No abstract available

[en] The possibility of a crossed beam facility of slow neutrons x unstable nuclei is examined in connection with the Japanese Hadron Project. With a pulsed proton beam of 50 Hz repetition with a 100 μA average beam current, one obtains a spallation neutron source of 2.4 x 10⁸ thermal neutrons/cm³/spill over a 60 cm length with a 3 msec average duration time by using a D₂O moderator. By confining radioactive nuclei of 10⁹ ions in a beam circulation ring of 0.3 MHz revolution frequency, so that they pass through the neutron source, one obtains a collision luminosity of 3.9 x 10²⁴/cm²/sec. A new research domain aimed at studying rapid processes in nuclear genetics at laboratory will be created. (author)

[en] A laser vaporization-microwave induced plasma system was used for the determination of various elements in solid samples such as brass, steel, and aluminum alloy. The emission signals of Al, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Tl, and Zn were traced with an oscilloscope, and those elements were determined with high-speed peak-holder and integrator. Precision (relative standard deviation) was 1.2% to 13.8% for the peak-height method, and 2.3% to 12.1% for the peak-area method. The detection limits in the solid samples ranged from 0.9 ppM (0.7 pg) for Zn in aluminum alloy to 22 ppM (20 pg) for Mo in steel. 9 figures, 2 tables

[en] The measured neutron energy spectra produced from thick targets by light-mass heavy ion beams were analyzed with the phenomenological hybrid model of equilibrium and pre-equilibrium emissions. The neutron energy spectra are fitted to two (in the energy region of incident projectile energy lower than 100 MeV) and three (in the energy region of incident projectile energy higher than 100 MeV) Maxwellian-type components. The lowest energy component corresponds to the evaporation neutrons from a compound nucleus having a nuclear temperature independent to the neutron emission angle and the higher two components to the pre-equilibrium neutron emission having a nuclear temperature depending on the angle. The total neutron yield was evaluated by surveying several published papers and estimating the neutron yield below a few MeV by fitting some spectra measured above that energy to the Maxwellian distribution. In order to use for the neutron activation cross section measurement and the induced radioactivity study, a pseudo-monoenergetic neutron beam course in the energy range from 15 to 40 MeV was installed by using the Be(p, n) reaction. The peak neutron energy changes with the proton energy and the beam intensity was relatively high. (author)

[en] The altitude variation of the cosmic-ray neutron energy spectrum and the dose equivalent rate was measured at an average geomagnetic latitude of 24 degrees N by using the high-efficiency multi-sphere neutron spectrometer and neutron dose-equivalent counter developed by the authors. The data were obtained from a 2-h flight over Japan on 27 February 1985. The neutron energy spectra measured at sea level and at altitudes of 4880 m and at 11,280 m were compared with the calculated spectra of O'Brien and with other experimental spectra, and they are in moderately good agreement with them. The dose equivalent rate increases according to a quadratic curve up to about 6000 m and then increases linearly between 6000 m and 11,280 m. The dependence of dose equivalent rates at sea level and at an altitude of 12,500 m on geomagnetic latitude also is given by referring to other experimental results

[en] Spectra and attenuation profiles of neutrons and gamma rays transmitted through graphite piles were measured by an organic scintillator with an n-γ discrimination technique. The neutrons and gamma rays were produced in a graphite target placed in front of the piles, which were bombarded by 52-MeV protons. The piles were 54 cm high, 90 cm wide, and 11.7, 23.5, and 44.9 cm thick. The energy spectra of neutrons and gamma rays were obtained after unfolding by the FERDO code, from pulse-height distributions. Spectra calculated by use of a Monte Carlo neutron transport code developed for neutrons of energy up to 50 MeV show good agreement with the measured spectra. 9 figures, 1 table

[en] The three-dimensional (surface and altitude) skyshine neutron-dose-equivalent distribution around the 1-GeV electron synchrotron (ES) of the Institute for Nuclear Study, University of Tokyo, was measured with a high-sensitivity dose-equivalent counter. The neutron spectrum in the environment was also measured with a multimoderator spectrometer incorporating a ³He counter. The dose-equivalent distribution and the leakage neutron spectrum at the surface of the ES building were measured with a Studsvik 2202D counter and the multimoderator spectrometer, including an indium activation detector. Skyshine neutron transport calculations, beginning with the photoneutron spectrum and yielding the dose-equivalent distribution in the environment, were performed with the DOT3.5 code and two Monte Carlo codes, MMCR-2 and MMCR-3, using the DLC-87/HILO group cross sections. The calculated neutron spectra at the top surface of the concrete ceiling and at a point 111 m from the ES agreed well with the measured results, and the calculated three-dimensional dose-equivalent distribution also agreed. The dose value increased linearly with altitude, and the slope was estimated for neutron-producing facilities. (author)

[en] Attenuation of neutrons and photons transmitted through grahite, iron, water and ordinary concrete assemblies were studied using gold foils for thermal neutron and an NE-213 organic scintillation detector with an (n-γ) discrimination technique for spectral measurements. Source neutrons and photons were produced by 52-MeV proton bombardment of a 21.4-mm-thick graphite target placed in front of the assembly. The distributions of the light output from the scintillator were unfolded by the revised FERDO code. These experimental results were used as benchmark data on neutron and photon penetration by neutrons energy above 15MeV. Multigroup Monte Carlo, one-dimensional ANISN and two-dimensional DOT-3.5 transport calculations were performed with the DLC-58/HELLO group cross sections to compare with the measurement and to evaluate the cross sections. The DOT code was also used for the estimation of room-scattered neutron and photon contribution to the measured spectra. The results of the ANISN calculation of neutrons and the three-dimensional Monte Carlo calculation agreed with the experimental values except for high energy neutrons transmitted through water and graphite. The agreement of both calculations was well within the accuracy of 7% in the measured attenuation coefficients. For photons, the ANISN calculation gave >20% overestimation of the attenuation coefficients in the case of deep penetration through the medium for which the photon mean-free-path is shorter than that of neutrons, such as in iron and concrete. The result of the DOT calculation of neutrons down to thermal energy agreed well with the gold foil measurement in the absolute value. (author)

[en] The possibility of a crossed beam facility of slow neutrons capturing unstable nuclei is examined in connection with the Japanese Hadron Project. With a pulsed proton beam of 50 Hz repetition and with a 100 μA average beam current, one obtains a spallation neutron source of 2.4x10⁸ thermal neutrons/cm³/spill over a 60 cm length with a 3 ms average duration time by using a D₂O moderator. By confining radioactive nuclei of 10⁹ ions in a beam circulation ring of 0.3 MHz revolution frequency, so that nuclei pass through the neutron source, one obtains a collision luminosity of 3.9x10²⁴/cm²/s. A new research domain aimed at studying rapid processes in nuclear genetics in a laboratory will be created. (orig.)

[en] We have measured the neutron activation cross sections for fifteen samples in the energy region from 15 MeV to 40 MeV by using the five monoenergetic neutrons produced from the ⁷Li(p, n) reaction. Two types of target were used; one is 2 mm-thick ⁷Li target backed by 12 mm-thick graphite and the other is only 12 mm-thick graphite target. The true neutron spectrum was obtained from the difference of two spectra produced from these two targets measured with the TOF method and the activation rate was also got from the difference of the repeated irradiations with two targets. The absolute value of the neutron spectrum was accurately estimated to measure the ⁷Be yield produced by the ⁷Li(p, n) reaction. As the first analysis, we could estimate the ¹⁹⁷Au(n, 4n) reaction cross section. (author)