International Journal of Modern Physics E

The Facility for Rare Isotope Beams (FRIB) Project has entered the phase of beam commissioning starting from the room-temperature front end and the superconducting linac segment of first 15 cryomodules. With the newly commissioned helium refrigeration system supplying 4.5K liquid helium to the quarter-wave resonators and solenoids, the FRIB accelerator team achieved the sectional key performance parameters as designed ahead of schedule accelerating heavy ion beams above 20MeV/u energy. Thus, FRIB accelerator becomes world’s highest-energy heavy ion linear accelerator. We also validated machine protection and personnel protection systems that will be crucial to the next phase of commissioning. FRIB is on track towards a national user facility at the power frontier with a beam power two orders of magnitude higher than operating heavy-ion facilities. This paper summarizes the status of accelerator design, technology development, construction, commissioning as well as path to operations and upgrades.

We have studied the proton capture reaction ${}^3\mathrm{\text{H}}{(p,\gamma )}^4\mathrm{\text{He}}$. It plays a role in the nucleosynthesis of primordial elements in the early Universe leading to the prestellar formation of ${}^4\mathrm{\text{He}}$ nuclei. All results of our researches and more new data from works show that the contribution of the ${}^3\mathrm{\text{H}}{(p,\gamma )}^4\mathrm{\text{He}}$ capture reaction into the processes of primordial nucleosynthesis is relatively small. However, it makes sense to consider this process for making the picture complete for the formation of prestellar ${}^4\mathrm{\text{He}}$ and clearing of mechanisms of this reaction. Furthermore, we have considered the ${}^3\mathrm{\text{He}}{{(}^2\mathrm{\text{H}},\gamma )}^5\mathrm{\text{Li}}$ reaction in the low energy. This reaction also forms part of the nucleosynthesis chain of the processes occurring in the early stages of formation of stable stars. They are possible candidates for overcoming the well-known problem of the $A=5$ gap in the synthesis of light elements in the primordial Universe. Continuing the study, we have considered the radiative capture ${}^4\mathrm{\text{He}}{{(}^3\mathrm{\text{He}},\gamma )}^7\mathrm{\text{Be}}$ at superlow energies, which has a undeniable interest for nuclear astrophysics, since it takes part in the proton–proton fusion chain, and new experimental data on the astrophysical $S$-factors of this process at energies down to 90 and 23keV and data on the radiative capture reaction ${}^4\mathrm{\text{He}}{{(}^3\mathrm{\text{H}},\gamma )}^7\mathrm{\text{Li}}$ down to 50keV appeared recently. Moreover, radiative capture reactions ${}^4\mathrm{\text{He}}{{(}^3\mathrm{\text{He}},\gamma )}^7\mathrm{\text{Be}}$ and ${}^4\mathrm{\text{He}}{{(}^2\mathrm{\text{H}},\gamma )}^6\mathrm{\text{Li}}$ may have played a certain role in prestellar nucleosynthesis after the Big Bang, when the temperature of the Universe decreased to the value of $0.3T_9$.

This paper studies the cross-correlation between the pseudorapidity and azimuthal distributions of the shower particles emitted in ${}^{32}$S-AgBr interactions at 200GeV and ${}^{16}$O-AgBr interactions at 60GeV applying Multifractal detrended cross-correlation analysis (MF-DXA) methodology. The cross-correlation between the pseudorapidity ($\eta$) space and the azimuthal ($\varphi$) space is found to exhibit multifractality in case of both the interactions. The results obtained from the analysis of the experimental data were compared with those obtained for the randomly shuffled data for both the interactions, and the results revealed that the multifractality is due to the presence of long-range correlations. The study clearly indicates that the strength of the cross-correlation depends on both the projectile mass and energy.

Whereas there is a slight information on the pre-saddle neutron emission rate and neutron multiplicity, as well as it is impossible to separate the pre-saddle and saddle to scission neutron contributions experimentally, the theoretical studies of pre-saddle neutron emission rate and neutron multiplicity are of great importance. In the present work, the calculations of pre-saddle neutron multiplicity are performed using the analysis of fission fragment angular anisotropy data for ${}^{16}\mathrm{\text{O}}+{}^{208}\mathrm{\text{Pb}}$ and ${}^{16}\mathrm{\text{O}}+{}^{209}\mathrm{\text{Bi}}$ reaction systems. The obtained results show that the pre-saddle neutron multiplicity decreases by increasing the initial excitation energy and it has found to be characterized by a nonlinear behavior. Through the analysis of pre-saddle neutron multiplicity and pre-saddle transition time by means of the neutron clock method, the pre-saddle neutron emission rate is calculated for the first time. The findings of this study show that the pre-scission neutron emission rate is lower than the pre-saddle neutron emission rate.

