Pb Reaction Research Articles

H 2 and CO oxidation process at the three-phase boundary of Cu-ceria cermet anode for solid oxide fuel cell

Abstract Cu-ceria cermets have been widely investigated as the anode materials for solid oxide fuel cells (SOFCs) that operated with hydrocarbon fuels. However, the anode reaction processes are not clear yet, especially those at the ceria-Cu-gas three phase boundary (3 PB). This work investigates samaria-doped ceria (SDC)-Cu-gas 3 PB reaction kinetics for the oxidation of H2 and CO, the products from hydrocarbons via external and internal reforming. Electrochemical conductivity relaxation measurement demonstrates that Cu is a synergistic catalyst that can significantly increase the reaction rate. The reaction at 3 PB contributes 81.3/66.8% of H2/CO oxidation when 5.4% SDC surface is covered with Cu particles. Combining with AC impedance analysis, elementary steps are proposed for the reaction at 3 PB. Water vapor combining to oxygen vacancy and carbon monoxide transforming to carbonate are the rate-determining steps for the oxidation of H2 and CO, respectively. Cu-SDC has shown much higher catalytic activity, i.e. about fivefold reaction rate, for the oxidation of CO than H2. In addition, Cu-SDC electrodes exhibit lower interfacial polarization resistance and lower activation energy for the electrochemical oxidation of CO than H2. Consequently, CO is easier to be oxidized than H2 when the Cu-ceria anode is fueled with syngas, the reforming product from hydrocarbons.

Hadron calorimeter (PSD) with new photo-detectors (MPPC) in NA61 experiment at CERN

The Projectile Spectator Detector (PSD) is a segmented hadron calorimeter used in NA61 experiment (CERN) to determine a collision centrality as well as an event plane orientation in nucleus-nucleus collisions. The main goal of the experiment includes studying the onset of de-confinement and searching for the critical point of strongly interacting matter. It is of crucial importance to have a precise characterization of the event class with the PSD for the analysis of event-by-event observables. The PSD has been already used for centrality selection on trigger level in measurements of Be+Be and Ar+Sc reactions at beam energies 13 − 158 AGeV and Pb+Pb reaction at beam energy 30 AGeV. In 2016, the central modules of PSD have been equipped with new Hamamatsu MPPC silicon photo-detectors in order to extend dynamic range for studying Pb+Pb reaction at the full energy range 13 − 158 AGeV. Results of the PSD response on proton and lead beams are presented.

Production of neutron-rich nuclides in the vicinity ofN= 126 shell closure in multinucleon transfer reactions

Multinucleon transfer in low-energy nucleus-nucleus collisions is widely discussed as a method of production of yet-unknown neutron-rich nuclei hardly accessible (or inaccessible) by other methods. Modeling of complicated dynamics of nuclear reactions induced by heavy ions is done within a multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations. The model gives a continuous description of the system evolution starting from the well-separated target and projectile in the entrance channel of the reaction up to the formation of final reaction products. In this paper, rather recent sets of experimental data for the 136 Xe+198 Pt,208 Pb reactions are analyzed together with the production cross sections for neutron-rich nuclei in the vicinity of the N = 126 magic shell.

Tomography of the QGP by heavy quarks

The dynamics of partons and hadrons in ultra-relativistic nucleus-nucleus collisions is analyzed within the Parton-Hadron-String Dynamics (PHSD) transport approach, which is based on a dynamical quasiparticle model for the partonic phase (DQPM) including a dynamical hadronization scheme while reproducing lattice QCD results in thermodynamic equilibrium for the equation-of-state as well as transport coefficients like shear and bulk viscosities, the electric conductivity or the charm diffusion coefficient of the hot QCD medium. In this contribution we report on the recent results on the charm dynamics and elliptic flow in Au+Au collisions at RHIC and Pb+Pb reactions at the LHC as well as on the single electron spectra from D— and B—meson semileptonic decays in Au+Au collisions at √sNN =200 and 62.4 GeV. We find that the PHSD approach well describes the Raa and elliptic flow v2 of open charm mesons in Au+Au collisions at √sNN = 200 GeV (from STAR) and 2.76 TeV (from ALICE) as well as the elliptic flow of single electrons at √sNN = 200 and 62.4 GeV (from PHENIX), however, the large Raa at √sNN = 62.4 GeV is not reproduced at all which might indicate a new ’PHENIX puzzle’.

