Measured Excitation Functions Research Articles

Impact of shell structure on the fusion of neutron-rich mid-mass nuclei

The influence of shell effects on fusion of mid-mass nuclei is explored using isotopic chains of K and Ar ions on an oxygen target. Comparison of the reduced excitation functions reveals that the fusion cross section for the open neutron-shell projectile nuclei $^{41}\mathrm{K}$ and $^{45}\mathrm{K}$ is systematically larger than for the closed neutron-shell projectiles $^{39}\mathrm{K}$ and $^{47}\mathrm{K}$. The S\~ao Paulo fusion model using matter densities from systematics fails to describe the measured excitation functions. Use of more realistic densities from a Dirac-Hartree-Bogoliubov (DHB) approach performs significantly better though it still overpredicts the closed-shell nuclei.

Effect of non- α -cluster projectile on incomplete-fusion dynamics: Experimental study of the N14+Ta181 system

In order to study incomplete fusion (ICF) reaction dynamics, the present work manifests the role of a non-$\ensuremath{\alpha}$-cluster $^{14}\mathrm{N}$ projectile on $^{181}\mathrm{Ta}$ target at energies $\ensuremath{\approx}4--7$ MeV/nucleon using the offline $\ensuremath{\gamma}$-ray spectroscopy. The excitation functions for 15 reaction residues populated in $^{14}\mathrm{N}+^{181}\mathrm{Ta}$ system have been measured and analyzed within the framework of statistical model code PACE4. The experimentally measured excitation functions of evaporation residues populated via xn/pxn channels are found to be well reproduced by the predictions of code PACE4, which confirms their production solely via complete fusion process. However, an enhancement in the measured excitation function as compared to PACE4 calculations, particularly in tail portion of $^{192}\mathrm{Hg}$ residue ($3n$ channel) has been observed indicating the presence of precompound emission. A significant contribution from precursor decay in pxn channels has also been observed. An enhancement in the measured excitation functions for $\ensuremath{\alpha}$-emitting channels as compared to the PACE4 predictions has been observed and attributed to the incomplete fusion process. Further, the contribution from incomplete fusion process in the $^{14}\mathrm{N}+^{181}\mathrm{Ta}$ system has also been deduced in terms of strength function (${F}_{\mathrm{ICF}}$). The results have been discussed in terms of the parameters which influence the dynamics of ICF process. The ${F}_{\mathrm{ICF}}$ is found to depend strongly on projectile energies, the product of projectile and target charges, and $\ensuremath{\alpha}\ensuremath{-}Q$ value of the projectile.

Experimental consolidation and absolute measurement of the ^text {nat}C(p,x)^{11}C nuclear activation cross section at 100\xa0MeV for particle therapy physics

The ^text {nat}C(p,x)^{11}C reaction has been discussed in detail in the past [EXFOR database, Otuka et al. (Nuclear Data Sheets 120:272–276, 2014)]. However, measured activation cross sections by independent experiments are up to 15% apart. The aim of this study is to investigate underlying reasons for these observed discrepancies between different experiments and to determine a new consensus reference cross section at 100 MeV. Therefore, the experimental methods described in the two recent publications [Horst et al. (Phys Med Biol https://doi.org/10.1088/1361-6560/ab4511, 2019) and Bäcker et al. (Nuclear Instrum Methods Phys Res B 454:50–55, 2019)] are compared in detail and all experimental parameters are investigated for their impact on the results. For this purpose, a series of new experiments is performed. With the results of the experiments a new reference cross section of (68±3) mb is derived at (97±3) MeV proton energy. This value combined with the reliably measured excitation function could provide accurate cross section values for the energy region of proton therapy. Because of the well-known gamma-ray spectrometer used and the well-defined beam characteristics of the treatment machine at the proton therapy center, the experimental uncertainties on the absolute cross section could be reduced to 3%. Additionally, this setup is compared to the in-beam measurement setup from the second study presented in the literature (Horst et al. 2019). Another independent validation of the measurements is performed with a PET scanner.

