Journal of Nuclear Physics, Material Sciences, Radiation and Applications

Iscovector Giant Dipole Resonance in 175Lu Within the Linear Response Theory

2022-11-21T09:22:44+00:00

We investigate the isovector giant dipole resonance (IVGDR) in a well-deformed odd-even ¹⁷⁵Lu within a microscopic approach for giant dipole resonance (GDR) where the linear response by the nuclear density to the dipole radiation is represented through the single-particle wavefunctions calculated with a triaxial Woods-Saxon (WS) potential. The nuclear shape is obtained using the same WS potential in a microscopic-macroscopic approach. The results for the photo-absorption cross-section are compared with the experimental data and show a splitting of GDR strength into K=0 and K=1 components due to large quadrupole deformation. The splitting of the GDR peak is consistent with the experimental data.

Systematic Compilation/Evaluation of Reduced B(E3) Transition Probabilities and Configurations of Octupole (∆I=3) Isomers in Mass A~200 Region

2022-05-03T15:07:06+00:00

Background: Strong octupole correlations are observed in mass region giving rise to a number of isomeric states decaying via type of transition involving interacting orbitals. Theoretically, the and neutron orbitals or the and proton orbitals are predicted to be involved in these enhanced decays.

Purpose: This work reports on the systematics of reduced transition probabilities and configurations of octupole isomers in order to compare them based on their structures such as even-even, even-odd, odd-even and odd-odd.

Methods: The data for a total of isomers is collected from the ENSDF/XUNDL Database of NNDC. The reduced transition probabilities are evaluated and compiled using the available data on half-life and branching ratios of the isomeric states having pure decay. In about cases, we have also evaluated the half-lives to get their adopted value to obtain the transition probability by RULER program.

Results: A systematic variation in the reduced transition strength is discussed as a function of neutron and proton number to see the contribution/effect from the core particles. An enhancement is observed experimentally for the isomeric states involving the and neutron orbitals or the and proton orbitals

Conclusions: The enhanced transitions rates are observed in nuclei having configurations with octupole effects.

Systematic of Signature Splitting in Ce Nuclei

2022-05-27T15:19:08+00:00

The signature splitting and signature inversion in rotational bands belonging to configurations in even-even deformed ^132,134,136Ce nuclei have been studied. These Ce isotopes are interesting candidates to probe for signature of triaxiality. The energy staggering index S(I) is found nearly constant for band 4 and 5 ¹³²Ce. similarly, S(I) is also found nearly constant as a function of spin ¹³⁴ Ce. The observed signature splitting in these two nuclei does not support low K (projection on symmetry axis) value for these bands on the other hand, high K value is not expected for and / orbitals at Z=58. Hence, this low and constant signature splitting is only possible due to triaxiality. However, in ¹³⁶Ce favored and unfavored partner bands (B1 and B2) Shows normal signature splitting and indicate axially symmetric shape for ¹³⁶Ce.

Heavy cluster radioactivity and decay mode of Superheavy element 306^120

2022-03-21T11:58:20+00:00

Background: Many theoretical studies and experimental attempts are conducted to synthesize SHN with Z =120 being an element with a proton magic number. The prediction of the island of stability also encourages scientists to search for the existence of super heavy nuclei near Z=120.
Purpose: Main aim of our work is to predict all heavy cluster emissions from superheavy nuclei (SHN) ³⁰⁶120.
Methods: Modified Generalized Liquid drop model (MGLDM) with Q value dependent pre-formation factor [Phys. Rev. C, 99, 064604 (2019)] is the theoretical model used to calculate the alpha and cluster decay half-life of SHN ³⁰⁶120. The spontaneous fission half-life is predicted using the shell effect and mass inertia dependent formula by our group [Phys. Rev. C, 104, 024617 (2021)].
Results: We investigate all cluster emissions from ³⁰⁶120, and the fragment combination ¹²³Cd (Z=48) leading to 183Hf daughter nucleus is predicted to be a probable heavy cluster decay with halflives comparable with alpha decay half-lives. The heavy cluster ¹³⁷Xe (N=83) with ¹⁶⁹Dy daughter nucleus is predicted to be the most probable cluster decay with the least half-life among all fragment combinations. Thus, our study shows the role of the magic number of proton and neutron in cluster decay. We also predict that the superheavy element ³⁰⁶120 decays by 4 alpha chains followed by spontaneous fission.
Conclusions: The predicted half-life in the case of alpha decay and heavy cluster emission from SHN ³⁰⁶120 are within experimental limits and we hope that our predictions will guide future experiments.

Deformation Effect on Proton Bubble Structure in N = 28 Isotones

2022-05-14T13:14:15+00:00

Purpose: To study the effect of nuclear deformation on proton bubble structure of N = 28 isotones and and compare it with the spherical limits. The reduction of depletion fraction due to deformation can be explained by studying the relative differences in the central densities.
Methods: In this work, we have employed relativistic Hartree-Bogoliubov (RHB) model with
density-dependent meson-exchange (DD-ME2) interaction and separable pairing interaction. We have performed axially constrained calculations to investigate the deformed proton bubble structure in ⁴⁰Mg, ⁴²Si,⁴⁴S, and ⁴⁶Ar, isotones of N = 28 shell closure.
Results: We have observed that the nuclear deformation play againsts the formation of bubble structure. In the spherical limits, the isotones of N = 28 shell closure have pronounced bubble structure with large value of depletion fraction. But, the increase in deformation leads to the disappearance of bubble structure. The internal densities in deformed nuclei are found to increase with deformation which can be related to the decrease in depletion fraction.
Conclusion: By using RHB model, we have investigated the ground state and proton bubble structure of N = 28 isotones. In ⁴⁴S, and ⁴⁶Ar, the 2s_1/21d_3/2 states get inverted due to the weakning of spin-orbit strength. Due to strong dynamical correlations, arising from deformation, the central depletion of proton density is greatly affected in these isotones. The decrease in depletion fraction can be related to increase in the internal density due to deformation

Assignment of the spin and parity to the excited states of the (85-86)^Rb nuclei

2022-05-03T15:10:00+00:00

Background: The isotopes of Rb (Z=37) are one proton away from semi-magic (Z=38) proton number and deficits the characteristic of a spherical nucleus. In the ^85,86Rb nuclei, the γ-ray spectroscopy are already performed and given an indication of Magnetic Rotation (MR) which usually observed in nearly spherical nuclei. The angular correlation measurements were used to find the spin and parity of the states.
Purpose: To confirm the spin and parity of the states in both the nuclei using Directional Correlation of Oriented (DCO) states ratio and polarization asymmetry (Δ) measurements.
Methods: The excited states of the 85,86Rb nuclei were populated via the ⁷⁶Ge(¹³C,p3n/p2n) reaction at a beam energy of 45 MeV. The γ-rays emitted from the excited states were detected using Indian National Gamma Array (INGA) spectrometer at the Tata Institute of Fundamental Research (TIFR), Mumbai India.
Results: The values of the DCO states ratio and polarization asymmetry (Δ) were obtained and utilized to confirm the spin-parity of the states in the ^85,86Rb nuclei. The polarization asymmetry (Δ) values were obtained for the first time using Compton-suppressed clover detectors.
Conclusions: In ⁸⁵Rb, the spin and parity of 3491.1-, 4135.4-, 4757.2- and 5419.3 keV levels
are confirmed and for the 5312.2-, 5611.8 and 6335.9 keV states, only the spin is established. The mul-tipolarity assignment of the 224.3-, 331.5-, 732.8-, 778.1-, 865.4-, 973.5-, 1002.4-,
1427.5-, 1453.7-, 1598.2-, 1814.1- and 1881.5 keV γ-ray transitions allowed to confirm the spin
and parity of most of the levels above the 6- isomer in ⁸⁶Rb.