Fusion suppression/fusion enhancement around the Coulomb barrier

This work explored the fusion dynamics of 36Li+2759Co, 49Be+50124Sn, 49Be+82208Pb, 2040Ca+50124Sn and 612C+82208Pb reactions by using energy dependent Woods–Saxon potential model (EDWSP model) and coupled channel model. The roles of projectile breakup channel on fusion process are directly reflected from fusion mechanism of 36Li+2759Co, 49Be+50124Sn and 49Be+82208Pb reactions. Whereas, the impacts of collective excitations and/or nucleon transfer channels on fusion process are evident from analysis of 2040Ca+50124Sn and 612C+82208Pb reactions. The total fusion data (sum of complete and incomplete fusion data) of 36Li+2759Co reaction is reasonably recovered by the EDWSP model calculations which in turn indicate that total fusion excitation function data is not suppressed with reference to theoretical predictions. In contrast, for 49Be+50124Sn (49Be+82208Pb) reaction, the above barrier fusion data is suppressed with respect to the expectations of coupled channel approach and single barrier penetration model by 28% (32%). However, the EDWSP model based calculations reduce the magnitude of suppression factor by 8% (12%) for 49Be+50124Sn (49Be+82208Pb) reaction and consequently the fusion data at above barrier energies is inhibited for both reactions by 20% with reference to the EDWSP model calculations. This fusion suppression can be correlated with loosely bound nature of the projectile. On the other hand, the above barrier fusion data of 2040Ca+50124Sn and 612C+82208Pb reactions is not inhibited with respect to the predictions of coupled channel approach and EDWSP method, henceforth, confirms stability of projectiles against breakup effects.

A study on Pb2+/Pb electrodes for soluble lead redox flow cells prepared with methanesulfonic acid and recycled lead

Electrodeposition and electrodissolution reactions of the Pb2+/Pb electrode were studied on a glassy carbon rotating disk electrode in aqueous solutions of CH3SO3H and Pb(CH3SO3)2. The electrolytic parameters, kinematic viscosity and ionic conductivity, were determined with various concentrations of CH3SO3H and Pb(CH3SO3)2. The diffusion coefficient of Pb2+ in this electrolyte prepared with CH3SO3H was determined by the Levich Equation. Both the concentrations of CH3SO3H and Pb(CH3SO3)2 were found responsible for the equilibrium potential shifts and exchange current density variations. The electrochemical processes at the Pb2+/Pb electrode were identified as being under mixed ohmic-diffusion control. The electrolyte conductivity and the ionic activity of Pb2+ were recognized as important parameters for designing the soluble lead redox flow cells. During constant current charge–discharge measurement, the specific capacity of the Pb2+/Pb electrode was about 253 mAh g−1Pb, about 98 % of the theoretical value. The impurity elements Fe, Ba, Al, and Zn in the Pb2+ electrolytes prepared with recycled lead exhibited insignificant influences on the Pb2+/Pb reactions. It is reasonable to believe that the recycled lead can be applied in soluble lead redox flow batteries, and the cost may be further reduced with recycled lead because expensive impurity-control processes seemed to be avoidable.

Influence of coalescence parameters on the production of protons and Helium-3 fragments

The time evolution of protons and $^3$He fragments from Au+Au/Pb+Pb reactions at 0.25, 2, and 20 GeV$/$nucleon is investigated with the potential version of the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) model combined with the traditional coalescence afterburner. In the coalescence process, the relative distance $R_0$ and relative momentum $P_0$ are surveyed in the range of 3-4 fm and 0.25-0.35 GeV$/$c, respectively. For both clusters, a strong reversed correlation between $R_0$ and $P_0$ is seen and it is time-dependent as well. For protons, the accepted ($R_0$, $P_0$) bands lie in the time interval 30-60 fm$/$c, while for $^3$He, a longer time evolution (at about 60-90 fm$/$c) is needed. Otherwise, much smaller $R_0$ and $P_0$ values should be chosen. If we further look at the rapidity distributions from both central and semi-central collisions, it is found that the accepted [$t_{\rm cut}, (R_0, P_0$)] assemble can provide consistent results for proton yield and collective flows especially at mid-rapdities, while for $^3$He, the consistency is destroyed at both middle and projectile-target rapidities.

