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  • 1
    Online Resource
    Online Resource
    Spectral calibration for electron beam ion trap and precision measurement of M1 transition wavelength in Ar〈sup〉13+〈/sup〉
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2022
    In:  Acta Physica Sinica Vol. 71, No. 3 ( 2022), p. 033201-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 71, No. 3 ( 2022), p. 033201-
    Abstract: The precise measurement of the transition wavelength of the fine structure of highly charged ions can not only test basic physical theories including the quantum electrodynamics effect and the electronic correlation effect but also provide key atomic data for astrophysics and fusion plasma physics. Furthermore, highly charged ions are considered as a potential candidate for optical clocks with extremely ultra-high precision. In this work, a new spectral calibration system is built in a high-temperature superconducting electron beam ion trap (SH-HtscEBIT) in the Institute of Modern Physics, Fudan University, and the uncertainty of its spectrum wavelength measurement is evaluated by combining internal and external calibrations. The minimum wavelength uncertainty caused by the new spectral calibration system in the visible light band reaches 0.002 nm. On this basis, the precise measurement of 2s〈sup〉2〈/sup〉2p 〈sup〉2〈/sup〉P〈sub〉1/2〈/sub〉－〈sup〉2〈/sup〉P〈sub〉3/2〈/sub〉 M1 transition wavelength for boron-like Ar〈sup〉13+〈/sup〉 is performed at the SH-HtscEBIT by utilizing the new calibration system. The experimentally measured transition wavelength is (441.2567 ± 0.0026) nm. It is currently the experimental result with the highest measurement accuracy of spectroscopy of highly charged ions at the SH-HtscEBIT, which lays the foundation for the precise measurement of the hyperfine splitting and isotope shift of highly charged ions in the future experiments.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.71.20211663
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2022
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  • 2
    Online Resource
    Online Resource
    Measurements of global polarization of QCD matter in heavy-ion collisions
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2023
    In:  Acta Physica Sinica Vol. 72, No. 7 ( 2023), p. 072401-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 72, No. 7 ( 2023), p. 072401-
    Abstract: The experimental data of the global polarization of Λ hyperon, ϕ and K〈sup〉*0〈/sup〉 vector mesons in high-energy heavy ion collision confirm the new phenomenon of global polarization of hot-dense QCD matter, which has attracted extensive attention from researchers and has become a new hot research direction in the frontier of high-energy nuclear physics. This paper reviews the recent global polarization measurements. We focus on the global polarization measurements of Λ hyperon and ϕ, K〈sup〉*0〈/sup〉 mesons, carried out by the solenoidal tracker detector (STAR) collaboration group at the Relativistic Heavy Ion Collider (RHIC) at its Phase I of Beam Energy Scan program, and extend to the global polarization measurements containing multiple strange quark particles, such as Ξ, Ω and the local polarization studies of Λ along the beam direction. In the paper, we also briefly comment on the measurements at higher energy from the large hadron collider (LHC) and at very low energy in HADES experiment. In the end of the paper, the physical information given by these experimental results is also briefly discussed.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Article
    DOI: 10.7498/aps.72.20222452
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2023
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  • 3
    Online Resource
    Online Resource
    Research advances in antimatter
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2024
    In:  Acta Physica Sinica Vol. 73, No. 19 ( 2024), p. 191101-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 73, No. 19 ( 2024), p. 191101-
    Abstract: The asymmetric origin of matter and antimatter in the universe is an important unsolved mystery in science today. In this paper, we briefly review the history of antimatter research and the recent international hotspots of related research. This paper focuses on the advances in antimatter research made in recent years at the large-scale international RHIC-STAR experiment at the Relativistic Heavy Ion Collider, including the discovery of the first antimatter hypernucleus (anti-hypertriton), antimatter helium 4 and antihyperhydrogen 4, the first measurements of antiproton interactions, and the precise measurements of the mass and binding energy of the hypertriton and anti-hypertriton. The antimatter hypertriton nucleus, composed of an antiproton, an antineutron, and an anti-Λ hyperon, is the first anti-hypernucleu to be discovered, extending the three-dimensional nuclide map from the anti-strange quark degree of freedom. Antimatter Helium 4 is the heaviest stable antimatter nucleus yet discovered. Anti-hyperhydrogen 4, just discovered in 2024, is composed of an antiproton, two antineutrons, and an anti-Λ hyperon, and is the heaviest antimatter hypernucleus to date. Equivalence to the proton-proton interaction was established by measurements of the antiproton-antiproton interaction. At the same time, precise measurements of the mass of hypertriton and anti-hypertriton nuclei confirmed the equivalence of matter and antimatter. And these also fully demonstrate that the CPT symmetry is also valid for antimatter nuclei. Measurements of the binding energy of the hypertriton nucleus indicate that the interaction between Λ and the nucleus of the hypertriton (the deuterium nucleus) is strong, which differs from the earlier common belief that the hypertriton nucleus is a weakly bound system. Furthermore, we discuss different physical mechanisms for the production of (anti) light nuclei, mainly including thermal, coalescence and relativistic kinetic models. Finally, we also present recent results from antihydrogen atom experiments at CERN, antimatter space probes, etc., and discuss the implications of these advances for understanding the structure of matter. Overall, the existing studies of antimatter nuclei and atoms have not yet provided clear evidence for the asymmetric origin of matter and antimatter in the universe, which can help further improve the accuracy of various measurements in antimatter research. Of course, other efforts in this direction in nuclear and particle physics are well expected.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Article
