Hidehiko Arima

Study on effective average (γ, n) Cross Section for 89Y, 90Zr, 93Nb, and 133Cs and (γ, 3n) cross section for 99Tc

A nondestructive detection technique was proposed for the easy assessment of long-lived radionuclides by the use of bremsstrahlung photons. The nuclide of 99Tc was considered for the assessment over an effective average 99Tc (γ, 3n) 96Tc cross section. For validating the experimental method on 99Tc, photonuclear (γ, n) cross sections of 89Y, 90Zr, 93Nb, and 133Cs were measured. Continuous-energy bremsstralung photons were generated from a platinum target bombarded by an electron beam of 32/36MeV from an electron linac. The photonuclear (γ, n) cross sections were previously measured by Saclay (France) and Livermore (USA) laboratories for 89Y, 90Zr, 93Nb, and 133Cs nuclides. For 89Y, 90Zr, and 133Cs, the present results were in good agreement, within 9% deviation with Saclay and an acceptable deviation of 14–36% from Livermore. In the case of 93Nb, the contribution for 93Nb (γ, n) 92Nb* in the metastable state was 55.2% of the total (γ, n) cross section of Saclay in an averaged form. The present experimental method was thus confirmed to show a good accuracy. The effective average cross section of 99Tc (γ, 3n) 96Tc was obtained as 2.30 mb in the energy range of 25.723–36 MeV.

Measurements of Neutron Spectra Produced from a Thick Tungsten Target Bombarded with 0.5- and 1.5-GeV Protons

For validation of calculation codes that are employed in the design of pulse spallation neutron source and accelerator driven system, spectrum of neutrons produced from a thick target plays an important role. However, appropriate experimental data were scarce for the incident energies higher than 0.8 GeV. In this study, the spectrum from a thick tungsten target was measured The experiment was carried out at the π2 beam line of the 12-GeV proton synchrotron at KEK. The tungsten target was bombarded by the 0.5- and 1.5-GeV secondary protons. Spectrum of neutrons was measured by the time-of-flight technique using organic scintillators of NE213, The calculated result with NMTC/JAM and MCNP-4A is compared with the measured data. It is found that the NMTC/JAM generally gives a good agreement with experiment. The NMTC/JAM, however, gives 50 % lower neutron flux in the energy region 20~80 MeV, which is consistent with the results in previous comparison of lead target. For the neutrons between 20 and 80 MeV, the calculation using with the in-medium nucleon-nucleon cross sections reproduced the experiment fairly well.

Multipole analysis for absolute magnetic field measured by multi-probe pulsed-NMR method

For accelerator dipole magnets, the study on multipole coefficients in a local region is useful for understanding magnet characteristics and checking construction procedure. The multi-probe pulsed-NMR method is a candidate for measurement of the local multipole coefficients. For the absolute fields measured by the multi-probe pulsed-NMR method, a rigorous application of the Fourier expansion is found to yield multipole coefficients. It is made clear that the direction of the dipole field is unable to be determined by the Fourier expansion alone. For estimating alignment accuracy of pulsed-NMR probes, the relationship between errors of multipole coefficients and those of probe position is derived by the Fourier expansion method. For applying of multi-probe pulsed-NMR method to accelerator dipole magnets, we designed and fabricated a field measuring system using two probes. The probes had NMR coils wound around glass ampoules with a diameter of about 1.4 mm. The NMR signal was processed with a phase lock loop circuit to produce the NMR frequency. Dipole field uniformity and multipole coefficients were measured at 0.35 T for a 1.5 m long dipole magnet. It was confirmed that the field data by this NMR system had an accuracy of 10/sup -6/.