Radii of Thorium Nuclides Lying in Between the Drip Lines

2022-03-21T14:50:48+00:00

Background: Nuclear rms radii give information about the nuclear structure, nuclear shape, deformation etc. Microscopic methods are widely used for the study of nuclear structure properties. Hartree-Fock method with an effective interaction of Skyrme force is used for studying the nuclear structure properties.
Purpose: To calculate the rms radii of proton and neutron for thorium nuclei, lying between the drip lines, by using the microscopic mean field theory. The nuclear rms radii data is useful for identifying the shape variation of thorium nuclei, from proton drip line to neutron drip line. It also helps to identify the trends in nuclear radii variation as we move towards the drip line. This nuclear data will be useful in designing experiments in future and also in understanding the behaviour of complex nuclei. Microscopic study of thorium nuclei is also important in the astrophysical environments.
Methods: This study is based on the Skyrme interacting potential in the Hartree-Fock mean field theory. Iterative diagonalization method with the help of a computational code is used for solving the Hartree-Fock equation.
Results: We have calculated the rms radii of neutron, proton and their total with SV, SLY4 and UDF2 parametrization of the Skyrme force. Neutron rms radii, proton rms radii and total rms radii of thorium nuclei are found to increase with neutron number. UDF2 parametrization shows an oscillatory nature in the rms radii. This may be due to the shape change of thorium nuclei when adding neutrons.
Conclusions: The rms radii of thorium nuclei are found to increase with neutron number. The Skyrme force with UDF2 parametrization is the most suitable one for the structure studies of thorium nuclei.

Charge Radius And Neutron Skin Thickness Of Platinum And Osmium Isotopes Near The Nuclear Drip Lines

2022-01-28T17:51:09+00:00

Background: The density distributions of exotic nuclei are different from that of stable nuclei. For stable nuclei, charge radii can be obtained through electron scattering experiments. The excessive neutrons in neutron-rich nuclei make a decoupling of neutron and proton distribution and as a result nuclear skin structures are appeared.
Purpose: The charge radius and the way by which nucleons are distributed can provide information about size, surface thickness and shell structure of nuclei. The information collected from such nuclei can be used for astrophysical studies to understand the origin of heavy elements.

Methods: In the present study, we have made an attempt to investigate the charge radii, rms radii and skin thickness of Pt and Os isotopes. Here, the calculations were made by using the HFB solver which utilizes HO single-particle basis and iteratively diagonalizes the HFB Hamiltonian based on the Skyrme forces.
Results: Here we can observe an increase in charge radius, rms radius and skin thickness with neutron number. The charge radii calculated are in good agreement with the experimental data and predictions of RCHB model. A linear dependence of skin thickness on neutron number is observed with the change in slope is noticed around N =126.
Conclusion: Using HFB theory, we have analyzed the charge radius and neutron skin thickness of Pt and Os isotopes. The drip line nuclei have larger charge radius in comparison to the stable nuclei. The redistribution of the nucleons due to addition of neutrons leads to the gradual increase in neutron skin. The sudden increase of skin thickness may be due to the extra stability and shell closure around the magic number.

A Hartree-Fock-Bogoliubov Study on the Pairing Correlations of the Isotopes of Cobalt

2022-01-28T17:11:24+00:00

Background: The phenomena of nucleon pairing could be outlined from the Bethe-Weizäcker semi-empirical formula, from which the nuclear properties, viz. the binding energy, stability, shape etc. could be clearly sketched. Though the pairing correlation seems to be a small correction to the binding energy term, it plays a determinative role in defining the structure of nuclear systems. The addition to the binding energy in turn affects the position of the isotope on the dripline and hence increases the stability.

Purpose: To study the effects of pairing on the ground state properties of the isotopes of Cobalt.

Methods: We use Hartree-Fock-Bogoliubov (HFB) theory for the study. The general wave functions for the HFB approach are determined from variational principle. The eigen functions for the Hamiltonian are connected with the particle operators through the Bogoliubov transformations. The Hartree-Fock energy is obtained through the minimization of the variational parameter and the HFB equation is solved by iterative diagonalization by restoring the particle number symmetry.

Results: The HFB analysis substantiates the effect of pairing correlation on binding energies, neutron and proton pairing energies, neutron and proton pairing gaps and one- and two-neutron separation energies of the Cobalt isotopes. The binding energies and one and two-neutron separation energies match with the experimental values and for pairing energies and pairing gaps, the regions where pairing is significant and the effects of shell closure at the vicinity of magic configuration of neutrons could be recognized.

Conclusion: The Hartree-Fock-Bogoliubov calculations of the effects of pairing could be used as an efficient tool to study the nuclear structure. It can be ascertained that pairing plays an important role in determining the ground state properties of atomic nuclei.

Evaluation of Natural Radioactivity Levels and Exhalation rate of 222Rn and 220Rn in the Soil Samples from the Kuthiran Hills, Kerala, India

2022-05-20T14:38:01+00:00

Background: Exposure to radon and its decay products is one of the important contributors of radiation doses to human population. Radon exhalation study is important for understanding the contribution of the soil towards the total radioactivity concentration found inside the dwellings.

Purpose: The aim of the present study is to investigate the radioactivity levels and radium and radon exhalation rates in soil samples collected from Kuthiran hills and nearby places in Thrissur district, Kerala state, India. On the basis of this data, radiological health hazard parameters are also evaluated.

Methods: About 18 soil samples were collected from the study location. The radium, thorium and potassium activity concentrations were analyzed by HPGe gamma ray spectrometer. The “can technique” using LR-115 type II plastic track detectors have been used for the measurement of radon exhalation rate in soil samples.

Results: The mean values of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were 64.60 Bqkg^-1, 109.03 Bqkg^-1and 972.67 Bqkg^-1respectively. The mean value of radon mass exhalation rate is 9.19 mBqkg^-1h^-1 and thoron surface exhalation rate is and 237.9 mBqm^-2s^-1. The radium equivalent activity concentration of all the soil samples was below the level of 370 Bqkg^-1, recommended for building materials, by OECD 1979 (Organization for Economic Cooperation and Development).

Conclusions: The results show that the study area is safe, as far as the health hazard effects of radium and radon exhalation rate are concerned. This data will be helpful in establishing new regulations and safety limits, related to the radiation dose and radon activity in Kuthiran hills.

