Vol.33,

Production routes were recorded on available reactions for ¹¹¹Ag production from nuclear reactors or cyclotrons using a natural palladium target based on ¹¹⁰Pd(n, γ) and ¹¹⁰pd(d, n) reactions, respectively. ^natCd(γ, x) based on ¹¹⁰Cd(γ, p) has also been studied as a prospective reaction for the production of ¹¹¹Ag. Unfortunately, these nuclear reactions are difficult to utlize because, in some cases, they reduce the specific activity of ¹¹¹Ag. This is a consequence of the stable silver isotopes produced in high concentrations. These isotopes include ^{107, 109}Ag and, in other cases, the high impurity of silver radioisotopes, such as ^{110m, 106m, 105}Ag, that are produced during parallel nuclear reactions. Due to a scarcity of data regarding the (γ, α) reaction, the gamma reaction on natural indium for ¹¹¹Ag production based on the ¹¹⁵In(γ, α) reaction was calculated. The ^natIn(γ, α) reaction satisfies the criteria as a possible reaction to produce ¹¹¹Ag with a sufficient yield and purity as consequence of the high ¹¹⁵In (95.7 %) abundance as an enriched form and a relatively soft background caused by the parallel nuclear reactions.

511

By implementing an additional heavy quark–antiquark pair production trigger in a multiphase transport (AMPT) model, we study the effect on anisotropy flows of identified particles with a focus on charged particles and quarkonium (J/Ψ and ϒ). A systematic increase in the collision rate for active partons in the AMPT model with such an implementation has been observed. It leads to a slight increase of identified particles anisotropy flows as a function of transverse momentum (p_T) and rapidity, and gives a better description of the experimental data of elliptic flow toward larger p_T. Our approach provides an efficient way to study the heavy quark dynamics in the AMPT model at LHC energies.

799

Collective flow is a powerful tool used to analyze the properties of a medium created during high-energy nuclear collisions. Here, we report a systematic study of the first two Fourier coefficients v₁ and v₂ of the proton and π⁺ from Au+Au collisions in the energy range sNN = 2.11 – 4.9 GeV within the framework of a hadronic transport model (UrQMD). Recent results from the STAR experiment were used to test the model calculations. A mean-field mode with strong repulsive interaction is needed to reproduce the 10–40% data at 3 GeV. This implies that hadronic interactions play an important role in the collective flow development in the high-baryon-density region. The mean values of the freeze-out time for protons and π⁺ are shifted earlier owing to the additional repulsive interactions. We predict the energy dependence of the mean values of the transverse momentum 〈pT〉, v₁, and v₂ for both protons and π⁺ from the Au+Au collisions.

562

The squeezed back-to-back correlation (SBBC) of a boson-antiboson pair is sensitive to the time distribution of the particle-emitting source, and the SBBC function for an evolving source is expected to be affected by the relaxation time of the system. In this study, we investigated the effect of relaxation time on the SBBC function. We propose a method for calculating the SBBC function with relaxation-time approximation for evolving sources. SBBC functions of D0D¯0 in relativistic heavy-ion collisions were investigated using a hydrodynamic model. We found that the relaxation time reduces the amplitudes of the SBBC functions. This becomes apparent for long relaxation times and large initial relative deviations of the chaotic and squeezed amplitudes from their equilibrium values in the temporal steps.

591

A 16-pole superconducting multipole wiggler with a large gap of 68 mm was designed and fabricated to serve as a multipole wiggler for HEPS-TF. The wiggler consists of 16 pairs of NbTi superconducting coils with a period length of 170 mm, and its maximum peak field is 2.6 Tesla. In magnet design, magnet poles were optimized. Furthermore, the Lorentz force on the coils and electromagnetic force between the upper and lower halves were computed and analyzed along with the stored energy and inductance at different currents. To enhance the critical current of the magnet coil, all the pole coils selected for the magnet exhibited excellent performance, and appropriate prestress derived from the coil force analysis was applied to the pole coils during magnet assembly. The entire magnet structure was immersed in 4.2-K liquid helium in the cryostat cooled solely by four two-stage cryocoolers, and the performance test of the superconducting wiggler were appropriately completed. Based on the measured results, the first and second field integrals on the axis of the superconducting wiggler were significantly improved at different field levels after the compensation of the corrector coils. Subsequently, the wiggler was successfully installed in the storage ring of BEPCII operation with beams.

