Neutron cross-sections of Pu in the energy range 5–20 MeV

The evaluation of neutron cross sections and angular distributions of ²⁴²Pu in the energy range 5–20 MeV was performed using the direct interaction treatment by coupled channel method and the compound nucleus mechanism (statistical model) taking account of pre-equilibrium effects. The calculated cross-sections are in very good agreement with the existing experimental data (total and fission cross-sections). More accurate theoretical data have been obtained by the extension of procedures and parameterizations (previously used only for the main compound nucleus) in the incident neutron energy range where more compound nuclei are involved.     

The determination of the Nb(n,n′) Nb cross-section in the neutron energy range 1–6 MeV

Measurements of the 30 keV isomer production cross-section in ⁹³Nb, excited by neutron inelastic scattering have been made at 10 neutron energies in the range 1–6 MeV. Small foils of niobium and suitable monitor elements were exposed to high fluences of monoenergetic neutrons and the cross-section was determined from the K X-ray activities so induced. The high purity Ge detector used in these X-ray measurements was calibrated against a standard solution of ^93mNb which is used as an international reference material for reactor neutron dosimetry. The neutron fluence of the irradiation was measured with a low-efficiency ²³⁵U fission chamber in which the thin fissile deposit was located immediately behind the niobium and monitor foils. The latter acted as secondary measures of the neutron fluence but could be used as the primary standard in the event of failure of the fission chamber. Thus, the production cross-section was measured relative to the ²³⁵U fission cross-section which is a standard reference cross-section. Comparisons are made with other experimental data and with nuclear model calculations of the cross-section and recommended values based on these and our experimental data are presented.     

Study of the excitation functions for K, Sc and Ti by proton irradiation on Sc up to 37 MeV

The excitation functions of proton induced reactions on Sc targets (100% ⁴⁵Sc), leading to the formation isotopes ⁴³K, ⁴³Sc, ^44mSc, ^44gSc and ⁴⁴Ti were studied by the stacked foil activation technique up to 37 MeV. High-resolution gamma-spectrometry measurements were performed on an HPGe detector in order to determine the activity of the irradiated Sc₂O₃ pellets and Ti monitor foils. The reaction cross-sections were measured from their respective thresholds up to E_p = 36.4 MeV and were compared with previous values reported in literature. Possible batch yields and optimal irradiation parameters for generator ⁴⁴Ti -^44gSc in high current accelerators are discussed.     

Systematics for (n, 2n) excitation functions in the neutron energy between 13.4 and 14.9 MeV

A systematics of (n, 2n) partial excitation functions was studied on the basis of our 58 sets of experimental data measured using intense neutron source facilities of FNS at the Japan Atomic Energy Agency and of OKTAVIAN at Osaka University. The empirically predictive formulas based on the evaporation theory are applicable for the neutron energy between 13.4 and 14.9 MeV, and in the mass range between 14 and 238. About 83% of the cross sections and the slopes of excitation functions can be reproduced within an uncertainty of 15%. The formulas were expressed in terms of a mass number A, an asymmetry parameter S = (N ? Z)/A, and threshold energies of the (n, 2n) and (n, 3n) reactions, where N and Z are the neutron and proton numbers for the target nuclei, respectively. The excitation functions were well reproduced for the nuclei in the region with S < 0.05 and 14 ? A ? 58 for the first time. The general characteristics of the excitation functions, consisting of steep rising in the light mass nuclei, gently-sloping or nearly flat in the middle and heavy mass nuclei, and slow falling in the heavy mass regions with possible (n, 3n) reactions, are well expressed.     

Neutron scattering cross sections of126Te and130Te in the energy range 1.5–5.0 MeV

Translated from Atomnaya Énergiya, Vol. 67, No. 2, pp. 147–149, August, 1989.     

