Increasing Projectile Energy Research Articles

First investigation on the isomeric ratio in multinucleon transfer reactions: Entrance channel effects on the spin distribution

The multinucleon transfer (MNT) reaction approach was successfully employed for the first time to measure the isomeric ratios (IRs) of 211Po isomer (25/2+) and its ground state (9/2+) at the IGISOL facility using a 945 MeV 136Xe beam impinged on 209Bi and natPb targets. The dominant production of isomers compared to the corresponding ground states was consistently revealed in the α-decay spectra. Deduced IR of 211Po populated through the 136Xe+natPb reaction was found to have an enhancement of ≈1.8-times than that observed for the 136Xe+209Bi. State-of-the-art Langevin-type model calculations have been utilized to estimate the spin distribution of an MNT residue. The computations qualitatively corroborate with the considerable increase in the IRs of 211Po produced from 136Xe+natPb compared to 136Xe+209Bi. Theoretical investigations indicate a weak dependence of target spin on the IRs. The enhancement of the 211Po isomer in the 136Xe+natPb over 136Xe+209Bi can be attributed to the different proton (p)-transfer production routes. Estimations demonstrate an increment in the angular momentum transfer, favorable for isomer production, with increasing projectile energy. Comparative analysis reveals the two entrance channel parameters, projectile mass and p-transfer channels, strongly influencing the population of the high-spin isomer of 211Po (25/2+). This letter reports the first experimental and theoretical study on the IRs of nuclei formed from two different p-transfer channels via two independent MNT reactions.

A Study of Reaction Dynamics in the Interaction of 14N+59Co System at 32-56 MeV

The present work was done to investigate the reaction mechanisms involved in the interaction of 14 N projectile with 59 Co target at beam energies ∼32-56 MeV. The experimentally measured excitation functions available in the literature [2] were compared and analyzed with the statistical model code PACE4 calculation. For non-α emitting channels populated via complete fusion reaction, the measured excitation functions, after correcting them for possible contributions coming from higher charge isobaric precursor decays, were in general found to be in good agreement with theoretical predictions. However, for α-emitting channels, the experimentally measured excitation functions had more production cross-sections than what PACE4 predicted. The observed enhancement in the present case may be attributable to process of incomplete fusion from break-up of 14 N projectile. It may be pointed out that incomplete fusion reaction increases with increase in projectile energy. The observation of high incomplete fusion reaction is attributable to the prompt breakup of 14 N projectile into α-cluster. DOI: 10.7176/APTA/86-03 Publication date: October 31 st 2022

A Study of excitation functions in the interaction of α + 59Co system at 4~9MeV/Nucleon

In this work, α-induced 59Co reactions in the energy range from 11- 41MeV were used in order to study the role of pre-equilibrium emission. The experimentally measured excitation functions for residues populated via (α, n),(α, 2n),(α,3n),(α,2p),(α, 3n 2p) and (α, 4n 2p) channels in the interaction of + 59Co system available in the literature [13] were compared with theoretical predictions obtained using the statistical model code COMPLET. It was observed that at higher energy points the pure compound nucleus predictions, in general, failed to reproduce the measured data at projectile energies ~11-41MeV, this shows significant contributions from pre-equilibrium emission. The study signified both equilibrium and pre-equilibrium emissions were required to reproduce the presently measured excitation functions. An attempt was made to deduce the contribution coming from pre-equilibrium emission. It was found that the pre-equilibrium contribution increases with increasing projectile energy. Furthermore, the present result revealed a strong correlation between pre-equilibrium contribution and particle multiplicity.

Measurements of natCd(γ, x) reaction cross sections and isomer ratio of 115m,gCd with the bremsstrahlung end-point energies of 50 and 60 MeV * *Supported by the National Research Foundation of Korea (NRF) through a grant provided by the Ministry of Science and ICT (NRF-2017R1D1A1B03030484, NRF-2013M7A1A1075764, NRF-2018R1A6A1A06024970)

