Measurement of neutron capture cross-section of indium in the energy region from 0.003 eV to 30 keV

The neutron capture cross-section of indium (In) has been measured in the energy region from 0.003 eV to 30 keV by the neutron time-of-flight (TOF) method with a 46-MeV electron linear accelerator (linac) of the Research Reactor Institute, Kyoto University. An assembly of Bi₄Ge₃O₁₂ (BGO) scintillators, which was composed of 12 pieces of BGO and placed at a distance of 12.7±0.02 m from the neutron source, was employed as a total energy absorption detector for the prompt capture γ-ray measurement from the sample. In order to determine the neutron flux impinging on the capture sample, a plug of ¹⁰B powder sample and the ¹⁰B(n,α) standard cross-section were used. The data measured by Haddad et al. (Haddad, E., Friesenhahn, S., Lopez, W.M., 1963. Report of Gulf Energy and Environmental Systems, p. 3874) seem to be in good agreement with the present measurement. Popov et al. obtained the poor energy resolution data in the resonance region with a lead slowing-down spectrometer and the consistent data with the present above about 300 eV. The experimental data measured by Kononov et al. (Kononov, U.N., Jurlov, B.D., Poletaev, E.D., Timokhov, V.M., Manturov, G.N., 1977. Report of Obninsk, pp. 22–29) and Gibbons et al. (Gibbons, J.H., Macklin, R.L., Miller, P.D., Neiler, J.H., 1961. Phys. Rev. 122, 182) showed good agreement with the present values in the higher energy region. However, the data measured by Block et al. (Block R.C., Kaushal, N.N., Hockenbury, R.W., 1972. Conference on New Developments in Reactor Physics and Shielding at Kiamesha Lake, Vol. 2, p. 1107) seem to be a little higher than the present measurement above 800 eV. The evaluated data in ENDF/B-VI, JENDL-3.2, and JEF-2.2 have been in general agreement with the present result in the relevant energy region, although the JENDL-3.2 are higher than the measurement, the ENDF/B-VI and the JEF-2.2 from 2 to about 10 keV. Most of the previous experimental and the evaluated thermal neutron cross-sections are generally close to the present value of 199.6±5.6 b at 0.0253 eV.     

Steady-State Power Coefficients of Fast Reactor Considering the Effects of Partial Load and Flow Control

High resolution neutron transmission and low background capture measurements were carried out on the separated rubidium isotopes, using the time-of-flight facility of the linear accelerator of Japan Atomic Energy Research Institute. Resonance parameters and associated quantities were deduced as follows:

For ⁸⁵Rb, gΓ _n values were determined for 138 resonance levels in the energy region below 18.5 keV. s-wave strength function was obtained to be S₀=(0.94±0.11)×10^?4, average level spacing ≤D>=133±11 eV and average radiative width ≤Γ _r >=328±18 me V. For ⁸⁷Rb, gΓ _n values were determined for 30 resonance levels in the energy region below 48.6 keV and the following quantities were deduced:

S₀=(1.15±0.3)×10^?4, D=1,380±250 eV and ≤Γγ>=166±30 meV.

For ⁸⁵Rb average properties of resonances are in good agreement with the prediction of the statistical model. On the other hand, for ⁸⁷R9b the average properties of resonances deviate from the prediction of the statistical model; four strong s-wave resonances cluster within an energy interval of 5 keV, and they carry about 37% of s-wave strength below 48.6 keV.     

Chemical states and thermal stability of hydrogen-implanted Ti and V studied by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) was applied to the chemical state studies of Ti and V metals bombarded with 8 keV hydrogen ions. The binding energies of the lines for the ion-implanted Ti and V shift from those for the metallic states by 0.3 eV, are consistent with the core-line shifts for the thermally synthesized hydrides such as TiH_1.97 and VH_0.55 The metal 3d-H1s bonding level for the hydrogen implanted Ti appears at ~ 3.5 eV below the Fermi level, which is lower by ~ 2.5 eV than the molecular-orbital energy previously calculated for TiH₂. In the case of the ion-implanted V, however, it appears at ~ 5.0 eV, which is almost equal to the molecular-orbital energy for VH₂. The photopeaks corresponding to the Ti-H and V-H bonds for the ion-implanted samples grew up on raising the annealing temperature up to 550°C and 150°C, respectively. The phenomena are interpreted by means of the thermal diffusion of the implanted hydrogen from bulk to surface.     