Study of negative parity Bands in 136 Ce

2022-05-27T15:34:13+00:00

Background: The band structures of Ce(Z=58) nuclei with A~135 were studied extensively with the physics interest such as triaxiality and rotation like-sequence i.e. shears mechanism etc. The level structures of ¹³⁶Ce, with 58 protons and 78 neutrons, were predicted to arise from the interaction between valence proton particles above the Z = 50 major shell and four neutron holes in the N = 82 major shell. The γ-ray spectroscopy of ¹³⁶Ce was performed here for experimental investigations.
Purpose: Study the states of two negative parity bands B1 and B2 with band head I^π = 5^- and
I^π = 6^- with level energy 1979 keV and 2425 keV respectively.

Methods: The excited states of ¹³⁶Ce are populated via the ¹²⁴Sn(16O, 4n ) ¹³⁶Ce fusion evaporation reaction at E_beam = 90 MeV. The emitted γ-rays from the excited nuclei were detected using the Indian National Gamma Array (INGA) spectrometer at IUAC, New Delhi India.
Results: States of two negative parity bands, with band-head I^π = 5^- state at 1979 keV and I^π = 6^- state at 2425 keV have been studied in the present work. The placement of γ-ray transitions of negative parity band B1 has been changed from the earlier reported work and hence the level energy of this band revised and the systematics study of negative parity bands of isotones with N=78, the ¹³⁶Ce, ¹³⁴Ba, ¹³⁸Nd has been carried out.
Conclusions: The 806.3 keV γ-ray is found altered with the placement of 971 keV γ-ray transition in the earlier reported work and a 1015.2 keV γ-ray transition is placed in the place of the previously reported 1013 keV γ-ray transition above I^π = 11^- state in band B1. Previously, B1 and B2 bands were predicted as signature partner bands associated with two-quasiparticle, ν[h_11/2⊗s_1/2/d_3/2] configuration. The present work does not support these bands as signature partner bands. Present results are discussed in view of systematics.

3He-α Elastic Scattering Phase Shifts in Various Channels Using Phase Function Method with Morse Potential

2022-03-21T15:55:04+00:00

Background: Typically ³He-α reaction has been modeled using Gaussian and Hulthen potentials without incorporating the non-local spin-orbit interaction.
Purpose: To obtain the scattering phase shifts (SPS) for α-³He radiative capture reaction for partial waves with total angular momentum J = 1/2, 3/2, 5/2, 7/2 having negative parities and J = 1/2 with positive parity, using Morse potential as the model of interaction along with the associated spin-orbit term.
Methods: Phase function method is employed for determining phase shifts in an iterative fashion, by making changes to model parameters, to ensure minimisation of mean absolute percentage error (MAPE) w.r.t. the experimental SPS.
Results: SPS have been obtained for 1/2+, 1/2-, 3/2-, 5/2- and 7/2- with MAPE values of 3.2, 1.0, 0.8, 17.6 and 6.5 respectively. The corresponding interaction potentials and partial cross-sections have been plotted. The resonance frequencies for the 5/2- and 7/2- scattering states are closely matching with experimental ones.
Conclusions: The interaction potentials for different ℓ-channels of ⁷Be have been constructed by considering Morse potential and spin-orbit terms by considering experimental scattering phase shifts for ³He-alpha reaction.

Revisiting Macro-microscopic Mass Formula using Atomic Mass Evaluation-2020 Data

2022-06-03T15:00:27+00:00

Background: The macro-microscopic model has been succesful in nuclear mass predictions
and in obtaining various other properties of nuclear and nucleon matter. The present status
of generalised liquid drop model (GLDM) has been based on atomic mass evaluation (AME)-
2003 data.
Purpose: In this work, the co-efficients of most efficient mass formulae from Royer et.al.,
have been re-optimised for 2451 selected nuclei from AME-2020 data.
Methods: The root mean squared deviation (RMS) is minimized to optimize seven model
parameters that correspond to various terms in the nuclear binding energy that come in
powers of mass number A and square of relative neutron excess I = N −Z/A .
Results: The RMS between the theoretical and experimental binding energies has been
obtained as 0.65 using both the formulae.
Conclusions: The best possible formula for nuclear binding energy has been obtained using
AME-2020 data and it needs to be seen how this would effect the various nuclear properties
and predictions.

Low Energy S-Wave Proton-Deuteron Scattering Phase-Shifts using Morse Potential

2022-05-26T10:00:39+00:00

Background: Study of nucleon-nucleus interaction is important to understand the stability
of nuclei. At small lab energies ≈ 1-10 MeV, the three body 3He system can be considered as
a combination of proton and deuteron two body system. The two body system can be modeled by a local central potential along with Coulomb potential to obtain phase-shifts.
Purpose: Molecular Morse potential has been successfully able to calculate scattering phase
shifts of neutron-Deuteron (3He). The main objective of this paper is to test if Morse potential proves to be a good interaction potential to study proton-Deuteron (3He) scattering as well.
Methods: The phase function method is solved numerically using RK-5 method for determining the S-wave scattering phase shifts (SPS) for proton-deuteron (p-D) scattering as a
function of proton laboratory energy ranging from 1-10.4 MeV. The model paramters of Morse potential have been varied to obtain best mean absolute percentage error (MAPE) w.r.t. experimental data.
Results: The calculated SPS are found to have MAPE less than 3 percent w.r.t experimental phase shifts. Partial scattering cross-section has been determined using the obtained SPS.
Conclusions: Morse potential has been found to be successful in explaining interaction
between proton and deuteron.

Phase Shift Analysis for Neutron-Alpha Elastic Scattering Using Phase Function Method with Local Gaussian Potential

2022-05-13T18:04:44+00:00

Background: The nucleon-nucleus scattering has been studied using Gaussain potential with
spin-orbit term of Thomas type to fit the experimental scattering phase shifts (SPS). Recently,
Hulthen potential without spin-orbit term has been utilised for studying α–nucleon scattering with phase function method (PFM).
Purpose: The main objectives of this paper are:
1. To obtain the best possible interaction potentials that best describe the neutron-α elastic
SPS in various channels.
2. To compute the partial cross-sections for scattering p-states and the total cross-section for
the reaction.
Methods: The local interaction potential is modeled using Gaussian function. The non-local
spin orbit term is chosen to be proportional to derivative of local potential. The phase function method has been numerically solved using 5th order Runge-Kutta method to compute the SPS. The model parameters are varied in an iterative fashion to minimise the mean absolute percentage error (MAPE) w.r.t. the experimental SPS.
Results:
1. The SPS for S, P and D channels have been obtained with MAPE values less than 3%.
2. The partial cross-sections for p 1/2 and p 3/2 have been plotted and the respective resonance energies and FWHM have been found to be in reasonable agreement with values in literature.
3. The total cross-section for the reaction has been determined and found to be matching well with experimental findings.
Conclusions: Gaussian potential with associated spin-orbit term has been shown to be a
reasonably good choice for explaining the n-α scattering reaction.

