Statistical Model Code Research Articles

Estimation of production yield of 93mMo and other residues from a 7Li-induced reaction

The crux of the present work is to analyze the yield of the residues produced in the 7Li-induced reaction on 89Y target in the low energy range. The experimental yields of 93mMo, which is a significant product in the energy range considered, and other coproduced radionuclides, such as 92mNb, 89Zr, 91mY, and 90mY have been measured within 19–40 MeV energy, and are compared with the compound and pre-compound models in the framework of the statistical reaction model code EMPIRE. The maximum measured yield for 93mMo is 374 MBq/C at 31.3 MeV in a 3 mg/cm2 thick 89Y target corresponding to a cross-section of 396.8 ± 38.6 mb from the 89Y(7Li,3n)93mMo reaction. The model estimations well reproduce the experimental yields of 93mMo. The possible production of stable isotopes has also been estimated theoretically from the model over the experimental energy range. The reaction could be an alternative route for the production of no-carrier-added 93mMo radionuclide provided that the radionuclides are chemically separated from the bulk 89Y matrix.

Sequential binary decay of light nuclear systems: An assessment of statistical model codes

The sequential decay of excited nuclei is described as a succession of binary processes involving fragments in their ground, excited-bound and unbound states. Primary together with secondary decays lead to the final mass and charge distributions. Asymmetric mass splittings involving nucleon emission up to symmetric binary ones are treated within the Weisskopf evaporation formalism, in a unified manner. This procedure was imple- mented in the Monte-Carlo multi-step statistical model code MECO (Multisequential Evaporation COde). We study the evolution of the calculated final mass and charge distributions from 40Ar* as a function of the excitation energy, up to complete dissociation. Our results are compared with the predictions of statistical evaporation codes based on different assumptions for the compound nucleus decay.

A statistical and numerical modeling approach for spatiotemporal reconstruction of glaciations in the Central Asian mountains

Reconstructing Quaternary regional glaciations throughout the Himalaya, Tibet, and the adjoining mountains in Central Asia is challenging due to geological biases towards limited preservation of glacial deposits and chronological uncertainties. Here, we offer several statistical and mathematical model codes in R, in excel, and in MATLAB useful to develop regional glacial chronostratigraphies, especially in areas with distinct orographically-modulated climate. A complete R code is provided to generate a regional climate map using Cluster Analysis (CA) and Principal Component Analysis (PCA). Additional R codes include reduced chi-squared, Chauvenet's criterion, radial plotter/abanico plot, finite mixture model, and Student's t-test. These methods are useful in reconstructing the timing of local and regional glacial chronologies. An excel code to calculate equilibrium-line altitudes (ELAs) and steps to reconstruct glacier hypsometry are also made available to further aid to our understanding of the extent of paleoglaciations. A MATLAB code of the linear glacier flow model is included to reconstruct paleotemperatures using the length and slope of a glacier during past advances.•R statistical codes can be used/modified without restrictions for other researchers.•Easy steps to calculate ELAs and glacier hypsometry from the same data.•Paleo-temperature reconstruction utilizes already developed glacial chronologies and maps.

Capture reaction cross-section measurements relevant to p process: the case of (α , γ) reactions on 63Cu, 72Ge,118Sn and the 107Ag(ρ, γ)108Cd reaction

The cross sections of the 72Ge( α , γ)76Se and 1°7Ag(ρ, γ)1°8Cd reactions were measured at energies relevant to p-process nucleosynthesis. The new data, together with cross section results from our previous ( α , γ) measure-ments on 65Cu and 118Sn and other ( α , γ) cross-section data reported in lit-erature are compared with statistical model calculations performed using the latest version (1.9) of the statistical model code TALYS. In addition, the effect on these calculations of different combinations of the optical model potentials (OMPs), nuclear level densities (NLDs) and γ-ray strength functions (γSFs) entering the calculations was investigated.

Effect of projectile breakup in the system 19F + 154Sm

An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19 F + 154 Sm at projectile energy ≈ 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of α-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19 F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles.

