The Einstein Probe(EP)mission,approved by the Chinese Academy of Sciences(CAS)in 2017 and launched in 2024,is a significant advancement in time-domain astronomy.The Follow-up X-ray Telescope(FXT),equipped with a Wolte...The Einstein Probe(EP)mission,approved by the Chinese Academy of Sciences(CAS)in 2017 and launched in 2024,is a significant advancement in time-domain astronomy.The Follow-up X-ray Telescope(FXT),equipped with a Wolter I focusing mirror system and a PNCCD detector,is critical for detecting and analyzing cosmic X-rays.To ensure its reliability in space,structural and structural-thermal models were developed,and mechanical and thermal tests were conducted to verify its ability to withstand launch stresses and space conditions.The Wolter I mirrors,manufactured and integrated by the HIT team,achieved an angular resolution of 57 arcseconds at 1.5 keV and an effective area of 250 cm^(2).This paper presents the verification results of these tests,including insights from the flight spare model,and discusses potential reasons for the observed loss of effective area,such as alignment imperfections or thermal distortions.These findings are essential for optimizing the FXT’s design and ensuring the mission’s success,highlighting the importance of rigorous testing in space-based observatory development.展开更多
Since laser intensity plays an important role in laser plasma interactions,a method of increasing laser intensity- focusing of an intense laser via a parabolic plasma concave surface- is proposed and investigated by t...Since laser intensity plays an important role in laser plasma interactions,a method of increasing laser intensity- focusing of an intense laser via a parabolic plasma concave surface- is proposed and investigated by three-dimensional particle-in-cell simulations.The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude.Compared with the improvement via laser optics approaches,this scheme is much more economic and appropriate for most femtosecond laser facilities.展开更多
We analyze the properties of a focused Laguerre–Gaussian(LG)beam propagating through anisotropic ocean turbulence based on the Huygens–Fresnel principle.Under the Rytov approximation theory,we derive the analytical ...We analyze the properties of a focused Laguerre–Gaussian(LG)beam propagating through anisotropic ocean turbulence based on the Huygens–Fresnel principle.Under the Rytov approximation theory,we derive the analytical formula of the channel capacity of the focused LG beam in the anisotropic ocean turbulence,and analyze the relationship between the capacity and the light source parameters as well as the turbulent ocean parameters.It is found that the focusing mirror can greatly enhance the channel capacity of the system at the geometric focal plane in oceanic turbulence.The results also demonstrate that the communication link can obtain high channel capacity by adopting longer beam wavelength,greater initial beam waist radius,and larger number of transmission channels.Further,the capacity of the system increases with the decrease of the mean squared temperature dissipation rate,temperature-salinity contribution ratio and turbulence outer scale factor,and with the increase of the kinetic energy dissipation rate per unit mass of fluid,turbulence inner scale factor and anisotropy factor.Compared to a Hankel–Bessel beam with diffraction-free characteristics and unfocused LG beam,the focused LG beam shows superior anti-turbulence interference properties,which provide a theoretical reference for research and development of underwater optical communication links using focused LG beams.展开更多
Photoacoustic imaging with a synthetic aperture focusing technique（SAFT） is an effective method to improve the lateral resolution for out-of-focus regions in scanning microscopy systems, which commonly require a dec...Photoacoustic imaging with a synthetic aperture focusing technique（SAFT） is an effective method to improve the lateral resolution for out-of-focus regions in scanning microscopy systems, which commonly require a decent motorized scanning stage for a lateral scan of a transducer to obtain a cross-sectional image. In this study, we propose and test a photoacoustic imaging system with a scanning mirror-based SAFT（SM-SAFT） for simple and fast data acquisition, without the need for a physical scan of the transducer. Photoacoustic images of hair phantoms acquired by SM-SAFT are demonstrated, serving as a proof-of-concept experiment to show the feasibility and potential of the proposed approach.展开更多
基金supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences,Grant No.XDA1531010301.
