Progtess Report on the Model Calculation of n ~9Be Reactions below 20 MeV

Introduction ~9Be has long been selected as the material for controlled thermonuclear reactors. The secondary particle energy spectra of n ~9Be reaction, especially the neutron spectrum needs further improvement to meet the needs of nuclear engineering and other applications. The neutron double differential cross sections have been measured by Drake et al. in 1977, Baba et al. in 1978 and Takahashi et al. in 1983. Perkins et al. evaluated the measured data mentioned above in terms of Monte Carlo technique and set up ENDF/B-6 in 1985.     

Geant4 simulation of multi-sphere spectrometer response function and the detection of ~(241)Am–Be neutron spectrum

This paper is aimed at detecting the neutron spectrum of~(241)Am–Be, a widely used neutron source, with the SP9 ~3He proportional counter, which is a multi-sphere spectrometer system of eight thermal neutron detectors embedded in eight polyethylene(PE) spheres of varying diameters. The transport processes of a neutron in the multi-sphere spectrometer are simulated using the Geant4 code. Two sets of response functions of the PE spheres are obtained for calculating the~(241)Am–Be neutron spectrum.Response Function 1 utilizes the thermal neutron scattering model G4 Neutron HPThermal Scattering for neutron energies of ≤4 eV, and Response Function 2 has no thermal treatment. Neutron spectra of an~(241)Am–Be neutron source are measured and compared to those calculated by using the response functions. The results show that response function with thermal treatment is more accurate and closer to the real spectrum.     

Measurement of Be-profiles by the 9Be(p,α)6Li reaction

The use of the ⁹Be(p,α)⁶Li (E_p = 330 keV) reaction as a tool for the profiling of implanted Be is described.Pile-up problems, caused by elastically scattered particles, requires a mylar foil to be introduced in front of the particle detector. This causes severe straggling and thus loss of depth resolution. A deconvolution technique, which is based on an iterative procedure, is described. With it, profiles are reconstructed with a depth resolution of 300 Å.The present technique was used to assess the diffusion of Be implanted into InSb and GaAs during annealing. Pronounced diffusion accompanied by Be loss was found for GaAs (T_ann = 1113 K, T_melt = 1511 K), while hardly any changes in Be profiles for InSb (T_ann = 670 K, T_melt = 798 K) could be detected.     

CTOF measurements and Monte Carlo analyses of neutron spectra for the backward direction from an iron target irradiated with 400–1200 MeV protons

A calorimetric-time-of-flight (CTOF) technique was used for real-time, high-precision measurement of the neutron spectrum at an angle of 175° from the initial proton beam direction, which hits a face plane of a cylindrical iron target of 20 cm in diameter and 25 cm thick. A comparison was performed between the neutron spectra predicted by the MARS and the MCNPX codes and that measured for 400, 600, 800, 1000 and 1200 MeV protons.     

Resonance analysis of 151,153Eu from neutron capture cross section measurements in the energy range from 1 to 20 eV

The neutron capture cross sections of Europium-151 and Europium-153 have been measured by the time-of-flight method in the energy range from 0.005 to 100 eV using the Kyoto University Research Reactor Institute-Linear Accelerator (KURRI-LINAC). An assembly of Bismuth Germanate (BGO) scintillators was used to detect the prompt capture of γ rays. The absolute values of the neutron capture cross sections of ¹⁵¹Eu and ¹⁵³Eu were deduced by normalizing the thermal capture cross sections in JENDL-4.0 and ENDF/B-VII.1, respectively. Then, we have obtained the resonance parameters of 20 resonances in ¹⁵¹Eu and 17 resonances in ¹⁵³Eu using the code SAMMY.

For the 3.36-eV resonance of ¹⁵¹Eu, the evaluated resonance peak area in JENDL-4.0 is about 95% smaller than the present result. For the 7.00-, 7.22-, and 7.42-eV resonance; we confirmed that there are significant differences between the measured peaks and evaluated peaks in JENDL-4.0, ENDF/B-VII.1, and JEFF-3.2. For the ¹⁵³Eu, the evaluated resonance peak areas in JENDL-4.0, ENDF/B-VII.1, and JEFF-3.2 are about 15% larger than the measured resonance peak areas at the 2.46-, 3.29-, and 3.94-eV resonances.     

