Relativistic electrons moving over a periodic metal grating can lead to an intriguing emission of light,known as Smith–Purcell radiation[SPR],the precursor of the free-electron laser.The speed of light plays a critic...Relativistic electrons moving over a periodic metal grating can lead to an intriguing emission of light,known as Smith–Purcell radiation[SPR],the precursor of the free-electron laser.The speed of light plays a critical role in the far-field emission spectrum.Inspired by this photonic SPR,here we experimentally demonstrate a photoacoustic phased array using laser-induced shock waves.We observe acoustic radiation spectrum in the far field,perfectly predicted by a universal theory for the SPR.This scheme provides a tool to control the acoustic radiation in the near field,paving the way toward coherent acoustic wave generation and microstructure metrology.展开更多
To protect superconducting qubits and enable rapid readout, optimally designed Purcell filters are essential. To suppress the off-resonant driving of untargeted readout resonators, individual Purcell filters are used ...To protect superconducting qubits and enable rapid readout, optimally designed Purcell filters are essential. To suppress the off-resonant driving of untargeted readout resonators, individual Purcell filters are used for each readout resonator.However, achieving consistent frequency between a readout resonator and a Purcell filter is a significant challenge. A systematic computational analysis is conducted to investigate how fabrication variation affects filter performance, through focusing on the coupling capacitor structure and coplanar waveguide(CPW) transmission line specifications. The results indicate that the T-type enclosing capacitor(EC), which exhibits lower structural sensitivity, is more advantageous for achieving target capacitance than the C-type EC and the interdigital capacitor(IDC). By utilizing a large-sized CPW with the T-type EC structure, fluctuations in the effective coupling strength can be reduced to 10%, given typical micro-nanofabrication variances. The numerical simulations presented in this work minimize the influence of fabrication deviations, thereby significantly improving the reliability of Purcell filter designs.展开更多
为解决气动调节阀控制过程中出现的超调大、精度低等问题,本文采用BP神经网络整定出较优的PID(Proportional Integral Derivative)控制参数,对Smith预估控制器以及模糊控制器进行设计,实现了基于BP神经网络的Smith-Fuzzy-PID控制方法。...为解决气动调节阀控制过程中出现的超调大、精度低等问题,本文采用BP神经网络整定出较优的PID(Proportional Integral Derivative)控制参数,对Smith预估控制器以及模糊控制器进行设计,实现了基于BP神经网络的Smith-Fuzzy-PID控制方法。搭建了实验平台,通过阶跃响应实验来对控制方法进行验证,验证结果表明,提出的方法调节过程无超调,调节时间仅为1.9 s,定位精度在±0.5%以内,有效提高了系统的稳定性,实现了气动调节阀的快速精准定位。展开更多
A novel Smith-Purcell （S-P） free electron laser composed of an electron gun, a semi-elliptical resonator, a metallic reflecting grating and a collector, is presented for the first time. This paper studies the charac...A novel Smith-Purcell （S-P） free electron laser composed of an electron gun, a semi-elliptical resonator, a metallic reflecting grating and a collector, is presented for the first time. This paper studies the characteristics of this device by theoretical analysis and particle-in-cell simulation method. Results indicate that tunable coherent S-P radiation with a high output peak power at millimeter wavelengths can be generated by adjusting the length of the grating period, or adjusting the voltage of the electron beam. The present scheme has the following advantages： the semi-elliptical resonator can reflect all radiation with the emission angle {？ and random azimuthal angles, back onto the electron beam with same-phase and causes the electrons to be modulated, so the output power and efficiency are improved.展开更多
With the aid of a three-dimensional particle-in-cell code simulation,the enhancement of Smith-Purcell radiation with a surface-plasmon mode excited by a single electron bunch and by a premodulated electron beam is con...With the aid of a three-dimensional particle-in-cell code simulation,the enhancement of Smith-Purcell radiation with a surface-plasmon mode excited by a single electron bunch and by a premodulated electron beam is considered in the paper.In the simulation,the model is a grating covered by Ag film.The results demonstrate that when the surface-plasmon mode is excited by a single electron bunch,the maximum radiation occurs at an observation angle depending on the surface-plasmon frequency,and the radiation power can be enhanced more than ten times.And for pre-bunched electron beam excitation,when one of the harmonics of the bunching frequency is resonant with that of the surface-plasmon mode,the radiation power is twenty times more than that from a perfectly conducting grating excited by the same premodulated electron beam.展开更多
We investigate a novel Smith–Purcell terahertz source. This device is composed of an electron gun, a cylindrical resonator, a metallic grating, and a collector. The characteristics of the Smith–Purcell terahertz sou...We investigate a novel Smith–Purcell terahertz source. This device is composed of an electron gun, a cylindrical resonator, a metallic grating, and a collector. The characteristics of the Smith–Purcell terahertz source are discussed with the help of three-dimensional particle-in-cell simulation. In this device, coherent and high-power Smith–Purcell radiation(SPR) at the terahertz frequency range can be produced for the reasonable parameters of charge energy and grating. Our results indicate that coherent SPR at 506.529 GHz with a power around 1000 W can be obtained for a grating of period l=0.3 mm operating at the beam energy E=50 keV and beam current I=10 A.展开更多
A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The char...A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.展开更多
基金supported by the National Natural Science Foundation of China(Nos.92050113 and 11674228)the National Key Research and Development Program of China(Nos.2016YFA0302500 and 2017YFA0303700)the Shanghai MEC Scientific Innovation Program(No.E00075)。
文摘Relativistic electrons moving over a periodic metal grating can lead to an intriguing emission of light,known as Smith–Purcell radiation[SPR],the precursor of the free-electron laser.The speed of light plays a critical role in the far-field emission spectrum.Inspired by this photonic SPR,here we experimentally demonstrate a photoacoustic phased array using laser-induced shock waves.We observe acoustic radiation spectrum in the far field,perfectly predicted by a universal theory for the SPR.This scheme provides a tool to control the acoustic radiation in the near field,paving the way toward coherent acoustic wave generation and microstructure metrology.
