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In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 72, No. 5 ( 2023), p. 056801-

Abstract: Tungsten is an important candidate of plasma-facing material for fusion reactors. Its irradiation response, especially the post-irradiation annealing (PIA) behavior needs further investigating. In addition, the practice of the “inside-outside” contrast method of determining the characteristics of irradiation induced dislocation loops has not been utilized frequently, and the present research serves as an example to present some practical considerations. In the present work, a tungsten thin-foil specimen is irradiated at 400 ℃ with 58 keV D〈sup〉+〈/sup〉 to a final fluence of 1× 10〈sup〉17〈/sup〉 cm〈sup〉–2〈/sup〉, corresponding to a dose of about 0.1 dpa. The specimen is prepared through the electro-polishing method by using a NaOH based electrolyte. The ion irradiation is carried out directly on the electro-polished specimen. The irradiated specimen is followed by isothermal annealing at 900 ℃ for 1 h. The as-irradiated and post-irradiation annealing modified defects are investigated with a transmission electron microscope (TEM) operated at 200 kV. The irradiation defects are characterized by using TEM bright-field imaging for the same imaging field with different 〈i〉 〈b〉g〈/b〉 〈/i〉 vectors around the three major zone axes: the [001], [111], and [011] zone axis of the body-center cubic lattice of W. For each 〈i〉 〈b〉g〈/b〉 〈/i〉 vector, the ±〈i〉 〈b〉g〈/b〉 〈/i〉 are characterized, and the corresponding contrast-extinctions and “inside-outside” contrasts of selected dislocation loops are identified. The indices of the 〈i〉 〈b〉g〈/b〉 〈/i〉 vectors around different zone axes are assigned consistently with the Kikuchi map. As a result, the D〈sup〉+〈/sup〉 irradiation increases a fine distribution of dislocation loops with an average size of (11.10±5.41) nm and a bulk density of 2.40×10〈sup〉22〈/sup〉 /m〈sup〉3〈/sup〉. Voids are not observed obviously. The post-irradiation annealing causes the loop size to increase and the loop density to decrease, with numbers of (18.25±16.92) nm and 1.19×10〈sup〉22〈/sup〉 /m〈sup〉3〈/sup〉, respectively. Through the contrast-extinction analysis, the dislocation loops in the irradiated and annealed specimen are identified to be 〈i〉 〈b〉a〈/b〉 〈/i〉/2〈inline-formula〉〈tex-math id="Z-20230218170937"〉\begin{document}$\langle {111} \rangle$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20222124_Z-20230218170937.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20222124_Z-20230218170937.png"/〉〈/alternatives〉〈/inline-formula〉-type dislocation loops. The post-irradiation annealing also causes the coalescence of large loops and forms large irregular-shaped dislocation loops. Voids with typical sizes of 1–2 nm are also observed in the annealed specimen. The PIA modified microstructure is consistent with the stage IV or stage V characterization of classical PIA induced microstructures. Through the “one-step” inside-outside contrast method, the dislocation loops are identified as an interstitial type. The influcing factors for the “one-step” method are discussed and the importance of consistent indexing is also noted.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Article

DOI: 10.7498/aps.72.20222124

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2023

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 73, No. 4 ( 2024), p. 042101-

Abstract: The interactions between hyperon-nucleon and hyperon-hyperon have been an important topic in strangeness nuclear physics, which play an important role in understanding the properties of hypernuclei and equation of state of strangeness nuclear matter. It is very difficult to perform a direct scattering experiment of the nucleon and hyperon because the short lifetime of the hyperon. Therefore, the hyperon-nucleon interaction and the hyperon-hyperon interaction have been mainly investigated experimentally by 〈 inline-formula 〉 〈 tex-math id="M4" 〉 \begin{document}$\gamma$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M4.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M4.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 spectroscopy of single- 〈 inline-formula 〉 〈 tex-math id="M5" 〉 \begin{document}$\Lambda$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M5.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M5.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hypernuclei or double- 〈 inline-formula 〉 〈 tex-math id="M6" 〉 \begin{document}$\Lambda$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M6.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M6.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hypernuclei. There are also many theoretical methods developed to describe the properties of hypernuclei. Most of these models focus mostly on the ground state properties of hypernuclei, and have given exciting results in producing the banding energy, the energy of single-particle levels, deformations, and other properties of hypernuclei. Only a few researches adopting Skyrme energy density functionals is devoted to the study of the collective excitation properties of hypernuclei. In present work, we have extended the relativistic mean field and relativistic random phase approximation theories to study the collective excitation properties of hypernuclei, and use the methods to study the isoscalar collective excited state properties of double 〈 inline-formula 〉 〈 tex-math id="M7" 〉 \begin{document}$\Lambda$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M7.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M7.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hypernuclei. First, the effect of 〈 inline-formula 〉 〈 tex-math id="M8" 〉 \begin{document}$\Lambda$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M8.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M8.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hyperons on the single-particle energy of 〈 sup 〉 16 〈 /sup 〉 O and 〈 inline-formula 〉 〈 tex-math id="M9" 〉 \begin{document}$^{18}_{\Lambda\Lambda}{\rm{O}}$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M9.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M9.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 are discussed in the relativistic mean field theory, the calculations are performed within TM1 parameter set and related hyperon-nucleon interaction, and hyperon-hyperon interaction. We find that it gives a larger attractive effect on the 〈 inline-formula 〉 〈 tex-math id="M10" 〉 \begin{document}${{\mathrm{s}}}_{1/2}$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M10.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M10.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 state of proton and neutron, while gives a weaker attractive effect on the state around Fermi surface. The self-consistent relativistic random phase approximation is used to study the collectively excited state properties of hypernucleus 〈 inline-formula 〉 〈 tex-math id="M11" 〉 \begin{document}$^{18}_{\Lambda\Lambda}{\rm{O}}$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M11.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M11.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 . The isoscalar giant monopole resonance and quadrupole resonance are calculated and analysed in detail, we pay more attention to the effect of the inclusion of 〈 inline-formula 〉 〈 tex-math id="M12" 〉 \begin{document}$\Lambda$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M12.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M12.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hyperons on the properties of giant resonances. Comparing with the strength distributions of 〈 sup 〉 16 〈 /sup 〉 O, changes of response function of 〈 inline-formula 〉 〈 tex-math id="M13" 〉 \begin{document}$^{18}_{\Lambda\Lambda}{\rm{O}}$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M13.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M13.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 are evidently found both on the isoscalar giant monopole resonance and quadrupole resonance. It is shown that the difference comes mainly from the change of Hartree energy of particle-hole configuration and the contribution of the excitations of 〈 inline-formula 〉 〈 tex-math id="M14" 〉 \begin{document}$\Lambda$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M14.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="4-20231531_M14.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hyperons. We find that the hyperon-hyperon residual interactions have small effect on the monopole resonance function and quadrupole response function in the low-energy region, and have almost no effect on the response functions in the high-energy region.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Article

