分类: 物理学 >> 核物理学 提交时间: 2023-06-20
摘要: Momentum correlation functions of light (anti)nuclei formed by the coalescence mechanism of (anti)nucleons are calculated in several relativistic heavy-ion collision systems, namely B +B, O +O, Ca +Ca as well as Au +Au, at di#11;erent centralities at center of mass energy 39 GeV within the framework of A Multi-Phase Transport (AMPT) model complemented by the Lednick#19; y and Lyuboshitz analytical method. Momentum correlation functions for identical or nonidentical light (anti)nuclei are constructed in the above collision systems at so high collision energy. The results suggest that emission of light (anti)nuclei occurs from a source of smaller spacetime extent in more peripheral collisions. The e#11;ect of system-size on the momentum correlation functions of identical or nonidentical light (anti)nuclei is also explored in several central collisions. The results indicate that the emission source-size of light (anti)nuclei pairs deduced from their momentum correlation functions and system-size is self-consistent. Momentum correlation functions of nonidentical light nuclei pairs gated on velocity are applied to infer the average emission sequence of them. The results indicate that protons are emitted in average on a similar time scale with neutrons but earlier than deuterons or tritons in the small relative momentum region. In addition, larger interval of the average emission order among them is observed by large centrality and smaller system collisions.
分类: 物理学 >> 核物理学 提交时间: 2023-09-07
摘要: In this study, we developed a neural network that incorporates a fully connected layer with a convolutional layer to predict the nuclear charge radii based on the relationships between four local nuclear charge radii.The convolutional neural network (CNN) combines the isospin and pairing effects to describe the charge radii of nuclei with A geq 39 and Z geq 20. The developed neural network achieved a root--mean--square (RMS) deviation of 0.0195 fm for a dataset with 928 nuclei. Specifically, the CNN reproduced the trend of the inverted parabolic behavior and odd--even staggering observed in the calcium isotopic chain, demonstrating reliable predictive capability.
分类: 物理学 >> 核物理学 提交时间: 2023-06-20
摘要: Two-nucleon momentum correlation functions are investigated for different single thermal sourcesat given initial temperature (T ) and density (). To this end, the evolutions of various singleexcited nuclei at T = 1 20 MeV and = 0.2 - 1.2 0 are simulated using the thermal isospindependent quantum molecular dynamics (T hIQMD) model. Momentum correlation functions ofidentical proton-pairs (Cpp(q)) or neutron-pairs (Cnn(q)) at small relative momenta are calculatedby Lednick y and Lyuboshitz analytical method. The results illustrate that Cpp(q) and Cnn(q) keepsensitivities to the source size (A) at lower T or higher , but almost not at higher T or lower . Andthe sensitivities become stronger for smaller source. Moreover, the T , and A dependencies of theGaussian source radii are also extracted by fitting the two-proton momentum correlation functions,and the results are consistent with the above conclusions.
分类: 物理学 >> 核物理学 提交时间: 2025-02-07
摘要: In this study, a compact 16-channel integrated charge and current sensitive preamplifier, called CCPA, was developed for the large-scale detector array used in nuclear physics experiments. The CCPA is designed to achieve the pulse shape discrimination method for silicon detectors. The CCPA has a fast response of typically less than 6 ns for the pulse rise time and a low equivalent noise of 1.5 keV at zero input capacitance. Energy dynamic range and pulse decay time can be easily adjusted for different applications by changing the feedback capacitance Cf and resistance Rf. A good energy resolution of 26.87 keV was achieved for 5.486 MeV αparticles from ^{241}\text{Am}. The pulse shape discrimination method was applied for the first time in the experiment carried out on the Radioactive Ion Beam Line in Lanzhou (RIBBL1), and the CCPA demonstrated high resolution and stability in beam experiments. The experiment has realized the identification of low energy α particles as low as 5 MeV by pulse shape discrimination method, as well as the hundreds MeV charged particle. It provides a new routine for high precision measurement of low energy charged particles emitted by light nuclear reactions.
分类: 物理学 >> 核物理学 提交时间: 2025-01-16
摘要: In this study, a compact 16-channel integrated charge and current sensitive preamplifier, called CCPA, was developed for the large-scale detector array used in nuclear physics experiments. The CCPA is designed to achieve the pulse shape discrimination method for silicon detectors. The CCPA has a fast response of typically less than 6 ns for the pulse rise time and a low equivalent noise of 1.5 keV at zero input capacitance. Energy dynamic range and pulse decay time can be easily adjusted for different applications by changing the feedback capacitance Cf and resistance Rf. A good energy resolution of 26.87 keV was achieved for 5.486 MeV αparticles from ^{241}\text{Am}. The pulse shape discrimination method was applied for the first time in the experiment carried out on the Radioactive Ion Beam Line in Lanzhou (RIBBL1), and the CCPA demonstrated high resolution and stability in beam experiments. The experiment has realized the identification of low energy α particles as low as 5 MeV by pulse shape discrimination method, as well as the hundreds MeV charged particle. It provides a new routine for high precision measurement of low energy charged particles emitted by light nuclear reactions.
