Elastic scattering of 21-MeV protons from nitrogen 14, oxygen 16, argon 40, nickel 58, and tin 116
Elastic scattering of 21 MeV protons from nitrogen 14, oxygen 16, argon 40, nickel 58, and tin 116
Baron, N.↗
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Advancing the Theory of Nuclear Reactions with Rare Isotopes: From the Laboratory to the Cosmos
The Main goal of my research is to develop indirect methods, which allows one to connect the reactions measured in the labs with astrophysical reactions.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Study of the (p, γ) and (α, γ) reactions for {sup 96,98,104}Ru and {sup 112,114,116}Sn at astrophysically relevant energies
Cross section and S factor of the proton- and alpha-induced reactions have been studied for the Ruthenium and tin isotopes in the effective energy range, i.e. Gamow window. These reactions are important for developing the understanding for nucleosynthesis, particularly for the synthesis of p nuclei (p process). In this work, cross sections and S factor have been calculated through TALYS in Hauser–Feshbach formalism using nuclear densities calculated in relativistic mean field (RMF) formalism. Calculated results of cross sections, S factor and nuclear structure have been compared with existing theoretical as well as experimental results available and are found to be in good agreement.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Investigation of double beta decay of {sup 116}Cd with the help of enriched {sup 116}CdWO{sub 4} crystal scintillators
An experiment to search for 2β processes in {sup 116}Cd with the help of enriched (to 82%) cadmium tungstate crystal scintillators is in progress at the Gran Sasso National Laboratory of the INFN (LNGS, Italy). After 11074 h of data taking in the last configuration, the preliminary estimate for the half-life of 116Cd relatively to 2ν2β decay is T{sub 1/2} = [2.52 ± 0.02(stat.) ± 0.14(syst.)] × 10{sup 19} yr. By using the data of previous stages of the experiment with a similar level of background (≈ 0.1 counts/(keV kg yr) in the energy interval 2.7 – 2.9 MeV; the total time of measurements is 19770 h) we have obtained a new limit on the 0ν2β decay of {sup 116}Cd to the ground state of {sup 116}Sn: T{sub 1/2} ≥ 1.9 × 10{sup 23} yr at 90% C.L. New limits on different 2β processes in {sup 116}Cd (decays with majorons, transitions to the excited levels) are obtained on the level of T{sub 1/2} ≥ 10{sup 20} – 10{sup 22} yr.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Effect of thermal neutrons on emission characteristics of InGaAs/AlGaAs heterolasers
It is studied how the threshold current of InGaAs/AlGaAs quantum-well injection heterolasers emitting near the wavelength λ = 0.7 μm changes under irradiation by thermal neutrons. It is found that the threshold pump current decreases at small doses (10{sup -2} neutron cm{sup -2}), while doses exceeding 6 × 10{sup 7} neutron cm{sup -2} cause an increase in this current and degradation of the structure. It is found that the main reasons for an increase in the threshold current at high irradiation doses are the nuclear reactions of the {sub 49}In{sup 115} (n, γ) → {sub 49}In{sup 116} type and the β-decay of the {sub 49}In{sup 116} isotope, which results in the appearance of {sub 50}Sn{sup 116} atoms. (lasers)
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Evaluated Cross Sections of Photoneutron Reactions on the Isotope {sup 116}Sn and Spectra of Neutrons Originating from These Reactions
With the aid of the results obtained by evaluating cross sections of partial photoneutron reactions on the isotope {sup 116}Sn and the energy spectra of neutrons originating from these reactions, the possible reasons for the well-known discrepancies between the results of different photonuclear experiments were studied on the basis of a combinedmodel of photonuclear reactions. On the basis of physical criteria of data reliability and an experimental–theoretical method for evaluating cross sections of partial reactions, it was found that these discrepancies were due to unreliably redistributing neutrons between (γ, 1n), (γ, 2n), and (γ, 3n) reactions because of nontrivial correlations between the experimentally measured energy of neutrons and their multiplicity.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Nuclear Data Sheets for A = 235
Spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented here for all nuclei with mass number A=235. The highlight of this evaluation consists of the precise and comprehensive Coulomb excitation study (2012Wa35) on {sup 235}U, which in addition to the 7/2[743] ground state rotational band, extended the 1/2[631], 5/2[622], 5/2[752], and 3/2[631] rotational bands up to Jπ=53/2+, 49/2+, 441/2−, and 43/2+, respectively. This evaluation presents a study (2010Hu02) of the {sup 237}Np({sup 116}Sn, {sup 118}Snγ) reaction where the ground state rotational band 5/2[642] was observed up to Jπ=(53/2+). It is worth for historical knowledge to mention the report on the “Discovery of isotopes of the transuranium elements with 93≤Z≤98” (2013Fr02), where the information for elements Np, Pu, and Am with mass number A=235 is given. {sup 235}Cf has not been observed. The alpha hindrance factors (HF) presented in this evaluation were calculated using values of the radius parameter (r{sub 0}) interpolated from those for even–even adjacent nuclei given by 1998Ak04.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Nucleon-nucleon correlations in heavy ion transfer reactions: Recent investigations at energies far below the Coulomb barrier
