自触发射电阵列的设计是宇宙线大气簇射的射电探测所面临的机遇和难题之一,例如由背景源产生高振幅的瞬时噪声会导致射电阵列的误触发,而阵列设计需要避免由噪声导致的误触发.大气簇射射电信号独有的偏振特征为解决阵列的误触发问题提...自触发射电阵列的设计是宇宙线大气簇射的射电探测所面临的机遇和难题之一,例如由背景源产生高振幅的瞬时噪声会导致射电阵列的误触发,而阵列设计需要避免由噪声导致的误触发.大气簇射射电信号独有的偏振特征为解决阵列的误触发问题提供了解决方案,而利用信号偏振特征解决阵列误触发的方法的前提是射电信号的电场重建.由于背景噪声也会通过天线响应耦合到最终的观测数据中,这对正确重建射电信号的电场构成不可忽视的挑战.基于GRAND(Giant Radio Array for Neutrino Detection)验证阵列GP300(GRAND-Proto 300)的样机,结合模拟软件ZHAireS(ZHS AIR-shower Extended Simulations)模拟大气簇射产生的射电信号,耦合三极化天线的真实响应并使用最小二乘法重建电场,研究了射电信号的偏振特性,最终统计了以偏振为基础的天线的触发效率.展开更多
The combat survivability is an essential factor to be considered in the development of recent military aircraft. Radar stealth and onboard electronic attack are two major techniques for the reduction of aircraft susce...The combat survivability is an essential factor to be considered in the development of recent military aircraft. Radar stealth and onboard electronic attack are two major techniques for the reduction of aircraft susceptibility. A tactical scenario for a strike mission is presented. The effect of aircraft radar cross section on the detection probability of a threat radar, as well as that of onboard jammer, are investigated. The guidance errors of radar guided surface to air missile and anti aircraft artillery, which are disturbed by radar cross section reduction or jammer radiated power and both of them are determined. The probability of aircraft kill given a single shot is calculated and finally the sortie survivability of an attack aircraft in a supposed hostile thread environment worked out. It is demonstrated that the survivability of a combat aircraft will be greatly enhanced by the combined radar stealth and onboard electronic attack, and the evaluation metho dology is effective and applicable.展开更多
The monolithic integration of vertical-cavity surface-emitting lasers (VCSEL) with photodetectors is very important in the application of free-space optical interconnects.Theoretical and experimental results on the re...The monolithic integration of vertical-cavity surface-emitting lasers (VCSEL) with photodetectors is very important in the application of free-space optical interconnects.Theoretical and experimental results on the resonant-cavity-enhanced (RCE) photodetector with VCSEL Structure are presented.The compatible requirement in input mirror reflectivity between the VCSEL and the RCE detector is achieved by precisely etching the top mirror.In this way,the RCE detector with relatively high quantum efficiency and necessary optical bandwidth has been obtained.[KH8/9D]展开更多
In the last years, the production of optical fibers cables has made possible the development of a range of spectroscopic probes for in situ analysis performing beyond nondestructive tests, environmental monitoring, se...In the last years, the production of optical fibers cables has made possible the development of a range of spectroscopic probes for in situ analysis performing beyond nondestructive tests, environmental monitoring, security investigation, application in radiotherapy for dose monitoring, verification and validation. In this work, a system using an optical fiber cable to electromagnetic signal transmission from a NaI（TI） radiation detector is presented. The innovative device takes advantage mainly of the optical fibers large passband, small signal attenuation and immunity to electromagnetic interference to application for radiation detection systems. The main aim was to simplify the detection system making it to reach areas where the conventional device cannot access due to its lack of mobility and external dimensions. Some tests with this innovative system are presented and the results stimulate the continuity of the researches.展开更多
A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher t...A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher than that with Fe converter plate. The designed detector has the merits of well processed and static vacuum keeping and can be used for intense pulsed gamma ray detecting.展开更多
The soft X-ray spectroscopy, laser Thomson scattering and electron cyclotron emission （ ECE ） are usually adopted for electron temperature measurement in fusion research of magnetic confinement. The particular soft ...The soft X-ray spectroscopy, laser Thomson scattering and electron cyclotron emission （ ECE ） are usually adopted for electron temperature measurement in fusion research of magnetic confinement. The particular soft X-ray spectroscopy has the very good spatial-temporal resolution and smaller measuring error than laser Thomson scattering, a close spatial-temporal resolution to ECE, absolute measurement ability, and smaller influence by suprathermal and runaway electrons than ECE.展开更多