Application of R-Matrix and Lagrange-Mesh Methods to Nuclear Transfer Reactions

2022-02-08T10:57:19+00:00

Background: Nuclear transfer reactions are a useful tool to study the structure of a nucleus. For reactions involving weekly bound nuclei, breakup effects can play significant role and theoretical calculations can be computational expensive in such cases.

Purpose: To utilize the Lagrange-mesh and R-matrix methods for nuclear transfer reactions.

Methods: We use the adiabatic distorted wave approximation (ADWA) method which can approximately treats the breakup effects in a simpler manner. In our approach, we apply the R-matrix method combining it with the Lagrange-mesh method, which is known to provide the fast and accurate computations.

Results: As a test case, we calculate the angular distribution of the cross sections for the ⁵⁴Fe(d,p)⁵⁵Fe reaction, where deuteron breakup effects play important role.

Conclusions: We show that these methods work well in the ADWA framework, and we look forward to applying these methods in coupled channel calculations.

Investigation for Suitable Target-Projectile combination for Fusion from the Isotopes of Ti and Nd using Intrinsic Fusion and Fission Barriers Analysis

2022-05-09T13:12:15+00:00

Background: A configuration is most suitable for the fusion if it corresponds to a minimum intrinsic fusion barrier and maximum fission barrier.
Purpose: To find a suitable target-projectile combination from the isotopes of Ti and Nd by analyzing the intrinsic fusion and fission barriers theoretically by including the deformations up to hexadecapole order.
Methods: The fragmentation theory has been used for the calculations.
Results: The intrinsic fusion barrier is minimum and fission barrier is maximum for the targetprojectile combination: ⁴³Ti+¹⁵⁰Nd in belly-belly configuration, and the inclusion of deformation of higher order leads to the decrease of fission barrier for the prolate shaped cases and compactness for most of the cases.
Conclusions: The most suitable target-projectile combination from the isotopes of Ti and Nd for the fusion is ⁴³Ti+¹⁵⁰Nd.

Theoretical Investigation of α-decay Chains of Fm-isotopes

2022-05-09T12:31:53+00:00

Background: The theoretical and experimental investigations of decay properties of heavy and superheavy nuclei are crucial to explore the nuclear structure and reaction dynamics.

Purpose: The aim of this study is to probe the α-decay properties of ²⁴³Fm and ²⁴⁵Fm isotopic chains using relativistic mean-field (RMF) approach within the framework of preformed cluster-decay model (PCM).

Methods: The RMF densities are folded with the relativistic R3Y NN potential to deduce the nuclear interaction potential between the α particle and daughter nucleus. The penetration probability is calculated within the WKB approximation.

Results: The α-decay half-lives of even-odd ²⁴³Fm and ²⁴⁵Fm isotopes and their daughter nuclei are obtained from the preformed cluster-decay model. These theoretically calculated half-lives are found to be in good agreement with the recent experimental measurements.

Conclusions: The novel result here is the applicability of the scaling factor within the PCM as a signature for shell/sub-shell closures in α-decay studies. As such, we have also demonstrated that N=137, 139 and Z=94 corresponding to ^231,233Pu could be shell/sub-shell closures. The least T_1/2 is found at ^243,245Fm which indicate their individual stability and α-decay as their most probable decay mode.

Phase Shift Analysis for Alpha-alpha Elastic Scattering using Phase Function Method for Gaussian Local Potential

2021-04-15T16:17:05+00:00

The phase shifts for α- α scattering have been modeled using a two parameter Gaussian local potential. The time independent Schrodinger equation (TISE) has been solved iteratively using Monte-Carlo approach till the S and D bound states of the numerical solution match with the experimental binding energy data in a variational sense. The obtained potential with best fit parameters is taken as input for determining the phase-shifts for the S channel using the non-linear first order differential equation of the phase function method (PFM). It is numerically solved using 5^th order Runge-Kutta (RK-5) technique. To determine the phase shifts for the ℓ=2 and 4 scattering state i.e. D and G-channel, the inversion potential parameters have been determined using variational Monte-Carlo (VMC) approach to minimize the realtive mean square error w.r.t. the experimental data.

Heavy Particle Accompanied Fission of 284Og - A Statistical Model Study

2021-06-02T16:14:05+00:00

The structural characteristics of SHN can be investigated through the decay of SHN. In the present work ternary fission of SHN ²⁸⁴Og for two proton magic fixed third fragment ⁴⁸Ca and ⁶⁸Ni is studied at three different excitation energies 20, 35 and 50 MeV. Interestingly, ¹⁶⁹Yb + ⁶⁷Ni + ⁴⁸Ca is having larger yield values and hence it is the most favoured way of fragmentation at intermediate excitation energy 35 MeV. It is observed that, asymmetric fission is favoured over symmetric fission at all the excitation for the third fragment ⁴⁸Ca. Asymmetric fission is the most favoured with the fragment combination ¹⁴⁸Sm + ⁶⁸Ni + ⁶⁸Ni for fixed A3 = ⁶⁸Ni at all the excitations. Unlike the Ca third fragment, near symmetric fission is also favoured with ¹¹³Ag + ¹⁰³Tc + ⁶⁸Ni for A3 = ⁶⁸Ni at all the three excitation energies.

Triton Scattering Phase-Shifts for S-wave using Morse Potential

2021-05-27T12:36:44+00:00

In this paper, the phase-shifts for neutron-dueteron (n-d) scattering have been determined using the molecular Morse potential as theoretical model of interaction. The Triton (n-d) ²S_1/2 ground state initially has been chosen as -7.61 MeV to determine the model parameters using variational Monte-Carlo technique in combination with matrix methods numerical approach to solving the time independent Schrodinger equation (TISE). The obtained potential is incorporated into the phase function equation, which is solved using Runge-Kutta (RK) 4,5 order technique, to calculate the phaseshifts at various lab energies below 15 MeV, for which experimental data is available. The results have been compared with those obtained using another molecular potential named Manning-Rosen (MR) and have been observed to fare better. Finally, the Triton ground state has been chosen as its binding energy (BE), given by -8.481795 MeV, as determined from experimental atomic mass evaluation data and the calculations are repeated. It has been found that these phase-shifts from BE data are slightly better matched with experimental ones as compared to those obtained using -7.61 MeV ground state for Triton (n-d two-body system) modeled using Morse potential.

Comparative Analysis of Woods-Saxon and Yukawa Model Nuclear Potentials

2021-05-27T12:06:23+00:00

In this paper, we model the nuclear potential using Woods-Saxon and Yukawa interaction as the mean field in which each nucleon experiences a central force due to rest of the nucleons. The single particle energy states are obtained by solving the time independent Schrodinger wave equation using matrix diagonalization method with infinite spherical well wave-functions as the basis. The best fit model parameters are obtained by using variational Monte-Carlo algorithm wherein the relative mean-squared error, christened as chi-squared value, is minimized. The universal parameters obtained using Woods-Saxon potential are found to be matched with literature reported data resulting a chi-square value of 0.066 for neutron states and 0.069 for proton states whereas the chi-square value comes out to be 1.98 and 1.57 for neutron and proton states respectively by considering Yukawa potential. To further assess the performance of both the interaction potentials, the model parameters have been optimized for three different groups, light nuclei up to ¹⁶O - ⁵⁶Ni, heavy nuclei ¹⁰⁰Sn - ²⁰⁸Pb and all nuclei ¹⁶O - ²⁰⁸Pb. It is observed that Yukawa model performed reasonably well for light nuclei but did not give satisfactory results for the other two groups while Woods-Saxon potential gives satisfactory results for all magic nuclei across the periodic table.