文摘The Einstein Probe(EP)mission,approved by the Chinese Academy of Sciences(CAS)in 2017 and launched in 2024,is a significant advancement in time-domain astronomy.The Follow-up X-ray Telescope(FXT),equipped with a Wolter I focusing mirror system and a PNCCD detector,is critical for detecting and analyzing cosmic X-rays.To ensure its reliability in space,structural and structural-thermal models were developed,and mechanical and thermal tests were conducted to verify its ability to withstand launch stresses and space conditions.The Wolter I mirrors,manufactured and integrated by the HIT team,achieved an angular resolution of 57 arcseconds at 1.5 keV and an effective area of 250 cm^(2).This paper presents the verification results of these tests,including insights from the flight spare model,and discusses potential reasons for the observed loss of effective area,such as alignment imperfections or thermal distortions.These findings are essential for optimizing the FXT’s design and ensuring the mission’s success,highlighting the importance of rigorous testing in space-based observatory development.
基金supported by National Natural Science Foundation of China(Nos.11174259,11175165)the Dual Hundred Foundation of China Academy of Engineering Physics
文摘Since laser intensity plays an important role in laser plasma interactions,a method of increasing laser intensity- focusing of an intense laser via a parabolic plasma concave surface- is proposed and investigated by three-dimensional particle-in-cell simulations.The geometric focusing via a parabolic concave surface and the temporal compression of high harmonics increased the peak intensity of the laser pulse by about two orders of magnitude.Compared with the improvement via laser optics approaches,this scheme is much more economic and appropriate for most femtosecond laser facilities.
基金This work was supported by the Science and Technology Innovation Training Program of Nanjing University of Posts and Telecommunications(Grant No.CXXZD2023080)the National Natural Science Foundation of China(Grant Nos.61871234 and 62001249)+1 种基金the Natural Science Foundation of Nanjing University of Posts and Telecommunications(Grant No.NY222133)the Open Research Fund of National Laboratory of Solid State Microstructures(Grant No.M36055).
文摘We analyze the properties of a focused Laguerre–Gaussian(LG)beam propagating through anisotropic ocean turbulence based on the Huygens–Fresnel principle.Under the Rytov approximation theory,we derive the analytical formula of the channel capacity of the focused LG beam in the anisotropic ocean turbulence,and analyze the relationship between the capacity and the light source parameters as well as the turbulent ocean parameters.It is found that the focusing mirror can greatly enhance the channel capacity of the system at the geometric focal plane in oceanic turbulence.The results also demonstrate that the communication link can obtain high channel capacity by adopting longer beam wavelength,greater initial beam waist radius,and larger number of transmission channels.Further,the capacity of the system increases with the decrease of the mean squared temperature dissipation rate,temperature-salinity contribution ratio and turbulence outer scale factor,and with the increase of the kinetic energy dissipation rate per unit mass of fluid,turbulence inner scale factor and anisotropy factor.Compared to a Hankel–Bessel beam with diffraction-free characteristics and unfocused LG beam,the focused LG beam shows superior anti-turbulence interference properties,which provide a theoretical reference for research and development of underwater optical communication links using focused LG beams.
基金supported by the National Natural Science Foundation of China (No. 61405112)the Shanghai Pujiang Program (No. 14PJ1404400)
文摘Photoacoustic imaging with a synthetic aperture focusing technique（SAFT） is an effective method to improve the lateral resolution for out-of-focus regions in scanning microscopy systems, which commonly require a decent motorized scanning stage for a lateral scan of a transducer to obtain a cross-sectional image. In this study, we propose and test a photoacoustic imaging system with a scanning mirror-based SAFT（SM-SAFT） for simple and fast data acquisition, without the need for a physical scan of the transducer. Photoacoustic images of hair phantoms acquired by SM-SAFT are demonstrated, serving as a proof-of-concept experiment to show the feasibility and potential of the proposed approach.
