Incomplete Fusion Mechanism Research Articles

Numerical simulation and experimental analysis of incomplete fusion mechanism of GH4169 and electroformed Ni electron beam welded joint

The quality of electron beam welding between GH4169 and electroformed Ni (E-Ni) has emerged as a pivotal factor in the manufacturing of hydrogen-oxygen engines. The welding process involving dissimilar materials, however, is susceptible to the occurrence of incomplete fusion defects, with the underlying causes of these defects remaining elusive. In order to enhance the welding quality of GH4169 and E-Ni and eliminate incomplete fusion defects, a novel finite element model integrating thermo-electro-magnetic multi-physical fields coupling was established in this study, revealing the formation mechanism of such defects. The results demonstrated that significant thermoelectric effects arose during the welding process due to the disparities in temperature gradients and Seebeck coefficients between GH4169 and E-Ni. The thermoelectric effect induces the emergence of a magnetic field, primarily concentrated within a 10 mm zone above the weld. Subsequently, this magnetic field causes a significant deflection of the electron beam towards the GH4169, specifically by 128 µm. This deviation ultimately results in the occurrence of incomplete fusion defects, compromising the welding quality. Based on the underlying mechanism of the thermoelectric effect on the electron beam, an inclined welding joint was designed, successfully eliminating the incomplete fusion defects at the root of the GH4169 and E-Ni electron beam welding joint. The resulting joint exhibited a remarkable strength of 411 MPa. The present analysis of the incomplete fusion defect formation mechanism provides theoretical support for the improvement of the electron beam welding process for GH4169 and E-Ni, pioneering a novel defect-free welding technique for these materials.

Disentangling fractional momentum transfer in the F19+Sm154 system

Forward recoil range distributions of evaporation residues produced in the system $^{19}\mathrm{F}+^{154}\mathrm{Sm}$ were measured at projectile energy $\ensuremath{\approx}107$ MeV using the offline $\ensuremath{\gamma}$-ray activation technique. The entire and fractional linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The forward recoil range distributions of measured evaporation residues populated through $x\mathrm{n}/\mathrm{p}x\mathrm{n}$ channels were found to be consisting of a single peak only while the evaporation residues populated through $\ensuremath{\alpha}$ emitting channel had contributions from incomplete fusion also. The observed incomplete fusion process in the population of $\ensuremath{\alpha}$ emitting channel residues is explained through the breakup fusion model. The results indicate the occurrence of incomplete fusion involving the breakup of $^{19}\mathrm{F}$ into $^{4}\mathrm{He}+^{15}\mathrm{N}$ and/or $^{8}\mathrm{Be}+^{11}\mathrm{B}$ followed by fusion of one of the fragments with target nucleus $^{154}\mathrm{Sm}$. From these measurements, the relative contributions of complete and incomplete fusion were separated out. The forward recoil range distributions data show that the incomplete fusion contribution in the fusion of fragment $^{15}\mathrm{N}$ is more dominant as compared to the fusion of fragment $^{11}\mathrm{B}$ with $^{154}\mathrm{Sm}$ target due to the smaller value of $\ensuremath{\alpha}$ breakup threshold energy $({E}_{\mathrm{B}.\mathrm{U}.}^{\ensuremath{\alpha}})$. The measured forward recoil range distributions of evaporation residues produced through $\ensuremath{\alpha}$ emitting channels provide experimental signature of strong clustering in $^{19}\mathrm{F}$ projectile as $\ensuremath{\alpha}$ and $^{15}\mathrm{N}$. The incomplete fusion strength function has also been deduced from the measured recoil range distributions and found to be compatible with those deduced from the measured excitation functions for the same system and beam energy.

Decay dynamics of 9Be + 89Y reaction in view of complete and incomplete fusion mechanisms

This work is aimed to explore the reaction mechanism induced via loosely bound projectile (9Be). Various peculiar properties of such projectiles for example low binding energy per nucleon leading to low breakup threshold, larger rms radii, higher transfer probability, captivate the attention of scientists working in related field. Thus, an effort is made to analyze the complete fusion (CF) and incomplete fusion (ICF) contributions in 9Be + 89Y reaction over energy range (Ec.m. = 17.7-29.8 MeV). The projectile used in the present reaction 9Be may dissociate via 5He, 4He and 1n, which subsequently lead to ICF contribution via three different channels. Thus, the cross-sections corresponding to these ICF channels (5He + 89Y→94Nb⁎, 4He + 89Y→93Nb⁎ and 1n+89Y→90Y⁎) are duly examined. The calculations are done for quadrupole (β2-deformed) choice of fragments using optimum orientations approach of dynamical cluster decay model (DCM). The calculated cross-sections for both CF and ICF channels find nice agreement with the available experimental data. Besides this, the CF contributions are estimated for different isotopes of Tc (with ACN = 96-104) and some predictions are made for future validation.