Energy calibration of the 500 kV heavy ion implanter ionas

Gamma ray yield functions of (p, αγ) and (p, γ) resonance reactions on semi-thick ¹⁹F, ²³Na, ^24,26Mg and ²⁷Al targets were measured and used to calibrate the accelerating voltage and energy resolution of the new 500 kV heavy ion implanter at Göttingen. The energy spread of the proton beam was found to vary linearly with the accelerating voltage from ΔE(200 keV) = 55 eV fwhm to ΔE(500 keV) = 105 eV; it is made up by a 0.012% high voltage ripple and the Doppler broadening of the resonances due to the thermal motion of the target nuclei. A long term stability of the proton energy of < 5 eV/h at 300 keV was achieved with new resistors in the voltage regulating system.Applications of the accelerator for the remeasurement of some resonance energies and widths and for depth profiling of light implanted ions in metals by the resonance broadening method will be briefly discussed.     

Neutron Resonance Parameters of Silver-107 and Silver-109

Neutron transmission measurements were carried out on the separated isotopes of silver using the time-of-flight facility at the Japan Atomic Energy Research Institute electron linear accelerator. Neutrons were detected with the ⁶Li-glass detectors at 56 and 191 m. The samples used were metallic powder enriched to 98.2% for ¹⁰⁷Ag and 99.3% for ¹⁰⁹Ag. Transmission data were analyzed with the multi-level Breit-Wigner formula incorporated in a least squares fitting program. Resonance energies and neutron widths were determined for the large number of resolved resonances in the neutron energy region of 400 eV~7 keV. The s-wave strength functions and average level spacings were obtained to be; S₀= (0.43±0.05) × 10^?4, D₀ = 20±2 eV for ¹⁰⁷Ag and S₀= (0.45 ± 0.05) × 10^?4, D₀ = 20 ± 2eV for ¹⁰⁹Ag.     

Self-Shielding Factors for Neutron Capture Reactions of Uranium-238 and Thorium-232 in Energy Range of 1–35 keV

Self-shielding factors for the neutron capture reactions of ²³⁸U and ²³²Th were measured in the resonance energy region of 1–35 keV, using a neutron time-of-flight method with an electron linear accelerator. The self-shielding factors for arbitrary dilution cross sections were obtained from sets of neutron transmission ratios and self-indication ratios measured with several transmission samples of different thicknesses. The maximum experimental errors for ²³⁸U and ²³²Th were about 3 and about 7%, respectively.

The experimental results were compared with calculations based on JENDL-2, JENDL-3 and ENDF/B-IV. For ²³⁸U, an energy dependent structure was observed in the experimental self- shielding factors. The calculations based on JENDL-2 and ENDF/B-IV did not show this structure in the unresolved resonance region and were smaller than the experimental values from 4 to 6 keV. The calculation based on the resolved resonance parameters in JENDL-3 showed better agreement with the experiment from 4 to 6 keV, but discrepancies still remained in other energy ranges.

For ²³²Th, no remarkable discrepancy was observed in the unresolved resonance region, but JENDL-2 and JENDL-3 tended to give smaller values than the experimental self-shielding factors in the resolved resonance region.     

Neutron Resonance Parameters of Ba-135, Ba-137 and Ba-138

Neutron transmission measurements were carried out on the separated isotopes of Ba at the JAERI electron linac. Resonance energies and neutron widths were determined for a large number of resonances in the neutron energy range from 400 eV to 4.6 keV for ¹³⁵Ba, 15 keV for ¹³⁷Ba and 63 keV for ¹³⁸Ba. Many of these resonances were newly observed in this experiment. The s-wave strength functions obtained are S ₀= (1.33±0.22) x ^10-4 for ¹³⁵Ba, and S ₀= (0.51±0.12) x ^10-4 for ¹³⁷Ba. An apparent energy dependence of the strength function was observed for ¹³⁵Ba. New resonance parameters of ¹³⁸Ba were also obtained for several weak P-wave levels.     