The effects of deformation and orientation on the nucleus–nucleus and proton–nucleus reaction cross-sections are investigated at intermediate and high energies, in the framework of the Coulomb modified Glauber model. The matter density of the projectile is treated by a deformed Fermi shape with quadrupole and hexadecapole deformations. In-medium effects are included through a local density- and an energy-dependent effective nucleon–nucleon total cross-section. Calculations are performed for the deformed projectiles ${}^{20}Ne,{}^{27}Al,{}^{64}Zn,{}^{181}Ta,{}^{197}Au$ colliding by ${}^{12}C$ and by protons. It is found that the average of reaction cross-section over all directions of the symmetry axis of the deformed projectile differs by about 2$\%$ compared with that calculated for a spherical projectile with the same rms matter radius as the deformed one. The difference between the cross-sections calculated with and without medium effects is of the order 2$\%$ for both deformed and spherical cases. The integrated reaction cross-sections over all orientation angles provide a consistent explanation of the experimental data. The orientation of the heavy projectile can produce a difference in the calculated cross-section about 35$\%$ for nucleus–nucleus and about 45$\%$ for proton–nucleus. This study is also useful for experiments of polarized beams that have created opportunities to study oriented collisions of deformed nuclei. The method is applied to extract the rms radius of ${}^{22}C$ and it is found to be about 3.56 and 3.45fm when using deformation with and without in-medium effects.

We construct a scheme to calculate the charge form factors for the elastic electron scattering. Our calculation is based on the relativistic eikonal approximation and the Skyrme–Hartree–Fock equation. To perform our calculation and benchmark the results, eight model nuclei with available experimental data: ${}^{12}\mathrm{\text{C}}$, ${}^{16}\mathrm{\text{O}}$, ${}^{24}\mathrm{\text{Mg}}$, ${}^{27}\mathrm{\text{Al}}$, ${}^{28}\mathrm{\text{Si}}$, ${}^{32}\mathrm{\text{S}}$, ${}^{40}\mathrm{\text{Ca}}$, and ${}^{208}\mathrm{\text{Pb}}$ are considered. For the comparison, the charge form factors calculated by the relativistic mean-field (RMF) model are also provided. Parameter set SLy5 is utilized for the Skyrme force, and the set NL3 is applied for the RMF model. It has been confirmed that combining of a nonrelativistic treatment for the target nucleus with a relativistic treatment for the incident electron may work better to reach highly descriptive and predictive results similar to the pure relativistic treatment. The results of this work are also useful for future experiments to test different inputs of densities for a specific nucleus.

Continuous wavelet transform approach has been applied to the pseudo-rapidity distribution of shower tracks produced in ${}^{16}$O–AgBr interactions at 60AGeV and ${}^{32}$S–AgBr interactions at 200AGeV. Multiscale analysis of wavelet pseudo-rapidity spectra has been performed in order to find out the overabundance of produced tracks at some preferred pseudo-rapidity values, i.e., production of particle clusters. Presence of ring-like correlation is not confirmed from the analysis in pseudo-rapidity space only. The clusterization effect may be attributed to the presence of Bose–Einstein correlation among the produced tracks. Comparison of experimental results with that obtained from analyzing events generated by FRITIOF and UrQMD codes is not reproduced.

In the present work, we intended to study the $\alpha$-decay half-lives of the even–even nuclei from ${}^{178}$Po to ${}^{226}$Ra in ground state. We investigated a semi-empirical, one-parameter model based on tunneling through a potential barrier with the centrifugal and overlapping effects. Half-lives of $\alpha$-decay of even–even nuclei calculated by using different versions of proximity potentials (gpp77, MCW76 and MB77) are compared to experimental data. Also, the computed half-lives are compared with the Royer formula, Akrawy and Poenaru (AKRE) formula, modify Ren (MRen B) formula and Denisov–Khudenko (DEKH) formula and with the experimental data. The results are in good agreement with the experimental data.

Event-by-event (ebe) fluctuations in mean pseudorapidity values of relativistic charged particles in full phase space are studied by analyzing experimental data on ${}^{16}O-AgBr$ collisions at 14.5A, 60A and 200A GeV/c and ${}^{32}S-AgBr$ collisions at 200A GeV/c. The findings are compared with the prediction of A Multi-Phase Transport (AMPT) model and those obtained from the analysis of correlation free Monte-Carlo events. Fluctuations in mean pseudorapidity distributions are noted to be in excess to that expected from the statistically independent particle emission. The observed dependence of the fluctuation strength measure parameter, $\mathrm{\Phi }$ on the beam energy and number of participating target nucleons indicate that nucleus–nucleus collisions cannot be treated as simple superposition of multiple nucleon–nucleon interactions. Presence of clusters or jet-like phenomena in multihadron final states are searched for on ebe basis by using the concept of Jaynes Shannon entropy. The findings indicate the presence of cluster-like objects in the experimental data with their size and frequency increasing with increasing beam energy. These observations in turn suggest that the clustering or jet-like algorithm adopted in the present study may be used as a tool for triggering different classes of events.

Quarter-wave resonators (QWRs) are being widely used in linear accelerators (linac) for acceleration of ions with low-$\beta$ velocity. Two effects of this kind of cavities are beam steering effect and RF defocusing effect caused by geometric asymmetry. Measurement for the two effects has been conducted by using beam position monitors (BPMs) and wires for a QWR type buncher whose frequency is 162.5MHz at Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS). Since experiment and simulation matches well, beam central position and beam envelope could be predicted in simulation code, which is beneficial for high-intensity proton accelerator design and commissioning.