Production of transuranium isotopes in Ne20 -induced incomplete fusion reactions

Using a semiclassical dynamical model that combines a classical trajectory model with stochastic breakup with a dynamical fragmentation theory treatment of two-body clusterization and decay of a projectile, results are presented for $^{20}\mathrm{Ne}$-induced incomplete fusion reactions for the production of superheavy elements. Targets include $^{247,248,250}\mathrm{Cm}$ and $^{251,252,254}\mathrm{Cf}$, and results include angular, excitation energy, and angular momentum distributions in addition to total integrated cross sections for heavy incomplete fusion products. The results show that at Coulomb energies, the studied Cf isotopes are generally the more favorable choice of target over the studied Cm isotopes for the production of `colder' and more stable $^{263}\mathrm{Lr}$, $^{263,264,266}\mathrm{Rf}$, and $^{265}\mathrm{Db}$ isotopes through the incomplete fusion mechanism. Also presented are evaporation residue cross sections for the dominant primary incomplete fusion products of each of the six reactions: $^{263,264,266}\mathrm{Rf}$ and $^{267,268,270}\mathrm{Sg}$, as well as for the primary incomplete fusion products $^{269,270,272}\mathrm{Bh}$.

Populating high spin states of a compound nucleus with the incomplete fusion mechanism: the effectiveness of heavy projectiles

Using a classical dynamical reaction model, angular momentum (L) values of a compound nucleus due to incomplete fusion (ICF) at energies near and above the Coulomb barrier are studied. In this model, a projectile consisting of two cluster nuclei is fired at a stationary target nucleus. After breakup of the projectile due to Coulombic and nuclear forces, an α-cluster fuses with a 208Pb target, forming an excited 212Po compound nucleus. Results show that all ICF reactions produced higher angular momentum in the compound nucleus compared to a direct beam of α particles at the same incident energy. The highest angular momentum values produced in 212Po for near and above Coulomb barrier energies were obtained using a 20Ne projectile at and , respectively. This produced 25% and 50% L values above the next highest-Z projectile used, 8Be, respectively.

New measurement of residues from Li7+Tanat reaction within 4–6.5 MeV/nucleon: Production yield for Os183

Exploration of reaction dynamics of the weakly bound heavy-ion interaction with an intermediate or heavy mass target in the low energy range has been a subject of interest over the past decades; however, different modes of fusion such as breakup fusion, incomplete fusion, and transfer phenomena observed experimentally are not yet fully understood. Experimental studies are therefore essential to address the problem. In this article, we report a new set of cross-section data of the residues produced in the weakly bound $^{7}\mathrm{Li}$ induced reaction on $^{\mathrm{nat}}\mathrm{Ta}$ within the 27--45 MeV energy range. Along with the major yield of $^{\text{183g+m}}\mathrm{Os}$, production of $^{\text{180m}}\mathrm{Hf}$ and $^{183}\mathrm{Ta}$ are also observed up to $\ensuremath{\sim}35\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}$, which is possibly an indication of the incomplete fusion mechanism or breakup-transfer phenomena. The trend of the isomeric cross-section ratio of $^{183}\mathrm{Os}$ indicates the role of angular momentum and spin distribution besides the excitation energy, and is interpreted by theory. The optimized production parameters and yields of $^{\text{183g,m}}\mathrm{Os}$ are assessed.

Is there incomplete fusion mechanism beyond 100A MeV?

Abstract Presented is a universal description of the generalized fusion excitation function which indicates that the fusion reaction mechanism should vanish at center-of-mass energy per nucleon of about 13 MeV/nucleon independently of the specific heavy-ion reaction system. Placing reliance on this result and comforted by semiclassical transport model simulations we suggest that the proposed persistence of the incomplete fusion cross sections in the measurement of the 14 N induced reactions on heavy targets at beam energies between 100 A and 155 A MeV should be attributed to a geometrical participant-spectator-like reaction mechanism.