Void Swelling of Solution-Annealed Type 316 Stainless Steel under Long Time Proton Irradiation

Solution-annealed type 316 stainless steel was irradiated by 150 keV proton to a dose of about 6 dpa at the irradiation temperature ranging 450–700°C. To examine the effect of aging during irradiation, the present proton irradiation was carried out for about 25 h at a low dose rate of 7×10–^?5dpa/s. The specimens without He preinjection showed much smaller void swelling than those preinjected with He to the content of 10 at.ppm. Similarly to the case of neutron irradiations, the void swelling in the He preinjected specimens showed the temperature dependence with double peaks, and the peak swelling temperatures were about 550 and 650°C. In these specimens with He preinjection. void number density decreased and average void diameter increased with the increase of irradiation temperature in the range of 450–600°C, but these trends were reversed between 600 and 650°C. The volume of the grain boudary M₂₃C6 precipitates increased with the increase of irradiation temperature from 600 to 700°C, and it was concluded that the decrease of soluble carbon due to the precipitation of M₂₃C6 caused the second swelling peak at 650°C.     

Neutron capture cross section measurements of 151,153Eu using a pair of C6D6 detectors

We have measured the neutron capture cross sections of ¹⁵¹Eu and ¹⁵³Eu by the time-of-flight (TOF) method in the range from 0.005 eV to keV region using the Kyoto University Research Reactor Institute - Linear Accelerator (KURRI-LINAC). We employed a pair of C₆D₆ liquid scintillators for the prompt capture γ-ray measurement. The pulse-height weighting technique was employed to obtain the capture yields from the γ-ray spectra of ^151,153Eu. The obtained thermal cross sections at 0.0253 eV are 9051 ± 683 b for ¹⁵¹Eu and 364 ± 44 b for ¹⁵³Eu, respectively. The resonance integrals have been derived as 3490 ± 162 b for ¹⁵¹Eu and 1538 ± 106 b for ¹⁵³Eu.

The obtained capture cross sections were compared with the previously reported experimental data and the evaluated data. The evaluated data in JENDL-4.0 and JEFF-3.2 show good agreement with the present experiment results of ¹⁵¹Eu, however, the evaluated data in ENDF/B-VII.1 are larger than the present experiment results of ¹⁵¹Eu about 10% to 20% in the energy region from 0.03 to 0.2 eV. For the neutron capture cross sections of ¹⁵³Eu, the evaluated data in ENDF/B-VII.1 and Widder's data are in good agreement with the present results in the energy region below 0.35 eV.     

New Evaluation of Neutron Nuclear Data for Zinc Isotopes

New evaluation of neutron-induced nuclear data for five stable isotopes of zinc (mass numbers A = 64, 66, 67, 68, and 70) was consistently carried out in the incident neutron energy range from 10^?5 eV up to 20MeV. In the low energy region up to about 100keV, the resonance parameters were evaluated by taking account of the available measured data. In the fast neutron region, the comprehensive calculations with nuclear reaction models, in which compound, preequilibrium, and direct processes are taken into account, were performed to estimate cross sections for various reactions and double differential cross sections of emitted neutrons and γ-rays. The comparisons of the evaluated cross sections with the experimental data and existing evaluated nuclear data libraries are made and show a good agreement with the measurements.     

Combination of resonance integral and Maxwellian 30 keV data – A sensitive test of the resonance region

This paper presents the approach of a combined use of resonance integrals and average Maxwellian cross sections (MACS) at kT = 30 keV to test and validate the resolved resonance range or its reconstructed cross section curve. Based on these two integral measurements a sensitive and energy dependent test can be provided. These two integral quantities cover with their neutron spectra the energy region between E_n = 0.5 eV up to several hundred keV, respectively, with different weighting. Our principal motivation is to produce a validation tool, sensitive to the lower and upper parts of the resonance region through the difference in the applied 1/E and kT = 30 keV Maxwell–Boltzmann spectra of the resonance integral and MACS data.     

Neutron total cross section measurements of polyethylene using time-of-flight method at KURNS-LINAC

ABSTRACT

The neutron total cross sections of polyethylene have been measured in the energy region from 0.001 eV to 40 keV by the time-of-flight (TOF) method using the Kyoto University Institute for Integrated Radiation and Nuclear Science – Linear Accelerator (KURNS-LINAC). A ⁶Li detector and a gas electron multiplier (GEM) detector have been used as a neutron detector, and the polyethylene plates of 0.31 and 0.20 cm thickness were employed for the neutron transmission measurement.