The flux-weighted average cross sections of natCd(γ, xn)115g,m,111m,109,107,105,104Cd and natCd(γ, x)113g,112,111g,110mAg reactions were measured at the bremsstrahlung end-point energies of 50 and 60 MeV. The activation and off-line γ-ray spectrometric technique was carried out using the 100 MeV electron linear accelerator at the Pohang Accelerator Laboratory, Korea. The natCd(γ, xn) reaction cross sections as a function of photon energy were theoretically calculated using the TALYS-1.95 and the EMPIRE-3.2 Malta codes. Then, the flux-weighted average cross sections were obtained from the theoretical values of mono-energetic photons. These values were compared with the flux-weighted values from the present study and were found to be in general agreement. The measured experimental reaction cross-sections and integral yields were described for cadmium and silver isotopes in the natCd(γ, xn)115g,m,111m,109,107,105,104Cd and natCd(γ, x)113g,112,111g,110mAg reactions. The isomeric yield ratio (IR) of 115g,mCd in the natCd(γ, xn) reaction was determined for the two bremsstrahlung end-point energies. The measured isomeric yield ratios of 115g,mCd in the natCd(γ, xn) reaction were also compared with the theoretical values of the nuclear model codes and previously published literature data of the 116Cd(γ, n) and 116Cd(n, 2n) reactions. It was found that the IR value increases with increasing projectile energy, which demonstrates the characteristic of excitation energy. However, the higher IR value of 115g,mCd in the 116Cd(n, 2n) reaction compared to that in the 116Cd(γ, n) reaction indicates the role of compound nuclear spin alongside excitation energy.

Examination of different features of fission fragments of the excited compound nucleus Np236 produced in the p+U235 reaction at 10.3≤Ep≤30.0MeV within a stochastic approach

A stochastic approach based on four-dimensional Langevin equations has been used to estimate the mass distributions of fission fragments, the average masses of heavy fragments, the average total kinetic energies of fragments, and the average number of neutrons emitted per fission of $^{236}\mathrm{Np}$ produced in the $p+^{235}\mathrm{U}$ reaction at $10.3\ensuremath{\le}{E}_{p}\ensuremath{\le}30.0\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis $K$ were considered in the four-dimensional dynamical model. The effects of shell corrections and dissipation coefficient of $K {\ensuremath{\gamma}}_{K}$ were considered in the dynamical calculations. Comparison of the theoretical results for the mass distributions of fission fragments, the average masses of heavy fragments, and the average number of neutrons emitted per fission with the experimental data showed that the results of calculations were in good agreement with the experimental data, although the results of calculations for the average total kinetic energies of fission fragments were slightly higher than the experimental data. It was also shown that the number of fission events increased with time, and almost all of the fission events occurred dynamically until $t=4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$ and that the number of fission events became saturated. Furthermore, it was also shown that the average masses of heavy fragments and the average total kinetic energies of fission fragments of $^{236}\mathrm{Np}$ decreased with increasing projectile energy.

Entanglement fidelity for electron–electron interaction in strongly coupled semiclassical plasma and under external fields

This letter presents the effects of AB-flux field and electric field on electron–electron interaction, encircled by a strongly coupled semiclassical plasma. We found that weak external fields are required to perpetuate a low-energy elastic electron–electron interaction in a strongly coupled semiclassical plasma. The entanglement fidelity in the interaction process has been examined. We have used partial wave analysis to derive the entanglement fidelity. We found that for a weak electric field, the fidelity ratio for electron–electron interaction increases as the projectile energy increases, but remains constant or almost zero for a strong electric field. Our results provide invaluable information on how the efficiency of entanglement fidelity for a low-energy elastic electron–electron interaction in a strongly coupled semiclassical plasma can be influenced by the presence of external fields.

Measurement of incomplete fusion cross sections in Li6,7+U238 reactions

Background: Incomplete fusion (ICF) in reactions involving weakly bound projectiles is understood to play an important role in enhancing the ratio of asymmetric to symmetric fission at $E\ensuremath{\le}{V}_{b}$, widening the fission fragment folding angle distribution at $E\ensuremath{\le}{V}_{b}$ and suppressing the complete fusion (CF) cross section at $Eg{V}_{b}$. Experimental cross sections for individual ICF channels are necessary to obtain quantitative estimates of the above effects.Purpose: Measurement of the cross sections for individual transfer-induced or ICF-fission channels in $^{6,7}\mathrm{Li}+^{238}\mathrm{U}$ reactions to explain quantitatively the difference in the ratio of asymmetric to symmetric fission for total fission and CF fission.Methods: Triple coincidence measurement of two fission fragments and one light charged projectilelike fragment (PLF) is carried out using two multiwire proportional counter (MWPC) detectors and an array of CSI(Tl) scintillation detectors at energies near the Coulomb barrier. By calculating the efficiency of the detectors by Monte Carlo simulation and fission probability by GEF code, the angle-integrated ICF cross sections corresponding to p, d, t, and $\ensuremath{\alpha}$ emission are obtained. Mass distributions for total fission are calculated by adding the distributions for CF fission and all ICF fissions with weight factors proportional to the measured cross sections.Results: ICF cross sections corresponding to $\ensuremath{\alpha}$ emission are found to be the highest in both the reactions. The relative contribution of ICF to total fusion at the lowest measured energy is found to be $\ensuremath{\approx}70%$ and it decreases with increasing projectile energy, consistent with the systematics of several reactions involving the same weakly bound projectiles. The simulated mass distributions for total fission are found to reproduce the experimental mass distributions.Conclusions: Deuteron (triton) capture is observed to be the major ICF channel in the reaction involving $^{6}\mathrm{Li}\phantom{\rule{0.28em}{0ex}}(^{7}\mathrm{Li})$ projectile. The ratio of the sum of ICF to total fusion cross section for the present systems are consistent with the systematics. The difference in the ratio of asymmetric to symmetric fission between total fission and CF fission is explained quantitatively.

