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Tian Y.,Tsinghua University | Yang Y.-G.,Tsinghua University | Pan J.-S.,North Night Vision Technology Co. | Li Y.-L.,Tsinghua University | Li Y.-J.,Tsinghua University
Chinese Physics C | Year: 2014

An event-counting thermal neutron imaging detector based on 3 mol % natGd2O3-doped micro-channel plate (MCP) has been developed and tested. A thermal neutron imaging experiment was carried out with a low flux neutron beam. Detection efficiency of 33% was achieved with only one doped MCP. The spatial resolution of 72 μm RMS is currently limited by the readout anode. A detector with larger area and improved readout method is now being developed. © 2014 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.


Pan J.,Changchun University of Science and Technology | Pan J.,North Night Vision Technology Corporation Ltd. | Yang Y.,Tsinghua University | Tian Y.,Tsinghua University | And 6 more authors.
Journal of Instrumentation | Year: 2013

Direct addition of neutron-absorbing atoms into MCP glass, such as 10B and 155,157Gd, without changing the remainder of MCP fabrication process, can make MCP sensitive to neutrons. Since the much larger cross section of 157Gd, the MCP doped with natGd 2O3 is more efficient than one doped with enriched 10B2O3, theoretical indicates that the detection efficiency of a MCP doped with 3 mole% of natGd 2O3 is equivalent even superior to a MCP doped with 20 mole% of 10B2O3. In this paper a 50 mm diameter rimless format 10 μm pore diameter MCP doped with 3 mole% natGd2O3 was fabricated, but the MCP glass doped with 20 mol% of natB2O3 failed to pass through the corrosive chemical processing necessary in MCPs manufacture. A primary experimental tests proved the MCP doped with 3 mole% natGd2O3 is capable of imaging thermal neutrons with 35% detection efficiency. A potential of enhancement on detection efficiency should be achieved for a optimized geometry MCP with an appropriate selection between bias angle, open area ratio and length to diameter ratio. © 2013 IOP Publishing Ltd and Sissa Medialab srl.


Tang Y.,Xi'an University of Science and Technology | Zhang R.,Xi'an University of Science and Technology | Gao H.,Xi'an University of Science and Technology | Liu K.,Xi'an University of Science and Technology | And 7 more authors.
Optics Express | Year: 2010

A partially lighbcontrolled imaging system is proposed as a novel device. It is used to improve the imaging quality at the illumination of 1979 × 105lx by means of mitigating image contrast. It consists of a High Temperature Poly-Silicon Thin Film Transistor-Liquid Crystal Display (HTPS TFT-LCD), which is set between the lens and CCD and is coupled with CCD by the optical fiber taper. The transmittance of pixelated LCD can be controlled by Field-Programmable Gate Array to realize the partially light-controlled and thus dynamic range of the imaging system can be extended. Samples of indoor objects and outdoor license plate are photographed by the prototype imaging system under strong light. The imaging results of this novel system are satisfactory with better restored details, compared with the photos taken by normal CCD camera (WAT231S2) which uses aperture and shutter to control the overall light intensity. ©2010 Optical Society of America.


Li X.-F.,1The Key Laboratory on Night Vision Technology | Li X.-F.,North Night Vision Technology Co.
Guangzi Xuebao/Acta Photonica Sinica | Year: 2013