Variation of ICF strength function with projectile energy for 12C + 165Ho system at Elab ≤ 7MeV/A

During the last few decades, research in heavy-ion induced nuclear reactions has opened numerous fields, in its theoretical and experimental domains. At energies, from near the Coulomb barrier to well above it, the complete fusion (CF) and incomplete fusion (ICF) reactions compete with each other. The relative contribution of these processes depends on various entrance channel parameters. In order to study the dependence of CF and ICF reaction dynamics on various entrance channel parameters, comparative studies with different parameters of the statistical model codes have been done. In this paper, an attempt has been made to study the dependence of incomplete fusion strength function on incident energy for 12 C + 165 Ho system at energies ≤ 7 MeV/A. The analysis of data has been done within the frame work of statistical model code PACE4, which do not take ICF into account; and thus predicts cross-section values only due to complete fusion process. For the present reaction system, the excitation functions (EFs) of xn/pxn channels, predicted by PACE4 code, well reproduces the experimentally measured values, indicating their production via CF process only. However, for α and 2α-emitting channels, calculated EFs through PACE4 code underpredict the experimentally measured cross-sections by »25-30%, in general. The enhancement of experimental cross-sections for α and 2α-emitting channels as compared to the PACE4 predictions, indicates that the major contribution of their production comes from the ICF of 12 C, if it breaks up into 8 Be and α-fragments, and one of the fragments fuses with the target nucleus. The incomplete fusion strength function (F ICF ), which gives relative importance of ICF processes over CF process has also been deduced and is found to depend sensitively on beam energy.

Systematic of fusion incompleteness in reactions induced by α cluster projectiles

In order to investigate the systematic of fusion incompleteness in reactions induced by $\ensuremath{\alpha}$ cluster projectiles, a detailed study was carried out using the $^{20}\mathrm{Ne}+^{165}\mathrm{Ho}$ system at energies above the barrier. Measurements of the excitation function (EF) of the observed evaporation residues (ERs) were carried out by employing the offline characteristic $\ensuremath{\gamma}$-ray detection method. The EFs of the ERs populated through $xn/pxn$ channels were found to be in good agreement with the prediction of the statistical model code pace4, whereas the EF of the ERs populated through the $\ensuremath{\alpha}$ emitting channels shows an enhancement over the pace4 prediction. The degree of fusion incompleteness in the $^{20}\mathrm{Ne}+^{165}\mathrm{Ho}$ reaction is estimated by comparing the fusion EF with coupled channels calculations and the extracted fusion function with the universal fusion function. The influence of input angular momentum on fusion reaction dynamics is explored in light of the sum-rule model. An attempt has also been made to examine the dependence of incomplete fusion probability on various entrance channel parameters.

Experimental measurement of the neutron ambient dose equivalent from 116 MeV 12C+12C reaction using monitoring instruments

The neutron ambient dose equivalent measured at 0º, 30º, 90º and 120º with respect to the incident beam for 116 MeV 12C projectiles incident on a thick carbon target are reported here. The measurements were carried out with a conventional moderated BF3 proportional counter based rem-meter and a spectrometry based neutron probe (N-probe) dose meter that measures the fluence and folds it with the appropriate fluence to dose conversion coefficients to give the ambient dose equivalent. The ambient dose equivalents are also estimated using the neutron spectra calculated by the PACE2 statistical nuclear reaction model code and folding it with the fluence to ambient dose equivalent conversion coefficients. The dose results are also obtained using an empirical technique reported in the literature. The doses measured by the rem-meter and N-probe, and that estimated from the PACE2 results agreed within 10% of each other while the results from the empirical relation under-predicted the dose rates in the forward direction and over predicted in the backward direction. The angular distribution of the dose from the empirical relation also did not agree with the results from the other techniques. The measured and the PACE2 calculated neutron spectra are not similar in the fluence, shape, peak energy or the slope. The integral doses are still comparable because of the compensation by the higher fluence in the PACE2 results and a corresponding higher fluence to ambient dose equivalent conversion coefficients at those energies.

Cross sections of proton capture reactions of Sr isotopes

Cross section measurements of the proton capture reactions of the 86Sr, 87Sr and 88Sr isotopes were carried out at energies Ep=1.4-5 MeV. At Ep <3.5 MeV an array of 4 HPGe detectors with 100% relative efficiency shielded with BGO scintillators for Compton background suppression was used, whereas at Ep >3.5 MeV, the measurements were performed by means of one HPGe detector of 80% relative efficiency. For the 87Sr(p,7)88Y and 88Sr(p,7)89Y reactions total cross sections ranging from 0.5 μο-5 mb were found. The data analysis of the 86Sr(p,7)87Y reaction is in progress. Cross sections have also been calculated by means of the statistical model code MOST. A very good agreement between the experimental data and the theoretical predictions has been found.