分类: 物理学 >> 核物理学 提交时间: 2024-05-24
摘要: The recently discovered, extremely proton-rich nuclide18Mg exhibits ground-state decay via two sequential two-proton (2p) emissions through the intermediate nucleus,16Ne. This study investigates the structure and the initial2pdecay mechanism of18Mgby examining the density and correlations of the valence protons using a three-body Gamow-coupled-channel method. The results show that the ground state of18Mgis significantly influenced by the continuum, resulting in a significants-wave component. However, based on the current frame- work, this does not lead to a significant deviation in mirror symmetry in either the structure or spectroscopy of the18Mg-18Cpair. Additionally, the time evolution analysis of the18Mgground state suggests a simultaneous2pemission during the first step of decay. The observed nucleon–nucleon correlations align with those of the light–mass2pemitters, indicating a consistent decay behavior within this nuclear region.
分类: 物理学 >> 核物理学 提交时间: 2023-10-07
摘要: In the RD for upgrading the KL0and detector (KLM) in Belle II experiment using scintillator and silicon photomultiplier (SiPM), we design a compact preamplifier with high#2;speed and low-noise. The preamplifier has a good gain stability, a baseline noise level of 0.3 mV, a good time resolution that can achieve < 20 ps, and can be applied comprehensively to SiPMs. To reduce the pile-up in using a large size SiPM or an array of SiPMs, which is due to the large capacitance and high dark count rate, we adopt pole#2;zero-cancellation which reduce both the rise time and the fall time of a SiPM signal. The combinations of the preamplifier and several kinds of SiPMs show time resolutions better than 50 ps for most of the cases; when the number of detected photons is larger than 60, a time resolution of about 25 ps can be achieved
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-09-01
摘要: Active Target Time Projection Chambers (AT-TPCs) are state-of-the-art tools in the field of low-energy nuclear physics, particularly suitable for experiments using low-intensity radioactive ion beams or gamma rays. The Fudan Multi-purpose Active Target Time Projection Chamber (fMeta-TPC) with 2048 channels has been developed to study \alpha-clustering nuclei. In this work, the focus is on the study of the photonuclear reaction with the Laser Compton Scattering (LCS) gamma source, especially for the decay of the highly excited \alpha-cluster state. The design of fMeta-TPC is described and a comprehensive evaluation of its offline performance is performed by ultraviolet (UV) laser and ^{241}Am \alpha source. The result shows that the intrinsic angular resolution of the detector is within \ang{0.30} and has an energy resolution of 6.85\% for \SI{3.0}{MeV} \alpha particles. The gain uniformity of the detector is about 10\% (RMS/Mean), tested by the ^{55}Fe X-ray source.
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: The exploration of exotic shapes and properties of atomic nuclei, e.g., α cluster and toroidal shape, is afascinating field in nuclear physics. To study the decay of these nuclei, a novel detector aimed at detectingmultiple alpha-particle events was designed and constructed. The detector comprises two layers of double-sidedsilicon strip detectors (DSSD) and a cesium iodide scintillator array coupled with silicon photomultipliers arrayas light sensors, which has the advantages of their small size, fast response, and large dynamic range. DSSDscouple with cesium iodide crystal arrays are used to distinguish multiple alpha hits. The detector array has acompact and integrated design that can be adapted to different experimental conditions. The detector array wassimulated using Geant4, and the excitation energy spectra of some alpha-clustering nuclei were reconstructedto demonstrate the performance. The simulation results show that the detector array has excellent angularand energy resolutions, enabling effective reconstruction of the nuclear excited state by multiple alpha particleevents. This detector offers a new and powerful tool for nuclear physics experiments and has the potential todiscover interesting physical phenomena related to exotic nuclear structures and their decay mechanisms
分类: 物理学 >> 核物理学 提交时间: 2024-03-19
摘要: In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-25
摘要: A combination of scintillator, wavelength shifting (WLS) fiber, and silicon photomultiplier (SiPM) shows excellent performance in the `KLandμdetector (KLM)' of the Belle II experiment. We describe the RD for a similar detection technology with a new scintillator and SiPM, which can be implemented for a muon detector for the proposed CEPC experiment and the upgrade of KLM in Belle II. The RD contains the study of the performance of a new scintillator with a length of 150 cm, the NDL SiPM with a sensitive surface of 3 mm×3 mm or the Hamamatsu MPPC with a sensitive surface of 1.3 mm×1.3 mm, the construction of a detector strip, and the methods to achieve excellent light collection. The cosmic ray tests show good photon collections by NDL SiPM or MPPC, efficiencies well above 90% with a threshold of 8 p.e., and time resolutions of better than 1.7 ns for the hits at the far end of a scintillator strip. The performance shows a good option for an excellent muon detector for CEPC and the possible upgrade of Belle II KLM.