Reference Input Parameter Library Research Articles

Development of nuclear de-excitation model EBITEM Ver.2

ABSTRACT The gamma de-excitation model of the general-purpose radiation transport code Particle and Heavy Ion Transport code System, called the Evaluated Nuclear Structure Data File (ENSDF)-Based Isomeric Transition and isomEr production Model (EBITEM) has been upgraded with a focus on precise neutron-capture reaction simulation. The first de-excitation subsequent to neutron capture of numerous nuclei, which was formerly simulated by a model based on the single particle model, is calculated using the Evaluated Gamma Activation File. The database used for further de-excitation, ENSDF, retrieved in 2013, was replaced with Reference Input Parameter Library 3 to consider internal conversion. The internal conversion process was interfaced with the atomic de-excitation model to assess the emission of Auger electrons and fluorescent X-rays. The spectra of gamma-rays from neutron-capture reactions calculated by the upgraded EBITEM correlate better with the evaluated cross-section data than those of the previous version.

Impact of the quenching of shell effects with excitation energy on nuclear level density

We investigate the nature and impact of shell effects on nuclear level density (NLD) and particle emission probability as a function of temperature in a microscopic theoretical framework of Statistical Model for nuclei ranging from neutron deficient to neutron rich isotopes of Z= 27−35. Critical temperatures are traced for neighbouring even, odd, closed shell and mid−shell nuclei which respond to excitations differently due to their varying stability and structural effects. Importance of the shell effects and shell correction energy is reflected significantly in NLD variation which slowly diminishes with increasing excitation energy indicating the quenching of shell effects. The enhancement of LD parameter with the deformation and rotation and the fade out of enhancement with increasing excitations has been shown. The weakening of magicity of N=28 near the proton drip line has been observed in the inverse level density parameter ‘K’(= A/a) and β variation though it is usually uncommon to see this effect in excited nuclei. Variation of our calculated NLD for odd 69As and even 70Ge exhibits structural effects and agrees very well with the variation of experimental values. Our evaluated level density parameter ‘a’ values are compared with RIPL-2 (Reference Input Parameter Library) data which show good agreement.

Estimations of level density parameters by using artificial neural network for phenomenological level density models

The main aim of this study is to develop accurate artificial neural network (ANN) algorithms to estimate level density parameters. An efficient Bayesian-based algorithm is presented for classification algorithms. Unknown model parameters are estimated using the observed data, from which the Bayesian-based algorithm is predicted. This paper focuses on the Bayesian method for parameter estimations of Gilbert Cameron Model (GCM), Back Shifted Fermi Gas Model (BSFGM) and Generalised Super Fluid Model (GSM), which are known as the phonemological level density models. Obtained level density parameters have been compared with the Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations (RIPL) data. R values of the Bayesian method have been found as 0.9946, 0.9981 and 0.9824 for BSFGM, GCM and GSM, respectively. In order to validate our results, default level density parameters of TALYS 1.95 code have been changed with our newly obtained results and photo-neutron cross-section calculations of the 117Sn(γ,n)116Sn, 118Sn(γ,n)117Sn, 119Sn(γ,n)118Sn and 120Sn(γ,n)119Sn reactions have been calculated by using these newly obtained level density parameters.

Estimations of giant dipole resonance parameters using artificial neural network

In this study; Giant Dipole Resonance (GDR) parameters of the spherical nucleus have been estimated by using artificial neural network (ANN) algorithms. The ANN training has been carried out with the Levenberg–Marquardt feed-forward algorithm in order to provide fast convergence and stability in ANN training and experimental data, taken from Reference Input Parameter Library (RIPL). R values of the system have been found as 0.99636, 0.94649, and 0.98318 for resonance energy, full width half maximum, and resonance cross-section, respectively. Obtained results have been compared with the GDR parameters which are taken from the literature. To validate our findings, newly acquired GDR parameters were then replaced with the existing GDR parameters in the TALYS 1.95 code and 142-146Nd(γ,n)141-145Nd reaction cross-sections have been calculated and compared with the experimental data taken from the literature. As a result of the study, it has been shown that ANN algorithms can be used to calculate the GDR parameters in the absence of the experimental data.