Sequential binary decay of highly excited 40Ar*

The sequential statistical binary decay of the highly excited compound nucleus 40Ar* is described with an extended evaporation formalism implemented in a Monte-Carlo multi-step statistical model code. Asymmetric mass splittings involving nucleon emission up to symmetric binary ones are treated within the evaporation formalism, in a unified manner. Emission of heavy fragments in their ground and excited (particle-bound or unbound) states is considered. The evolution of the final mass distributions from 40Ar* is studied as a function of the initial excitation energy, in the range from 45 up to 405 MeV. The population of final states originating from the decay of intermediate mass fragments in particle-bound and particle-unbound states (side-feeding) is discussed. Results are compared with an alternative description in which the time-dependent decay process is described by rate equations for the generation of different fragment species.

Determination of Mn53(n,xp) cross sections using the surrogate reaction ratio method

The $^{54}\mathrm{Mn}^{*}$ (surrogate of $n+^{53}\mathrm{Mn}$) and $^{61}\mathrm{Ni}^{*}$ (surrogate of $n+^{60}\mathrm{Ni}$) compound systems have been populated at overlapping excitation energies by transfer reactions $^{52}\mathrm{Cr}(^{6}\mathrm{Li},\ensuremath{\alpha})^{54}\mathrm{Mn}^{*}$ at ${E}_{\mathrm{lab}}=33.0\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$ and $^{59}\mathrm{Co}(^{6}\mathrm{Li},\ensuremath{\alpha})\phantom{\rule{0.16em}{0ex}}^{61}\mathrm{Ni}^{*}$ at ${E}_{\mathrm{lab}}=40.5\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$, respectively. The proton decay probabilities of the compound systems have been determined by measuring evaporated protons at backward angles in coincidence with projectilelike fragments detected around the grazing angle. The $^{53}\mathrm{Mn}(n,xp)$ cross sections in the equivalent neutron energy range of 8.2--16.4 MeV have been determined within the framework of the surrogate reaction ratio method using $^{60}\mathrm{Ni}(n,xp)$ cross-section values from the literature as a reference. The measured $^{53}\mathrm{Mn}(n,xp)$ cross-section values are found to be consistent with the predictions of the talys-1.8 statistical model code using microscopic level densities and results of various evaluated nuclear data libraries: eaf-2010, rosfond-2010, and jeff-3.3 within the experimental uncertainties.

Excitation functions of the Zn(p,xn)Ga reactions

The excitation functions for 64,66,67,68,70Zn(p,n)64,66,67,68,70Ga and 64,66,67,68,70Zn(p,2n)63,65,66,67,69Ga have been calculated for incident proton energies from threshold values to 30 MeV using the statistical model code TALYS-1.6. The (p,n) and (p,2n) cross sections have been calculated using both phenomenological Koning and Delaroche (KD) and semimicroscopic Jeukenne-Lejeune-Mahaux-Bruyeres (JLMB) optical model potentials. The phenomenological back-shifted Fermi gas model (BFM) and microscopic Hartree-Fock (HF) approaches for calculation of level densities have been compared in the present work. The pre-equilibrium process has been treated using exciton model. The sensitivity of cross section data to different models of optical model potential and level density have been investigated. It is found that the (p,n) and (p,2n) cross section calculations with semimicroscopic JLMB optical model potential and microscopic HF level density show agreement with the data. The (p,n) and (p,2n) cross section calculations have been compared with corresponding cross sections from nuclear data library, TENDL-2019. The (p,xn) cross sections obtained will be useful in several applications, particularly, for optimization of production routes for Ga isotopes.

Investigating entrance channel influences in the fusion of some heavy–ion systems

The dynamics of heavy-ion fusion reaction involved in the interaction of 12C,14N and 16O projectiles with,59Co, 51V,128Te and165Ho targets at≈3-8MeV/nucleon specific energies was studied. This study focus on the correlation between entrance channel properties and incomplete fusion reaction. The experimentally measured excitation functions of various reaction products populated by complete and/or incomplete fusions of 12C+59Co, 128Te,14N+128Teand 16O+ 51V, 165Hoprojectile-target systems available in the literature. Were compared and analyzed with the predicted excitation functions, using the statistical model code PACE4. For representative non-α-emitting channels, the experimentally measured excitation functions were, in general, found to be in good agreement with the theoretical predictions. However, for α-emitting channels in the present systems, the measured excitation functions were higher than the predictions of the theoretical model code, which may be credited to incomplete fusion reactions at these energies. An attempt was made to approximate the incomplete fusion fraction that explains the relative importance of incomplete fusion processes. The incomplete fusion fraction was found to be sensitive to the projectile energy and mass-asymmetry of the entrance channel

Investigating the Influence of Incomplete Fusion on Complete Fusion of 16 O –Induced Reaction ≈ 3-8 MeV/nucleon

