First proof-of-principle experiment with the post-accelerated isotope separator on-line beam at BRIF:measurement of the angular distribution of ^(23)Na+^(40)Ca elastic scattering

The reaction dynamics of exotic nuclei near the drip line is one of the main research topics of current interest.Elastic scattering is a useful probe for investigating the size and surface diffuseness of exotic nuclei.The development of rare isotope accelerators offers opportunities for such studies.To date,many relevant measurements have been performed at accelerators using the projectile fragmentation technique,while the measurements at accelerators using isotope separator on-line(ISOL)systems are still quite scarce.In this work,we present the first proof-of-principle experiment with a post-accelerated ISOL beam at the Beijing Radioactive Ion Beam Facility(BRIF)by measuring the angular distribution of elastic scattering for the stable nucleus^(23)Na from the doubly magic nucleus^(40)Ca at energies above the Coulomb barrier.The angular distribution measured by a silicon strip detector array in a scattering chamber using the ISOL beam at BRIF is in good agreement with that measured by the high-precision Q3 D magnetic spectrograph using the nonISOL beam at nearly the same energy.This work provides useful background for making BRIF a powerful tool for the investigation of the reaction dynamics of exotic nuclei.

Compact 16-channel integrated charge-sensitive preamplifier module for silicon strip detectors

In this study,a compact 16-channel integrated charge-sensitive preamplifier named the smart preamplifier(SPA)was developed to support the large-scale detector array used in modern nuclear physics experiments.Two types of SPA,namely SPA02 and SPA03(with external field effect transistor),have been manufactured to match silicon detectors with small and large capacitances,respectively.The characteristics of the SPA include fast response of typically less than 6 ns for pulse rising time and low equivalent noise of 1.5 keV at zero input capacitance.The energy sensitivity and pulse decay time can be easily adjusted by changing the feedback capacitance Cfand resistance Rfin various applications.A good energy resolution of 24.4 keV for 5.803-MeV alpha particles from 244 Cm was achieved using a small-sized Si-PIN detector;for the silicon strip detectors in the test with the alpha source,a typical energy resolution of 0.6–0.8%was achieved.The integrated SPA has been employed in several experiments of silicon strip detectors with hundreds of channels,and a good performance has been realized.

Positive Q-Value Neutron Transfer Mediated Sub-Barrier Fusion Reactions

Positive Q-value neutron transfer mediated sub-barrier fusion reactions are studied with an empirical coupled channels model, which takes into account neutron rearrangement related only to the dynamical matching condition with no free parameters. Fusion cross sections of collision systems ^32S＋^90,94,96Zr are calculated and analyzed. Logarithmic residual enhancement （LRE） is proposed to evaluate the discrepancy between calculated results and experimental data. The experimental data can be described well with this model for the first time as a whole, while the LRE analysis shows that there are still theoretical systematic deviations.

Systematic extraction of the strong absorption distance and Coulomb barrier from elastic scattering

The reduced strong absorption distance d_(S) and Coulomb barrier height V_(B) are extracted from the quarter-point recipe from a series of experimental elastic scattering angle distributions.The nuclei with different binding energies are systematically studied as the projectile,including the tightly bound,weakly bound,and halo nuclei.It is found that the mean d_(S) for halo nuclei is significantly larger than that of tightly and weakly bound nuclei.The complex behavior of d_(S) regarding the binding energy and properties of the target is observed for halo nuclei.The linear relationship of the reduced distance with system size may be used to estimate the Coulomb barrier radius R_(B),which is difficult to obtain from fusion reactions.The rule of V_(B) concerning the Coulomb parameter z is in agreement with other theoretical barrier laws extracted from the fusion reaction.Furthermore,the reason why the binding energy or deformation has little effect on the linear relationship of V_(B) as a function of z is clarified.

Bayesian analysis on non-resonant behavior of 12C+12C fusion reaction at sub-barrier energies

Controversies exist among experiments and theories on the S^(*)factor of the astrophysical important reaction ^(12)C+^(12)C for energies below 3 MeV.Only frequentist approaches have been used so far for data analysis,and the confidence levels or theoretical errors are not available from previous theoretical predictions.In this study,the Bayesian method is employed to provide theoretical predictions and its 1σconfidence level based on all the currently available experimental data for the first time.The improved coupled-channels model CCFULL-FEM implemented with the finite element method as well as the Markov chain Monte Carlo approach emcee are adopted to analyze the non-resonant behavior of this reaction.The posterior distribution of the Woods-Saxon potential parameters is investigated.Compared with the widely used frequentist method MIGRAD within the Minuit minimization program,the Bayesian method has a significant advantage for exploring the potential parameter space.When the existing experimental data measured down to subbarrier energies are considered,the potential parameters are constrained to a very narrow range,and the predictions of the S^(*) factor showed no sharp decrease in the low-energy region.

Relative probabilities of breakup channels in reactions of^(6.7)Li with^(209)Biat energies around and above the Coulomb barrier

Coincidence measurements of breakup fragments in reactions of^(6.7)with^(209)Bi at energies around and above the Coulomb barrier were carried out using a large solid-angle covered detector array.Through the Q values along with the relative energies of the breakup fragments,different breakup components(prompt breakups and delayed breakups)and different breakup modes(α+t,α+d,α+p,andα+α)are distinguished.A new breakup mode,α+t,is observed in^(6)Li-induced reactions at energies above the Coulomb barrier.Correlations between breakup modes and breakup components as well as their variations with the incident energy are investigated.The results will help us better understand the breakup effects of weakly bound nuclei on the suppression of a complete fusion,particularly for the above-barrier energies.

Fully self-consistent calculation ofβ-decay half-lives within Skyrme energy density functional

β-decay half-lives of some magic and semi-magic nuclei have been studied in a fully self-consistent Skyrme Hartree-Fock(HF) plus charge-exchange random phase approximation(RPA).The self-consistency is addressed,in that the same Skyrme energy density functional is adopted in the calculation of ground states and Gamow-Teller excited states.First,the impact of J2 terms on the β-decay half-lives is investigated by using the SGII interaction,revealing a large influence.Subsequently,numerical calculations are performed for the selected nuclei with Skyrme energy density functionals SGII,LNS,SKX,and SAMi.Finally,comparisons to available experimental data and predictions of different theoretical models are discussed.