Effect of neutron excess in the entrance channel on the O18+Nb93 system: An experimental study relevant to incomplete-fusion dynamics

The incomplete fusion dynamics in the $^{18}\mathrm{O}+^{93}\mathrm{Nb}$ system at energies above the Coulomb barrier has been investigated. The experimentally measured cross sections have been compared with the theoretical predictions of the statistical model code pace4. To examine the effect of entrance channel parameters on the onset and strength of incomplete fusion, relative contributions of complete and incomplete fusion have been deduced from the analysis of measured excitation functions. The contribution of incomplete fusion deduced from the analysis of excitation functions has been studied in terms of various entrance channel parameters, namely, entrance channel mass asymmetry (${\ensuremath{\mu}}_{A}$) of interacting projectile and target combination, Coulomb factor (${Z}_{P}{Z}_{T}$), ground state $\ensuremath{\alpha}\text{\ensuremath{-}}Q$ value of the reaction, and neutron skin thickness of target nuclei. It has been found that the probability of incomplete fusion depends strongly on entrance channel parameters. Further, the incomplete fusion contribution for the $^{18}\mathrm{O}$ projectile with two excess neutrons is noticed to be relatively larger as compared to $^{16}\mathrm{O}$. This may be due to the larger probability of breakup for the $^{18}\mathrm{O}$ projectile resulting in rather weak binding forces as compared to $^{16}\mathrm{O}$. The existence of incomplete fusion below critical angular momentum (${\ensuremath{\ell}}_{\mathrm{crit}}$), i.e., $\ensuremath{\ell}\ensuremath{\leqslant}\phantom{\rule{4pt}{0ex}}{\ensuremath{\ell}}_{\mathrm{crit}}$, has also been observed for the studied system.

Elliptic (v 2) and triangular (v 3) anisotropic flow of identified hadrons from the STAR Beam Energy Scan program

Elliptic (v 2) and triangular (v 3) anisotropic flow coefficients for inclusive and identified charged hadrons ( π ±, K ±, p, ) at midrapidity in Au+Au collisions, measured by the STAR experiment in the Beam Energy Scan (BES) at the Relativistic Heavy Ion Collider at , are presented. We observe that the triangular flow signal (v 3) of identified hadrons exhibits similar trends as first observed for v 2 in Au+Au collisions, i.e. (i) mass ordering at low transverse momenta, pT < 2 GeV/c, (ii) meson/baryon splitting at intermediate pT , 2 < pT < 4 GeV/c, and (iii) difference in flow signal of protons and antiprotons. New measurements of v3 excitation function could serve as constraints to test different models and to add new information about the temperature dependence of the transport properties of the strongly interacting matter.

Strong Resonances at High Excitation Energy in $${}^{\mathbf{17}}$$O $$+$$ Alpha Resonance Scattering

The Thick Target Inverse Kinematic (TTIK) approach was used to measure excitation functions for the elastic 17O ({\alpha}, {\alpha}) scattering at the initial 17O beam energy of 54.4 MeV. We observed strong peaks corresponding to highly excited {\alpha}-cluster states in the 21Ne excitation energy region of 8-16 MeV, which have never been investigated before. Additional tests were done at a 17O beam energy of 56.4 MeV to estimate a possible contribution of resonance inelastic scattering.

Investigation of the deuteron induced nuclear reaction cross sections on lutetium up to 50\xa0MeV: review of production routes for 177Lu, 175Hf and 172Hf via charged particle activation

In a systematic study of light charged particle induced nuclear reactions we investigated the excitation functions of deuteron induced nuclear reactions on natural lutetium targets. Experimental excitation functions up to 50 MeV on high purity natLu were determined using the standard stacked foil activation technique. High resolution off-line gamma-ray spectrometry was applied to assess the activity of each foil. From the measured activity direct and/or cumulative elemental cross-section data for production of 171,172,173,175Hf, 171,172,173,174g,176m,177m,177gLu and 169Yb radioisotopes were determined. The experimental data were compared to results of the TALYS theoretical code taken from the TENDL databases and results of our calculations using the ALICE-IPPE-D and the EMPIRE-D codes. No earlier experimental data were found in the literature. Thick target yields for the investigated radionuclides were calculated from the measured excitation functions.

