Reactions In Inverse Kinematics Research Articles

Evolution of the nuclear spin-orbit splitting explored via the 32Si(d,p)33Si reaction using SOLARIS

The spin-orbit splitting between neutron 1p orbitals at 33Si has been deduced using the single-neutron-adding (d,p) reaction in inverse kinematics with a beam of 32Si, a long-lived radioisotope. Reaction products were analyzed by the newly implemented SOLARIS spectrometer at the reaccelerated-beam facility at the National Superconducting Cyclotron Laboratory. The measurements show reasonable agreement with shell-model calculations that incorporate modern cross-shell interactions, but they contradict the prediction of proton density depletion based on relativistic mean-field theory. The evolution of the neutron 1p-shell orbitals is systematically studied using the present and existing data in the isotonic chains of N=17, 19, and 21. In each case, a smooth decrease in the separation of the 1p3/2-1p1/2 orbitals is seen as the respective p-orbitals approach zero binding, suggesting that the finite nuclear potential strongly influences the evolution of nuclear structure in this region.

On the kinematics of (p, pX) knockout reactions in normal and inverse kinematics

Abstract The kinematics of (p, pX) knockout reactions is overviewed. Consistent descriptions of the kinematical quantities for normal and inverse kinematics are given. Starting from the kinematics of p-X elastic scatterings, which are elementary processes of the (p, pX) knockout reactions, effects of the separation energy of the knocked-out particle SX, its in-nucleus momentum $\vec{k}_{F}$, and a momentum transfer q are investigated. The three quantities are called “knockout feature quantities” in this article. The main conclusions are: SX dependences of the (p, pX) kinematics are mainly through changes in the p-X center-of-momentum energy $\sqrt{s_{pX}}$ for which no difference exists between normal and inverse kinematics. Effects of longitudinal-to-the-beam component of $\vec{k}_{F}$ cause a significant difference between normal and inverse kinematics through changes in βpX and $\sqrt{s_{pX}}$. On the other hand, the transverse-to-the-beam component of $\vec{k}_{F}$ changes energy sharing between the scattered proton and the knocked-out particle in both normal and inverse kinematics.

Neutron capture reaction cross-section of 79Se through the 79Se(d,p) reaction in inverse kinematics

γ emission probabilities from unbound states in 78,80Se, populated by a neutron-transfer reaction (d,p) on 77,79Se nuclei in inverse kinematics, were measured by directly detecting reaction residues. Assuming the spin distribution at the respective excitation energy of the unbound state, the cross-sections of the 79Se(n,γ)80Se reaction were evaluated using the γ emission probabilities. The surrogate-ratio method with the experimental γ emission probabilities of 78,80Se was also employed to deduce the cross-sections of 79Se(n,γ) reaction by incorporating the theoretical evaluations of the neutron-capture reaction on the isomeric state in 77Se. Our two cross-sections are in good agreement with existing nuclear data compilations for the neutron-capture reaction on 79Se. The presented method contributes to the body of existing knowledge by providing approaches for determining the neutron capture cross-sections of radioactive nuclei at various neutron energies.

Complete kinematics studies of fission reactions induced by quasi-free nucleon scattering collisions

Measurements of spallation, fragmentation and Coulomb-induced fission reactions in inverse kinematics have provided valuable data in the last decades to accurately investigate the fission dynamics and nuclear structure at large deformations of a large variety of stable and non-stable heavy nuclei. To go further, quasi-free scattering (QFS) reactions in inverse kinematics are proposed as a new surrogate method to induce fission, which allows to reconstruct the excitation energy of compound fissioning systems by using the four-momenta of the two outgoing nucleons. This new approach would permit therefore to correlate the excitation energy with the charge and mass distributions of the fission fragments and with the fission probabilities, given for the first time direct access to the simultaneous measurement of the fission yield dependence on temperature and fission barrier heights of exotic heavy nuclei, respectively. The first experiment based on this approach was recently performed at the GSI/FAIR facility and a description of the methodology based on model calculations is given here.