Theoretical detection limit of PIXE analysis using 20 MeV proton beams

Abstract Particle-induced X-ray emission (PIXE) analysis is usually performed using proton beams with energies in the range 2∼3 MeV because at these energies, the detection limit is low. The detection limit of PIXE analysis depends on the X-ray production cross-section, the continuous background of the PIXE spectrum and the experimental parameters such as the beam currents and the solid angle and detector efficiency of X-ray detector. Though the continuous background increases as the projectile energy increases, the cross-section of the X-ray increases as well. Therefore, the detection limit of high energy proton PIXE is not expected to increase significantly. We calculated the cross sections of continuous X-rays produced in several bremsstrahlung processes and estimated the detection limit of a 20 MeV proton PIXE analysis by modelling the Compton tail of the γ-rays produced in the nuclear reactions, and the escape effect on the secondary electron bremsstrahlung. We found that the Compton tail does not affect the detection limit when a thin X-ray detector is used, but the secondary electron bremsstrahlung escape effect does have an impact. We also confirmed that the detection limit of the PIXE analysis, when used with 4 μm polyethylene backing film and an integrated beam current of 1 μC, is 0.4∼2.0 ppm for proton energies in the range 10∼30 MeV and elements with Z = 16–90. This result demonstrates the usefulness of several 10 MeV cyclotrons for performing PIXE analysis. Cyclotrons with these properties are currently installed in positron emission tomography (PET) centers.

Measurement of thick target neutron yield from the reaction [formula omitted] with projectiles in the range of 6–20 MeV

181Ta is a commonly used backing material for many targets in nuclear reaction studies. When the target thickness is less than the range of bombarded projectiles, the interaction via Ta(p,n) reactions in the backing can be a significant source of background. In this study, the neutron spectral yields from the reaction of protons of different energies (between 6 to 20 MeV) with a thick Ta target were determined using CR-39 detectors. The results from this study can be used as a correction factor in such situations. The parameters of registered tracks in CR-39 were analysed using an in-house image analysing program autoTRAK_n and then to derive the associated dose values. The spectral yields obtained experimentally were compared with those obtained from the theoretical calculations. The neutron yield was found to increase with increase in projectile energy mainly due to the opening of reaction channels from (p, n) to (p, 3n).

Regge pole analysis of elastic scattering of α particles by even isotopes of Ni target nuclei at incident energies above Coulomb barrier

Regge pole model is adopted to account for the angular distribution at backward angles for a set of elastic scattering processes of incident [Formula: see text]-particles by different isotopes of nickel ions, [Formula: see text]Ni, at different laboratory energies above Coulomb barrier. The reproduction of cross-sections at backward angles is preceded by an attempt to fit the experimental data at forward angles of the scattering. Three-parameter McIntyre model which is based on concept of strong absorption parametrization of the scattering matrix elements, has been employed to analyze and reproduce the experimental data of angular distribution of different elastic scattering reactions at forward angles. The three parameters extracted from McIntyre model analysis are employed as fixed entries in the fitting process of the full angle-range of angular distribution where another four free parameters are employed using the Regge pole model. Diffractive features observed in the angular distributions are studied. The Fresnel-type diffraction pattern is found dominant for all investigated elastic scatterings where Coulomb interaction is strong. The interaction radius of elastic scattering is found decreasing and the total cross-section increasing when the incident projectile energy increases. Moreover, the interaction radius and total reaction cross-section are found increasing with the increase in the size of target ion. Such diffractive behavior is consistent with the prescriptions of strong absorption model (SAM). Furthermore, the explanation of the diffractive features of studied elastic scattering reactions is model-independent. The Regge pole analysis reveals the existence of a pole which has its location, width, amplitude and phase angle exhibiting a common peak at energy of 24.1[Formula: see text]MeV with oscillatory behaviour at energies around this peak energy, for all elastic scattering of alpha particle on isotopes of Ni targets except that of [Formula: see text]Ni target which exhibits extra peaks for energy larger than 24.1[Formula: see text]MeV. We believe that the presence of poles is responsible for the oscillatory structure of the backward cross-sections. The variation of Regge pole parameters with both incident energy and size of target nucleus is illustrated.

