Vol.33,

We report a reconstruction method for fast-fission events in 25 MeV/u ⁸⁶Kr + ²⁰⁸Pb reactions at the Compact Spectrometer for Heavy Ion Experiment (CSHINE). The fission fragments (FFs) are measured using three large-area parallel-plate avalanche counters, which can deliver the position and arrival timing information of the fragments. The start timing information is provided by the radio frequency of the cyclotron. Fission events were reconstructed using the velocities of the two FFs. The broadening of both the velocity distribution and azimuthal difference of the FFs decreases with the folding angle, in accordance with the picture that fast fission occurs. The anisotropic angular distribution of the fission axis also consistently reveals the dynamic features of fission events.

493

A low-background neutron detector array was developed to measure the cross section of the ¹³C(α,n)¹⁶O reaction, which is the neutron source for the s-process in AGB stars, in the Gamow window (E_c.m. = 190 ± 40 keV) at the China Jinping Underground Laboratory (CJPL). The detector array consists of 24 ³He proportional counters embedded in a polyethylene cube. Owing to the deep underground location and a borated polyethylene shield around the detector array, a low background of 4.5(2)/h was achieved. The ⁵¹V(p, n)⁵¹Cr reaction was used to determine the neutron detection efficiency of the array for neutrons with energies E_n< 1 MeV. Geant4 simulations are shown to effectively reproduce the experimental results. They were used to extrapolate the detection efficiency to higher energies for neutrons emitted in the ¹³C(α,n) ¹⁶O reaction. The theoretical angular distributions of the ¹³C(α,n)¹⁶O reaction were shown to be important in the estimation of the uncertainties of the detection efficiency.

514

We study the energy and centrality dependence of deuteron and triton (helium-3) production in relativistic heavy-ion collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) using the Tsallis distribution, blast-wave (BW) model, and stationary Fokker-Planck (FP) solution. Our study shows that good agreement can be reached between the fitting results from the stationary FP solution and the experimental data for Au+Au collisions from the beam energy scan (BES) program of RHIC at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV and for Pb+Pb collisions at sNN=2.76 TeV. The Tsallis distribution and BW model can reasonably describe the deuteron and triton (helium-3) transverse momentum spectra obtained at RHIC and LHC. A more comprehensive comparison among the three methods suggests that the stationary FP solution is a sensible method, which is able to describe the energy dependence of the light nuclei yield ratio NtNp/Nd2 and provide a coherent description of deuteron and triton (helium-3) production for all centralities and various colliding energies at RHIC and LHC.

496

The global nuclear mass based on the macroscopic-microscopic model was studied by applying a newly designed multitask-learning artificial neural network (MTL-ANN). First, the reported nuclear binding energies of 2095 nuclei (Z ≥ 8, N ≥ 8) released in the latest Atomic Mass Evaluation AME2020 and the deviations between the fitting result of the liquid drop model(LDM) and data from AME2020 for each nucleus were obtained. To compensate for the deviations and investigate the possible ignored physics in the LDM, the MTL-ANN method was introduced in the model. Compared to the single-task-learning (STL) method, this new network has a powerful ability to simultaneously learn multi-nuclear properties, such as the binding energies and single neutron and proton separation energies. Moreover, it is highly effective in reducing the risk of overfitting and achieving better predictions. Consequently, good predictions can be obtained using this nuclear mass model for both the training and validation datasets and for the testing dataset. In detail, the global root mean square (RMS) of the binding energy is effectively reduced from approximately 2.4 MeV of LDM to the current 0.2 MeV, and the RMS of S_n, S_p can also reach approximately 0.2 MeV. Moreover, compared to STL, for the training and validation sets, 3∼9% improvement can be achieved with the binding energy, and 20∼30% improvement for S_n, S_p; for the testing sets, the reduction in deviations can even reach 30∼40%, which significantly illustrates the advantage of the current MTL.

540

In this work, we explore the use of an iterative Bayesian Monte Carlo (iBMC) method for nuclear data evaluation within a TALYS Evaluated Nuclear Data Library (TENDL) framework. The goal is to probe the model and parameter space of the TALYS code system to find the optimal model and parameter sets that reproduces selected experimental data. The method involves the simultaneous variation of many nuclear reaction models as well as their parameters included in the TALYS code. The 'best’ model set with its parameter set was obtained by comparing model calculations with selected experimental data. Three experimental data types were used: (1) reaction cross sections, (2) residual production cross sections, and (3) the elastic angular distributions. To improve our fit to experimental data, we update our 'best’ parameter set - the file that maximizes the likelihood function - in an iterative fashion. Convergence was determined by monitoring the evolution of the maximum likelihood estimate (MLE) values and was considered reached when the relative change in the MLE for the last 2 iterations was within 5%. Once the final 'best’ file is identified, we infer parameter uncertainties and covariance information to this file by varying model parameters around this file. In this way, we ensured that the parameter distributions are centered on our evaluation. The proposed method was applied to the evaluation of p+⁵⁹Co between 1 - 100 MeV. Finally, the adjusted files were compared with experimental data from the EXFOR database as well as with evaluations from the TENDL-2019, JENDL/He-2007 and JENDL-4.0/HE nuclear data libraries.