The present results were compared with the previous results and the evaluated data in JENDL-4.0. In the energy region below 0.01 eV, the present results are in good agreement with the data measured by Herdade et al. (1973) and by Granada et al. (1987). On the other hand, the evaluated data in JENDL-4.0 are larger than all the measured data. In the energy region from 0.035 to 0.15 eV, the data measured by Granada et al. and the evaluated data in JENDL-4.0 are up to about 4 ~ 6% larger than the present results.     

Neutron Total Cross Sections of 239Pu from Transmission Measurements in the Energy Range of 1–500keV

The average neutron total cross sections of ²³⁹Pu were obtained in the energy range of 1~500 keV from the high resolution transmission measurements performed by Harvey et al. at the Oak Ridge Electron Linear Accelerator (ORELA). In the energy range of 1~10 keV, the average effective cross sections of three samples were extrapolated to the total cross section for zero sample thickness. Above 10 keV the resonance self-shielding corrections to the effective cross sections of the thick sample were calculated by simulation of the cross sections from the resonance parameters. The results are given with 2% to 4% accuracy in the energy range of 1~10 keV and with better than 1% accuracy in the energy range above 10 keV. They are particularly useful to meet the needs of accurate experimental data in the energy range of 1~50 keV.     

Neutron Irradiation Effects on Thermally Activated Process of Tensile Properties of Titanium

This paper deals with the relationship between mechanical properties and irradiation, effects for titanium irradiated to fast neutron fluxes. The neutron fluences applied are 6.9×10¹⁸, 8.6 × 10¹⁸ and 3.0 × 10¹⁹ n/cm². Tensile deformation is carried out over the temperature range of 77–about 600°K retaining the strain rate constant on one hand and changing the strain rate by a factor of about 5 and 10 on the other.

The fluence (φ) dependence of the yield stress at room temperature for an athermal component of the stress, σμ is greater than that for a thermal component σ* which does not change remarkably after irradiation. Their increments Δσ, Δμ and Δ σ* are proportional toσ ^1/3, σ^1/2σ^1/4 and, respectively.

The relationship between activation volume V* and effective shear stress τ* is investigated for both the unirradiated and irradiated specimens. In terms of the τ*/τ*₀ analysis (τ*_o is the value of τ* at T = 0°K), V* shows a tendency to decrease with increase in neutron fluence.

Irradiation defects observable by electron microscopy seem to be related to the athermal activation stress (σ_u) and those too small to be observed by electron microscopy to the thermal activation stress. The yield stress in the thermal activation can be given by Conrad's formula. The activation energy H₀ shows a constant value of about 1.8 eV irrespective of the neutron fluence applied. This value is 0.3–0.4eV higher than that for unirradiated specimens.     

Slow Neutron Resonances in Terbium-159

An experiment of neutron resonances in ¹⁵⁹Tb was carried out using the Japan Atomic Energy Research Institute linac time-of-flight facility. Transmission and capture measurements were made on terbium samples of two thicknesses, using ⁶Li-glass and Moxon Rae detectors at the 47 m station; the neutron flux was monitored with a ⁶Li-glass transmission type flux monitor. Transmission data were analyzed with an area program up to 1.2 keV, and capture data with Monte-Carlo program CAFIT, to obtain 2gΓ⁰ _n Γ and Γ_γ Resonance parameters of 209 levels below 1.2 keV are obtained, and 52 levels between 754eV and 1.2keV are new ones. The results are; average level spacing <D>=4.4±0.4eV below 600 eV, s-wave strength function S₀=(1.55 ±0.15)10⁴ below 1.2 keV, and average radiation width <Γ_γ>=107±7 meV for lower 25 levels. Average capture cross section <σ_c> were obtained from 50 eV to 30keV.     