Angular- and state-selective differential cross sections for single-electron capture inp-He collisions at intermediate energies

State-selective electron capture cross sections and projectile scattering-angle differential cross sections for single-electron capture in collisions of protons with He at energies ranging from 50 to 100 keV have been experimentally investigated by means of a reaction microscope. It is shown that for single-electron capture the ground-state transfer is the dominant reaction channel, and excited-state transfer has relative small contributions to the cross sections. The transfer-excitation process has a minor contribution to the total cross sections. As the projectile energy increases, ground-state transfer remains dominant, but the relative contributions of the excited-state transfers become more important. The minor contribution of transfer excitation remains almost unchanged. Furthermore, it was found that for single transfer the present results are in good agreement with independent electron model predictions in the energy regime considered. For transfer excitation, however, there are obvious discrepancies between our measurements and theoretical results. We concluded that the electron-electron-correlation effects may play a role at least in transfer excitation in collisions of protons with He in the energy range considered.

Simultaneous detection and localization of secondary ions and electrons from single large cluster impacts.

The use of large cluster primary ions (e.g. C60, Au400) in secondary ion mass spectrometry has become prevalent in recent years due to their enhanced emission of secondary ions, in particular, molecular ions (MW ≤ 1500 Da). The co-emission of electrons with SIs was investigated per projectile impact. It has been found that SI and electrons yields increased with increasing projectile energy and size. The use of the emitted electrons from impacts of C60 for localization has been demonstrated for cholesterol deposited on a copper grid. The instrumentation, methodologies, and results from these experiments are presented.

Magnetic field and quantum screening effects on the occurrence time advance in quantum magnetoplasmas

The magnetic field and quantum screening effects on the occurrence scattering time advance for the electron-ion collision are investigated in quantum magnetoplasmas. The result shows that the occurrence scattering time advance decreases with an increase of the magnetic-field strength. It is also found that the occurrence time advance decreases with increasing projectile energy and increases with increasing scattering angle. In addition, the occurrence time advance decreases with an increase of the quantum effect, i.e., Fermi wavelength.

Oscillatory quantum screening effects on the transition bremsstrahlung radiation in quantum plasmas

The oscillatory screening effects on the transition bremsstrahlung radiation due to the polarization interaction between the electron and shielding cloud are investigated in dense quantum plasmas. The impact-parameter analysis with the modified Debye-Hückel potential is applied to obtain the bremsstrahlung radiation cross section as a function of the quantum wave number, impact parameter, photon energy, and projectile energy. The results show that the oscillatory quantum screening effect strongly suppresses the transition bremsstrahlung radiation spectrum in dense quantum plasmas. It is also found that the oscillatory quantum screening effect is more significant near the maximum peak of the bremsstrahlung radiation cross section. In addition, the maximum peak of the bremsstrahlung radiation cross section is getting close to the center of the shielding cloud as increasing quantum wave number. It is interesting to note that the range of the bremsstrahlung photon energy would be broadened with an increase of the oscillatory screening effect. It is also found that the oscillatory screening effects on the transition bremsstrahlung spectrum decreases with increasing projectile energy.

Dynamic Screening Effects on Collisional Orientation Phenomena in Nonideal Plasmas

Dynamic screening effects on orientation phenomena of 1s→2p±1 excitations in nonideal plasmas are investigated. A semiclassical method is employed to describe the motion of the projectile electron in order to investigate the variation of the orientation parameter as a function of the impact parameter, projectile energy, thermal energy, and Debye length. The result shows that the preference for the 1s→2p−1 transition significantly decreases with increasing projectile energy. It is found that the dynamic screening effect increases with increasing impact parameter and also with increasing projectile energy. It is also found that the 1s → 2p−1 preference decreases with increasing thermal energy.