An understanding of the absorption of light is essential for efficient photovoltaic and photodetection applications with III-V nanowire arrays. Here, we correlate experiments with modeling and verify experimentally th...An understanding of the absorption of light is essential for efficient photovoltaic and photodetection applications with III-V nanowire arrays. Here, we correlate experiments with modeling and verify experimentally the predicted absorption of light in InP nanowire arrays for varying nanowire diameter and length. We find that 2,000 nm long nanowires in a pitch of 400 nm can absorb 94% of the incident light with energy above the band gap and, as a consequence, light which in a simple ray-optics description would be travelling between the nanowires can be efficiently absorbed by the nanowires. Our measurements demonstrate that the absorption for long nanowires is limited by insertion reflection losses when light is coupled from the air top-region into the array. These reflection losses can be reduced by introducing a smaller diameter to the nanowire-part closest to the air top-region. For nanowire arrays with such a nanowire morphology modulation, we find that the absorptance increases monotonously with increasing diameter of the rest of the nanowire.展开更多
In this paper, we have designed and proofed a widely tunable microwave photonic filter (MPF) on the basis of self-adaptive optical carrier regeneration method through stimulated Brillouin scattering (SBS) amplificati...In this paper, we have designed and proofed a widely tunable microwave photonic filter (MPF) on the basis of self-adaptive optical carrier regeneration method through stimulated Brillouin scattering (SBS) amplification. The MPF system features with a single microwave passband as the result of the processed signal sideband beating with the regenerated optical carrier. Since the Brillouin-laser optical carrier and the SBS amplification are generated from one laser source, the optical carrier regeneration process of the proposed MPF is self- adaptive and carrier-frequency independent. Moreover, by simply varying the wavelength spacing between the optical carrier and the optical filter, the central passband of the MPF can be continuously tuned from 6 to 32 GHz, which is limited by the bandwidth of the modulator and the photodetector. The 3 dB bandwidth and the out-of-band suppression ratio of the MPF can reach 640 MHz and 21 dB, respectively.展开更多
Particle bursts （PBs）, the phenomena characterized by short-term increases of particle counting rates （CRs）, were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by Na...Particle bursts （PBs）, the phenomena characterized by short-term increases of particle counting rates （CRs）, were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by National Oceanic and Atmospheric Ad- ministration （NOAA）-18 satellite, the occurrence of PBs in the inner belt （I〈~L〈2 and B〉20.5 gT） were derived for years 2006-2011. The monthly occurrence number of PBs exhibits a strong maximum in northern summer （May-August）. In associ- ation with global lightning data, the seasonal occurrence of PBs is found to be consistent with the lightning activity, especially if only lightning flashes at latitudes 〉20~ are taken into account. The positive correlation between PBs and mid-latitude light- ning discharges indicates the role of lightning-induced whistler waves, and is consistent with the expected pitch-angle scatter- ing by wave-particle interactions. The contribution of lightning is so significant that it forms a non-negligible seasonal back- ground of PBs. If one connects PBs to seismoelectromagnetic emissions （SEME） in attempt to find the earthquake precursor, the lightning background needs to be considered with great care.展开更多
文摘自触发射电阵列的设计是宇宙线大气簇射的射电探测所面临的机遇和难题之一,例如由背景源产生高振幅的瞬时噪声会导致射电阵列的误触发,而阵列设计需要避免由噪声导致的误触发.大气簇射射电信号独有的偏振特征为解决阵列的误触发问题提供了解决方案,而利用信号偏振特征解决阵列误触发的方法的前提是射电信号的电场重建.由于背景噪声也会通过天线响应耦合到最终的观测数据中,这对正确重建射电信号的电场构成不可忽视的挑战.基于GRAND(Giant Radio Array for Neutrino Detection)验证阵列GP300(GRAND-Proto 300)的样机,结合模拟软件ZHAireS(ZHS AIR-shower Extended Simulations)模拟大气簇射产生的射电信号,耦合三极化天线的真实响应并使用最小二乘法重建电场,研究了射电信号的偏振特性,最终统计了以偏振为基础的天线的触发效率.
文摘The combat survivability is an essential factor to be considered in the development of recent military aircraft. Radar stealth and onboard electronic attack are two major techniques for the reduction of aircraft susceptibility. A tactical scenario for a strike mission is presented. The effect of aircraft radar cross section on the detection probability of a threat radar, as well as that of onboard jammer, are investigated. The guidance errors of radar guided surface to air missile and anti aircraft artillery, which are disturbed by radar cross section reduction or jammer radiated power and both of them are determined. The probability of aircraft kill given a single shot is calculated and finally the sortie survivability of an attack aircraft in a supposed hostile thread environment worked out. It is demonstrated that the survivability of a combat aircraft will be greatly enhanced by the combined radar stealth and onboard electronic attack, and the evaluation metho dology is effective and applicable.