Systematics for (n,p) excitation functions in the neutron energy between 13.3 and 15.0 MeV

Systematics of (n,p) excitation functions in the neutron energy between 13.3 and 15.0 MeV were studied on the basis of experimental data measured by the Nagoya and Fusion Neutronics Source groups. The empirical formulae of a cross section (σ₁₄) at 14.0 MeV and a relative slope (S) of excitation functions were deduced. These formulae covered the mass range between 19 and 188. The empirical formula of S was expressed as a function of (N—Z)/A and threshold energy, where N, Z and A are the mass, proton and neutron numbers numbers for the target nuclei, respectively. The empirical formula of σ₁₄ was expressed by a simple formula with two fitting parameters. By using the proposed empirical formulae, the partial excitation functions between 13 and 15 MeV were reproduced. Comparing the experimental data with the calculated excitation functions, we concluded that the accuracy of the proposed empirical formulae was ± 20%.     

Systematics of the (p, n) excitation functions belonged to several isotopes at energies <60 MeV

Excitation functions of proton induced charge exchange reaction on nuclei between A = 11 and 238 are studied. All the studied excitation functions of (p, n) reaction show systematic variation with atomic mass in connection with nucleon binding energy. Islands of higher reaction yield appeared to be for nuclei with mass number A = 49, 72, 89, 109, and 139, and proton energy range from 9 to 12 MeV. The more probable occurrence of proton induced charge exchange reaction in these regions are attributed to its extra binding energy per nucleon than other nuclei. The larger contribution of pre-equilibrium processes on the neutron emission appeared on the linearity of the log(σ)–log(E_p) in some energy ranges. The slopes of these linear segments may be related to the excitons configuration in which the neutron is emitted by.     

Photoluminescence and photoluminescence excitation studies in 80 MeV Ni ion irradiated MOCVD grown GaN

We report damage creation and annihilation under energetic ion bombardment at a fixed fluence. MOCVD grown GaN thin films were irradiated with 80 MeV Ni ions at a fluence of 1 × 10¹³ ions/cm². Irradiated GaN thin films were subjected to rapid thermal annealing for 60 s in nitrogen atmosphere to anneal out the defects. The effects of defects on luminescence were explored with photoluminescence measurements. Room temperature photoluminescence spectra from pristine sample revealed presence of band to band transition besides unwanted yellow luminescence. Irradiated GaN does not show any band to band transition but there is a strong peak at 450 nm which is attributed to ion induced defect blue luminescence. However, irradiated and subsequently annealed samples show improved band to band transitions and a significant decrease in yellow luminescence intensity due to annihilation of defects which were created during irradiation. Irradiation induced effects on yellow and blue emissions are discussed.     

Neutron damage calculations in Cu,Nb and Au to 32 MeV: Application to sputtering and deuteron-breakup neutron sources

Primary recoil distributions and specific damage energies have been computed for high energy deuteron-breakup neutrons in Cu, Nb and Au. The calculations are based on theoretical neutron cross sections and consider in particular a d-Be spectrum broadly peaked at 15 MeV with some neutrons above 30 MeV. The theoretical results are similar to corresponding calculations for monoenergetic 15-MeV neutrons and are in good agreement with range measurements of (n, 2n) recoils generated by high energy d-Be neutrons in Nb and Au. The calculations are also consistent with recent d-Be neutron sputtering experiments in Nb and Au and demonstrate the usefulness of deuteron-breakup neutron sources for simulating fusion neutron effects.     

Level excitation cross sections of Mg,Cr52, Ni58, Ni60 and Nb93 by inelastic neutron scattering

The excitation cross sections of certain levels of Mg²⁴, Mg²⁵, Mg²⁶, Ni⁵⁸, Ni⁶⁰ Cr⁵², and Nb⁹³ by neutrons were measured over the energy range 1 to 4 MeV. Experimental results are compared with calculated results obtained on the basis of the optical model of the nucleus from the Woods-Saxon potential.Translated from Atomnaya Énergiya, Vol. 16, No. 2, pp. 103–110, February, 1964     

Growth of amorphous carbon films by carbon atom bombardment in the energy range 10–500 eV

Molecular dynamics (MD) simulations were carried out of the energetic impact of C atoms on amorphous carbon (a-C) substrates in the energy range 10–500 eV. The results show that a densification of the deposited material occurs up to 150 eV energy but with a low sp³ bond content. At 500 eV impact the substrate material shows a significant decrease in density and a porous a-C structure forms.     