L x-ray production in 57La, 58Ce, 60Nd and 62Sm by 35–60 MeV carbon and oxygen ions

L x-ray production cross sections have been measured for thin solid targets (∼50μg/cm2) of 57La, 58Ce, 60Nd and 62Sm for 35–60MeV C4+ and O5+ ions. There is an increase in these cross sections with the increasing projectile energy and the ratio of its atomic number to the atomic number of the target nucleus (Z1/Z2). The measured L x-ray production cross sections have been compared with the predicted values of the first Born approximation (FBA) and of the ECPSSR theory that accounts for the projectile energy loss and Coulomb deflection and the perturbed stationary-state and relativistic nature of the L-shell. For C4+ ions, there is a reasonable agreement with the ECPSSR predicted values for the higher Z elements (Nd and Sm), while for the lower Z elements (La and Ce), the FBA is in a better accord with the data. For O5+ ions, the FBA gives a better agreement for all the elements than the ECPSSR theory.

Tracing the evolution of temperature in near Fermi energy heavy ion collisions

The kinetic energy variation of emitted light clusters has been employed as a clock to explore the time evolution of the temperature for thermalizing composite systems produced in the reactions of 26A, 35A and 47A MeV $^{64}$Zn with $^{58}$Ni, $^{92}$Mo and $^{197}$Au. For each system investigated, the double isotope ratio temperature curve exhibits a high maximum apparent temperature, in the range of 10-25 MeV, at high ejectile velocity. These maximum values increase with increasing projectile energy and decrease with increasing target mass. The time at which the maximum in the temperature curve is reached ranges from 80 to 130 fm/c after contact. For each different target, the subsequent cooling curves for all three projectile energies are quite similar. Temperatures comparable to those of limiting temperature systematics are reached 30 to 40 fm/c after the times corresponding to the maxima, at a time when AMD-V transport model calculations predict entry into the final evaporative or fragmentation stage of de-excitation of the hot composite systems. Evidence for the establishment of thermal and chemical equilibrium is discussed.

Stopping of relativistic electrons in a partially degenerate electron fluid

The stopping mechanisms of relativistic electron beams in superdense and partially degenerate electron fluid targets are investigated in the framework of the fast ignitor concept for inertial confinement fusion. In order to comply with specific demands in this area, we focus attention on the target partial degeneracy parameter theta= T(e) / T(f) , in terms of the thermal to Fermi temperature ratio. The target electron fluid is thus modeled very accurately with a random phase approximation dielectric function. The stopping results are shown to be very weakly theta dependent. However, a quantum target description is needed to recover their correct increasing trend with increasing projectile energy. The ranges and effective penetration depths in precompressed thermonuclear fuels are shown to be nearly a factor of 2 shorter than earlier classical estimates in the same conditions. The overall conclusions pertaining to the feasibility of fast ignition thus remain unchanged.

Experimental studies and nuclear model calculations on (p,xn) and (p,pxn) reactions on85Rb from their thresholds up to 100 MeV

SummaryExcitation functions were measured by the stacked-foil technique for the reactions85Rb(p,pxn)84m, g,83, 82m, 81Rb from their thresholds up to 100 MeV. Nuclear model calculations were performed using the code ALICE-IPPE both on (p,xn) reactions reported earlier and (p,pxn) reactions described here. The experimental excitation curves and the results of nuclear model calculations were found to be qualitatively in agreement. With the exception of the (p,n) reaction above 40 MeV, the theory appears to reproduce all the experimental data within deviations of about 50 %. The cross section ratios for the isomeric pairs85m,gSr and84m,gRb are discussed qualitatively in terms of the spins of the states involved and the increasing projectile energy.

Dynamic screening effects on semiclassical electron captures in kappa-Maxwellian plasmas

Dynamic plasma screening effects on the electron capture process in kappa-Maxwellian plasmas are investigated using the semiclassical version of the Bohr–Lindhard model. The interaction potential and screened electron capture radius are obtained by considering the longitudinal component of the plasma dielectric function. The semiclassical electron capture probability is also obtained as a function of the impact parameter, Debye length, projectile velocity, and spectral index. It is found that the dynamic screening effects on the electron capture probability are more significant for low projectile energies. The maximum position of the scaled electron capture probability approaches the target nucleus with increasing projectile energy. The dynamic screening effect is also found to decrease with increasing spectral index.