Pikoe: A computer program for distorted-wave impulse approximation calculation for proton induced nucleon knockout reactions

pikoe, Proton-Induced KnockOut reaction calculation for Exclusive processes, is a Fortran 90 program that calculates triple- and quadruple-differential cross sections, vector analyzing powers, and momentum distributions of reaction residues, for proton-induced nucleon knockout reactions in normal and inverse kinematics. The distorted-wave impulse approximation with the factorization approximation to the nucleon-nucleon transition matrix is adopted, and the distorted waves of the incoming proton and the outgoing two nucleons are calculated quantum mechanically. Kinematics of the reaction particles are treated in a relativistic manner, which gives the proper asymptotics of the three-body scattering wave in the plane-wave limit. Program summaryProgram Title: pikoeCPC Library link to program files:https://doi.org/10.17632/m594h58kck.1Licensing provisions: MITProgramming language: Fortran 90Supplementary material: See https://www.rcnp.osaka-u.ac.jp/~kazuyuki/pikoe/index.phpNature of problem: Calculation of triple- and quadruple-differential cross sections, vector analyzing powers, and momentum distributions of reaction residues, for nucleon knockout reactions with proton beams/targets in normal/inverse kinematics.Solution method: Numerov method for solving single-channel second-order differential equations; multi dimensional integration with the Gauss-Legendre quadrature rule.Additional comments including restrictions and unusual features: The global optical potential by Koning and Deraloche [1] for nucleons at energies from 1 keV to 200 MeV, for (near-)spherical nuclei with mass number between 24 and 209, is implemented in the program. Tables of nucleon-nucleon (NN) elastic differential cross sections and NN transition amplitudes calculated with the NN effective interaction by Franey and Love [2] are provided as external files for pikoe (included in the package). Users are encouraged to prepare tables for the optical potentials and the cross sections of the elementary process according to the reaction system of interest by themselves. With external files thus prepared, pikoe can be applied to various kinds of knockout processes such as α or deuteron knockout by proton, α-induced knockout reactions, etc. Calculation of spin observables, the vector analyzing power in fact, however, is restricted to nucleon-induced nucleon knockout processes with the coplanar kinematics.

BlueSTEAl: A pair of silicon arrays and a zero-degree phoswich detector for studies of scattering and reactions in inverse kinematics

BlueSTEAl, the Blue (aluminum chamber of) Silicon TElescope Arrays for light nuclei, has been developed to study direct reactions in inverse kinematics, as well as scattering and breakup reactions using radioactive ion beams. It is a detector system consisting of a pair of annular silicon detector arrays and a zero-degree phoswich plastic scintillator. For typical binary reaction studies in inverse kinematics, light ions are detected by the Si array in coincidence with heavy recoils detected by the phoswich placed at the focal-plane of a zero-degree magnetic spectrometer. The Si array can also be used to detect light nuclei such as beryllium and carbon with clear isotope separation, while the phoswich can also be placed at zero degrees without a spectrometer and used as a high-efficiency beam counting monitor with particle identification capability at the rate of up to ∼5 × 104 particles per second. This paper reports on the capabilities of BlueSTEAl as determined by recent experiments performed at the Texas A&M Cyclotron Institute. The device is also anticipated to be used in future experiments at other radioactive ion beam facilities.

Status of experimental knowledge on the unbound nucleus 13Be

The structure of the unbound nucleus 13Be is important for understanding the Borromean, two-neutron halo nucleus 14Be. The experimental studies conducted over the last four decades are reviewed in the context of the beryllium chain of isotopes and some significant theoretical studies. The focus of this paper is the comparison of new data from a 12Be(d,p) reaction in inverse kinematics, which was analyzed using Geant4 simulations and a Bayesian fitting procedure, with previous measurements. Two possible scenarios to explain the strength below 1 MeV above the neutron separation energy were proposed in that study: a single p-wave resonance or a mixture of an s-wave virtual state with a weaker p- or d-wave resonance. Comparisons of recent invariant mass and the (d,p) experiments show good agreement between the transfer measurement and the two most recent high-energy nucleon removal measurements.