Probing of incomplete fusion dynamics in $${}^{{14}}\text {N} + {}^{{124}}\text {Sn}$$ system and its correlation with various entrance channel effects

Measurements of excitation functions were done for the evaporation residues populated in $${}^{{14}}\text {N}+{}^{{124}}\text {Sn}$$ system at low energy. The present analysis shows the appearance of incomplete fusion by the breakup of non- $$\upalpha $$ cluster structured projectile $$^{{14}}\text {N}$$ into $$\upalpha + {}^{{10}}\text {B}$$ . A correlation between the combined effects of total asymmetry and $$\text {Z}_{\mathrm {P}}\text {Z}_{\mathrm {T}}$$ has been studied through three new parameters total asymmetry ( $$S_{{ TAS}}$$ ), Coulomb asymmetry parameters; $$Z_{P} Z_{T} /S_{{ TAS}} $$ and $$Z_{P} Z_{T} .S_{{ TAS}} $$ . These new parameters were found more sensitive and effective to encounter the combined effects of coulomb interactions and entire asymmetry effect of the system on incomplete fusion dynamics. The complete fusion and total fusion cross-sections of two systems $${}^{{14}}\text {N}+{}^{{124}}\text {Sn}$$ and $${}^{{16}}\text {O}+{}^{124}\text {Sn}$$ have been reduced using two different standard reduction procedures, which shows that the incomplete fusion probability for reactions induced by projectile $${}^{{16}}\text {O}$$ is generally larger than $${}^{{14}}\text {N}$$ induced reactions. The experimental fusion functions are found to be suppressed as compared to universal fusion function for systems $${}^{{14}}\text {N}+{}^{{124}}\text {Sn}$$ and $${}^{{16}}\text {O}+{}^{{124}}\text {Sn}$$ . The different values of suppression factor for projectiles $${}^{{14}}\text {N}$$ and $${}^{{16}}\text {O}$$ indicate that the probability of $$\upalpha $$ -breakup is different for these projectiles. Further, the total fusion functions for systems $${}^{{14}}\text {N}+{}^{{124}}\text {Sn}$$ and $${}^{{16}}\text {O}+{}^{{124}}\text {Sn}$$ agree well with the universal fusion function. However, the present results clearly show that the shell closure of nuclei also affect the low energy incomplete fusion dynamics along with the structure of projectile.

Excitation functions for proton-induced reactions on Te and natTi targets: Measurements and model calculations special relevant to the 128Te(p,n)128I reaction

The excitation functions for the natTe(p,x)121,123,124,126,128,130I, 128Te(p,n)128I, natTi(p,x)48V and 43,44g,47Sc reactions were measured for proton energies ranging from about 14 MeV down to threshold energy for each reaction. Stacked foils combined with gamma ray spectroscopy techniques were used. Te targets were prepared using electrodeposition method, while Ti targets are thin foils with high purity. Theoretical codes calculation, TALYS-1.9 and EMPIRE-3.2.3 results are compared with the measured excitation functions.

Production cross sections of thulium radioisotopes for alpha-particle induced reactions on holmium

The production cross sections of 165–168Tm radioisotopes produced in α-particle induced reactions on 165Ho were measured from 49.6 MeV down to the respective thresholds using the stacked-foil activation technique and HPGe gamma-ray spectrometry. The measured excitation functions were compared with previous measurements as well as the TENDL-2019 library. We also calculated the thick target yields for all the assessed radioisotopes by integration of the measured excitation functions and found that they show good agreement with the directly measured thick target yields except for 168Tm production.

