Nuclear Science and Techniques最新文献

Accurate and efficient online parameter identification and state estimation are crucial for leveraging digital twin simulations to optimize the operation of near-carbon-free nuclear energy systems. In previous studies, we developed a reactor operation digital twin (RODT). However, non-differentiabilities and discontinuities arise when employing machine learning-based surrogate forward models, challenging traditional gradient-based inverse methods and their variants. This study investigated deterministic and metaheuristic algorithms and developed hybrid algorithms to address these issues. An efficient modular RODT software framework that incorporates these methods into its post-evaluation module is presented for comprehensive comparison. The methods were rigorously assessed based on convergence profiles, stability with respect to noise, and computational performance. The numerical results show that the hybrid KNNLHS algorithm excels in real-time online applications, balancing accuracy and efficiency with a prediction error rate of only 1% and processing times of less than 0.1 s. Contrastingly, algorithms such as FSA, DE, and ADE, although slightly slower (approximately 1 s), demonstrated higher accuracy with a 0.3% relative (L_2) error, which advances RODT methodologies to harness machine learning and system modeling for improved reactor monitoring, systematic diagnosis of off-normal events, and lifetime management strategies. The developed modular software and novel optimization methods presented offer pathways to realize the full potential of RODT for transforming energy engineering practices.

Fast neutron flux measurements with high count rates and high time resolution have important applications in equipment such as tokamaks. In this study, real-time neutron and gamma discrimination was implemented on a self-developed 500-Msps, 12-bit digitizer, and the neutron and gamma spectra were calculated directly on an FPGA. A fast neutron flux measurement system with BC-501A and EJ-309 liquid scintillator detectors was developed and a fast neutron measurement experiment was successfully performed on the HL-2 M tokamak at the Southwestern Institute of Physics, China. The experimental results demonstrated that the system obtained the neutron and gamma spectra with a time accuracy of 1 ms. At count rates of up to 1 Mcps, the figure of merit was greater than 1.05 for energies between 50 keV and 2.8 MeV

Accurate measurement of the transverse position of a beam is crucial in particle accelerators because it plays a key role in determining the beam parameters. Existing methods for beam-position measurement rely on the detection of image currents induced on electrodes or narrow-band wake field induced by a beam passing through a cavity-type structure. However, these methods have limitations. The indirect measurement of multiple parameters is computationally complex, requiring external calibration to determine the system parameters in advance. Furthermore, the utilization of the beam signal information is incomplete. Hence, this study proposes a novel method for measuring the absolute electron beam transverse position. By utilizing the geometric relationship between the center position of the measured electron beam and multiple detection electrodes and by analyzing the differences in the arrival times of the beam signals detected by these electrodes, the absolute transverse position of the electron beam crossing the electrode plane can be calculated. This method features absolute position measurement, a position sensitivity coefficient independent of vacuum chamber apertures, and no requirement for a symmetrical detector electrode layout. The feasibility of this method is validated through numerical simulations and beam experiments.

The exploration of exotic shapes and properties of atomic nuclei, e.g., (alpha) cluster and toroidal shape, is a fascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detecting multiple (alpha)-particle events was designed and constructed. The detector comprises two layers of double-sided silicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers array as light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDs coupled with cesium iodide crystal arrays are used to distinguish multiple (alpha) hits. The detector array has a compact and integrated design that can be adapted to different experimental conditions. The detector array was simulated using Geant4, and the excitation energy spectra of some (alpha)-clustering nuclei were reconstructed to demonstrate the performance. The simulation results show that the detector array has excellent angular and energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple (alpha) particle events. This detector offers a new and powerful tool for nuclear physics experiments and has the potential to discover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms.

The BL07U beamline is a new extreme ultraviolet and soft X-ray beamline housed in the Shanghai Synchrotron Radiation Facility. Beamlines are used in nano-resolved angle-resolved photoemission spectroscopy (nano-ARPES), spin-resolved angle-resolved photoemission spectroscopy (spin-ARPES), X-ray magnetic circular dichroism spectroscopy, and X-ray magnetic linear dichroism spectroscopy for certain scientific research. The BL07U beamline, which is based on a pair of elliptical polarized undulators and a variable-included-angle plane-grating monochromator, delivers circularly or linear polarized X-rays within the energy range of 50–2000 eV. The beamline features two branches: One dedicated to nano-ARPES, which has a minimum spot size of only ~ 200 nm, and another branch comprising spin-ARPES, a vector magnetic field, and superconductive magnetic end-station.