Impact of Nuclear Deformation on Neutron Dripline Prediction: A Study of Mg Isotopes

2021-06-02T10:56:59+00:00

We have employed the relativistic Hartree-Bogoliubov (RHB) model with density-dependent meson-exchange interaction and separable pairing to investigate neutron dripline mechanisms for heavy Mg isotopes. In the present study, ⁴⁰Mg is predicted to be dripline nuclei. The calculations are carried out by taking axial deformation into account. An investigation of shape transition is also done for even-even ^32-42Mg isotopes. Our prediction for neutron dripline for ⁴⁰Mg is consistent with some recent studies.

Study of the Production Cross-Sections of the Neutron-rich 184Ta and 186Ta

2021-04-15T17:07:58+00:00

Synthesizing nuclei through reactions that produce a reasonable yield is important for the experimental study of neutron-rich nuclei. In this study, the cross-section values of ¹⁸⁴Ta and ¹⁸⁶Ta nuclei in various experiments were reviewed and analysed. The experimental data of (n, p), (p, x) and (n, α) reactions were compared to identify the best reaction to produce these nuclei for further study. Our study shows that (n, p) reactions on natural Tungsten targets are the most feasible reactions with a good yield of the neutron-rich Tantalum isotopes. New reactions have been proposed for the effective synthesis of ¹⁸⁴Ta and ¹⁸⁶Ta using tritium beams on Hafnium targets. The cross-section values of the proposed reactions were calculated by PACE4 software simulations.

Effect of Oriented Nuclei on the Competing Modes of α and One-Proton Radioactivities in the Vicinity of Z = 82 Shell Closure

2021-06-02T11:43:40+00:00

The purpose of the present work is to investigate the alpha (α) emission as competing mode of one proton emission using the preformed cluster decay model (PCM). PCM is based on the quantummechanical tunneling mechanism of penetration of the preformed fragments through a potential barrier, calculated within WKB approximation. To explore the competing aspects of α and one proton radioactivity, we have chosen emitters present immediately above and below the Z = 82 shell closure i.e. ¹⁷⁷Tl and ¹⁸⁵Bi by taking into account the effects of deformations (β₂) and orientations of outgoing nuclei. The minimized values of fragmentation potential and maximized values of preformation probability (P₀) for proton and alpha fragment demonstrated the crucial role played by even Z - even N daughter and shell closure effect of Z = 82 daughter, in ¹⁷⁷Tl and ¹⁸⁵Bi, respectively. The higher values of P₀ of the one proton further reveal significance of nuclear structure in the proton radioactivity. From the comparison of proton and α decay, we see that the former is heavily dominating with larger values of P₀ in comparison to the later. Theoretically calculated half-lives of one proton and α emission for spherical and deformed considerations have also been compared with available experimental data.

Recalculated Viola-Seaborg Coefficients for Partial Alpha Half-lives Based on AME2016

2021-04-15T17:22:32+00:00

In this paper, the systematics for obtaining the Viola-Seaborg formula (VSF) for logarithmic partial alpha half-lives (T^α_1/2) have been undertaken based on the NUBASE2016 evaluation. The constants Az and Bz in Geiger-Nuttal law for determination of T^α_1/2 , are obtained using gs-gs transitions data, of even-even nuclei for two sets of nuclei with Z = 84 - 102 and Z = 86 - 98 with N > 126. The Viola-Seaborg co-efficients are determined for both the sets. The obtained parameters for both sets are tested on even-even nuclei for Z ranging from 104 - 118 and it is observed that first set parameters fare better. This formula for estimating α-decay half-lives of heavy nuclei can be extrapolated to predict those of super-heavy nuclei. The logarithmic half-lives T^α_1/2 obtained for isotopes of Z = 121 and 122 using current modified VSF (AME2016) are compared with those obtained from theoretical considerations using Coulomb and proximity potential model (CPPM) and observed to be much larger. They are also much larger than those obtained from the previous coefficients based on AME2003 data.

Enhanced Fission Probability of Even-Z Fragments in the Decay of Hot and Rotating 210Rn* Compound System

2021-04-15T17:32:43+00:00

Mass and charge distribution of the cross-section for the fission fragments obtained in the decay of hot and rotating compound system formed in the reaction ⁴⁸Ca +¹⁶²Dy →²¹⁰Rn^* at an incident energy 139.6 MeV has been calculated using the dynamical cluster-decay model. Isotopic composition for each element belonging to the symmetric mass region has been obtained. The shell closure at N=50 for light and at Z=50 for heavy mass binary fragments gives a deep minima in the fragmentation potential at touching configuration and governs the fission partition of the compound system. The fission fragments of the symmetric mass region have their dominating presence along with strong odd-even staggering i.e., even-Z fission fragments are more probable than the odd ones, similar to the observed trends of the yield.

Comparative Analysis of 13,14C Induced Reactions on 232Th Target

2021-04-15T17:58:34+00:00

We have investigated the pairing and magicity effect in context of a comparative study of ^13,14C induced reactions on ²³²Th target at energies in the vicinity of Coulomb barrier. The fission distribution and related properties are explored in terms of the summed-up preformation probabilities. The barrierpenetrability is found to be higher for fragments emitted from²⁴⁶Cm* formed in ¹⁴C+²³²Th reaction than those emitted in the fission of²⁴⁵Cm*, leading to higher magnitude of cross-section for earlier case. The DCM calculated fusion-fission cross-sections using ΔR=0 fm are normalised to compare with the available experimental data. The calculations are done for spherical shape of fragments and it will be of further interest to explore the fission mass distribution after the inclusion of deformations.

T-dependent RMF Model Applied to Ternary Fission Studies

2021-06-02T16:11:49+00:00

Ternary decay is comparatively a rare phenomenon. The yield distribution for the thermal neutroninduced fission of ²³⁶U was investigated within the Temperature-dependent Relativistic Mean Field (TRMF) approach and statistical theory. Binding energy obtained from TRMF for the ground state and at a specific temperature is used to evaluate the fragment excitation energy, which is needed to calculate the nuclear level density. Using the ternary convolution, the yield for α-accompanied fission of ²³⁶U^* is calculated. Initial results are presented which shows a maximum yield for the fragment pair Tc + Ag +α. Further, the ternary pre-existence probability for the spontaneous fission of ²³⁶U was studied considering fixed third fragments of α,¹⁰Be and ¹⁴C using the area of the overlapping region. No significant change in the yield distribution was observed when fragment deformations are considered. However, the heavy group for the probable pair remains as ¹³²Sn with a change in mass number of the lighter fragment.