Catalytic Conversion of Empty Fruit Bunch (EFB) Fibres into Lactic Acid by Lead (II) ions

Lactic acid (LA) is a potential platform chemical that can be produced from lignocellulosic biomass. The development of a cost-competitive, catalytic-based LA production system is gaining significant attention in modern biorefineries. A series of experimental study was carried out to investigate the chemocatalytic effect of the conversion of oil palm empty fruit bunch (EFB) fibers into lactic acid under hydrothermal conditions. Synthesis of chemicals from lignocellulosic biomass involves complex mechanisms because of the complex composition of the biomass. Therefore, experimental parameters, i.e., temperature, Pb(II) concentration, and reaction time were studied. It was found that production of LA is highly dependent on the experimental conditions. In this study, the highest LA yield obtained from EFB fibers was > 46% (230 °C, 2 mM Pb(II) after 4 h of reaction). However, a similar yield can be achieved either using higher Pb(II) and shorter reactions time or vice versa. The selective production of chemical compounds (glucose, 5-hydroxymethyl furfural (5-HMF), furfural, levulinic acid, and lactic acid) from EFB fibers is highly dependent on the availability of Pb(II) ions.

Study of two- and multi-particle correlations in12C+24Mg and12C+208Pb reactions at E=35 AMeV

Two and multi particle correlations from the decay of sources produced in 12 C+ 24 Mg and 12 C+ 208 Pb collisions at E=35 AMeV have been studied by using the forward part (1 ° lab 30 ° ) of the CHIMERA multi-detector. Correlations and invariant mass spectroscopy are used to explore simultaneous and sequential decays of resonances in light isotopes with Z ∼ 3-6, produced in peripheral collisions via the break-up of excited quasi-projectiles. Among them we mention 5 Li, 6 Li, 6 Be, 8 Be and the astrophysically important state in 12 C decaying into three alpha particles. Results and future perspectives at the INFN-LNS will be presented.

SHE research at RIKEN/GARIS

In this contribution, heavy-element research at RIKEN, Japan is reviewed. Nuclei of the heaviest elements were produced by the reactions 208Pb(64Ni, n)271Ds, 209Bi(64Ni, n)272Rg, 208Pb(70Zn, n)277Cn, and 209Bi(70Zn, n)278113. Alpha decays of those products and their consecutive alpha/spontaneous fission decays were studied using a gas-filled type recoil separator. New nuclei, 278113, 274Rg, and 270Mt, were observed in the 209Bi + 70Zn reaction.

Neutron flux spectra investigations in breeding blanket assembly containing lithium titanate and Lead irradiated with DT neutrons

A benchmark experiment was performed to obtain the neutron spectra in a breeding blanket assembly consisting of lithium titanate and Lead using multiple foil activation technique with unfolding code SAND-II-SNL. The purpose of the experiment was to validate the calculated neutron spectra and neutron induced reaction rates with MCNP-4A code and FENDL-2.1 & FENDL-3.0 transport libraries in the layered geometry of lithium titanate and Lead. Measured reaction rates in different activation foils were compared with MCNP-IRDFF-1.05 and FISPACT-EAF2007 calculated values. In general, FENDL-3.0 calculated reaction rates are closer to the measured reaction rates than FENDL-2.1 calculated rates. Calculated Lead multiplication is improved from FENDL-2.1 to FENDL-3.0 up to 2%. Unfolded neutron spectra in the multiplier zones are slightly underestimated by calculations in the secondary neutron emission range of Pb(n, xn) reactions indicating the need of improvement in the (n, 2n) cross-section of Lead isotopes. The observed underestimation in the Lead multiplication puts the tritium production calculations of breeding blankets using Lead as multiplier on conservative side. The inelastic scattering range of Lead isotopes is overestimated by calculations as large as 80% in one of the breeder zone. This observation requires improvement in the inelastic scattering cross-sections of Lead isotopes in FENDL evaluations.