Multi-alkali photocathode in super generation image intensifier is different from previous multi-alkali photocathode between the production processes, so the photoelectric emission characteristics are different from previous multi-alkali photocathode. In this paper, through the measurement of multi-alkali photocathode spectral reflectivity and transmissivity, according to the law of conservation of energy, cathode spectral absorption rate was obtained. Spectral absorption rate indicates that, only when the photon energy greater than 1.333 eV, cathode absorption rates began to increase quickly. The cathode spectral absorption shows that cathode will not absorb any photons if light incident photon energy is less than the absorption limit, i.e. 933 nm wave absorption limit. In the cathode surface electron affinity further reduced circumstances, cathode photoemission long wave theory threshold is determined by long-wave absorption limit. In the electronic transition process after absorption of a photon, transition energies increase less than the absorption of the incident photon energy, i.e. the presence of an "energy loss". The higher energy of a photon is, the higher electronic transition energy level is, the more energy loss is. At the same time, the higher energy of a photon is; the higher-energy level transition electron, the lower electronic transition probability is. Photocathode quantum efficiency is determined by the absorption rate, the transition probability and transition level, energy loss of diffusion process and other factors, thus photocathode quantum efficiency is in the presence of long wave threshold and shortwave threshold also. Photocathode quantum efficiency in 587 nm reaches the maximum value, after that decreases with the photon energy increases, when 3.6 eV, the quantum efficiency is reduced to zero. Cathode in photon energy of 3.6 eV the absorption coefficient is still high, but due to the electronic transition probability is low, while the electron diffusion process of energy loss is big, thus in spite of cathode on lower wavelength has high absorption coefficient, but the quantum efficiency is still low. Therefore on shortwave, cathode absorbed shortwave photon energy is converted into a photoconductive, lattice vibration and other forms of energy; the photoelectric emission utilization rate is very low.


Li Y.,Beijing Institute of Technology | Li Y.,Light Technology | Li Y.,North Night Vision Technology Co. | Chen X.,Beijing Institute of Technology | Ni G.,Beijing Institute of Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The Microchannel plate (MCP) is the main noise source of low-level light (LLL) image intensifier. Material and the whole manufacturing process of MCP have great impact on the noises of MCP. In this paper, based on the physical mechanisms of MCP, noises of MCP are classified scientifically. By using the data obtained from the actual production and the process test, the regression equation of the noise figure of MCP is derived, and the theoretical model of MCP noise figure is established, including the background noise figure model caused by the dark current of the MCP primarily about the time of the alkali corrosion technic, the ion feedback induced noise figure model caused by the patterns of the MCP channel wall primarily about the time and temperature of the hydrogen reduction technic, and the electronic scattering noise figure model caused by the open area ratio of the MCP primarily about the time of the alkali corrosion technic. Guided by the theoretical model of noise figure, the methods of suppressing noises of MCP are obtained and the technics are optimized. Taking advantage of the new techniques, the noise figure of the third generation MCP has been reduced to below 1.8. © 2013 Copyright SPIE.


Li Y.,Beijing Institute of Technology | Li Y.,North Night Vision Technology Co. | Chen X.,Beijing Institute of Technology | Ni G.,Beijing Institute of Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Microchannel plate (MCP) is a photoelectron multiplier as the core component of low-level light (LLL) image intensifier. MCP has two-dimensional space, time, and energy resolution, fast response time, low background noise, wide dynamic range and high gain characteristics, as well as electrons, ions, UV and soft X-ray photon detection capability directly. In recent years, with the publication of foreign advanced technology and Chinese research staff in-depth understanding of MCP's unique characteristics, the applications of MCP have extended into many new fields accordingly in China. In addition to the image intensifier, the MCP can be used in deep space exploration and scientific experiments, detecting kinds of trace rays and particles, such as pulsars navigation, nuclear simulation diagnostics, UV, EUV, neutron, neutrino detection and imaging. North Night Vision Technology Co. Ltd (NVT) as the only unit possessing MCP production capacity in China is constantly working on improving, innovation and application research on MCP technology. In this paper, based on the researches on MCP in some new fields the NVT Company has undertaken and ongoing, the technological breakthroughs and application research progresses achieved are described. © 2015 SPIE.