Decay Analysis of 197Tl* Compound Nucleus Formed in 16O + 181Ta Reaction at above Barrier Energy Ec.m.~100 MeV

2021-06-02T16:16:21+00:00

The decay dynamics of ¹⁹⁷Tl^* compound nucleus has been studied within the framework of the dynamical cluster-decay model (DCM) at above barrier energy Ec.m. ≈ 100 MeV using quadrupole deformed configuration of decay fragments. The influence of various nuclear radius parameters on the decay path and mass distributions has been investigated by analysing the fragmentation potential and preformation probability. It is observed that ¹⁹⁷Tl^* nucleus exhibits the triple-humped mass distribution, independent of nuclear radius choice. The most preferred fission fragments of both fission modes (symmetric and asymmetric) are identified, which lie in the neighborhood of spherical and deformed magic shell closures. Moreover, the modification in the barrier characteristics, such as interaction barrier and interaction radius, is observed with the variation in the radius parameter of decaying fragments and influences the penetrability and fission cross-sections. Finally, the fission cross-sections are calculated for considered choices of nuclear radii, and the results are compared with the available experimental data.

Binary and Ternary Fragmentation Analysis of 252Cf Nucleus using Different Nuclear Radii

2021-06-02T14:36:54+00:00

Pioneering study reveals that a radioactive nucleus may split into two or three fragments and the phenomena are known as binary fission and ternary fission respectively. In order to understand the nuclear stability and related structure aspects, it is of huge interest to explore the fragmentation behavior of a radioactive nucleus in binary and ternary decay modes. In view of this, Binary and ternary fission analysis of ²⁵²Cf nucleus is carried out using quantum mechanical fragmentation theory (QMFT). The nuclear potential and Coulomb potential are estimated using different versions of radius vector. The fragmentation structure is found to be independent to the choice of fragment radius for binary as well
as ternary decay paths. The deformation effect is included up to quadrupole (β₂) with optimum cold orientations and their influence is explored within binary splitting mode. Moreover, the most probable fission channels explore the role of magic shell effects in binary and ternary fission modes.

Role of Polar vs Non-polar Configurations in the Decay of 268Sg* Compound Nucleus Within the Skyrme Energy Density Formalism

2021-04-19T13:20:12+00:00

The effect of polar and non-polar configurations is investigated in the decay of ²⁶⁸Sg^* compound nucleus formed via spherical projectile (³⁰Si) and prolate deformed target (²³⁸U) using the dynamical cluster decay model. The SSK and GSkI skyrme forces are used to investigate the impact of polar and nonpolar (equatorial) configurations on the preformation probability P0 and consequently on the fission cross-sections of ²⁶⁸Sg^* nucleus. For non-polar configuration some secondary peaks corresponding to magic shells Z=28 and N=50 are observed, whose magnitude is significantly suppressed for the polar counterpart. The effect of polar and non-polar configurations is further analyzed in reference to barrier lowering parameter ΔV_B. The calculated fission cross-section find adequate agreement with experimental data for chosen set of skyrme forces.

Texture One Zero Model Based on A4 Flavor Symmetry and its Implications to Neutrinoless Double Beta Decay

2021-06-02T15:04:16+00:00

Neutrinos are perhaps the most elusive particles in our Universe. Neutrino physics could be counted as a benchmark for various new theories in elementary particle physics and also for the better understanding of the evolution of the Universe. To complete the neutrino picture, the missing information whether it is about their mass or their nature that the neutrinos are Majorana particles could be provided by the observation of a process called neutrinoless double beta (0νββ) decay. Neutrinoless double beta decay is a hypothesised nuclear process in which two neutrons simultaneously decay into protons with no neutrino emission. In this paper we proposed a neutrino mass model based on A4 symmetry group and studied its implications to 0νββ decay. We obtained a lower limit on |M_ee| for inverted hierarchy and which can be probed in 0νββ experiments like SuperNEMO and KamLAND-Zen.

Appearance / Disappearance of Magic Number in Light Nuclei

2021-06-02T16:18:55+00:00

The shell structure of a nucleus is important to study their observed characteristic features. The classic magic numbers are successful in explaining the nuclear properties for nuclei lying near the stability line. The advent of radioactive ion beam facilities has permitted to examine nuclei in their extreme proton to neutron ratio. The light exotic nuclei were found to exhibit unique shell closure behaviour which is different from the medium mass nuclei near the stability line. The two nucleon separation energy difference systematics was used as a probe to study the magic character of light nuclei. New proton and neutron magic numbers were predicted among the available even Z isotopes and even N isotones. For certain systems, the classic magic numbers were found to be non-magic, while for some systems the magic property is retained even at the drip lines. The shell closure behaviour predicted is found to depend on the version of the mass table.

Effect of the Width of Gaussian Wave Packets on the Stability of the Nuclei

2021-04-15T15:59:39+00:00

The role of the range of interaction on the stability of the nuclei propagating with and without momentum dependent interactions is analyzed within the framework of Quantum Molecular Dynamics (QMD) model. A detailed study is carried out by taking different equations of state (i.e., static soft and hard and the momentum dependent soft and hard) for the selected nuclei from ¹²C to ¹⁹⁷Au. Comparison is done by using the standard and the double width of the Gaussian wave packets. We find that the effect of the double width of the Gaussian wave packets on the stability of the initial stage nuclei cannot be neglected. The nuclei having double width do not emit free nucleons for a long period of time. Also, the ground state properties of all the nuclei are described well. In the low mass region, the obtained nuclei are less bound but stable. Heavy mass nuclei have proper binding energy and are stable.

Nonfactorizable Contribution to B-Meson Decays to s-Wave Mesons

2021-06-02T15:27:48+00:00

Two-body weak decays of bottom mesons into two pseudoscalar and pseudoscalar and vector mesons, are examined under isospin analysis to study nonfactorizable contribution.

Neutron-Proton Scattering Phase Shifts in S-Channel using Phase Function Method for Various Two Term Potentials

2021-04-20T22:28:03+00:00

The scattering phase shifts for n-p scattering have been modeled using various two term exponential type potentials such as Malfliet-Tjon, Manning-Rosen and Morse to study the phase shifts in the S-channels. As a first step, the model arameters for each of the potentials are determined by obtaining binding energy of the deuteron using matrix methods vis-a-vis Variational Monte-Carlo (VMC) technique to minimize the percentage error w.r.t. the experimental value. Then, the first order ODE as given by phase function method (PFM), is numerically solved using 5th order Runge-Kutta (RK-5) technique, by substituting the obtained potentials for calculating phase shifts for the bound ³S₁ channel. Finally, the potential parameters are varied in least squares sense using VMC technique to obtain the scattering phase-shifts for each of the potentials in the ¹S₀ channel. The numerically obtained values are seen to be matching with those obtained using other analytical techniques and a comparative analysis with the experimental values up to 300 MeV is presented.