Reaction mechanisms in the systemNe20+Ho165: Measurement and analysis of forward recoil range distributions

Keeping in view the study of complete and incomplete fusion of heavy ions with a target, the forward recoil range distributions of several evaporation residues produced at 164 MeV $^{20}\mathrm{Ne}$-ion beam energy have been measured for the system $^{20}\mathrm{Ne}+^{165}\mathrm{Ho}$. The recoil catcher activation technique followed by off-line gamma spectroscopy has been employed. Measured forward recoil range distributions of these evaporation residues show evidence of several incomplete fusion channels in addition to complete fusion. The entire and partial linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The results indicate the occurrence of incomplete fusion involving the breakup of $^{20}\mathrm{Ne}$ into $^{4}\mathrm{He}+^{16}\mathrm{O}$ and/or $^{8}\mathrm{Be}+^{12}\mathrm{C}$ followed by fusion of one of the fragments with target nucleus $^{165}\mathrm{Ho}$. Complete and incomplete fusion reaction channels have been identified in the production of various evaporation residues and an attempt has been made to separate out relative contributions of complete and incomplete fusion components from the analysis of the measured recoil range distribution data. The total contribution of complete and incomplete fusion channels has also been estimated.

Isomer ratio measurements as a probe of the dynamics of breakup and incomplete fusion

The incomplete fusion mechanism following breakup of {sup 6,7}Li and {sup 9}Be projectiles incident on targets of {sup 209}Bi and {sup 208}Pb is investigated through isomer ratio measurements for the {sup 212}At and {sup 211}Po products. The phenomenological analysis presented in this paper indicates that incomplete fusion brings relatively more angular momentum into the system than equivalent reactions with a direct beam of the fused fragment. This is attributed to the trajectories of breakup fragments. Calculations with a 3D classical trajectory model support this. Isomer ratio measurements for incomplete fusion reactions can provide a test of new theoretical models of breakup and fusion.

Incomplete fusion mechanism in 16O + 93Nb reaction at 6 MeV/nucleon: Recoil range measurements

Summary Recoil range distribution of evaporation residues formed in complete and incomplete fusion of 96 MeV 16O with 93Nb has been measured by recoil catcher technique followed by off-line gamma-ray spectrometry. The cross sections for complete and incomplete fusion were delineated from the earlier measured excitation function data at the same beam energy. The results show that incomplete fusion is associated with angular momentum values close to the critical angular momentum for complete fusion of the projectile and target.

Excited states in 163,164Ho populated through incomplete-fusion reactions

High-spin states in 163,164Ho were investigated by means of in-beam $\gamma$ -ray spectroscopy techniques using the multidetector array GASP. Excited states in 163,164Ho were populated predominantly through the incomplete-fusion mechanism in the 160Gd (11B $,\alpha xn)$ reaction at a beam energy of 61 MeV. Known rotational bands in 163 Ho have been extended to higher spins and a three-quasiparticle band has been observed in this nucleus. Rotational bands have been identified in 164Ho and their configurations have been discussed. Empirical Gallagher-Moszkowski (GM) splitting energies were extracted from the $\pi 7/2^-[523]\otimes\nu 5/2^-[523]$ and $\pi 7/2^-[523]\otimes\nu 5/2^ + [642]$ GM doublets. Alignments, band crossing frequencies, and electromagnetic properties have been analyzed in the framework of the cranking model.

Fusion and binary-decay mechanisms in the35Cl+24Mg system atE/A≈8MeV

Compound-nucleus fusion and binary-reaction mechanisms have been investigated for the ${}^{35}$Cl+${}^{24}$Mg system at an incident beam energy of E${}_{\mathrm{lab}}$= 282 MeV. Charge distributions, inclusive energy spectra, and angular distributions have been obtained for the evaporation residues and the binary fragments. Angle-integrated cross sections have been determined for evaporation residues from both the complete and incomplete fusion mechanisms. Energy spectra for binary fragment channels near the entrance-channel mass partition are characterized by an inelastic contribution that is in addition to a fully energy damped component. The fully damped component which is observed in all the binary mass channels can be associated with decay times that are comparable to, or longer than, the rotation period. The observed mass-dependent cross sections for the fully damped component are well reproduced by the fission transition-state model, suggesting a fusion followed by fission origin. The present data cannot, however, rule out the possibility that a long-lived orbiting mechanism accounts for part or all of this yield.

Binary channels of the19F-on-12C reaction at 92 MeV

Binary-reaction channels of {sup 19}F+{sup 12}C have been studied at E{sub lab}({sup 19}F)=92 MeV using kinematic coincidence techniques. The results are discussed in the light of previous inclusive measurements performed at the same incident energy and for which the occurrence of an important incomplete fusion mechanism after projectile breakup was proposed. Evidence for strong damped binary, especially quasisymmetric, decay processes is found. {copyright} {ital 1997} {ital The American Physical Society}

Investigations of complete and incomplete fusion in 12C+93Nb and 16O+89Y by recoil range measurements.