Excitation functions of one- and two-neutron transfer channels have been measured for the {sup 96}Zr+{sup 40}Ca and {sup 116}Sn+{sup 60}Ni systems at bombarding energies ranging from the Coulomb barrier to ∼25% below. Target-like recoils have been identified in A, Z and velocity with the large solid angle magnetic spectrometer PRISMA. The experimental transfer probabilities have been compared, in absolute values and in slope, with semiclassical microscopic calculations which incorporate nucleon-nucleon pairing correlations. For the first time in a heavy ion collision, one was able to provide a consistent description of one and two neutron transfer reactions by incorporating, in the reaction mechanism, all known structure information of entrance and exit channels nuclei. In particular, there is no need to introduce any enhancement factor for the description of two neutron transfer, of course very important are the correlations induced by the pairing interaction.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Investigation into the semimagic nature of the tin isotopes through electromagnetic moments
A complete set of electromagnetic moments, B(E2;0 + 1 2 + 1 ), Q(2 + 1 ), and g(2 + 1 ), have been measured from Coulomb excitation of semi-magic 112,114,116,118,120,122,124 Sn (Z = 50) on natural carbon and titanium targets. The magnitude of the B(E2) values, measured to a precision of ~4%, disagree with a recent lifetime study [Phys. Lett. B 695, 110 (2011)] that employed the Doppler- shift attenuation method. The B(E2) values show an overall enhancement compared with recent theoretical calculations and a clear asymmetry about midshell, contrary to naive expectations. A new static electric quadrupole moment, Q(2 + 1 ), has been measured for 114 Sn. The static quadrupole moments are generally consistent with zero but reveal an enhancement near midshell; this had not been previously observed. The magnetic dipole moments are consistent with previous measurements and show a near monotonic decrease in value with neutron number. The current theory calculations fail to reproduce the electromagnetic moments of the tin isotopes. The role of 2p-2h and 4p-4h intruders, which are lowest in energy at mid shell and outside of current model spaces, needs to be investigated in the future.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Electric and magnetic dipole strength in 112,114,116,118,120,124 Sn
Background: There is renewed interest in electric dipole strength distributions for a variety of reasons including the extraction of the dipole polarizability related to properties of the symmetry energy and a measure for the neutron skin thickness, understanding the structure of low-energy $\textit{E}$1 strength in nuclei with neutron excess, and establishing the systematics of the isovector giant dipole resonance (IVGDR). Inelastic proton scattering at energies of a few hundred MeV and very forward angles including 0° has been established as a tool for the study of electric and magnetic dipole strength distributions in nuclei. Purpose: The present work aims at a systematic investigation of the electric and magnetic dipole strength distributions in the chain of stable even-mass tin isotopes. Methods: Inelastic proton scattering experiments were performed at the Research Center for Nuclear Physics, Osaka, with a 295-MeV beam covering laboratory angles 0°–6° and excitation energies 6–22 MeV. Cross sections due to $\textit{E}$1 and $\textit{M}$1 excitations were extracted with a multipole decomposition analysis (MDA) and then converted to reduced transition probabilities with the “virtual photon method” for $\textit{E}$1 and the “unit cross section method” for $\textit{M}$1 excitations, respectively. Including a theory-aided correction for the high-excitation-energy region not covered experimentally, the electric dipole polarizability was determined from the $\textit{E}$1 strength distributions. Results: In this work, total photoabsorption cross sections derived from the $\textit{E}$1 and $\textit{M}$1 strength distributions show significant differences compared to those from previous ($\textit{γ, xn}$) experiments in the energy region of the IVGDR. The widths of the IVGDR deduced from the present data with a Lorentz parametrization show an approximately constant value of about 4.5 MeV in contrast to the large variations between isotopes observed in previous work. The IVGDR centroid energies are in good correspondence to expectations from empirical systematics of their mass dependence. Furthermore, a study of the dependence of the IVGDR energies on bulk matter properties is presented. The $\textit{E}$1 strengths below neutron threshold show fair agreement in this work with results from ($\textit{γ, γ'}$) experiments on 112,116,120,124 Sn in the energy region between 6 and 7 MeV, where also isoscalar $\textit{E}$1 strength was found for 124 Sn. At higher excitation energies, large differences are observed, pointing to a different nature of the excited states with small ground-state branching ratios. The isovector spin-$\textit{M}$1 strengths exhibit a broad distribution between 6 and 12 MeV in all studied nuclei. Conclusions: The present results contribute to the solution of a variety of nuclear structure problems including the systematics of the energy and width of the IVGDR, the structure of low-energy $\textit{E}$1 strength in nuclei, new constraints to energy density functionals (EDFs) aiming at a systematic description of the dipole polarizability across the nuclear chart, from which properties of the symmetry energy can be derived, and the systematics of the isovector spin-$\textit{M}$1 strength in heavy nuclei.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Gamma ray induced thermoluminescence properties of Eu{sup 3+} doped SnO{sub 2} phosphor