648

Over 70% of the treated contaminated water at the Fukushima Daiichi Nuclear Power Station contains radionuclides beyond the regulatory standard for discharge that need to be re-purified. Technetium-99 (⁹⁹Tc), mainly in the form of pertechnetate Tc(VII)O₄⁻, is one of the main sources of long-term radiotoxicity that jeopardizes the environment and human health. Herein, we used a series of dicationic pyridinium (DCP) derivative groups (–Py⁺C_nH_2nN⁺Me₃, n = 2, 3, and 5) to modify commercial Reillex 425 resins containing tertiary pyridyl groups to improve the adsorption performance of rhenium (Re, an analog of radioactive Tc) and Tc. As the quaternary pyridinium and ammonium sites in one DCP group can adsorb ReO₄⁻ simultaneously, DCP-modified Reillex 425 (Reillex-Cn) exhibited high maximum adsorption capacities for Re under neutral conditions. Adsorption capacities reached 344.8, 416.7, and 588.2 mg g⁻¹ for Reillex 425-C2, Reillex 425-C3, and Reillex 425-C5, respectively. Intraparticle diffusion of ReO₄⁻/TcO₄⁻ in Reillex 425-Cn was verified to be the rate-limiting step of adsorption. However, adsorption can be adjusted by the length of the alkyl spacers between the two positively charged N sites in DCP. –Py⁺C₂H₄N⁺Me₃ significantly enhanced intraparticle diffusion compared to –Py⁺C₅H₁₀N⁺Me₃. The two positive sites in –Py⁺C₂H₄N⁺Me₃ would be laterally distributed, leading to a smaller steric hindrance for ReO₄^–/TcO₄⁻ transport inside the microporous channels. Meanwhile, the longer alkyl spacers in –Py⁺C₅H₁₀N⁺Me₃ formed hydrophobic microphases, repulsing the hydrated ReO₄^–/TcO₄⁻ anions. Thus, the adsorptions of both ReO₄⁻ and TcO₄⁻ on Reillex 425-C2 were faster than those on Reillex 425-C5. Moreover, Reillex 425-Cn exhibited an exothermic nature, good selectivity, excellent reusability, and strong salinity tolerance. This study provides a simple strategy to enhance the Tc removal performance of adsorbents containing abundant micropores, which implies enormous environmental and economic benefits.

433

Oil cleaning agents generated from nuclear power plants (NPPs) are radioactive organic liquid wastes. To date, because there are no satisfactory industrial treatment measures, these wastes can only be stored for a long time. In this work, the optimization for the supercritical water oxidation (SCWO) of the spent organic solvent was investigated. The main process parameters of DURSET (oil cleaning agent) SCWO, such as temperature, reaction time, and excess oxygen coefficient, were optimized using response surface methodology (RSM), and a quadratic polynomial model was obtained. The determination coefficient (R²) of the model is 0.9812, indicating that the model is reliable. The optimized process conditions were at 515℃, 66 s, and an excess oxygen coefficient of 211%. Under these conditions, the chemical oxygen demand (COD) removal of organic matter could reach 99.5%. The temperature was found to be the main factor affecting the SCWO process. Ketones and benzene-based compounds may be the main intermediates in DURSET SCWO. This work provides basic data for the industrialization of the degradation of spent organic solvents from NPP using SCWO technology.