Measurements of the erosion of stainless steel, carbon, and SiC by hydrogen bombardment in the energy range of 0.5 – 7.5 keV

Total erosion yields by sputtering and blistering for 1 to 15 keV H₂⁺ bombardment at normal incidence have been measured by weight loss of 304 stainless steel, pyrolytic graphite, carbon fibres, glassy carbon and SiC. The erosion yields are in the range of 3 × 10⁻³ to 2.6 × 10⁻² atoms per incident hydrogen atom. Observation in the scanning electron microscope shows that blisters occur in stainless steel and SiC at doses of 5 × 10¹⁸ particles/cm², but disappear at doses of 5 × 10 particles/cm² . The surface roughening observed depends largely on grain orientation. On carbon no blistering could be found. After bombardment the carbon surfaces are generally more smooth than before.     

Effective atomic numbers for photon energy absorption of essential amino acids in the energy range 1 keV to 20 MeV

Effective atomic numbers for photon energy-absorption (Z_PEAeff) of essential amino acids histidine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine have been calculated by a direct method in the energy region of 1 keV to 20 MeV. The Z_PEAeff values have been found to change with energy and composition of the amino acids. The variations of mass energy-absorption coefficient, effective atomic number for photon interaction (Z_PIeff) and Z_PEAeff with energy are shown graphically. Significant differences exist between Z_PIeff and the Z_PEAeff in the energy region of 8-100 keV for histidine and threonine; 6-100 keV for leucine, lysine, tryptophan, phenylalanine and valine; 15-400 keV for methionine. The effect of absorption edge on effective atomic numbers and the possibility of defining two set values of these parameters at the K-absorption edge of high-Z element present in the amino acids are discussed. The reasons for using Z_PEAeff rather than the commonly used Z_PIeff in medical radiation dosimetry for the calculation of absorbed dose in radiation therapy are also discussed.     

Activation Cross Section Measurements for ~(93)Nb(n,2n)~(92g)Nb Reaction Induced by 14 MeV Neutron

The cross section for the ~(93)Nb(n,2n)~(92g)Nb reaction is measured by activation method. The experimental result is 1355±149 mb at the neutron energy of 14.6±0.3 MeV. And the excitation curve of ~(93)Nb(n,2n)~(92g)Nb reaction is calculated by using HFTT program in neutron energy range from 9 MeV to 16 MeV.     

Experimental study of the excitation functions of deuteron induced reactions on Sn up to 40 MeV

Using the stacked-foil activation technique, cross-sections of deuteron induced reactions on natural Sn were measured up to 40 MeV. Excitation functions are reported for the product nuclides ¹¹¹In, ¹¹³Sn, ^117mSn, ^125mSn, ^125gSn, ¹¹⁵Sb, ^116mSb, ¹¹⁷Sb, ^118mSb ^120mSb, ¹²²Sb, ¹²⁴Sb and ¹²⁵Sb and compared with the earlier published data sets. For all excitation functions comparisons with theoretical calculations using the ALICE-IPPE, EMPIRE, EAF and the TALYS codes were performed.     

Proton elastic scattering cross sections of carbon,nitrogen and silicon for backscattering analysis in the energy range 0.7—2.5 MeV

Differential elastic scattering cross sections of 0.7—2.5 MeV protons for carbon, nitrogen and silicon have been determined at a scattering angle θ = 170°. Results from previous measurements near θ = 170° show large variations, of the order of 10–30% in the nonresonant regions. The purpose of the present investigations is to tabulate cross section data for backscattering analysis at a single scattering angle for many elements. Proton backscattering in the non-Rutherford energy region is more sensitive in the detection of C, N and many other light elements than other ion beam methods when a high background from the matrix is absent. Proton backscattering by using the present scattering cross sections and computer data analysis are outlined. The possible interference from other nuclear reactions is considered.