Probing the neutron-skin thickness by photon production from reactions induced by intermediate-energy protons

Photon from neutron-proton bremsstrahlung in p+Pb reactions is examined as a potential probe of the neutron-skin thickness in different centralities and at different proton incident energies. It is shown that the best choice of reaction environment is about 140MeV for the incident proton and the 95\%-100\% centrality for the reaction system since the incident proton mainly interacts with neutrons inside the skin of the target and thus leads to different photon production to maximal extent. Moreover, considering two main uncertainties from both photon production probability and nucleon-nucleon cross section in the reaction, I propose to use the ratio of photon production from two reactions to measure the neutron-skin thickness because of its cancellation effects on these uncertainties simultaneously, but the preserved about 13\%-15\% sensitivities on the varied neutron-skin thickness from 0.1 to 0.3fm within the current experimental uncertainty range of the neutron-skin size in $^{208}$Pb.

Production of heavy neutron-rich nuclei in transfer reactions within the dinuclear system model

The dynamics of nucleon transfer processes in heavy-ion collisions is investigated within the dinuclear system model. The production cross sections of nuclei in the reactions 136Xe+208Pb and 238U+248Cm are calculated, and the calculations are in good agreement with the experimental data. The transfer cross sections for the 58Ni+208Pb reaction are calculated and compared with the experimental data. We predict the production cross sections of neutron-rich nuclei Eu, Tb, Ho, and based on the reaction 176Yb+238U. It can be seen that the production cross sections of the neutron-rich nuclei 165Eu, 169Tb, 173Ho, and 181Yb are 2.84 μb, 6.90 μb, 46.24 μb, and 53.61 μb, respectively, which could be synthesized in experiment.

Ba5Tr2(Ge,Sn)2P8 and Ba5Tr5(Ga,Tt)2P12 (Tr = Al, Ga; Tt = Ge, Sn): Phosphides with Triel and Tetrel Mixing

AbstractA series of new multinary phosphide Zintl compounds, Ba5Ga2GeSnP8, Ba5Al2GeSnP8, Ba5Ga6GeP12, and Ba5Ga6SnP12, have been synthesized through high‐temperature Pb or Sn flux reactions. The structures of the compounds, which have been determined by single‐crystal X‐ray diffraction, feature two different new structural types bearing various polyanion chain fragments. Ba5Tr2GeSnP8 (Tr = Al, Ga) crystallize in the monoclinic C2/m (No. 12) space group with cell parameters: a = 16.8211(10)/16.7586(21) Å, b = 6.0115(4)/6.0867(8) Å, c = 9.5873(6)/9.5983(12) Å, β = 111.9270(10)/112.1880(10)° for the Al‐ and Ga‐containing compounds, respectively. For Ba5Ga6TtP12 (Tt = Ge, Sn), the compounds belong to a different orthorhombic system [space group: Cmcm (No. 63)] with the cell dimensions: a = 10.5222(6)/10.5802(9) Å, b = 16.2717(10)/16.3529(14) Å, c = 13.9093(8)/13.9643(12) Å for Ba5Ga6GeP12 and Ba5Ga6SnP12. Despite the clear differences in the crystallographic parameters, these two types of structures are closely related through the [Tr2P4] and [Tr5P12] polyanion chains (Tr = triels) as well as the significant mixing between the triel and tetrel atoms. The close relationships between these phases and some previously reported analogues are also discussed in detail. Theoretical calculations based on DFT methods confirm the precise electron nature of these compounds, which are also consistent with results from crystallographic data and the optical absorption measurements.

Analysis of orbital occupancy of valence neutron in 15C through Coulomb breakup reactions

The Coulomb breakup reactions 208Pb(15C, 14C + n)208Pb and 181Ta(15C, 14C + n)181Ta have been studied at 68 and 85 A MeV beam energies, respectively, within the framework of the eikonal approximation to investigate the orbital occupancy of valence neutron in the 15C nucleus. The outcomes of the present work favor 0+ ⊗ 2s1/2 as the core-neutron coupling for the ground-state structure with 0.91 as a spectroscopic factor.

Study of fusion and fission cross sections and pre-fission particles multiplicities for excited nuclei 227Pa

In the framework of a modified statistical model we analyze experimental data on the pre-fission proton and alpha multiplicities, fission cross section and the anisotropy of the angular distribution of fission fragments for 227Pa formed in 19F+208Pb reactions, and results are compared with the experimental data. To calculate the above mentioned experimental data, the effects of spin K about the symmetry axis and temperature have been considered in calculations of the fission widths and potential energy surfaces. It is shown that the results of calculations are in good agreement with the experimental data by using values of the temperature coefficient of the effective potential and the scaling factor of the fission-barrier height equal to α=0.005±0.003MeV-2 and rs=1.006±0.002, respectively. Furthermore, the pre-fission proton and alpha multiplicities are analyzed for 227Pa nuclei in the framework of the three-dimensional Langevin equations and the results of calculations are shown to be in good agreement with the results of statistical model.