600

This study aimed to exploit a new virtual block method to spare normal lung tissue in VMAT planning for patients with locally advanced non-small cell lung cancer (LA-NSCLC). The previous method was used to manually restrict the angle of the beam passing through, which ignored the location and shape of large targets that varied between different slices and did not block the beamlets precisely. Unlike the previous method, this new virtual block method was used to block the beamlets when necessary by closing the Multileaf Collimator (MLC) at prerequisite angles. The algorithm for closing the MLC depended on the thickness of the beamlets passing through the lungs and avoided only the entrance radiation beamlet. Moreover, this block can be automatically contoured. A retrospective study was performed to compare the VMAT plans with and without the virtual block method for 17 LA-NSCLC patients, named the block plan (B-plan)/non-block plan (N-plan). All cases were selected in this study because of the large tumor size and unmet dose constraints of the lungs. In addition to the maximum dose constraint for the virtual block, B-plans adopted identical optimization parameters to N-plans for each patient. These two types of plans were compared in terms of dosimetric indices and plan scores. The results were statistically analyzed using the Wilcoxon nonparametric signed-rank test. B-plans have advantages in the following dosimetric metrics that have statistical significance (p < 0.05):1) lower V₅/V₁₀/D_mean/normal tissue complication probability (NTCP) of total lungs; 2) reductions in V₅/V₁₀ for the contralateral lung; 3) decrease in D_mean/V₄₀ of the heart; 4) decrease in esophagus V₄₀; 5) reductions in D_mean, V₅/V₁₀ of normal tissue. B-plans (82.51 ± 7.07) achieved higher quality scores than N-plans (80.74 ± 7.22). The new virtual block spared the lungs as well as other normal structures in VMAT planning for LA-NSCLC. Thus, the block method may decrease the risk of radiation-related toxicity in patients.

535

In this study, the effects of changing first wall materials and their thicknesses on a reactor were investigated to determine the displacement per atom (DPA) and gas production (helium and hydrogen) in the first wall, as well as the tritium breeding ratio (TBR) in the coolant and tritium breeding zones. Therefore, the modeling of the magnetic fusion reactor was determined based on the blanket parameters of the International Thermonuclear Experimental Reactor (ITER). Stainless steel (SS 316 LN-IG), Oxide Dispersion Strengthened Steel alloy (PM2000 ODS), and China low-activation martensitic steel (CLAM) were used as the first wall (FW) materials. Fluoride family molten salt materials (FLiBe, FLiNaBe, FLiPb) and lithium oxide (LiO₂) were considered the coolant and tritium production material in the blanket, respectively. Neutron transport calculations were performed using the well-known 3D code MCNP5 using the continuous-energy Monte Carlo method. The built-in continuous energy nuclear and atomic data libraries along with the Evaluated Nuclear Data file (ENDF) system (ENDF/B-V and ENDF/B-VI) were used. Additionally, the activity cross-section data library CLAW-IV was used to evaluate both the DPA values and gas production of the first wall (FW) materials. An interface computer program written in the FORTRAN 90 language to evaluate the MCNP5 outputs was developed for the fusion reactor blanket. The results indicated that the best TBR value was obtained for the use of the FLiPb coolant, whereas depending on the thickness, the first wall replacement period in terms of radiation damage to all materials was between 6 and 11 years.

423

We report our recent progress in the design and simulation of a high-brightness S-band photo-injector with a ballistic bunching scheme aimed at driving an inverse Compton scattering (ICS) X-ray source. By adding a short standing-wave buncher between the RF gun and first booster in a conventional S-band photo-injector, electron bunches with a 500 pC charge can be compressed to the sub-picosecond level with very limited input RF power and an unchanged basic layout of the photo-injector. Beam dynamics analysis indicates that fine tuning of the focusing strength of the gun and linac solenoid can well balance additional focusing provided by the standing wave buncher and generate a well-compensated transverse emittance. Thorough bunching dynamics simulations with different operating conditions of the buncher show that a buncher with more cells and a moderate gradient is suitable for simultaneously obtaining a short bunch duration and low emittance. In a typical case of a 9-cell buncher with a 38 MV/m gradient, an ultrashort bunch duration of 0.5 ps (corresponding to a compression ratio of > 5) and a low emittance of < 1 mm·mrad can be readily obtained for a 500 pC electron pulse. This feasible ballistic bunching scheme will facilitate the implementation of an ultrashort pulse mode inverse Compton scattering X-ray source on most existing S-band photo-injectors.

568

The output-signal models and impulse response shaping (IRS) functions of semiconductor detectors are important for establishing high-precision measurement systems. In this paper, an output-signal model for semiconductor detector systems is proposed. According to the proposed model, a multistage cascade deconvolution IRS algorithm was developed using the C-R inverse system, R-C inverse system, and differentiator system. The silicon drift detector signals acquired from the analog-to-digital converter were tested. The experimental results indicated that the shaped pulses obtained using the proposed model had no undershoot, and the average peak base width of the output shaped pulses was reduced by 36% compared with that for a simple model proposed in a previous work [1]. Offline processing results indicated that compared with the traditional IRS algorithm, the average peak base width of the output shaped pulses obtained using the proposed algorithm was reduced by 11%, and the total elapsed time required for pulse shaping was reduced by 26%. The proposed algorithm avoids recursive calculation. If the sampling frequency of the digital system reaches 100 MHz, the proposed algorithm can be simplified to integer arithmetic. The proposed IRS algorithm can be applied to high-resolution energy spectrum analysis, high-counting rate energy spectrum correction, and coincidence and anti-coincidence measurements.

661