504

The significant advantage of proton therapy over other particle-based techniques is in the unique physical characteristics of the Bragg peak. It can achieve a highly conformal dose distribution and maximize the probability of tumor control by varying the irradiation energy. Most proton facilities use cyclotrons for fixed energy beam extraction and are equipped with degrader and collimator systems for energy modulation and emittance suppression. However, interactions between charged particles and degrader materials inevitably cause beam loss and divergence, and deteriorate beam performance, which present great challenges for downstream transport and clinical treatment. In this work, we investigate a method of energy reduction by combining boron carbide and graphite in a degrader to obtain greater beam transmission at lower energy. The results demonstrate that the beam size and emittance at the exit of the combined degrader diverge less than those of multi-wedge one in the energy range of 70−160 MeV. Correspondingly, the transmission efficiency after the first dipole also shows improvements of 36.26% at 70 MeV and 70.55% at 110 MeV. As a component with a high activity level, the degrader causes additional ambient radiation during operation. Residual induced radiation even remains several hours after system shutdown. Analysis of material activation and induced radiation based on 1 h irradiation with a 400 nA beam current show that the combined degrader has a definite advantage in shielding despite producing more secondary particles. Both radioactivity and average ambient dose equivalent are reduced by 50% compared with the multi-wedge degrader at the important cooling time of 1 h. After 12 h and 24 h of cooling, the radiation levels of degraders decrease slightly due to the presence of long half-life residual nuclides. The average dose generated from the multi-wedge degrader is still 1.25 times higher than that of the combined one.

606

In this study, a multi-physics and multi-scale coupling program, Fluent/KMC-sub/NDK, was developed based on the user-defined functions (UDF) of Fluent, in which the KMC-sub code is a sub-channel thermal-hydraulic code and the NDK code is a neutron diffusion code. The coupling program framework adopt the "master-slave" mode, in which Fluent is the master program while NDK and KMC-sub are coupled internally and compiled into the dynamic link library (DLL) as slave codes. The domain decomposition method was adopted, in which the reactor core was simulated by NDK and KMC-sub, while the rest of the primary loop was simulated using Fluent. A simulation of the reactor shutdown process of M²LFR-1000 was carried out using the coupling program, and the code-to-code verification was performed with ATHLET, demonstrating a good agreement, with absolute deviation was smaller than 0.2%. The results show an obvious thermal stratification phenomenon during the shutdown process, which occurs 10 s after shutdown, and the change in thermal stratification phenomena is also captured by the coupling program. At the same time, the change in the neutron flux density distribution of the reactor was also obtained.

537

A severe accident in a marine nuclear reactor leads to radionuclide leakage, which causes hidden dangers to workers and has adverse effects of environmental pollution. It is necessary to propose a novel approach to radionuclide diffusion in a confined environment after a severe accident in a marine nuclear reactor. Therefore, this study proposes a new method for the severe accident analysis program MELCOR coupled with computational fluid dynamics scSTREAM to study radioactive diffusion in severe accidents. The radionuclide release fraction and temperature calculated by MELCOR were combined with the scSTREAM calculations to study the radionuclide diffusion behavior and the phenomenon of radionuclide diffusion in different space environments of the reactor under the conditions of varying wind velocities of the ventilation system and diffusion speed. The results show that the wind velocity of the ventilation system is very small or zero, and the turbulent diffusion of radionuclides is not obvious and diffuses slowly in the form of condensation sedimentation and gravity settlement. When the wind speed of the ventilation system increases, the flow of radionuclides meets the wall and forms eddy currents, affecting the time variation of radionuclides diffusing into chamber 2. The wind velocity of the ventilation system and the diffusion speed have opposite effects on the time variation trend of radionuclide diffusion into the four chambers.

661

In vivo measurement of radioactivity based on various body counters is arguably the leading measure used to determine the distribution and activity of radionuclides in human subjects, such as I-131 in the thyroid, Am-241 in the lungs, and Pb-210 in the skull. Throughout the measurements, the radiation background is the key factor that determines the sensitivity of the counter. Therefore, to facilitate in vivo measurements, a well-designed shielding room is required to create a low-background environment. However, because the compositions of the radiation background are quite complicated, the respective contributions from each source remain obscure, which places a considerable burden on seeking an optimized design of shielding rooms that strikes the optimum balance between the construction cost and background suppression effect. In this study, we conducted a systematic experimental investigation on the radiation background outside and inside four representative body counters with assorted designs using a variety of radiation detectors, including high-purity germanium detectors, CdZnTe detector, radon emanometer, and gamma-ray dosimeter. By carefully controlling the experimental conditions and synergetic analysis of the measurement results, in conjunction with previous studies, we separated and determined the relative contributions induced by environmental radiation (4%), airborne radon and its daughters (2%), the normal radioactivity of human subjects arising from K-40 (58%), cosmic rays (12%), and radioactivity in shielding materials and measuring instruments (24%). Furthermore, based on these results, we discuss practical guidelines to design a shielding room for body counters.

476