Mev). The cross section of S32( gamma ,p)P31 was estimated from experiments on P/sup 31/(p, gamma )S32. Such comparisons were possible for C12, O16, Ne20, Mg24, Si28, and Ca40 for which (p, gamma ) were previously studied.

Photoprotons from Silicon and Phosphorus

Photoprotons from Si and P produced a 24-MeV betatron have been observed in nuclear emulsions. Fine structures are observed in the energy spectrum of Si, showing a fairly similar shape to the excitation curve of Al ( p , γ) reaction. The appearance of these structures is expected resonating group model and probably the channel coupling theory as well. The distances of the proton peaks in the spectrum are nearly equal to those expected these theories. The type of spectrum of Si is different from that of P, and such difference seems to appear between even and odd Z neighbouring nuclei. The angular distributions for P have large maxima around 90°, but those for Si have not so large maxima and minima. This suggests that the shell structure may have some effects on the photonuclear reactions.

Photoneutron Cross Sections for Ag107, Mo92 and Zr90

Photoneutron cross sections and the yield curves were taken by the residual activity method for Ag 107 , Mo 92 and Zr 90 . Threshold energy were obtained as 9.35±0.1 MeV, 9.15±0.1 MeV, 12.38±0.1 MeV and 12.3±0.1 Mev for Ag 107,109 , Mo 92 and Zr 90 respectively. The energy for the maximum cross section was obtained as 14.5 MeV for Ag 107 , 16.5 MeV for Mo 92 and 17 MeV for Zr 90 . The giant resonance widths were measured about 5.3 MeV, 2.7 MeV and 2.9 MeV respectively. Intrinsic quadrupole moment determined from above data was (1.9±0.7)×10 -24 cm 2 for Ag 107 .

Structure of the giant resonance in the Al27(p, γ) reaction

Abstract The variation of the cross section for Al27(p, γ0 + γ1)Si28 with proton energy from 7.5 to 14.7 MeV, reveals the full structure of the giant resonance. Gamma ray yields for transitions to the ground and first excited states of the product nucleus were measured using a large NaI(Tl) crystal spectrometer. The width of the giant resonance is of the order of 4 MeV, with many resonance peaks and possibly with a splitting due to deformation.

Detector system for the analysis of scattered electrons in Tohoku University 300-MeV linac

Abstract The magnetic spectrometer to analyze the elastically and inelastically scattered electrons in combination with the Tohoku University 300-MeV electron linear accelerator is described with emphasis on its electron ladder and the data acquisition system. We employed Si(Li) semiconductor detectors combined with the conventional logic circuits for the coincidence counter telescopes and also for the other circuitry system. Three detector pieces were used per channel and a total of 33 such channels were employed. Data was collected during the beam pulse intervals of about 3.3 msec, after each pulse. The stability of the counting efficiency of the detector channel and the angular constancy of the effective solid angle of the spectrometer were examined.

On the Study of P31(γ, n) and S32(γ, n) Reaction

Photoneutron cross sections of P³¹ and S³² were measured up to 24 Mev by using bremsstrahlung from a 25 Mev betatron. Each neutron yield point was the result of four or five measurements involving a count of about 10⁴ for each point. Cross section curves and characteristic constants are shown. (W.D.M.)

NEUTRON DEBYE--SCHERRER DIFFRACTION WORKS USING A LINEAR ELECTRON ACCELERATOR.

Abstract Neutron diffraction patterns were obtained by the time-of-flight method using Tohoku linac for the case of powdered samples as well as for single crystals. Thermal neutron beams of 35–50 μsec pulse width were obtained by poisoned water moderator. Powder patterns of Al at different temperatures have shown many lines of high indices, which enabled to calculate the Debye temperature with considerable accuracy. Several other powdered samples including Si, ZnO were also examined. Magnetic peaks of α-Fe 2 O 3 , CaFe 2 O 4 were identified. Count collecting time of 2 or 3 h was enough to reach the reliability R to the level of a several percent. High index lines appeared very conspicuously, in contrast to the reactor-chopper results. The fwhm of the diffraction lines was 2.0–1.5% in case the scattering angle 2θ was 90°. It depended on the energy of diffracting neutrons, becoming smaller for neutrons of wavelength shorter than 1 A, that is for higher index lines.

Level Structure of Nd144

The energies and spins of lower excited levels in Nd 144 have been established by studies of the beta decay of Ce 144 –Pr 144 and the electron capture decay of Pm 144 . The experiments include the energy and relative intensity measurements, and directional correlation measurements of gamma rays by several NaI (T1) scintillation counters. The level of Nd 144 is populated at the 695 keV and 2190 keV from decay of Pr 144 , and the 695 keV, 1310 keV, and 1780 keV from the decay of Pm 144 . The levels at the 1220 keV and the 1560 keV which have been found by the neutron capture gamma ray measurements could not be found in both decay in the limit of about one percent.

Photoneutron Reaction of S32

The photoneutron cross section of S 32 was observed up to 22 MeV with good energy resolution, together with the photoneutron spectrum using a stilbene scintillation spectrometer. Fine structures were observed in either of the two measurements. Taking into account the threshold energy and the excitation energies of the residual nucleus, these structures have been shown to be consistently related with each other. Experimental results were discussed using the statistical model calculation, assuming that the emitted particles were only p -wave and f -wave particles. The integrated cross section ratio for S 32 (γ, n ) to P 31 (γ, n ) reaction and the same ratio for S 32 (γ, p ) to S 32 (γ, n ) reaction were well explained by the calculations. The difference between the energy spectrum of the photoprotons from P 31 and that from Si 28 also seemed to be well explained qualitatively. In the appendix, the contributions of the f -wave protons for the energy spectrum of photoprotons were shown. Summarizing the discu...