Experimental Neutron-Production Double-Differential Cross Section for the Nuclear Reaction by 1.5-GeV π+ Mesons Incident on Iron

The neutron-production double-differential cross sections were measured for 1.5 GeV π + mesons incident on the iron target. It is shown that adoption of the in-medium NN cross sections leading to the longer mean free path improves the agreement between the calculations and the experiments

Brief Calculation of Neutrino Energy Spectra by the Use of Nuclear Data Files

Nuclear reactors generate a highly intense flux of electron-antineutrinos from fission products through β− decay, and a slight amount of electron-neutrinos through either β+ decay or electron capture. Neutrino energy spectra are usually calculated by the β decay theory. Since the reactor neutrinos are emitted from a great number of nuclides, the calculation requires a lot of level scheme of these nuclides. Nuclear data files, however, are available these days. It is possible to evaluate the electron-antineutrino and -neutrino spectra for a nuclear reactor on the basis of nuclear data files (JENDL-FP-Decay-Data-File-2000, JENDL-3.3)1, 2). In the study, we consider β transition of 420 nuclides for electron-antineutrino spectra and 120 nuclides for electron-neutrinos. We derive electron-neutrino and -antineutrino spectra in the energy range of 10 keV to 8 MeV from nuclear data files. The method gives good agreement with other studies for electron-antineutrino spectra. We show a simple method to estimate the reactor neutrino spectra without complicated computation.

Measurement of the photonuclear (γ, n) reaction cross section for 129I using bremsstrahlung photons

Abstract Nuclear waste contains a significant amount of long-lived non-gamma-emitting nuclei such as 129I and 14C. A method of nondestructive detection for monitoring long-lived waste products is proposed as an application of the (γ,n) reaction. This method is useful for surveying long-lived “difficult-to-measure” nuclides, e.g., 129I. Iodine-128 produced from the reaction of 129I(γ,n)128I emits gamma rays that can easily be measured by a gamma-ray counter. We measured the inclusive photonuclear 129I(γ,n)128I reaction cross section induced by bremsstrahlung photons. The photons were produced at a Ta target bombarded by 30-MeV electrons from a linear accelerator. The intensity of the slow neutrons was considered in the reactions of 127I(n, γ)128I and 129I(n, γ)130I. The activity of 128I was measured by a high-purity germanium spectrometer. The gamma-ray flux and the neutron flux were calculated using the EGS and MCNP codes, respectively. The average activation cross section of the 129I(γ,n)128I reaction had a 12% deviation from the evaluated International Atomic Energy Agency photonuclear data.

KYUSHU UNIVERSITY POLARIZED ION SOURCE.

A compact atomic‐beam type of polarized ion source, under construction at Kyushu University, is described. Newly developed permanent sextupole magnets are used and their operational characteristics are measured precisely and analyzed. In order to optimize the strong magnetic field electron impact ionizer performances, a computer code has been developed which simulates the trajectories in the ionizing volume of the electrons and the positive ions produced. A method of optimizing the radio‐frequency unit is proposed. This polarized ion source will be used for a variety of research, especially for the polarized fuel fusion reaction study.

Polarized ion source for low energy nuclear fusion research

A compact polarized ion source is under construction at Kyushu University. The ion source is designed to produce the polarized deuteron beam for measurements of the fusion reaction rate up to the deuteron energy of Ed=150 keV. Components of the ion source such as the dissociator, the high field permanent sextupole magnets, the rf‐transition units, and the electron bombardment type ionizer had been fabricated. In this paper, performance and present status of the ion source are summarized and a future prospect of experiment of a polarized nuclear fusion reaction is described.

Simple Calculation of Reactor Antineutrino Energy Spectrum by the Use of Nuclear Data Libraries

We calculated the nuclear reactor antineutrino spectrum on the basis of nuclear data libraries (JENDL-3.2, JNDC-V2). The antineutrino spectrum was first calculated with neglecting energy dependence of matrix element, and the result had tendency to be larger than the experimental data in the high energy region. We introduced an adjustable parameter for correcting the spectrum calculation. The method gives a good agreement between calculated and experimental spectra.

Incorporation of the Fragmentation Process into High Energy Transport Code (HETC)

High Energy Transport Code (HETC) based on the intranuclear-cascade-evaporation model is modified for calculating the proton-induced fragmentation cross sections. The systematics of the fragmentation reaction are empirically formulated using the excitation energy after the cascade collision. The systematics are incorporated into the HETC as a subroutine set. The free-space nucleon-nucleon collision cross sections in the HETC were replaced by the in-medium ones. The fragmentation cross sections by the modified HETC (HETC-FRG) are compared with the results by other codes based on the intranuclear-cascade-evaporation model. It is shown that the HETC-FRG reproduces experimental data particularly on emission of fragments such as 7Be typically within an accuracy of a factor of 2.