The dynamics of heavy-ion fusion reaction elaborate in the interaction of 1616O "> projectiles with 16165Ho "> and 51 V targets at ≈3-8MeV/nucleon specific energies were studied. This study were emphases on the relationship between entrance channel belongings and incomplete fusion reaction. The experimentally measured excitation functions of various reaction products duplicated by complete or incomplete fusions of 1616O "> + 1651V"> , 16165Ho "> projectile-target systems had been compared and analyzed within the predicted excitation functions, using the statistical model code PACE4. For α-emitting channels in the present systems, the measured excitation functions had been highest than the predictions of the theoretical model code, which may focuses at these energies. However for non-alpha emitting channels in this system the measured excitation function had been nice agreement with the theoretical values. An endeavor were made to nearly the incomplete fusion fraction that designates importance of incomplete fusion process. Keywords: Alpha emitted, CF reaction, Entrance channel, Heavy ion fusion, ICF reaction, Non alpha emitted DOI : 10.7176/APTA/79-03 Publication date :September 30 th 2019

Systematic study of the break-up fusion process in the C12+Ho165 system and interplay of entrance channel parameters

To understand the low-energy incomplete fusion (ICF) reaction dynamics, the excitation function measurements of $^{12}\mathrm{C}+^{165}\mathrm{Ho}$ system has been performed in the energy region of \ensuremath{\approx} 4--7 MeV/nucleon, by employing the stacked foil activation technique. The cross sections of the measured evaporation residues are compared with the theoretical predictions of statistical model code PACE4, which takes into account only the complete fusion (CF) reaction cross section. It is observed that residues populated via xn and pxn channels are in good agreement with the PACE4 predictions, implying that these residues are populated via CF process. However, in the case of \ensuremath{\alpha}-emission channels a significant enhancement from the PACE4 predictions is observed even after the deduction of precursor contribution, which is accredited to ICF process. The projectile break-up probability is found to increase with increment in the incident projectile energy. Further, the dependence of incomplete fusion dynamics on entrance channel parameters like mass asymmetry, Coulomb effect (${Z}_{\mathrm{P}}{Z}_{\mathrm{T}}$), and projectile ${Q}_{\ensuremath{\alpha}}$ value is systematically studied. The present results reveal that a single entrance channel parameter does not oversee the ICF reaction dynamics but have varying contributions depending upon the projectile-target combination. Moreover, the effect of projectile break-up on complete fusion cross section at energies above the Coulomb barrier is also studied. The suppression in fusion cross section is observed when compared with the universal fusion function.

Role of viscosity in fusion-fission dynamics via simultaneously measured neutron and α -particle multiplicities

The multiplicities of $\ensuremath{\alpha}$ particles and neutrons have been measured simultaneously for the reaction $^{16}\mathrm{O}+^{196}\mathrm{Pt}$ forming $^{212}\mathrm{Rn}$ compound nucleus at excitation energies of 56 MeV, 61 MeV, and 68 MeV. Neutrons and $\ensuremath{\alpha}$ particles were detected at various angles in coincidence with the fission fragments. To extract the contribution of pre- and postmultiplicities using the total $\ensuremath{\alpha}$-particle and neutron spectra, moving source formalism was implemented. In the case of $\ensuremath{\alpha}$ particle, near scission contribution has also been extracted. Study of the fission mechanism using light particle emissions are helpful in understanding the detailed fusion-fission reaction dynamics. The statistical model code joanne2, which includes deformation-dependent particle transmission coefficients, binding energies and level densities, has been used to reproduce the measured multiplicities of neutrons and $\ensuremath{\alpha}$ particles by varying the transient (${\ensuremath{\tau}}_{tr}$) and saddle to scission (${\ensuremath{\tau}}_{ssc}$) times. It is found that the fission time scales of the order of $50--70\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}21}$ sec are required to reproduce the neutron and $\ensuremath{\alpha}$-particles multiplicities simultaneously. The fission time scales are the measure of the nuclear viscosity, which is responsible for the dynamic hindrance of the fission process.

Cross section measurements of proton capture reactions on Mo isotopes relevant to the astrophysical p process

Cross section measurements of ($p, \gamma$) reactions on the Mo isotopes have been performed at beam energies from 2 to 6.2 MeV that are relevant to the p-process. Partial cross sections and isomeric ratios were also determined for the 92Mo case. Astrophysical S factors as well as reaction rates were derived from the experimental cross sections. Statistical model calculations were performed using the latest version (1.9) of the statistical model code TALYS and were compared with the new data. An overall good agreement between theory and experiment was found. In addition, the effect of different combinations of the nuclear input parameters entering the stellar reaction-rate calculations was investigated. It was found that, for certain combinations of optical-model potentials, nuclear level densities and $\gamma$-ray strength functions, the nuclear uncertainties propagated through the Hauser-Feshbach calculations are less than a factor of 2 which is well below the average discrepancies of the calculated p-nuclei abundances and the observations.