Determining neutron-induced reaction cross sections through surrogate reactions at storage rings

Determining the cross sections of neutron-induced reactions on short-lived nuclei is imperative to rate calculations in stellar nucleosynthesis and applications of nuclear physics. It is also an immense experimental challenge due to the radioactivity of the targets involved. Our goal is to circumvent this obstacle by using surrogate reactions in inverse kinematics at the heavy-ion storage rings of GSI/FAIR. We present here preliminary results from the first proof of principle experiment, where a beam of 208Pb impinged on a H2 gas jet target in the Experimental Storage Ring (ESR).

Skin values and matter radii of 208Pb and 58,60,64Ni based on reaction cross section of 3,4He scattering

Background:The PREX group reported a new skin value, rskin208(PREX2)=0.283±0.071=0.212∼0.354fm. Using the chiral (Kyushu) g-matrix folding model with the proton and neutron densities determined with D1S+GHFB+AMP, we determined neutron skin thickness rskin208(exp)=0.278±0.035 fm from reaction cross sections σR(exp) of p+208Pb scattering, where D1S-GHFB+AMP denotes Gogny-D1S HFB with angular momentum projection (AMP). The method also yielded rskin208(exp)=0.416±0.146 from σR(exp) of 4He+208Pb scattering. In our previous work, we accumulated the 206 EoSs and determined a sloop parameter L=76∼165MeV from the 206 EoSs. The value of L yields rskin208=0.102∼0.354fm. As for 58Ni, a novel method for measuring nuclear reactions in inverse kinematics with stored ion beams was successfully used to extract matter radii rm of 58Ni at the GSI facility. Purpose:As the first aim, we first determine rskin208(exp) from σR(exp) of 3He scattering on 208Pb target and take the weighted mean and its error for rskin208(PREX2), three skin values of p+208Pb, 3,4He+208Pb scattering and rskin208=0.102∼0.354fm based on the 206 EoSs. As the second aim, we determine matter radii rm(exp) of 58,60,64Ni from σR(exp) of 3,4He scattering on 58,60,64Ni targets. Results:Our result is rskin208(exp)=0.512±0.268fm for 3He+208Pb scattering. Our results based on 4He+58,60,64Ni scattering are rm58(exp)=3.734±0.091 fm, rm60(exp)=3.815±0.094 fm, rm64(exp)=4.001±0.093 fm. Our results based on 3He+58,60,64Ni scattering are rm58(exp)=3.709±0.098 fm, rm60(exp)=3.753±0.112 fm, rm64(exp)=3.822±0.142 fm. Conclusion:Our conclusion is rskin208=0.285±0.030fm. It is determined from the 5 skin values mentioned above.

Enhancing the performance of solenoidal spectrometers for inverse reactions

Helical-orbit solenoidal spectrometers, in which the target and detector are placed inside a uniform magnetic field, have been utilized for more than a decade to study nuclear reactions in inverse kinematics, induced by radioactive beams. Methods to improve the final-state energy resolution are presented, and the inclusion of an active gas target is proposed to improve the performance of the spectrometer.

Simulations and analysis tools for charge-exchange (d, 2He) reactions in inverse kinematics with the AT-TPC

Charge-exchange (d,2He) reactions in inverse kinematics at intermediate energies are a very promising method to investigate the Gamow–Teller transition strength in unstable nuclei. A simulation and analysis software based on the attpcroot package was developed to study this type of reactions with the active-target time projection chamber (AT-TPC). The simulation routines provide a realistic detector response that can be used to understand and benchmark experimental data. Analysis tools and correction routines can be developed and tested from simulations in attpcroot, because they are processed in the same way as the real data. In particular, we study the feasibility of using coincidences with beam-like particles to unambiguously identify the (d,2He) reaction channel, and to develop a kinematic fitting routine for future applications. More technically, the impact of space-charge effects in the track reconstruction, and a possible correction method are investigated in detail. This analysis and simulation package constitutes an essential part of the software development for the fast-beams program with the AT-TPC.