Cluster Radioactivity

2020-12-15T15:57:24+00:00

Cluster radioactivity (spontaneous emission of heavy particles from nuclei) is presented from a theoretical point of view in good agreement with experimental results. After a brief historical account, we give details about the analytical super asymmetric fission (ASAF) model extensively used for predicting the half-lives of heavy and superheavy (Z ≥ 104) elements. For the already measured 26 cluster decays (from ¹⁴C to ^32,34Si of parent nuclides with Z = 87-96) it is clear that cluster radioactivity is a rare phenomenon in the best case about 9 orders of magnitude weaker than the competing alpha decay. Then we show the theoretical possibility of a strong cluster decay compared to alpha decay for some superheavy nuclei with Z ≥ 122, e.g. ³⁰⁶122; ^310-314122; ^306-324124, and ^311-323124.

Surface modification of polyethylene terephthalate (PET) by corona discharge plasma

2021-02-13T11:03:20+00:00

Surface modification of polyethylene terephthalate (PET) was studied by corona discharge plasma at different exposure times using air as working gas. The modification of the surface properties are characterized, those are morphology and wettability. Corona plasma treatment was found to modify the PET surface in both morphology and wettability. The corona discharge at atmospheric pressure is a heterogeneous with multiple current pulses, which generates an asymmetric pattern of erosion on the PET surface. The corona discharge treatment erodes the surface and therefore modifies the surface morphology. The roughness of the PET surface increases in the impact point of the corona discharge on the PET surface. An increase in the wettability of PET was also observed after corona discharge treatment at atmospheric pressure.

Gamma Irradiation of Aqueos Solution of L-Aspartic Acid, L-Aspartic Acid in Solid State, and L-Aspartic Acid Adsorbed into Na-Montmorillonite: Its Relevance in Chemistry Prebiotic

2021-02-13T11:01:06+00:00

Aspartic acid is an amino acid present in the modern proteins, however, is considered a primitive amino acid hence its importance in prebiotic chemistry experiments studies. In some works of prebiotic chemistry have been studied the synthesis and the stability of organic matter under high energy sources, and the role of clays has been highlighted due to clays that can affect the reaction mechanisms in the radiolytic processes. The present work is focused on the study of the role of Namontmorillonite in the gamma radiolysis processes of L-aspartic acid. Gamma radiolysis processes were carried out in three different systems a) L-aspartic acid in aqueous solution; b) L-aspartic acid in solid-state; and c) L-aspartic acid adsorbed into Na-montmorillonite. L-aspartic acid was analyzed by high-performance liquid chromatography−electrospray ionization−mass spectrometry (HPLCESI-MS). The results showed that the decomposition of L-aspartic acid considerably decreased in the presence of clay thus highlighting the protector role of clays and favors the stability of organic matter even under the possible high energy conditions of primitive environments. The principal product of
gamma radiolysis of L-aspartic acid was succinic acid produced by deamination reaction. On the other hand, when aspartic acid was irradiated in solid-state the main product was the L-aspartic acid dimer. Both radiolysis products are important for chemical evolution processes for L-aspartic acid in primitive environments.

Effect of Magnetic Fields on Charged B Meson Decays

2021-01-04T16:04:30+00:00

The effect of magnetic fields on the leptonic decay of charged B meson B⁻ → l^-v^- is investigated. The decay rate of the process is calculated both in the absence and presence of magnetic field. The non-perturbative parameters f_B± (B), f'_B± and M_B±(B) are also estimated.

Receptor Binding Domain (RBD) Structural Susceptibility in the SARS-CoV-2 Virus Spike Protein Exposed to a Pulsed Electric Field

2021-02-13T11:08:48+00:00

SARS-CoV-2 is responsible for causing the Coronavirus disease 2019 (COVID-19) pandemic, which has so far infected more than thirty million people and caused almost a million deaths. For this reason, it has been a priority to stop the transmission of the outbreak through preventive measures, such as surface disinfection, and to establish bases for the design of an effective disinfection technique without chemical components. In this study, we performed in silico analysis to identify the conformational alterations of the SARS-CoV-2 Spike Receptor Binding Domain (RBD) caused by the effect of a pulsed electric field at two different intensities. We found that both stimuli, especially the one with the highest angular frequency and amplitude, modified the electrical charge distribution in the RBD surface and the number of hydrogen bonds. Moreover, the secondary structure was significantly affected, with a decrease of the structured regions, particularly the regions with residues involved in recognizing and interacting with the receptor ACE2. Since many regions suffered conformational changes, we calculated RMSF and ΔRMSF to identify the regions and residues with larger fluctuations and higher flexibility. We found that regions conformed by 353-372, 453-464, and 470-490 amino acid residues fluctuate the most, where the first is considered a therapeutic target, and the last has already
been characterized for its flexibility. Our results indicate that a pulsed electric field can cause loss of stability in the Spike-RBD, and we were able to identify the vulnerable sites to be used as a starting point for the development of viral inhibition or inactivation mechanisms.

Study through Geant4, for Time Resolution characterization of different detectors arrays coupled with two SiPMs, as a function of: the scintillator plastic material, its volumetric dimensions and the location of the radiation emission source

2021-02-13T11:12:20+00:00

The high time resolution detectors are relevant in those experiments or simulations were the particles to detect, have a very short time of flight (TOF), and due this it´s required that the detections times are ranged between ns. & ps.
Using Geant4 software, it was made thirty simulations of coupled detectors to plastic scintillators with two silicon photomultipliers (SiPMs) located on the scintillator’s central sides. To characterize the time resolution, it was required to quantify the optical photons that reach the Score in a certain time, which are generated by muons on the surface of the plastic scintillator. Different configurations of muon beams were simulated at energy of 1 GeV, to interact with the configuration of the scintillator material of its corresponding arrangement. The simulations were made varying three parameters: the scintillator material “BC404 & BC422”, its size, and the location of the radiation source. Fifteen simulations correspond to BC404 material & fifteen simulations to BC422 material respectively. The first five simulations consisted in varying the scintillator’s volumetric size and collocate the muons beam guided randomly distributed over it, the next five simulations differentiate from setting up a directly centered beam, and the last five simulations for guide the beam on the left lower corner of each scintillator.
The best time resolution achieved was σ= 8.67 +/− 0.26 ps., reported by the detector with BC422 scintillator material which has a volume of 20x20x3 mm³.

Wear Behavior of a Ni/Co Bilayer Coating by Physical Vapor Deposition on AISI 1045 Steel

2021-02-13T11:11:50+00:00

Coatings by physical vapor deposition (PVD) have become highly relevant due to their wide range of applications and the rapid rate of coating formation. In this work, AISI steel 1045 was coated with two layers, Ni and Co using the PVD technique. Each coating was deposited with a thickness of 1 μm. After applying the coatings, a post-treatment was applied in an AC plasma reactor using a boron nitride blank in an Ar atmosphere at a pressure of 3 Torr, 0.3 A, and 460 V at 4, 8, and 12h. The post-treatment was characterized by optical emission spectroscopy (OES) in a range of 200-1100 nm. The main species observed by OES were Ar⁺, N₂, N₂⁺, and B⁺. The coatings on 1045 steel and posttreatment were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Also, were subjected to tribological tests to analyze wear resistance, using the Pin-on-Disk technique. The coatings on steel 1045 present remarkably better wear properties than the uncoated 1045 steel, being the sample post-treated at 4h that showed a lower wear rate.