Search for the high-spin members of the α:2n:α band in Be10

Method: Measuring excitation functions for $^{6}$He+$\alpha$ scattering, populating states in the excitation energy range from 4.5 MeV to 8 MeV in $^{10}$Be using a $^6$He rare-isotope beam and a thick helium gas target. Results: No new excited states in $^{10}$Be have been observed. Stringent limitation on the possible degree of $\alpha$-clustering of the hypothetical yrast 6$^+$ state has been obtained. Conclusions: The high-spin members of the $\alpha$:2n:$\alpha$ molecular-like rotational band configuration, that is considered to have a 0$^+$ bandhead at 6.18 MeV, either do not exist or have small overlap with the $^{6}$He(g.s.)+$\alpha$ channel.

Preequilibrium strength in light heavy-ion induced reactions up to 7 MeV/nucleon

The crux of this article is to analyze the contribution of the preequilibrium reaction process to the production of residues in the low energy heavy-ion reactions. The production cross-sections of a few radionuclides produced through the 3n-emission channel have been measured from the 7Li-, 11B- and 12C-induced reactions in the 89Y and 93Nb targets within the energy range of ∼2.4–6.4 MeV/nucleon. The measured excitation functions have been analyzed by comparing them with the statistical nuclear reaction models, based on the equilibrium and preequilibrium reaction mechanisms, in the framework of ALICE91 and EMPIRE3.2.2. The result shows that the mixing of equilibrium and preequilibrium emission of light or cluster particles is essential for the better reproduction of the measured cross-section data. Variation of the preequilibrium fractions with derived energy parameters has also been demonstrated.

Measurement of residual cross sections in the Li7+Y89 reaction up to 5.7 MeV/nucleon and analysis of fusion mechanisms

Different modes of fusion phenomena observed in the isolated experiments are not yet fully understood. To comprehend these fusion mechanisms, more experimental studies are necessary. In view of this, a new measurement of residual cross sections from the $^{7}\mathrm{Li}$-induced reaction on $^{89}\mathrm{Y}$ has been reported in this article within the 2.7--5.7 MeV/nucleon energy range. The $\ensuremath{\gamma}$-ray spectrometry has been used to identify the residues $^{93m}\mathrm{Mo}, ^{92m}\mathrm{Nb}, ^{89}\mathrm{Zr}, ^{91m}\mathrm{Y}$, and $^{90m}\mathrm{Y}$ produced in the reaction. A systematic analysis of the complete and incomplete fusion dynamics has been carried out by comparing the measured excitation functions with the equilibrium and pre-equilibrium reaction models in the framework of empire3.2.2 and alice19. A strong indication of the occurrence of incomplete fusion has been realized within the energy range considered; hence the incomplete fusion strength is discussed in detail. The product yield of $^{93m}\mathrm{Mo}$, which is a candidate radionuclide for radiopharmaceuticals, has been estimated.

Comparative study and TALYS 1.6 code calculations for the excitation functions of P and α-induced reactions on Bi target with special attention to the medical radioisotope 211At

The induced reactions by light ions such as protons, deuterons, 3He and α-particles on 209Bi, as the heaviest stable isotope in the periodic table, are important for the production of heavy radioactive isotopes. These radioactive isotopes are mainly α-emitters and could be used in cancer therapy. In this study, 209Bi(p,2n)208Po, 209Bi(p,3n)207Po, 209Bi(p,4n)206Po and 209Bi(p,5n)205Po reactions were studied by collecting the previously measured excitation functions, holding an inter-comparison and performing code calculations using the TALYS 1.6 code. As a result of the inter-comparison, mathematical fit for each reaction was given. α-induced reactions on 209Bi target leading to the formation of 210,211At and 210Po radioisotope were also studied through this work. The production of 211At without considerable isotopic 210At impurities was discussed. The previously measured excitation functions were fitted as before, and TALYS 1.6 code calculation was performed. The code calculations were compared with the mathematical fitted excitation functions.