Cross sections of the Rb83(p,γ)Sr84 and Kr84(p,γ)Rb85 reactions at energies characteristic of the astrophysical γ process

We have measured the cross section of the $^{83}\mathrm{Rb}(p,\ensuremath{\gamma})^{84}\mathrm{Sr}$ radiative capture reaction in inverse kinematics using a radioactive beam of $^{83}\mathrm{Rb}$ at incident energies of 2.4 and $2.7\phantom{\rule{0.16em}{0ex}}A$ MeV. Prior to the radioactive beam measurement, the $^{84}\mathrm{Kr}(p,\ensuremath{\gamma})^{85}\mathrm{Rb}$ radiative capture reaction was measured in inverse kinematics using a stable beam of $^{84}\mathrm{Kr}$ at an incident energy of $2.7A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\ensuremath{\gamma}$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17--0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{84}\mathrm{Sr}$, caused by the reduced rate of the $^{84}\mathrm{Sr}(\ensuremath{\gamma},p)^{83}\mathrm{Rb}$ reaction derived from the present measurement.

Apparent temperatures of neutron-poor and neutron-rich compound nuclei

The possibility of the dependence of the nuclear caloric curve on neutron excess sets a limit on the accuracy of our knowledge of the nuclear equation of state, and thus impacts predictive capabilities of nuclear reaction and nuclear astrophysics models. To date, theoretical models have not reached consensus on the magnitude or sign on the asymmetry dependence. To provide constraints, we have measured evaporated particles and heavy residues for complete and incomplete fusion-evaporation reactions in inverse kinematics. The temperatures extracted from the observed light charged particles tend to favor higher temperatures for the neutron-rich fused systems, though they are near the limits of the systematic uncertainty. The present measurement may be used as an upper limit to constrain the asymmetry dependence of the nuclear caloric curve.

Comprehensive investigation of fission yields by using spallation- and (p,2p)- induced fission reactions in inverse kinematics

In the last decades, measurements of spallation, fragmentation and Coulex induced fission reactions in inverse kinematics have provided valuable data to accurately investigate the fission dynamics and nuclear structure at large deformations of a large variety of stable and non-stable heavy nuclei. To go a step further, we propose now to induce fission by the use of quasi-free (p,2p) scattering reactions in inverse kinematics, which allows us to reconstruct the excitation energy of the compound fissioning system by using the four-momenta of the two outgoing protons. Therefore, this new approach might permit to correlate the excitation energy with the charge and mass distributions of the fission fragments and with the fission probabilities, given for the first time direct access to the simultaneous measurement of the fission yield dependence on temperature and fission barrier heights of exotic heavy nuclei, respectively. The first experiment based on this methodology was realized recently at the GSI/FAIR facility and a detailed description of the experimental setup is given here.

Study of (p,2p) fission reactions in inverse kinematics using the R3B set-up

A new experimental fission approach is presented in the context of the R3B (Reactions with Relativistic Radioactive Beams) collaboration, at the GSI/FAIR facility, in which knockout reactions in inverse kinematics are used to induce fission of 238U that will allow to characterise the excitation energy of the fission process and all the fission products. The CALIFA (CALorimeter for In-Flight detection of γ-rays and high energy charged pArticles) calorimeter, a key part of the R3B set-up, is used to reconstruct the momenta of the two protons from the (p, 2p) reactions. Preliminary results show that kinematic variables and first estimates for nucleon-removal cross sections are well reconstructed and in good agreement with other experimental measurements.

Proton capture on stored radioactive 118Te ions

Experimental determination of the cross sections of proton capture on radioactive nuclei is extremely difficult. Therefore, it is of substantial interest for the understanding of the production of the p-nuclei. For the first time, a direct measurement of proton-capture cross sections on stored, radioactive ions became possible in an energy range of interest for nuclear astrophysics. The experiment was performed at the Experimental Storage Ring (ESR) at GSI by making use of a sensitive method to measure (p,γ) and (p,n) reactions in inverse kinematics. These reaction channels are of high relevance for the nucleosyn-thesis processes in supernovae, which are among the most violent explosions in the universe and are not yet well understood. The cross section of the 118Te(p,γ) reaction has been measured at energies of 6 MeV/u and 7 MeV/u. The heavy ions interacted with a hydrogen gas jet target. The radiative recombination process of the fully stripped 118Te ions and electrons from the hydrogen target was used as a luminosity monitor. An overview of the experimental method and preliminary results from the ongoing analysis will be presented.