DOI: 10.7498/aps.73.20231531

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2024

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 71, No. 18 ( 2022), p. 188703-

Abstract: To realize the diversified applications of terahertz wave, a new method to realize 2-bit (4 states) coding metasurface with only two hybrid units is proposed, which combines the phase transition characteristics of VO〈sub〉2〈/sub〉 and is different from the traditional metasurface. The metal wire threaded through the patch makes single-line control possible. The method of preparing the VO〈sub〉2〈/sub〉 thin film and the voltage control mechanism make the design more practical. The highlight of this design is that the fixed structure array can encode different state sequences and then tune the reflected beam. On this basis, a visual design is carried out for the calculation of the coding metasurface array antenna by MATLAB. The state sequence and radiation results are predicted by actively setting the operating frequency, beam deflection angle, etc., so as to achieve active adjustment. The system does not limit the unit structure and is universal to all arrays that meet the coding conditions. In addition, a deep neural network is introduced into the array arrangement, and the structure sequence is predicted by algorithm training and verified by numerical calculation and full-wave simulation. The results show that the proposed method is effective in beam deflection angle and structure arrangement. This study presents a new way of actively and flexibly controlling terahertz waves, which has potential applications in terahertz imaging, phase-controlled radar, communication and other fields.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Article

DOI: 10.7498/aps.71.20220817

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2022

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 72, No. 3 ( 2023), p. 034203-

Abstract: Laser has the advantages of high brightness, good monochromaticity, high coherence and good directionality, however, in some cases such as laser imaging and laser processing where only its high brightness or high monochromaticity is desired, the interference effect caused by high coherence can affect and limit its effective applications. In this work, a new single glass tube decoherence lens (SGTDL) is designed for soft X-ray laser decoherence through the simulation calculations. The simulation results show that an SGTDL with an entrance diameter of 5 mm, exit diameter of 0.6 mm and a length of 15 cm can effectively reduce the coherence of the X-ray laser with a wavelength of 10 nm and a beam waist radius of 1.25 mm. At the same time, the exit beam with a divergence range of 30–50 mrad is obtained at the SGTDL’s exit, and the transmission efficiency and gain in power density of the SGTDL are 78% and 52.74, respectively. For a laser beam with a wavelength of up to 1 nm, this model of SGTDL can maintain the transmission efficiency of the beam at more than 30%. This work also discusses the influence of the X-ray laser energy and the SGTDL’s length on the transmission performances of the SGTDL. The results show that the SGTDL designed according to the total reflection principle can meet the application requirements for laser decoherence in a range from the extreme ultraviolet to X-ray wavelength, and has a wide application prospect in X-ray laser imaging, laser processing, etc.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Article

DOI: 10.7498/aps.72.20221917

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2023

In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 71, No. 13 ( 2022), p. 131201-

Abstract: In this review article, we show an important aspect of electron-positron pair production from vacuum under strong background field where the frequency chirping plays a key role in enhancing the pair production. A series of researches on the enhancement effect of frequency chirp on electron-positron pair production in strong field is summarized. Three approaches are introduced, i.e. the Dirac-Heisenberg-Wigner formalism used to treat the spatial inhomogeneous field or/and multidimensional homogeneous time-dependent field, quantum Vlasov equation to cope with the one-dimensional homogeneous time-dependent field, and the computation quantum field theory employed to study the problem with external potential. Some interesting results about the momentum spectrum structure of created particle and the yielding of pair numbers are demonstrated for various different field parameters such as field strength and central frequency, in particular their significant influence on results when the frequency chirping form or/and strength are changed. In general, the number density can be improved by 2-3 orders of magnitude with the strengthening of frequency chirping in comparison with that without chirping for low frequency field, which is attributed to the effect that the dynamically assisted mechanism plays a significant role since the chirping expands the frequency spectrum of field. For high frequency field, however, this effect is suppressed so that the number density is enhanced by about a few times. For spatially inhomogeneous field, field changing on a small scale does not make the number density so high and the frequency chirping can enhance the yield in the order of magnitude, while the field changing on a large scale makes the number density to approach to that of homogeneous field and the chirping increases the yield by a few times. These numerical results can be understood by the Wentzel-Kramer-Brillouin (WKB) approximation and the structure of turning points. Finally the possible applicable prospects of the electron-positron pair production by the frequency chirping are presented briefly.

Type of Medium: Online Resource

ISSN: 1000-3290 , 1000-3290

URL: Article

DOI: 10.7498/aps.71.20220148

Language: Unknown

Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences

Publication Date: 2022