Measurements of production cross-sections of medical radioisotopes (57Ni, 55,57,58Co, 54Mn, 51Cr) and other by-products (56Ni, 56Co, 56Mn) from the 59Co(p,x) reactions

We studied the excitation functions of 59Co(p,x) reactions and measured the production cross-sections of medical radioisotopes (57Ni, 55,57,58Co, 54Mn, 51Cr) and other by-products (56Ni, 56Co, 56Mn) from their threshold to a proton energy of 43.7 MeV. The stacked-foil activation method was employed to irradiate the samples with an external beam from the MC-50 cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS), Korea. Off-line γ-ray spectrometry was used to measure the activities of the produced radionuclides. The integral yields for the thick target of the investigated radionuclides were also calculated from the measured excitation functions. The measured results were compared with the literature data as well as with theoretical values obtained from the TENDL-2017 library based on the TALYS-1.9 code.

Systematic study of incomplete fusion reactions: Role of various entrance channel parameters

The evaporation residues, populated through complete and incomplete fusion processes in the reaction of 18O+ 165Ho, have been analyzed via excitation function measurements at projectile energies ≈ 4-7 MeV/nucleon. The cross-sections measured experimentally have been compared with the predictions of the compound nucleus model code PACE-4 calculations which only considers complete fusion (CF) reaction cross-sections. The experimental cross-section of the reaction residues populated through xn and pxn channels matches well with the theoretical model code PACE-4 predictions. On the other hand, α-emitting channels show an enhancement in the measured cross-section over PACE-4 calculations which reveals the occurrence of incomplete fusion (ICF) at the studied energy range. The relative percentage of incomplete fusion has been calculated from the experimental data and its dependence on various entrance channel parameters like projectile energy, mass-asymmetry, α-Q value and Coulomb factor (ZPZT) has been studied. The strength of incomplete fusion function obtained in the 18O+ 165Ho interaction has been compared with the previously studied systems. Results of the present study indicate that 18O (two neutron excess) projectile shows more incomplete fusion contribution as compared to 12C,13C and 16O projectiles due to its relatively small negative α-Q value.

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

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

Measurements of the excitation functions of radon and astatine isotopes from 7Li-induced reactions with 209Bi for development of a 211Rn–211At generator

We have measured excitation functions of 209Bi(7Li, 5n)211Rn, 209Bi(7Li, 6n)210Rn, and other reactions, with the aim of realizing a 211Rn/211At generator for cancer therapy. On the basis of a comparison with theoretical predictions, we found that nuclides of 210At are produced via a break-up process rather than from the 209Bi(7Li, p5n)210At reaction. The excitation functions obtained in this study provide the most favorable conditions for 211Rn production in terms of available radioactivity and nuclide purity of the irradiated material.

Study of Complete and Incomplete Fusion Reaction in the Interaction of 12C+ 128 Te and 14N + 128 Te system below 7 MeV/A.

In this paper, an attempt was made to measure the excitation function for the disappearance residues recognized in the interaction of 12 C+ 128 Te and 14 N + 128 Te system with the observation to investigating the complete and incomplete fusion reaction dynamics in heavy ion induced reaction. The incentive of this study was break up of 12 C and 14 N in reaction below 7MeV/A and associate the excitation function for 12 C and 14 N with the same target 128 Te prominent different compound system. PACE-4 were used for analysis of the system, and the measured excitation functions for precise decay channel in two case i.e. ( 12 C+ 128 Te and 14 N + 128 Te) have been associated and established in Bohr assumption in case of complete fusion channels. The properties of coulomb barrier and other entrance channel parameters were established to be relatively significant in decisive the decay mode of composite system. Additionally the incomplete fusion dynamics were also perceived to be of significant importance in present energy section. Keywords : Complete Fusion, Incomplete fusion, non-α-emitting, α-emitting DOI : 10.7176/APTA/81-01 Publication date: December 31 st 2019

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

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