Fragmentation-induced fission reactions of 236U in inverse kinematics to investigate the pre-fragment angular momentum parameterizations

In the last decades, measurements of spallation, fragmentation and Coulex induced fission reactions in inverse kinematics have provided valuable data to accurately investigate the fission dynamics and nuclear structure at large deformations of a large variety of stable and non-stable heavy nuclei. The collected data were used to constrain dynamic and nuclear structure parameters of different de-excitation models, such as ABLA and GEF, but the data can also be used to constrain the parameterizations describing the pre-fragment properties after the nuclear collision, such as the angular momentum gained by the pre-fragment. In this work, the fissioning system yields are compared to calculations assuming different parameterizations for modeling the angular momentum gained by the compound nuclei. Our findings indicate that the parameterizations utilized by abrasion models clearly underestimate the angular momentum, resulting in the underestimation of the production of lighter fissioning systems.

Direct measurement of the 26Si(α, p)29P reaction at CRIB for the nucleosynthesis in the X-ray bursts

Several (α, p) reactions with radioactive-ions (RI) in the αp-process are important to characterize X-ray bursts. However, some of them do not have sufficient experimental data, and the 26Si(α, p)29P reaction is one of such reactions. We performed a direct measurement of the reaction in inverse kinematics with a thick target at the CNS RI beam separator (CRIB).We used a multiplexer circuit, Mesytec MUX, to acquire data from many channels of silicon detectors. In this experimental setup, a resonant elastic scattering was measured simultaneously. The details of the experimental conditions and the preliminary results of the analysis are discussed.

Neutron-proton pairing in the N=Z radioactive fp-shell nuclei 56Ni and 52Fe probed by pair transfer

The isovector and isoscalar components of neutron-proton pairing are investigated in the N=Z unstable nuclei of the fp-shell through the two-nucleon transfer reaction (p,3He) in inverse kinematics. The combination of particle and gamma-ray detection with radioactive beams of 56Ni and 52Fe, produced by fragmentation at the GANIL/LISE facility, made it possible to carry out this study for the first time in a closed and an open-shell nucleus in the fp-shell. The transfer cross-sections for ground-state to ground-state (J=0+, T=1) and to the first (J=1+, T=0) state were extracted for both cases together with the transfer cross-section ratios σ(0+,T=1)/σ(1+,T=0). They are compared with second-order distorted-wave born approximation (DWBA) calculations. The enhancement of the ground-state to ground-state pair transfer cross-section close to mid-shell, in 52Fe, points towards a superfluid phase in the isovector channel. For the “deuteron-like” transfer, very low cross-sections to the first (J=1+, T=0) state were observed both for 56Ni(p,3He) and 52Fe(p,3He) and are related to a strong hindrance of this channel due to spin-orbit effect. No evidence for an isoscalar deuteron-like condensate is observed.

In-flight production of an isomeric beam of 16N

An in-flight beam of 16N was produced via the single-neutron adding (d,p) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the 16N beam which resided in its excited 0.120 MeV Jπ=0− isomeric state (T1/2≈5 μs) was determined to be 40(5)% at a reaction energy of 7.9(3) MeV/u, and 24(2)% at a reaction energy of 13.2(2) MeV/u. The isomer measurements took place at an experimental station ≈30 m downstream of the production target and utilized an Al beam-stopping foil and a HPGe Clover detector. Composite 16N beam rate determinations were made at the experimental station and the focal plane of the Argonne in-flight radioactive ion-beam separator (RAISOR) with Si ΔE-E telescopes. A Distorted Wave Born Approximation (DWBA) approach was coupled with the known spectroscopic information on 16N in order to estimate the relative 16N isomer yields and composite 16N beam rates. In addition to the observed reaction-energy dependence of the isomer fraction, a large sensitivity to the angular acceptance of the recoils was also observed.