Reference database for photon strength functions

Photon strength functions describing the average response of the nucleus to an electromagnetic probe are key input information in the theoretical modelling of nuclear reactions. Consequently they are important for a wide range of fields such as nuclear structure, nuclear astrophysics, medical isotope production, fission and fusion reactor technologies. They are also sources of information for widely used reaction libraries such as the IAEA Reference Input Parameter Library and evaluated data files such as EGAF. In the past two decades, the amount of reaction gamma-ray data measured to determine photon strength functions has grown rapidly. Different experimental techniques have led to discrepant results and users are faced with the dilemma which (if any) of the divergent data to adopt. We report on a coordinated effort to compile and assess the existing experimental data on photon strength functions from the giant dipole resonance region to energies below the neutron separation energy. The assessment of the discrepant data at energies around or below the neutron separation energy has been possible only in a few cases where adequate information on the model-dependent analysis and estimation of uncertainties was available. In the giant dipole resonance region, we adopt the recommendations of the new IAEA photonuclear data library. We also present global empirical and semi-microscopic models that describe the photon strength functions in the entire energy region and reproduce reasonably well most of the experimental data. The compiled experimental photon strengths and recommended model calculations are available from the PSF database hosted at the IAEA (URL:www-nds.iaea.org/PSFdatabase).

Analysis of neutron capture cross section using different level density models on cadmium isotopes up to 250 keV neutron-induced energy and GEANT4 simulation

The neutron capture cross-sectional reactions for 106,108,110,111,112,113,114,116Cd isotopes have been calculated with different level density models which are constant temperature Fermi gas (CTFG) model, back-shifted Fermi gas model, generalized superfluid model and Hartree–Fock–Bogoliubov model by using TALYS 1.9 and EMPIRE 3.2 codes for incident neutron energies up to 250 keV. The obtained results have been analyzed with each level density model parameters existing in Reference Input Parameter Library (RIPL-3) and available experimental data. As an outcome, to obtain more precise and coherent calculations with the experimental values, level density model and its parameters have been determined. Also, hadronic interactions of low-energy neutrons have been investigated for a situation by using GEANT4.

Comprehensive overview of the Point-by-Point model of prompt emission in fission

The investigation of prompt emission in fission is very important in understanding the fission process and to improve the quality of evaluated nuclear data required for new applications. In the last decade remarkable efforts were done for both the development of prompt emission models and the experimental investigation of the properties of fission fragments and the prompt neutrons and $\gamma$ -ray emission. The accurate experimental data concerning the prompt neutron multiplicity as a function of fragment mass and total kinetic energy for 252Cf(SF) and 235 (n, f) recently measured at JRC-Geel (as well as other various prompt emission data) allow a consistent and very detailed validation of the Point-by-Point (PbP) deterministic model of prompt emission. The PbP model results describe very well a large variety of experimental data starting from the multi-parametric matrices of prompt neutron multiplicity $\nu (A,TKE)$ and $\gamma$ -ray energy $E_{\gamma}(A,TKE)$ which validate the model itself, passing through different average prompt emission quantities as a function of A (e.g., $\nu(A)$ , $E_{\gamma}(A)$ , $\langle \varepsilon \rangle (A)$ etc.), as a function of TKE (e.g., $\nu (TKE)$ , $E_{\gamma}(TKE)$ ) up to the prompt neutron distribution $P (\nu)$ and the total average prompt neutron spectrum. The PbP model does not use free or adjustable parameters. To calculate the multi-parametric matrices it needs only data included in the reference input parameter library RIPL of IAEA. To provide average prompt emission quantities as a function of A, of TKE and total average quantities the multi-parametric matrices are averaged over reliable experimental fragment distributions. The PbP results are also in agreement with the results of the Monte Carlo prompt emission codes FIFRELIN, CGMF and FREYA. The good description of a large variety of experimental data proves the capability of the PbP model to be used in nuclear data evaluations and its reliability to predict prompt emission data for fissioning nuclei and incident energies for which the experimental information is completely missing. The PbP treatment can also provide input parameters of the improved Los Alamos model with non-equal residual temperature distributions recently reported by Madland and Kahler, especially for fissioning nuclei without any experimental information concerning the prompt emission.

Low-energy behavior ofE2strength functions

Electric quadrupole strength functions have been deduced from averages of a large number of $E2$ transition strengths calculated within the shell model for the nuclides $^{94}\mathrm{Mo}$ and $^{95}\mathrm{Mo}$. These strength functions are at variance with phenomenological approximations as provided by the Reference Input Parameter Library RIPL-3 for calculations of reaction rates on the basis of the statistical model.

Structure for Storing Properties of Particles (PoP)

Evaluated nuclear databases are critical for applications such as nuclear energy, nuclear medicine, homeland security, and stockpile stewardship. Particle masses, nuclear excitation levels, and other “Properties of Particles” are essential for making evaluated nuclear databases. Currently, these properties are obtained from various databases that are stored in outdated formats. A “Properties of Particles” (PoP) structure is being designed that will allow storing all information for one or more particles in a single place, so that each evaluation, simulation, model calculation, etc. can link to the same data. Information provided in PoP will include properties of nuclei, gammas and electrons (along with other particles such as pions, as evaluations extend to higher energies). Presently, PoP includes masses from the Atomic Mass Evaluation version 2003 (AME2003), and level schemes and gamma decays from the Reference Input Parameter Library (RIPL-3). The data are stored in a hierarchical structure. An example of how PoP stores nuclear masses and energy levels will be presented here.