<Superscript>243</Superscript>Am neutron fission cross section and resonance parameters

The SVZ-100 lead moderation time neutron spectrometer at the Institute of Nuclear Physics of the Russian Academy of Sciences was used to measure the fission cross section for ²⁴³Am in the neutron energy range E_n = 0.3 eV – 10 keV. The resonance fission integrals and the area and fission width of the resolved resonances were calculated. The properties of the intermediate-structure resonances were evaluated. The results were compared with existing data and recommended evaluations.     

Electron paramagnetic resonance dose response studies for neutron irradiated human teeth

The dosimetric response of neutron irradiated human tooth enamel has been investigated using electron paramagnetic resonance (EPR) dosimetry. Continuous energy fast neutrons of mean energy less than 450 keV were produced from the McMaster University 3 MV K.N. Van de Graaff accelerator employing a thick lithium target via ⁷Li(p,n)⁷Be interaction. Prior to its use for various experiments, the gamma dose contamination of the neutron beams was determined at the selected proton beam energies using the tissue-equivalent proportional counter (TEPC). The neutron sensitivity (/Gy-100 mg) of human tooth enamel remained constant for various mean neutron energies ranging from 167 to 450 keV. Similarly, the EPR signal intensity remained independent of the neutron dose rate variation from 0.5 to 2.4 Gy/h.     

Energy distributions of charged and neutral hydrogen atoms backscattered from metal surfaces bombarded with 5 to 18 keV protons

Polycrystalline targets of Be, V, Nb, Mo and Ta have been bombarded with protons with primary energies in the range from 5 to 18 keV. The energy distributions of the charged and the neural particles backscattered at 135° with respect to the primary beam direction have been measured between 200 eV and 18 keV. The energy distribution of the neutrals has a pronounced maximum between 0.5 and 1 keV whose position does not depend on the primary energy or the target material, or the angle of emergence of the scattered particles. The energy distribution of the charged particles shows a less pronounced maximum between 1 and 1.5 keV. Only slight differences in the shape of the energy distributions have been observed for different target materials. The fractional number of charged backscattered particles increases from $\text{≈; 3\%}$ at 300 eV to $\text{≈; 40\%}$ at 18 keV.     

Neutron Capture Cross Section Measurement of Praseodymium in the Energy Region from 0.003 eV to 140 keV

The neutron capture cross section of praseodymium (¹⁴¹Pr) has been measured relative to the ¹⁰B(n,αγ) standard cross section in the energy region from 0.003 eV to 140 keV by the neutron time-of-flight (TOF) method with a 46-MeV electron linear accelerator (linac) of the Research Reactor Institute, Kyoto University (KURRI). An assembly of Bi₄Ge₃O₁₂ (BGO) scintillators was used for the capture cross section measurement. In addition, the thermal neutron cross section (2,200 m/s value) of the ¹⁴¹Pr(n, γ)¹⁴²Pr reaction has been also measured by an activation method at the heavy water thermal neutron facility of the Kyoto University Reactor (KUR). The thermal neutron flux was monitored with the ¹⁹⁷Au(n, γ)¹⁹⁸Au standard cross section. The above TOF measurement has been normalized to the current activation data (11.6±1.3 b) at 0.0253 eV.

The evaluated data in JENDL-3.3, ENDF/B-VI, and JEF-2.2 have been in general agreement with the current result, except that the JENDL-3.3 and the JEF-2.2 values are clearly lower than the measurement in the cross section minimum region from about 10 to 500 eV.     

Design of moderator and multiplier systems for D–T neutron source in BNCT

Boron Neutron Capture Therapy (BNCT) is an outstanding way to treat Glioblastoma Multiforme. Epithermal neutrons with energy from 1 eV to 10 keV represent the most effective range for brain tumor therapy. In this research we have focused on ³H(d, n)⁴He reaction as a neutron source using Cock Craft Walton accelerator. High neutron yield with 14.1 MeV energy can be generated via accelerating a deuteron beam with 110 keV energy.A Monte Carlo simulation code (MCNP4C) was used to design the D–T source. Pb and ²³⁸U are suggested as neutron multipliers; AlF₃ and BeO as a moderator and reflector, respectively. An Al layer is used for decreasing the ratio of fast to total neutron fluxes. Epithermal neutron flux in the suggested system is 10⁸ n/cm² s and is a suitable flux for BNCT applications. Finally the suggested configuration is compared to the most recent works and it is shown that the proposed configuration works better.