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Neutron emission spectra and production rates of radioactive nuclide 7Be in the (d, n) reactions on thick lithium and 9Be targets have been measured for 25 MeV deuterons at the Tohoku University AVF cyclotron (K=110) facility to provide basic data for the design of the intense neutron source, International Fusion Reactor Material Irradiation Test Facility (IFMIF).Neutron spectra were measured with the time-of-flight method at ten laboratory angles between 0° and 90° by using a beam swinger system. Data were obtained down to ~1 MeV from the highest energy, using a two-gain NE213 detector system. Induced radioactivity of 7Be was measured by detecting the 478 keV γ-rays from 7Be with a pure Ge detector.The experimental results of neutron spectra revealed clearly the entire shape of the neutron emission spectrum and the angular dependence including so called “high energy tail” extending up to ~40 MeV. The present data at 0° are in reasonable agreement with corresponding value by Lone et al.at 23 MeV above ~5 MeV, but show large discrepancy in the lower energy region. The results of 7Be production for both nuclei were much larger than expected by the calculation with a recent code IRAC.

Double differential cross sections of several ten’s of MeV neutron induced reactions for elements composing the human tissue were measured using specially designed spectrometers at TIARA 7Li(p,n) neutron source. In spectroscopy of particles from neutron induced reactions, a large solid angle and particle acceptance detector is indespensable. For particles from 5 MeV a to 70 MeV proton, a spectrometer consisting of three counter telescopes and a vacuum chamber was used. For heavier particles, a Bragg curve spectroscopy technique was adopted to neutron field. Double differential cross section of p,d,t,a emission for N and O were obtained using the former spectrometer. In the later method we fabricated a test spectrometer to check applicability and signal to noise ratio in neutron field. Using the spectrometer, energy spectra of heavier particles (Li, Be, B, C) from carbon were observed.

Wattempted to improve the detector consisting of a6 LiF film and aZ nS(Ag) scintillator coupled to an optical fiber for light transimission to photomultiplier tube. For theZnS(Ag)scintillator, we employed two types of scintillator; (1) ZnS(Ag) doped on a Mylar film (commercial one)and (2) an NE426 scintillator. By employing the combination of ZnS(Ag) and 6LiF films with appropriate thicknesses and arrangement, we could improve the pulse-height distribution. Moreover, we found that pulse shape discrimination (PSD) technique is applicable and effective to distinguish tritons and a particles from proton by Mylar. Applying this technique, we could distinguish thermal neutron events from background events existing in low pulse-height rcgion. The present detector system was tested in the accelerator-based neutron filed and applied to thermal neutron profi1ing in the mockup system of tritium breeding blanket in fusion reactors. By using this detector, we could measure spatial distribution of thermal neutron in real time with high precision by rejecting background components.

Neutron activation cross sections between 30 and 70 MeV were measured by the activation method using a semi-monoenergetic neutron field settled at the AVF cyclotron of the Cyclotron and Radioisotope Center(CYRIC), Tohoku University. Natural samples of N, O, Si, Na, Ca and Mg which are the major elements of water, air and soil were irradiated in this neutron field generated through the 7Li(p,n)7Be reaction by 30, 35,40, 50,60 and 70 MeV protons on thin Li target. Neutron yields were measured with the time-of-flight method using a calibrated NE213 organic liquid scintillator. From the induced activities measured with the HPGe detectors, we estimated the excitation functions of 15 cross sections.

Prompt fission neutron spectra of 233U, 238U and 232Th for mono-energetic fast neutrons were measured by using the time-of-flight (TOF) method at Tohoku University 4.5 MV Dynamitron accelerator facility. Data were obtained for 233U at En=0.55, 1.9, 4.1 MeV, 238U at En=1.9, 4.1 MeV, and 232Th at En=4.1 MeV using solid samples. The data of 233U and 232Th were obtained in absolute scale (mb sr–1MeV–1) by normalizing the data to the 238U spectrum as a standard.

Consistent analysis of neutron scattering data of 238U and 232Th with Hauser-Feshbach-Moldauer theory and coupled channel model is carried out. Collective bands structures are reproduced within soft deformable rotator model. The direct excitation of ground state and vibrational band levels is calculated within rigid rotator and soft (deformable) rotator models, respectively. Structures evident in measured neutron emission spectra are correlated with excitation of vibrational levels of Kπ= 0−and Kπ= 0+, 2+bands. Prompt fission neutron spectra data are described. Contributions of neutrons, emitted in (n, nf) reactions are shown to be strongly dependent on the emissive fission contribution to the observed fission cross section.

Experimental data of 58Ni(n, α) reaction cross sections are analyzed with the Hauser-Feshbach statistical model with the width fluctuation correction by Moldauer. A neutron optical potential which was derived from neutron elastic scattering data is used for an entrance channel in order to fix the total reaction cross sections at reliable values. Global optical potentials are used for the proton and α-particle emission channels, and level density parameters of the residual nuclei are determined from the cumulative plot of discrete levels. These parameters are adjusted to the experimental data of 58Ni(n, α) and (n, p) reaction cross sections, including the angular distribution of the emitted α-particles. The parameters thus obtained yield a good fit to the experimental cross sections of those reactions up to 8 MeV.

Double differential (n, α) reaction cross sections of 58Ni and natNi were measured for 4.2–6.5 MeV neutrons with energy resolution good enough to separate α-particles from the low-lying levels of residual nuclei by using a gridded ionization chamber. Angular distribution and excitation functions were derived for α0, α1and αi≥2 components (α-particles to the ground level, the 1st level and levels higher than the 2nd level, respectively). The experimental results were compared with these obtained from calculation based on Hauser-Feshbach model employing the optical potential and the level density parameters derived to reproduce the experimental values of total, (n,p) and (n,α)cross sections. The calculation showed fair agreement with the experimental data while it underestimated the (n,α)cross section above 6 MeV.

Double-differential neutron emission cross sections (DDXs) of 6Li, 7Li and 9Be were measured for 18.0 MeV and 11.5 MeV incident neutrons produced by the T(d, n) and 15N(d, n) reactions respectively, using the Tohoku University Dynamitron time-of-flight (TOF) spectrometer. The data were obtained at 13 laboratory angles, and angular-differential cross sections (ADXs) of elastic and inelastic scattering neutrons were derived from the DDXs. For 11.5 MeV neutrons, we obtained the neutron emission spectra over the secondary neutron energies by newly employing the double TOF method as well as the conventional one. In the measurements at 18.0 MeV, we achieved better energy resolution than in our previous studies by using a neutron detector that has a larger solid angle and a thinner tritium target. The experimental results of DDXs and ADXs were compared with our previous results and the evaluated data given in JENDL-3.2, JENDL Fusion File and ENDF/B-VI. It is found that the JENDL data reproduce the experimental ones very well.

Measurement of the neutron energy spectrum in the epithermal energy region is very important for accelerator-based Boron Neutron Capture Therapy (BNCT), but the measuring technique is not well established. We developed a new multi-moderator spectrometer using boron-loaded siHcon rubber and polyethylene for epithermal neutrons.In this paper, the response functions of the new multi-moderator neutron spectrometer were calculated with the MCNPX code, and were compared with the measured results in a neutron calibration field using a 252Cf neutron source.This spectrometer can be applied to measure the neutron spectrum to be used in accelerator-based Boron Neutron Capture Therapy.