Radon Dose Determination and Radiological Risk in Some Mexican Caves with CR-39 Detectors

2021-02-13T11:08:12+00:00

Radon (²²²Rn) is a radioactive gas, from the ²³⁸U decay chain, that contributes in large part of the natural radiation dose to which humans are exposed. Radon is the second cause of lung cancer after tobacco. The US-EPA considers a concentration of 148 Bq/m³ for homes and 400 Bq/m³ for workplaces as the reference level. Caves are closed spaces where ²²²Rn, which emanates from the surrounding minerals and rocks, can accumulate and reaches large concentrations that can represent a health risk for the guides, speleologists and visitors who spend time in these spaces. This work uses the previously recorded radon concentrations in 8 caves in Mexico and calculates the average dose range and the average annual dose for each of them with the “Wise” public domain program (http://www.wise-uranium.org/rdcrn.html) to determine the level of radiological risk with 2,000 1,000 and 500 working hours per year. Karmidas cave had the highest average ²²²Rn concentration with 27,633.3 Bq/m³ and for 2,000 working hours per year an average annual dose rate of 347.1 mSv/y. Los Riscos cave had the lowest average concentration with 384.7 Bq/m³ and for 2,000 working hours per year an average annual dose rate of 4.832 mSv/y. These results show that all the caves studied present values,
with 2,000 working hours per year, that exceed 3 mSv/y for workplaces and must be considered by the people who work in these places. A casual tourist visiting the caves does not present any radiological risk, while guides and speleologists should consider it.

Changes of the Neutron Flux of the Nuclear Reactor Triga Mark III Since the Conversion from High to Low 235U Enrichment

2021-02-13T11:05:42+00:00

The neutron flux of the Triga Mark III research reactor was studied using nuclear track detectors. The facility of the National Institute for Nuclear Research (ININ), operates with a new core load of 85 LEU 30/20 (Low Enriched Uranium) fuel elements. The reactor provides a neutron flux around 2 × 10¹² n cm^-2s^-1 at the irradiation channel. In this channel, CR-39 (allyl diglycol policarbonate) Landauer® detectors were exposed to neutrons; the detectors were covered with a 3 mm acrylic sheet for (n, p) reaction. Results show a linear response between the reactor power in the range 0.1 - 7 kW, and the average nuclear track density with data reproducibility and relatively low uncertainty (±5%). The method is a simple technique, fast and reliable procedure to monitor the research reactor operating power levels.

Simulation of Dose Estimations from Solar Protons: A PMMA-Bi2O3 Shielding Model for Space Exploration

2021-02-13T11:06:37+00:00

Adverse effects of long-term exposure to galactic cosmic radiation (GCR) pose a non negligible obstacle for future space exploration programs; the high-LET-particle-rich environment has an adverse effect on human health. Concomitant to GCR we have as well solar particle radiation. Long term space exploration will rely on adequate and highly efficient shielding materials that will reduce exposure of both biosystems and electronic equipment to GCR and solar particles. The shield must attenuate efficiently heavy GCR ions, by breaking them up into less-damaging fragments and secondary radiation: biologically damaging energetic neutrons and highly charged and energetic HZE- particles. An approach to this problem is the development of shielding compounds. Shielding materials should address the conditions of different aspects of a given mission, e.g. time duration and travel path. The Monte Carlo method (GEANT4) is here employed to estimate the effects of a shielding material based on the recently developed Bi2O3-based compound (Cao et al., 2020). In the present study GEANT4 code is used to make estimations of attenuation of solar protons. The objective is to provide some insight about the effect of the new composite shield that has an intrinsic capability for dose reduction.

Structural Shielding Design of CT Facility using Monte Carlo Simulation

2021-02-13T11:05:00+00:00

Radiation application in medicine offers extraordinary benefits. But radiation is like a double-edged sword, it has both benefits and associated risks on the community in contact. To justify the safety of workers and members of the public, regulated use of radiation is assessed by the radiation protection protocols. The aim of this study is to design a Computed Tomography (CT) facility with a simplified model of CT scanner, whose shielding follows the guidelines of National Council on Radiation Protection and Measurements (NCRP) Report No. 147. To design the study model, Monte Carlo (MC) radiation transport code in MCNPX 2.6.0 was used for the simulation. Furthermore, MCNPX was used to measure the photon flux in a vicinity or the detector cell. To validate the functioning of the X-ray tube, the experimental results were compared with the X-ray Transition Energies Database of National Institute of Standards and Technology, U.S. Department of Commerce. The results obtained were within 0.60% of relative error. To confirm the functioning of shielding design, radiation protection quantity, air kerma was measured at several points outside, and inside of the CT room and they were under the radiation dose recommended by NCRP, which demonstrates that the shielding design was
successful in blocking the radiation. The study can be used for an easy evaluation of any CT room within the framework of the model of the study.

Determination of 234U and 238U Activities in Soil by Liquid Scintillation and High-Resolution Alpha Spectrometry

2021-02-13T11:02:13+00:00

Uranium is a radioactive element with a special presence in the rocks, waters, sediments, soils, and plants at the state of Chihuahua. The activity ratio of 238U/234U is used to explain the uranium transport by surface water and its deposition in arid environments. In this work, the activity concentration of natural U isotopes is determined by PERALS liquid scintillation and high-resolution alpha spectrometry (AS, Canberra camera 7401VR) in the Environmental Radiological Surveillance Laboratory (LVRA) at CIMAV, Chihuahua. Uranium is extracted from soils through the scintillating liquid extractor URAEX for PERALS, with chemical recovery (CR) of 80 - 85 %, and through the ion exchange resin UTEVA + electrode position by the Hallstadius method, with CR of 85 - 90 %, for AS. The procedures of 234U and 238U activity concentration (AC) determination in soils were validated by their application to the certified reference material IAEA-375. The resulting values were in the reference range of the certified or informative values. Both procedures were applied to 6 representative soil samples, with AC of the same order of magnitude or greater, and similar CR and compatible results. Both procedures are satisfactory for the purposes of LVRA research and in general.

Charged Lepton Masses as a Possible CPV Source

2021-02-13T11:07:28+00:00

We realize a model-independent study of the so-called Tri-Bi-Maximal pattern of leptonic flavor mixing. Different charged lepton mass matrix textures are studied. In particular, we are interested in those textures with a minimum number of parameters and that are able to reproduce the current experimental data on neutrino oscillation. The textures studied here form an equivalent class with two texture zeros. We obtain a Tri-Bi-Maximal pattern deviation in terms of the charged leptons masses, leading to a reactor angle and three CP violation phases non-zero. These lastest are one CP violation phase Dirac-like and two phases Majorana-like. Also, we can test the phenomenological implications of the numerical values obtained for the mixing angles and CP violation phases, on the neutrinoless double beta decay, and in the present and upcoming experiments on long-base neutrino oscillation, such as T2K, NOvA, and DUNE.