Highlights: • TL properties of SnO{sub 2}:Eu{sup 3+} were reported upon γ-ray irradiation. • Effect of doping, irradiation dose and heating rate on TL properties were studied in detail. • The kinetic parameters associated with TL were calculated for first time in SnO{sub 2}:Eu{sup 3+}. • Existence of second-order kinetics indicates the occurrence of retrapping phenomena. • Retrapping of electrons at deep traps occurred due to thermal energy stimulation. - Abstract: This paper reports the thermoluminescence properties of Eu{sup 3+} doped SnO{sub 2} phosphors synthesized by combustion method. The thermoluminescence (TL) studies were carried out after irradiating the sample by γ-rays in the dose range 100 Gy to 1 KGy. The glow curves of γ-irradiated phosphors were resolved into two peaks, one centred at 116 °C and other at 300 °C. Intensity of the glow peak increases linearly in the studied dose range of γ-rays. Kinetic parameters such as order of kinetics, trap depth and frequency factor associated with the glow peak were calculated by various glow curve methods.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Unitary plate electrode
The unitary electrode (10) comprises a porous sheet (12) of fiberglass the strands (14) of which contain a coating (16) of conductive tin oxide. The lower portion of the sheet contains a layer (18) of resin and the upper layer (20) contains lead dioxide forming a positive active electrode on an electrolyte-impervious layer. The strands (14) form a continuous conduction path through both layers (16, 18). Tin oxide is prevented from reduction by coating the surface of the plate facing the negative electrode with a conductive, impervious layer resistant to reduction such as a thin film (130) of lead or graphite filled resin adhered to the plate with a layer (31) of conductive adhesive. The plate (10) can be formed by casting a molten resin from kettle (60) onto a sheet of glass wool (56) overlying a sheet of lead foil and then applying positive active paste from hopper (64) into the upper layer (68). The plate can also be formed by passing an assembly of a sheet ( 80) of resin, a sheet (86) of sintered glass and a sheet (90) of lead between the nip (92) of heated rollers (93, 95) and then filling lead oxide into the pores (116) of the upper layer (118).
Rowlette, John J.↗
Effect of alloying elements, cold work, and hydrogen on the irradiation-induced growth behavior of zirconium alloy variants - 2016-0040
In-reactor dimensional changes in zirconium-based alloys result from a complex interplay of many factors, such as (1) alloy type and composition, including the addition of elements such as niobium, iron, and tin; (2) fabrication process, including cold work, texture, and residual stresses; (3) irradiation temperature; and (4) hydrogen levels. In many cases, the observed dimensional changes in light water reactor fuel-assembly components-especially at high exposures-cannot be fully explained based on current growth and creep models. Therefore, a systematic approach was taken in this multi-year (2005-2011) Nuclear Fuel Industry Research Program investigation. The objective was to measure stress-free irradiation-induced growth (IIG) of specially fabricated alloys through irradiation under controlled conditions in the BOR-60 fast-flux test reactor up to a high fluence of approximately 2X10{sup 26} m{sup -2} (E>1 MeV)-equivalent to maximum of approximately 37 dpa exposure-followed by postirradiation examinations (PIEs). Irradiation temperature was within a narrow temperature range (320±10 deg. C). The PIEs included dimensional-change and microhardness measurements, metallography and hydride etching, and scanning transmission electron microscopy (STEM) or transmission electron microscopy (TEM). All irradiation samples (typically flat rectangular coupons or curvilinear cutouts of cladding tubes sized 35 by 6.5 by 0.8 mm) were pre-filmed to avoid the uptake of impurity hydrogen from sodium-cooled BOR-60. A wide variety of samples representing standard LWR cladding alloys with and without pre-hydriding (approximately 116 to approximately 718 ppm) as well as special compositions with iron contents (100 to 4,000 ppm) were irradiated. The irradiation in BOR-60 was done in five different stages (eight micro-cycles) and lasted approximately 18 months with interim and final growth measurements made using a high precision-length measurement device. Results of the extensive investigation include: significant effects of Fe, Nb, and hydrogen additions; quantification of growth rates from low to very high fluences (dpas); measurement of volume changes; and correlation of growth with -component dislocation densities. (authors)
36 MATERIALS SCIENCE↗