The recoil range distribution of the radioactive evaporation residues in the reaction of 63 and 77.5 MeV $^{12}\mathrm{C}$ with $^{93}\mathrm{Nb}$ and that of 68 MeV $^{16}\mathrm{O}$ with $^{89}\mathrm{Y}$ have been measured using the recoil catcher technique followed by gamma spectrometry. The linear momentum transfers inferred from these recoil range distributions were used to identify the evaporation residues formed by complete and incomplete fusion mechanisms. The data are compared with Monte Carlo simulation of recoil range distributions of products formed by complete fusion to extract the contribution of incomplete fusion in the individual channels. The observations are discussed in the framework of existing models.

Dynamical calculations of linear momentum transfer in α-induced reactions

Linear momentum transfers in α-induced reactions with 20 MeV per nucleon are calculated by considering all important direct and incomplete fusion mechanisms along with complete fusion. The calculated results agree very well with the experimental data. Calculated total inelastic cross section and various incomplete fusion cross sections (including the stripping reactions to bound discrete states) also agree well with the experimental data.

Dissipative mechanisms in the 120 MeV 19F+64Ni reaction.

Energy spectra and angular distributions of projectile-like fragments, ranging from {sup 7}Be to {sup 18}O, have been measured for the 120 MeV {sup 19}F+{sup 64}Ni reaction. Experimental evidence is given for the presence of two dissipative components attributed, on the basis of optimum {ital Q} values, to incomplete fusion and deep-inelastic collision mechanisms. Measured {ital Q}-value spectra show the dominance of the incomplete fusion mechanism in N and O isotopes production, while deep-inelastic collisions increase with the charge transfer. Furthermore, angular distributions and optimum {ital Q} values display larger relative contributions of incomplete fusion with respect to deep inelastic collisions for heavier isotopes of each {ital Z}. An incomplete fusion model reproduces the cross sections for most of the channels where this mechanism is prevalent. An attempt to include deep inelastic mechanisms in the same model is presented.

Ejectile emission in the 120 MeV 30Si + 30Si reaction

Inclusive emission of ejectiles spanning from He to Ti has been studied in the 120 MeV 30Si + 30Si reaction. Indications are presented for the presence of both mechanisms: deep inelastic collisions and incomplete fusion. In particular, most probable energies of projectile-like fragments with 10 ⩽ Z ⩽ 18 are well reproduced by Q-values calculated for deep inelastic collisions in the sticking limit. On the other hand the observation of ejectiles corresponding to large massive transfers with Z < 10 and with Z > 18 suggests the presence of incomplete fusion mechanisms. A comparison between the angle-integrated cross sections of the observed ejectiles and those calculated with a sum-rule model for incomplete fusion is presented.

Target residue cross sections and recoil energies from the reaction of 1760 MeV 40Ar with medium and heavy targets

Cross sections and recoil range measurements of the rare-earth isotones ( N = 84–85) formed in 40Ar induced reactions at E lab = 1.76 GeV have been performed. An electrostatic collection method associated to a gas flow transport was used. The various experimental results plead in favor of an origin of these residues in the decay of highly excited precursors. Such excited precursors can be explained by an incomplete fusion mechanism. Comparisons with existing theoretical models (an extended abrasion-ablation model and intranuclear cascade calculations) have been performed.

Limitation to complete fusion in the reactions 12,13C+ 48Ti and 30Si+ 30Si

Excitation functions of the reactions 12, 13C+ 48Ti and 30Si+ 30Si were measured by in-beam γ-ray spectrometry in the energy ranges 20–60 MeV for the 12, 13C induced reactions and 55–126 MeV for the 30Si+ 30Si reaction. Light-particle angular distributions were measured at 46 MeV and 47.5 MeV for the 13C and 12C induced reactions. Measurements of elastic scattering angular distribution and particle-γ coincidences were carried out for the system 13C+ 48Ti at 46 MeV. The limitation to complete fusion detected for the system 30Si+ 30Si appears to be related to entrance channel effects and is well reproduced by a barrier penetration calculation using the KNS potential. The angular distribution measurements carried out for the 12C+ 48Ti and 13C+ 48Ti systems allowed to identify an incomplete fusion mechanism with emission of direct α-particles before the formation of a fully equilibrated system.

Reaction mechanisms investigated in interactions of 12C at 360 MeV on medium-mass targets

Cross sections, mean recoil ranges and isomeric ratios of radioactive α residues produced in 12C-induced reactions at 360 MeV on medium-mass targets are measured using on-line electrostatic collection. The isoproduction cross-section lines in the N- Z plane are drawn. The behavior of the mean recoil energies and of the isomeric ratios as a function of the mass and charge gain or loss by the target is obtained. It is shown that qualitatively most of the results can be understood in the framework of an incomplete fusion mechanism.