Secondary particle yield and energy release data from intranuclear-cascade-evaporation model calculations of high energy (20–1100 MeV) neutron interaction with elements of shielding and biological importance

Secondary particle (neutron, proton, pion and heavy ion) yields and energy release data for 20, 50, 100, 300, 500, 800 and 1100 MeV neutron collisions with H, C, N, O, Al, Si, Ca, Fe and Pb have been calculated using the intranuclear-cascade-evaporation model. The low-energy limit is discussed and compared with the ENDF/B-IV neutron data. The mean elastic recoil energies have also been estimated by means of the Ranft formula for angular distribution. The multigroup response functions (kerma factors and production cross-sections) have been obtained and applied calculating the energy deposition and particle yields in the deep-penetrated graphite and iron spheres. The results for energy deposition of the ANISN neutron transport code using a high energy cross-section library and the derived kermas are about 10% overestimated relative to the thick-target results from the high energy particle transport code HETC. In the neutron transport discrete ordinates calculation the secondary production is underestimated when comparing with the HETC code.     

Measurement of thick-target gamma-ray production yields of the 7Li(p,p′)7Li and 7Li(p, γ)8Be reactions in the near-threshold energy region for the 7Li(p,n)7Be reaction

The gamma-ray production reactions, ⁷Li(p, p′)⁷Li and ⁷Li(p, γ)⁸Be, occur along with the neutron production reaction ⁷Li(p, n)⁷Be in a p-Li neutron source. These gamma-ray production reactions contribute to a patient's absorbed dose in boron neutron capture therapy (BNCT) when using a neutron beam from the ⁷Li(p, n)⁷Be reaction. The present work experimentally determined the thick-target gamma-ray production yields of the ⁷Li(p, p′)⁷Li and ⁷Li(p, γ)⁸Be reactions at incident proton energies of 1.670 and 1.870 MeV. The present results were compared with previous measurements. The gamma-ray production yield of ⁷Li(p, p′)⁷Li was measured to be 30%–50% smaller than as reported by previous studies. For the ⁷Li(p, γ)⁸Be reaction, the present thick-target yield is 30% smaller than one estimated from cross-section data measured in previous studies. The results must be included in future dose evaluation for BNCT using a p–Li neutron source.     

Cross-section measurements for the (n,p) and (n,α) reactions on 23Na and for the (n,p) reaction on 26Mg at the neutron energies from 13.6 to 14.9 MeV

Cross sections were measured at neutron energies from 13.6 to 14.9 MeV for the reactions ²³Na(n,p)²³Ne and ²³Na(n,α)²⁰F, and ²⁶Mg(n,p)²⁶Na leading to short-lived products. The production of short-lived nuclei and the spectra accumulation have been carried out by cyclic activation method. Corrections were made for the effects of gamma ray attenuation, coincidence summing, pulse pile-up, dead time, neutron flux fluctuations and scattered low energy neutrons.     

Measured activation cross-section ratios for 7Li(n,n′t)4He and 60Ni(n,p)60Co relative to 27Al(n,p)27Mg and 27Al(n,α)24Na in the 9Be(d,n)10B thick-target neutron spectrum at 7-MeV deuteron energy

The activation method is used to measure integral cross-section ratios for ⁷Li(n,n′t)⁴He and ⁶⁰Ni(n,p)⁶⁰Co relative to ²⁷Al(n,p)²⁷Mg and ²⁷Al(n,α)²⁴Na in the neutron spectrum produced by bombarding a thick Be metal target with 7-MeV deuterons. The results of these measurements are found to support the evaluated differential cross-section values from ENDF/B-V (1979, 1981).     

Comparison of Level Density Models for the <Superscript>60,61,62,64</Superscript>Ni(p,n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on ^60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for ^60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.     

A new measurement of the 429 keV 15N(p, αλ) 12C resonance. Applications of the very narrow width found to 15N and 1H depth location: II. Applications

The unexpectedly narrow width Γ_p = 120 eV or Γ_N¹⁵ = 1.8 keV of this resonance opens quite new possibilities for its use in ¹⁵N or ¹H depth location and for hydrogen adsorption studies using ¹⁵N beams. Resonance depth profiling of ¹⁵N is possible with much better near-surface depth resolution than thought until recently. In ¹H resonance depth profiling the indeep background originating from the surface contamination peak is also much smaller than previously assumed. These features are illustrated by ¹⁵N self-diffusion experiments in NbN films and by ¹⁵N adsorption experiments on copper single crystals in ultrahigh vacuum. The strong effect of Doppler broadening on the actual ultimate near-surface depth resolution of hydrogen depth profiling with ¹⁵N beams is discussed as well as the use of this resonance for the direct measurement, based on the Doppler effect, of the vibration speed distribution of hydrogen atoms adsorbed on clean surfaces.