EGAF: Measurement and Analysis of Gamma-ray Cross Sections

The Evaluated Gamma-ray Activation File (EGAF) is the result of a 2000–2007 IAEA Coordinated Research Project to develop a database of thermal, prompt γ-ray cross sections, σγ, for all elemental and selected radioactive targets. No previous database of this kind had existed. EGAF was originally based on measurements using guided neutron beams from the Budapest Reactor on all elemental targets from Z=1–82, 90 and 92, except for He and Pm. The EGAF σγ data were published in the Database of Prompt Gamma Rays from Slow Neutron Capture for Elemental Analysis [1]. An international collaboration has formed to continue the EGAF measurements with isotopically enriched targets, derive total radiative thermal neutron cross sections, σ0, extend the σγ data from thermal to 20 MeV neutrons, compile a completed activation data file, improve sections of the Reference Input Parameter Library (RIPL) with more complete and up to date level and γ-ray data, evaluate statistical γ-ray data from reaction studies, and determine recommended neutron separations energies, Sn, for atomic mass evaluations. A new guided neutron beam facility has become available at the Garching (Munich) FRM II Reactor, and high energy neutron experimental facilities are being developed by a Berkeley area collaboration where 5–33 MeV neutron beams are available at the LBNL 88” cyclotron, 2.5 and 14 MeV beams at the University of California, Berkeley neutron generator laboratory, and high flux, 1027–33 n⋅cm⋅−2 s−1, neutron pulses available from the LLNL National Ignition Facility (NIF).

RIPL – Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluations

We describe the physics and data included in the Reference Input Parameter Library, which is devoted to input parameters needed in calculations of nuclear reactions and nuclear data evaluations. Advanced modelling codes require substantial numerical input, therefore the International Atomic Energy Agency (IAEA) has worked extensively since 1993 on a library of validated nuclear-model input parameters, referred to as the Reference Input Parameter Library (RIPL). A final RIPL coordinated research project (RIPL-3) was brought to a successful conclusion in December 2008, after 15 years of challenging work carried out through three consecutive IAEA projects. The RIPL-3 library was released in January 2009, and is available on the Web through (http://www-nds.iaea.org/RIPL-3/). This work and the resulting database are extremely important to theoreticians involved in the development and use of nuclear reaction modelling (ALICE, EMPIRE, GNASH, UNF, TALYS) both for theoretical research and nuclear data evaluations. The numerical data and computer codes included in RIPL-3 are arranged in seven segments: MASSES contains ground-state properties of nuclei for about 9000 nuclei, including three theoretical predictions of masses and the evaluated experimental masses of Audi et al. (2003). DISCRETE LEVELS contains 117 datasets (one for each element) with all known level schemes, electromagnetic andmore » {gamma}-ray decay probabilities available from ENSDF in October 2007. NEUTRON RESONANCES contains average resonance parameters prepared on the basis of the evaluations performed by Ignatyuk and Mughabghab. OPTICAL MODEL contains 495 sets of phenomenological optical model parameters defined in a wide energy range. When there are insufficient experimental data, the evaluator has to resort to either global parameterizations or microscopic approaches. Radial density distributions to be used as input for microscopic calculations are stored in the MASSES segment. LEVEL DENSITIES contains phenomenological parameterizations based on the modified Fermi gas and superfluid models and microscopic calculations which are based on a realistic microscopic single-particle level scheme. Partial level densities formulae are also recommended. All tabulated total level densities are consistent with both the recommended average neutron resonance parameters and discrete levels. GAMMA contains parameters that quantify giant resonances, experimental gamma-ray strength functions and methods for calculating gamma emission in statistical model codes. The experimental GDR parameters are represented by Lorentzian fits to the photo-absorption cross sections for 102 nuclides ranging from {sup 51}V to {sup 239}Pu. FISSION includes global prescriptions for fission barriers and nuclear level densities at fission saddle points based on microscopic HFB calculations constrained by experimental fission cross sections.« less

IAEA Coordinated Research Projects in Nuclear Data

The International Atomic Energy Agency (IAEA) supports free information exchange and international collaboration by its statute. Out of several possibilities the mechanism of Co-ordinated Research Projects (CRP) is described, which can bring together scientists and research groups from developing and developed counties to form teams on projects of mutual interest. Examples of successful CRP’s in the nuclear data field are described, which include the production of the reference input parameter library for nuclear model codes, photonuclear data library, an updated processed WIMS-D library for reactor lattice calculations and evaluated nuclear data files for the thorium-uranium fuel cycle.