A charged particle array named MATE-PA, which serves as an auxiliary detector system for a Multi-purpose Active-target Time projection chamber used in nuclear astrophysical and exotic beam Experiments (MATE), was constructed. The array comprised of 20 single-sided strip-silicon detectors covering approximately 10% of the solid angle. The detectors facilitated the detection of reaction-induced charged particles that penetrate the active volume of the MATE. The performance of MATE-PA has been experimentally studied using an alpha source and a 36-MeV (^{14})N beam injected into the MATE chamber on the radioactive ion beam line in Lanzhou (RIBLL). The chamber was filled with a gas mixture of 95(%) (^4)He and 5(%) CO(_2) at a pressure of 500 mbar. The results indicated good separation of light-charged particles using the forward double-layer silicon detectors of MATE-PA. The energy resolution of the Si detectors was deduced to be approximately 1(%) ((sigma)) for an energy loss of approximately 10 MeV caused by the (alpha) particles. The inclusion of MATE-PA improves particle identification and increases the dynamic range of the kinetic energy of charged particles, particularly that of the (alpha) particles, up to approximately 15 MeV.

The evolution of dislocation loops in austenitic steels irradiated with Fe(^+) is investigated using cluster dynamics (CD) simulations by developing a CD model. The CD predictions are compared with experimental results in the literature. The number density and average diameter of the dislocation loops obtained from the CD simulations are in good agreement with the experimental data obtained from transmission electron microscopy (TEM) observations of Fe(^+)-irradiated Solution Annealed 304, Cold Worked 316, and HR3 austenitic steels in the literature. The CD simulation results demonstrate that the diffusion of in-cascade interstitial clusters plays a major role in the dislocation loop density and dislocation loop growth; in particular, for the HR3 austenitic steel, the CD model has verified the effect of temperature on the density and size of the dislocation loops.

The circular electron-positron collider (CEPC) is designed to precisely measure the properties of the Higgs boson, study electroweak interactions at the Z-boson peak, and search for new physics beyond the Standard Model. As a component of the (4^{text {th}}) conceptual CEPC detector, the drift chamber facilitates the measurement of charged particles. This study implemented a Geant4-based simulation and track reconstruction for the drift chamber. For the simulation, detector construction and response were implemented and added to the CEPC simulation chain. The development of track reconstruction involves track finding using the combinatorial Kalman filter method and track fitting using the tool of GenFit. Using the simulated data, the tracking performance was studied. The results showed that both the reconstruction resolution and tracking efficiency satisfied the requirements of the CEPC experiment.

We systematically studied the evaporation residue cross sections of (^{48}hbox {Ca})-induced reactions on lanthanide and actinide target nuclei under the Dinuclear System (DNS) model framework to check the reliability and applicability of the model. To produce new proton-rich Fl and Lv isotopes through hot fusion reactions in the superheavy element region with (Zge 104), we utilized the reactions (^{48}hbox {Ca}+^{236,238,239}hbox {Pu}) and (^{48}hbox {Ca}+^{242,243,244,250}hbox {Cm}). However, owing to the detection limit of available equipment (0.1 pb), only (^{283}hbox {Fl}) and (^{287-289}hbox {Lv}), which have the maximum evaporation residue cross section values of 0.149, 0.130, 9.522, and 0.309 pb, respectively, can be produced. Furthermore, to produce neutron-deficient isotopes of actinides near the proton drip line with (Z=93-100), we attempted to generate the new isotopes ((^{224-227}hbox {Pu}), (^{228-232,237}hbox {Cm})) using the reactions (^{48}hbox {Ca}+^{180, 182, 183}hbox {W}) and (^{48}hbox {Ca}+^{184, 186, 187, 192}hbox {Os}). The maximum evaporation residue cross section values are 0.07, 0.06, 0.26, and 0.30 nb for the former set of reactions, and 1.96 pb, 5.73 pb, 12.16 pb, 19.39 pb, 54.79 pb, and 6.45 nb for the latter, respectively. These results are expected to provide new information for the future synthesis of unknown neutron-deficient isotopes.