Nuclear Science and Techniques最新文献

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.

The hard X-ray nanoprobe beamline BL13U is a phase-II beamline project at the Shanghai Synchrotron Radiation Facility. The beamline aims to enable comprehensive experiments at high spatial resolutions ranging from 50 to 10 nm. The X-ray energy range of the beamline, 5–25 keV, can detect most elements in the periodic table. Two operating modes were designed to accommodate the experimental requirements of high-energy resolution or high photon flux, respectively. X-ray nanofluorescence, nanodiffraction, and coherent diffraction imaging are developed as the main experimental techniques for BL13U. This paper describes the beamline optics, end station configurations, experimental methods under development, and preliminary test results. This comprehensive overview aims to provide a clear understanding of the beamline capabilities and potential applications.

Cone-beam computed tomography (CBCT) is mostly used for position verification during the treatment process. However, severe image artifacts in CBCT hinder its direct use in dose calculation and adaptive radiation therapy re-planning for proton therapy. In this study, an improved U-Net neural network named CBAM-U-Net was proposed for CBCT noise reduction in proton therapy, which is a CBCT denoised U-Net network with convolutional block attention modules. The datasets contained 20 groups of head and neck images. The CT images were registered to CBCT images as ground truth. The original CBCT denoised U-Net network, sCTU-Net, was trained for model performance comparison. The synthetic CT(SCT) images generated by CBAM-U-Net and the original sCTU-Net are called CBAM-SCT and U-Net-SCT images, respectively. The HU accuracies of the CT, CBCT, and SCT images were compared using four metrics: mean absolute error (MAE), root mean square error (RMSE), peak signal-to-noise ratio (PSNR), and structure similarity index measure (SSIM). The mean values of the MAE, RMSE, PSNR, and SSIM of CBAM-SCT images were 23.80 HU, 64.63 HU, 52.27 dB, and 0.9919, respectively, which were superior to those of the U-Net-SCT images. To evaluate dosimetric accuracy, the range accuracy was compared for a single-energy proton beam. The (gamma)-index pass rates of a 4 cm (times) 4 cm scanned field and simple plan were calculated to compare the effects of the noise reduction capabilities of the original U-Net and CBAM-U-Net on the dose calculation results. CBAM-U-Net reduced noise more effectively than sCTU-Net, particularly in high-density tissues. We proposed a CBAM-U-Net model for CBCT noise reduction in proton therapy. Owing to the excellent noise reduction capabilities of CBAM-U-Net, the proposed model provided relatively explicit information regarding patient tissues. Moreover, it maybe be used in dose calculation and adaptive treatment planning in the future.