Sensitivity of charged particle activation analysis for long-lived radioactive nuclide determination

ABSTRACT Charged Particle Activation Analysis (CPAA) utilizing an 8-MeV proton beam has been studied for determination of 35 long-lived radioactive nuclides. We accumulated the reaction cross section and nuclear decay data by referring to nuclear database supplied by National Nuclear Data Center in Brookhaven National Laboratory. We also calculated the reaction cross sections by using statistical model code ALICE. By using the nuclear data, we have derived determination sensitivity of the radioactive nuclides relative to unit weight and specific radioactivity. The result indicates that several hardly measurable nuclides with long half-lives such as 135Cs, 244Pu, 129I, 126Sn, 93Mo, 107Pd, 236U, 248Cm, and 237Np have high sensitivity. It may be concluded that CPAA can be applied to determination of several long-lived nuclei and will provide a quick and non-destructive analysis method.

Insights into the low energy incomplete fusion

In the present work, channel-by-channel excitation functions of different evaporation residues populated via complete and/or incomplete fusion in C12+169Tm system have been measured for an energy range Elab≈53–90MeV, using recoil-catcher activation technique followed by off-line γ-spectroscopy. Experimentally measured excitation functions have been analysed in the framework of statistical model code pace. To probe the effect of entrance-channel parameters on the onset and strength of incomplete fusion, relative contributions of complete and incomplete fusion have been deduced from the analysis of experimentally measured excitation functions. The percentage fraction of incomplete fusion deduced from the analysis of excitation functions has been studied in terms of incident energy, entrance-channel mass-asymmetry, ground state alpha-Q-value, neutron skin thickness of target nuclei, and nuclear potential parameters. It has been found that incomplete fusion start competing with complete fusion even at slightly above barrier energies where complete fusion is assumed to the sole contributor. The probability of incomplete fusion increases with incident energy, entrance channel mass-asymmetry, large negative ground state alpha-Q-value, neutron skin thickness, and nuclear potential parameters for individual projectiles.

Effects of projectile break-up on fusion cross sections at energies near and above the Coulomb barrier: A case of incomplete fusion

In the present work, the experimental studies of projectile break-up (incomplete fusion) at energies $\ensuremath{\approx}4$--7 MeV/nucleon have been performed by using offline $\ensuremath{\gamma}$-ray spectroscopy. The excitation functions of reaction residues populated in the $^{19}\mathrm{F}+^{175}\mathrm{Lu}$ system via complete fusion and/or incomplete fusion processes were measured and analyzed within the framework of the statistical model code pace4. The measured excitation functions of $xn$ and $pxn$ channels are found to be well reproduced by the predictions of pace4, which clearly indicates the population of these residues, predominantly, via complete fusion processes. However, in the case of residues involving $\ensuremath{\alpha}$ particles in the exit channels, the experimentally measured cross sections are found to show a significant enhancement when compared with pace4 predictions. This enhancement points toward the onset of incomplete fusion reactions at the studied range of energies and is found to be projectile energy dependent. Further, an attempt was made to study the influence of projectile (strongly bound) break-up on fusion cross sections, above the Coulomb barrier, within the framework of the universal fusion function, which is a benchmark function that does not depend on the system parameters. The experimental fusion function was deduced for the complete fusion (CF) cross section $(\ensuremath{\sum}{\ensuremath{\sigma}}_{\text{CF}}=\ensuremath{\sum}{\ensuremath{\sigma}}_{xn+pxn}^{\text{expt}})$ and total fusion (TF) cross section $(\ensuremath{\sum}{\ensuremath{\sigma}}_{\text{TF}}=\ensuremath{\sum}{\ensuremath{\sigma}}_{\text{CF}\phantom{\rule{4.pt}{0ex}}\text{+}\phantom{\rule{4.pt}{0ex}}\text{ICF}}^{\text{expt}})$ for three strongly bound projectiles $^{13}\mathrm{C},^{16}\mathrm{O}$, and $^{19}\mathrm{F}$ (present work) on different target nuclei and compared with the universal fusion function. Analysis of data indicates 10--$35%$ complete fusion suppression above the barrier, indicating that it is essentially due to the prompt break-up (incomplete fusion) of the strongly bound projectiles. Moreover, the deduced complete fusion suppression factor for the present work shows a conspicuous exponential relation with the break-up threshold of the projectile.