Kyue Fukuda

ALPHA-PARTICLES FROM SEVERAL ELEMENTS BOMBARDED WITH 30, 43 AND 56 Mev PROTONS

Abstract Several elements were bombarded with 30, 43 and 56 MeV protons from the INS(Tokyo) syncho-cyclotron. Energy spectra and angular distributions of emitted α-particles were measured by an emulsion camera. The dependence of total cross sections, angular distributions and peak energies of the spectra on the bombarding energy as well as the atomic number of target nuclei is described. The cross sections were separated into two parts, the direct process and the compound process. Energy spectra ascribed to the direct process are not inconsistent with the picture of knockout process of quasi-free α-particles.

Emission of Photoneutrons form 29Si at Photon Energies up to 13 MeV

The photoneutron cross section of 29 Si has been studied by irradiating silicic anhydride, enriched in 29 Si, in the X-ray beam of a 15 MeV linear electron accelerator. The photoneutron cross-section shows maxima at about 10.6 and 12.2 MeV. The integrated cross-section form the threshold to 13.0 MeV is 11 MeV·mb. The angular distribution of photoneutrons has also been measured to fit with a curve of the form a + b sin 2 θ. The values for b / a are found to be 2.1±1.0 and 3.9±0.8 for measurements with bremsstrahlung having maximum energies of 11.7 and 12.9 MeV, respectively. The significant features of the photoneutron cross-section and the angular distribution are discussed and compared with theoretical calculations for the E 1 transition of a valence neutron.

The effect of high gamma-ray doses on the thermal properties of muscovite mica: Application to dosimetry

Abstract Differential thermal analysis has been made for muscovite mica exposed to 60 Co gamma rays of doses up to 1.2×10 10 R. The thermal curves show a endothermic peak below 950°C. The starting temperature of the endothermic reaction increases from 770 to 855°C with increasing dose. The resistance to the thermal decomposition of muscovite mica is increased by gamma-ray irradiation. The change in thermal properties has been utilized for measuring and recording high gamma-ray and electron doses. A simple mechanism is suggested to understand the radiation-induced effect on the thermal properties of muscovite mica.

Influence of a dye film dosimeter inserted in a solid on electron behavior and dosimetry

Abstract The depth-dose distribution in aluminum irradiated with a 15 MeV electron beam has been measured by inserting a dye film dosimeter in parallel with the beam. The distribution near the irradiated surface has shown a profile theoretically unexpected. The cause of this erroneous profile has been studied and attributed to the streaming of the incident electrons through air gaps formed between the film and the medium. This effect has been found to be suppressed by the increase of the angle between the film and the electron beam.

Dosimetry and processing anomalies due to heterogeneities of materials irradiated with high-energy electrons. Influence of heterogeneities on e-irradiation☆

Abstract Nonuniform dose distributions in heterogeneous materials irradiated by high-energy electron beams were mapped by using blue cellophane thin dosimeter strip (20μm thickness). The absorbed doses and dose distributions in solid-state dosimeters and in products irradiated for practical use have been estimated from the measurements. Deviations from uniformity of absorbed doses as large as several tens of percent have been found near material interfaces.

LOWER EXCITED STATES IN P

The gamma-rays from the Si 28 ( p , γ) P 29 reaction at the E p =369 kev resonance were studied with a large NaI(Tl) crystal scintillation spectrometer. The resonance state, corresponding to the 3.116±0.012 Mev fourth excited state in P 29 , was found to decay by (74±4)% to the first excited state at 1.384±0.008 Mev and by (26±4)% to the second excited state at 1.961±0.013 Mev which decays predominantly to the ground state. From the angular distribution measurements of each gamma-ray line, spins and parities of these lower levels in P 29 were unambiguously assigned as follows: 1.38 Mev(1st), J =3/2+; 1.96 Mev(2nd), J =5/2+; 3.12 Mev(4th), J =5/2+. These assignments are all consistent with the known character of the corresponding levels in the mirror nucleus Si 29 , and are also in agreement with the theoretical predictions. From the precise gamma-ray energy measurements, the Q -value of this reaction was estimated as 2.760±0.013 Mev, which is by about 36 kev larger than the published value based on the β-...

sup 29

The gamma-rays from the Si 28 ( p , γ) P 29 reaction at the E p =369 kev resonance were studied with a large NaI(Tl) crystal scintillation spectrometer. The resonance state, corresponding to the 3.116±0.012 Mev fourth excited state in P 29 , was found to decay by (74±4)% to the first excited state at 1.384±0.008 Mev and by (26±4)% to the second excited state at 1.961±0.013 Mev which decays predominantly to the ground state. From the angular distribution measurements of each gamma-ray line, spins and parities of these lower levels in P 29 were unambiguously assigned as follows: 1.38 Mev(1st), J =3/2+; 1.96 Mev(2nd), J =5/2+; 3.12 Mev(4th), J =5/2+. These assignments are all consistent with the known character of the corresponding levels in the mirror nucleus Si 29 , and are also in agreement with the theoretical predictions. From the precise gamma-ray energy measurements, the Q -value of this reaction was estimated as 2.760±0.013 Mev, which is by about 36 kev larger than the published value based on the β-...