CERN achievements in relativistic heavy ion collisions

Twenty years after a Letter of Intent by the GSI and LBL groups for the “Study of particle production and target fragmentation in central 20Ne on Pb reactions, at 12 GeV per nucleon energy of the CERN PS external beam" [1], based on the results found by the NA45/CERES, NA49, NA50, and WA97/NA57 experiments at the SPS, CERN announced compelling evidence for the formation of a new state of matter in heavyion collisions at CERN-SPS energies [2]. Some of the experiments were indeed the 2nd or 3rd generation successors of the apparatuses originally proposed by the GSI-LBL collaboration. Actually, the CERN ion program initiated at the SPS with the acceleration of oxygen ions at 60 and 200 GeV/nucleon only in 1986, and continued with sulphur ions at 200 GeV/nucleon up to 1993. The rest is history: lead-ion beams at 160 GeV/nucleon became available at the SPS in 1994; the LHC accelerated and collided lead beams at a center of mass energy per nucleon pair √sNN = 2.76 TeV in 2010. Heavy ion physics is definitely in the future program of CERN: ALICE will operate a major upgrade of its detectors during the second long shutdown of the LHC, in 2018-2019, and the associated physics program will span the third and fourth LHC runs, till late 2020s.

CERN achievements in relativistic heavy ion collisions

Twenty years after a Letter of Intent by the GSI and LBL groups for the “Study of particle production and target fragmentation in central 20 Ne on Pb reactions, at 12 GeV per nucleon energy of the CERN PS external beam [1], based on the results found by the NA45/CERES, NA49, NA50, and WA97/NA57 experiments at the SPS, CERN announced compelling evidence for the formation of a new state of matter in heavyion collisions at CERN-SPS energies [2]. Some of the experiments were indeed the 2nd or 3rd generation successors of the apparatuses originally proposed by the GSI-LBL collaboration. Actually, the CERN ion program initiated at the SPS with the acceleration of oxygen ions at 60 and 200 GeV/nucleon only in 1986, and continued with sulphur ions at 200 GeV/nucleon up to 1993. The rest is history: lead-ion beams at 160 GeV/nucleon became available at the SPS in 1994; the LHC accelerated and collided lead beams at a center of mass energy per nucleon pair √s NN = 2.76 TeV in 2010. Heavy ion physics is definitely in the future program of CERN: ALICE will operate a major upgrade of its detectors during the second long shutdown of the LHC, in 2018-2019, and the associated physics program will span the third and fourth LHC runs, till late 2020s.

Breakup phenomena study in7Li+208Pb reaction using 8PLP

Inclusive α particle spectra for 7 Li+208 Pb reaction has been studied. There are different reaction mechanism such as pickup/transfer including breakup influence the observed α particle spectra . Presence of different bands of triton indicates the origin is different which needs more study.

Fission dynamics of240Cf*formed in34,36S induced reactions

We have studied the entrance channel effects in the decay of Compound nucleus 240 Cf * formed in 34 S+ 206 Pb and 36 S+ 204 Pb reactions by using energy density dependent nuclear proximity potential in the framework of dynamical cluster-decay model (DCM). At different excitation energies, the fragmentation potential and preformation probability of decaying fragments are almost identical for both the entrance channels, which seem to suggest that decay is independent of its formation and entrance channel excitation energy. It is also observed that, with inclusion of deformation effects upto quadrupole within the optimum orientation approach, the fragmentation path governing potential energy surfaces gets modified significantly. Beside this, the fission mass distribution of Cf* isotopes is also investigated. The calculated fission cross-sections using SIII force for both the channels find nice agreement with the available experimental data for deformed choice of fragments, except at higher energies. In addition to this, the comparative analysis with Blocki based nuclear attraction is also worked out. It is observed that Blocki proximity potential accounts well for the CN decay at all energies whereas the use of EDF based nuclear potential suggests the presence of some non-compound nucleus process (such as quasi-fission (qf)) at higher energies.