    DOI: 10.7498/aps.73.20241020
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2024
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  • 4
    Online Resource
    Online Resource
    Theoretical calculation of response sensitivity of CsI photocathode of soft X-ray streak camera
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2023
    In:  Acta Physica Sinica Vol. 72, No. 24 ( 2023), p. 245203-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 72, No. 24 ( 2023), p. 245203-
    Abstract: The response sensitivity of CsI photocathode is an important parameter for the quantitative diagnosis of X-ray spectroscopy by soft X-ray streak camera, and its theoretical calculation has important guiding significance. The current theoretical analytical models are based on the one-dimensional random walking model of secondary electrons generated by thin film photocathodes, including the Henke model under the condition of normal incidence of X-rays and energy greater than 1 keV, and the Fraser model under variable angle incidence and photocathode thickness greater than 100 nm, which have certain limitations. In this paper, the basic expression of the probability of secondary electron transmission is introduced, and the general expression of the response sensitivity of CsI photocathode is deduced, which varies with X-ray energy 〈 i 〉 E 〈 /i 〉 , photocathode thickness 〈 i 〉 t 〈 /i 〉 , and angle 〈 i 〉 θ 〈 /i 〉 between X-ray and cathode surface in a larger parameter range (X-ray energy 0.1–10 keV, photocathode thickness 10–200 nm). Finally, the theoretical calculation results of this paper are discussed by comparing it with those from the Henke model, Fraser model, literature data and experimental data on Beijing synchrotron radiation facility, which verifies the accuracy and universality of the computational model, and a theoretical reference is provided for optimally designing the CsI photocathode in high-time-resolution spectrometric quantitative measurement.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Article
    DOI: 10.7498/aps.72.20231043
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2023
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  • 5
    Online Resource
    Online Resource
    Prediction of short range order in high-entropy alloys and its effect on the electronic, magnetic and mechanical properties
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2020
    In:  Acta Physica Sinica Vol. 69, No. 4 ( 2020), p. 046102-
    Details
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 69, No. 4 ( 2020), p. 046102-
    Abstract: The prediction of stable state of high-entropy alloys (HEAs) is crucial to obtain fundamental insight to the excellent properties of HEAs. Taking a FeCuCrMnMo alloy as a case study, we combined Monte Carlo (MC) method with the density functional thoery (DFT) calculations (MC/DFT) to predict the equilibrium structure of high-entropy alloys in a finite unit cell. Instead of approaching the ideal random state obtained from special quasi-random approximation (SQS) method, physical factors such as atomic size, mixing enthalpy of atomic pairs, and interatomic interactions in the alloy are fully considered and implemented in our simulation by MC/DFT calculations. MC codes ensure the energy convergence of the system to the equilibrium state through the atom exchange process. The equilibrium structures exhibit Cu-rich short-range orders (SRO), which is consistent with the observation in experiments. Comparing with ideal random state structure, SRO structure is more stable in energy, and more closely packed in atomic arrangement. Moreover, the analyses of order parameters and radial distribution functions (RDFs) are performed to character the structure of high-entropy alloy. The order parameter of Cu-Cu atomic pair reaches to –0.53 in the SRO equilibrium structure, which indicates that Cu-rich regions appear in the alloy. The RDFs show that the atomic distance distribution of the SRO structure is between 2.25 Å to 2.7 Å, which is smaller than the range of 2.16 Å to 2.84 Å in the SQS structure, indicating that the lattice distortions is relatively small in the SRO structure after structural optimization. The appearing of SRO phenomena is attributed to the inherent characteristics of atoms, including (i) atomic size, (ii) interatomic mixing enthalpy and (iii) the interaction of atoms. Atomic sizes in the FeCuCrMnMo alloy are in the order of Fe (11.78) 〈 Cu (11.81) 〈 Cr (11.97) 〈 Mn (14.38) 〈 Mo (15.58), in unit of Å〈sup〉3〈/sup〉/atom. The relatively large sizes of Mn and Mo atoms should disadvantage the pairing of Mo-Mo and Mn-Mn. The mixing enthalpy of Cu with other atoms are all positive values, indicating that Cu is not favor of pairing other elements and precipitate itself. The analyses of density of state (DOS) and Crystal Orbital Hamilton Population (COHP) also support the results. The reason is exactly attributed to the inactive valence electrons of Cu. Furthermore, the effect of SRO on the magnetic and mechanical properties are investigated. The existence of SRO decreases the mean value of magnetic moment, and results in an increase of elastic moduli (〈i〉B〈/i〉, 〈i〉G〈/i〉 and 〈i〉E〈/i〉) and a decrease in the ductility and anisotropy properties.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    URL: Journal
    URL: Article
    DOI: 10.7498/aps
    DOI: 10.7498/aps.69.20191671
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2020
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