文摘The monolithic integration of vertical-cavity surface-emitting lasers (VCSEL) with photodetectors is very important in the application of free-space optical interconnects.Theoretical and experimental results on the resonant-cavity-enhanced (RCE) photodetector with VCSEL Structure are presented.The compatible requirement in input mirror reflectivity between the VCSEL and the RCE detector is achieved by precisely etching the top mirror.In this way,the RCE detector with relatively high quantum efficiency and necessary optical bandwidth has been obtained.[KH8/9D]
文摘In the last years, the production of optical fibers cables has made possible the development of a range of spectroscopic probes for in situ analysis performing beyond nondestructive tests, environmental monitoring, security investigation, application in radiotherapy for dose monitoring, verification and validation. In this work, a system using an optical fiber cable to electromagnetic signal transmission from a NaI（TI） radiation detector is presented. The innovative device takes advantage mainly of the optical fibers large passband, small signal attenuation and immunity to electromagnetic interference to application for radiation detection systems. The main aim was to simplify the detection system making it to reach areas where the conventional device cannot access due to its lack of mobility and external dimensions. Some tests with this innovative system are presented and the results stimulate the continuity of the researches.
文摘A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher than that with Fe converter plate. The designed detector has the merits of well processed and static vacuum keeping and can be used for intense pulsed gamma ray detecting.
文摘The soft X-ray spectroscopy, laser Thomson scattering and electron cyclotron emission （ ECE ） are usually adopted for electron temperature measurement in fusion research of magnetic confinement. The particular soft X-ray spectroscopy has the very good spatial-temporal resolution and smaller measuring error than laser Thomson scattering, a close spatial-temporal resolution to ECE, absolute measurement ability, and smaller influence by suprathermal and runaway electrons than ECE.
文摘An understanding of the absorption of light is essential for efficient photovoltaic and photodetection applications with III-V nanowire arrays. Here, we correlate experiments with modeling and verify experimentally the predicted absorption of light in InP nanowire arrays for varying nanowire diameter and length. We find that 2,000 nm long nanowires in a pitch of 400 nm can absorb 94% of the incident light with energy above the band gap and, as a consequence, light which in a simple ray-optics description would be travelling between the nanowires can be efficiently absorbed by the nanowires. Our measurements demonstrate that the absorption for long nanowires is limited by insertion reflection losses when light is coupled from the air top-region into the array. These reflection losses can be reduced by introducing a smaller diameter to the nanowire-part closest to the air top-region. For nanowire arrays with such a nanowire morphology modulation, we find that the absorptance increases monotonously with increasing diameter of the rest of the nanowire.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61501422 & 61377071)the Equipment Development Project of Chinese Academy of Sciences (Grant No. YZ201201)
文摘In this paper, we have designed and proofed a widely tunable microwave photonic filter (MPF) on the basis of self-adaptive optical carrier regeneration method through stimulated Brillouin scattering (SBS) amplification. The MPF system features with a single microwave passband as the result of the processed signal sideband beating with the regenerated optical carrier. Since the Brillouin-laser optical carrier and the SBS amplification are generated from one laser source, the optical carrier regeneration process of the proposed MPF is self- adaptive and carrier-frequency independent. Moreover, by simply varying the wavelength spacing between the optical carrier and the optical filter, the central passband of the MPF can be continuously tuned from 6 to 32 GHz, which is limited by the bandwidth of the modulator and the photodetector. The 3 dB bandwidth and the out-of-band suppression ratio of the MPF can reach 640 MHz and 21 dB, respectively.
基金supported by the National Basic Research Program of China("973" Project)(Grant Nos.2012CB957801,2011CB811405)the National Natural Science Foundation of China(Grant Nos.41274155,40904036)+1 种基金the Public Science and Technology Research Funds Projects of Ocean,State Oceanic Administration of China(Grant No.201005017)the Specialized Research Fund for State Key Laboratories
文摘Particle bursts （PBs）, the phenomena characterized by short-term increases of particle counting rates （CRs）, were observed by space-borne radiation belt particle detectors. With the electron CR data obtained by National Oceanic and Atmospheric Ad- ministration （NOAA）-18 satellite, the occurrence of PBs in the inner belt （I〈~L〈2 and B〉20.5 gT） were derived for years 2006-2011. The monthly occurrence number of PBs exhibits a strong maximum in northern summer （May-August）. In associ- ation with global lightning data, the seasonal occurrence of PBs is found to be consistent with the lightning activity, especially if only lightning flashes at latitudes 〉20~ are taken into account. The positive correlation between PBs and mid-latitude light- ning discharges indicates the role of lightning-induced whistler waves, and is consistent with the expected pitch-angle scatter- ing by wave-particle interactions. The contribution of lightning is so significant that it forms a non-negligible seasonal back- ground of PBs. If one connects PBs to seismoelectromagnetic emissions （SEME） in attempt to find the earthquake precursor, the lightning background needs to be considered with great care.