基金Project support by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (CAS) (Grant No. 2019319)the Start-up Foundation of Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou, China (Grant No. Y9AAD110)+1 种基金the Innovative and Entrepreneurial Talents Project of Jiangsu Province, China (Grant No. JSSCBS20221743)the Excellent Postdoctoral Talent Program of Jiangsu Province, China (Grant No. 2023ZB816)。
文摘To protect superconducting qubits and enable rapid readout, optimally designed Purcell filters are essential. To suppress the off-resonant driving of untargeted readout resonators, individual Purcell filters are used for each readout resonator.However, achieving consistent frequency between a readout resonator and a Purcell filter is a significant challenge. A systematic computational analysis is conducted to investigate how fabrication variation affects filter performance, through focusing on the coupling capacitor structure and coplanar waveguide(CPW) transmission line specifications. The results indicate that the T-type enclosing capacitor(EC), which exhibits lower structural sensitivity, is more advantageous for achieving target capacitance than the C-type EC and the interdigital capacitor(IDC). By utilizing a large-sized CPW with the T-type EC structure, fluctuations in the effective coupling strength can be reduced to 10%, given typical micro-nanofabrication variances. The numerical simulations presented in this work minimize the influence of fabrication deviations, thereby significantly improving the reliability of Purcell filter designs.
文摘为解决气动调节阀控制过程中出现的超调大、精度低等问题,本文采用BP神经网络整定出较优的PID(Proportional Integral Derivative)控制参数,对Smith预估控制器以及模糊控制器进行设计,实现了基于BP神经网络的Smith-Fuzzy-PID控制方法。搭建了实验平台,通过阶跃响应实验来对控制方法进行验证,验证结果表明,提出的方法调节过程无超调,调节时间仅为1.9 s,定位精度在±0.5%以内,有效提高了系统的稳定性,实现了气动调节阀的快速精准定位。
基金Project supported by the National Natural Science Foundation of China (Grant No. 60871047)the Natural Science Foundation of Liaocheng University of China (Grant No. X0810018)
文摘A novel Smith-Purcell （S-P） free electron laser composed of an electron gun, a semi-elliptical resonator, a metallic reflecting grating and a collector, is presented for the first time. This paper studies the characteristics of this device by theoretical analysis and particle-in-cell simulation method. Results indicate that tunable coherent S-P radiation with a high output peak power at millimeter wavelengths can be generated by adjusting the length of the grating period, or adjusting the voltage of the electron beam. The present scheme has the following advantages： the semi-elliptical resonator can reflect all radiation with the emission angle {？ and random azimuthal angles, back onto the electron beam with same-phase and causes the electrons to be modulated, so the output power and efficiency are improved.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61001031)
文摘With the aid of a three-dimensional particle-in-cell code simulation,the enhancement of Smith-Purcell radiation with a surface-plasmon mode excited by a single electron bunch and by a premodulated electron beam is considered in the paper.In the simulation,the model is a grating covered by Ag film.The results demonstrate that when the surface-plasmon mode is excited by a single electron bunch,the maximum radiation occurs at an observation angle depending on the surface-plasmon frequency,and the radiation power can be enhanced more than ten times.And for pre-bunched electron beam excitation,when one of the harmonics of the bunching frequency is resonant with that of the surface-plasmon mode,the radiation power is twenty times more than that from a perfectly conducting grating excited by the same premodulated electron beam.
基金National Natural Science Foundation of China(NSFC)(11275089,11375081)Natural Science Foundation of Shandong Province(ZR2011FQ001)
文摘We investigate a novel Smith–Purcell terahertz source. This device is composed of an electron gun, a cylindrical resonator, a metallic grating, and a collector. The characteristics of the Smith–Purcell terahertz source are discussed with the help of three-dimensional particle-in-cell simulation. In this device, coherent and high-power Smith–Purcell radiation(SPR) at the terahertz frequency range can be produced for the reasonable parameters of charge energy and grating. Our results indicate that coherent SPR at 506.529 GHz with a power around 1000 W can be obtained for a grating of period l=0.3 mm operating at the beam energy E=50 keV and beam current I=10 A.
文摘A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.