Li X.-F.,The Key Laboratory on Night Vision Technology | Li X.-F.,North Night Vision Technology Co. | Lu Q.,North Night Vision Technology Co. | Guo Q.,North Night Vision Technology Co.
Guangzi Xuebao/Acta Photonica Sinica | Year: 2013

The characteristics of photoluminescence and the measuring principle of photoluminescence of LLL image intensifier were discussed, and the fluorescence spectrum of multi-alkali photocathode of FOP (optical fiber panel) input window was measured. The test results suggest that the fluorescence spectrum of multi-alkali photocathode of FOP window is not a smooth Gauss curve, but a curve with some small interference peaks being added to a Gauss curve, for there are two special light beams in the fluorescence transmitted by FOP window. One light beam is collimated light and the other is the folded light beam at the very moment when the incidence angle is equivalent to critical angle of total reflection. Both light beams have fixed phase difference or optical path. When the difference between the phase differences of the two light beams lives up to the integral multiple of λ, they will interfere to produce constructive interference peak; when the difference between the phase differences of the two light beams lives up to the odd multiple of 1/2λ, they will interfere to produce destructive interference peak. If constructive interference peak is produced exactly at the peak wavelength of fluorescence spectrum, then the measured peak fluorescence intensity is higher than its inherent peak fluorescence intensity; on the contrary, if destructive interference is produced exactly at the peak wavelength of fluorescence spectrum, then the measured fluorescence intensity is lower than its inherent fluorescence intensity. Furthermore, due to the impact of interference, the half peak width of fluorescent curve can not be accurately determined. Hence, the impact of interference factors should be taken into consideration when analyzing the fluorescence spectrum of photocathode of FOP window.


Li X.-F.,The Key Laboratory on Night Vision Technology | Li X.-F.,North Night Vision Technology Co. | Yang W.-B.,North Night Vision Technology Co. | Wang J.,North Night Vision Technology Co. | Qiu Y.-S.,North Night Vision Technology Co.
Guangzi Xuebao/Acta Photonica Sinica | Year: 2012

The characteristics of multi-alkali photocathode and its application in low light level image intensifier are introduced, the principle of light induced fluorescence is described, the method to study electron transition probability of Na2KSb cathode film by use of light induced fluorescence is explored, and the fluorescence spectrum of two different cathodes in the states of work and non work are measured respectively. The test results show that, the fluorescence intensity of cathode is proportional to both its electronic transition probability and sensitivity, at the same time fluorescence intensity in work states declines compared to that in non work states. The reason is that part of the transition electrons escape from cathode surface and produce photoelectric emission. These transition electrons do not return to the ground state, therefore they do not emit fluorescence no longer. In this paper the fluorescence spectrum of cathode is also measured excited at different wavelengths of incident light. The results show that, compared with short waves excitation, long waves excitation can obtain higher intensity, which shows long waves excitation can get higher transition electron probability as well; at the same time wavelength shifts between fluorescence peak wavelength and excitation light wavelength is smaller; therefore, the energy loss is small, the photoelectric emission is more favorable. Compared the fluorescence spectrum with multi-alkali photocathode quantum efficiency, it can be concluded that transition electron energy level plays more important role in the process of photoelectric emission between transition electron number and the energy level. As to the multi-alkali cathode, due to electron transition probability of short wave excitation is relatively small, and energy loss of the transition electron diffusion process is bigger, therefore the short-wave quantum efficiency decreases as wavelength decreases. Practice has proved that the photoluminescence is an effective study way of cathode photoemission process, through the study of cathode fluorescence spectrum the cathode photoelectric emission mechanism is further revealed. This provides important reference value for further improving the process and raising the cathode sensitivity.


Li X.,North Night Vision Technology Co. | Guo Q.,North Night Vision Technology Co. | Lu Q.,North Night Vision Technology Co.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

In this paper, by comparing the fluorescent spectrum of the multi-alkali cathode with a surface layer of Cs-Sb and that of the multi-alkali cathode without a surface layer of Cs-Sb, we find that the peak wavelength of the fluorescent spectrum of the multi-alkali cathode with a surface layer of Cs-Sb moves towards the SW, and the fluorescent peak is enhanced. This phenomenon shows that after a Cs-Sb surface layer is produced on the multi-alkali cathode Na2KSb basic layer, the work function of multi-alkali cathode decreases; besides, the structure of the Na2KSb basic layer is changed. This means that with the incident light of the same power and the same frequency, the Na2KSb basic layer that has gone through the Cs-Sb surface processing can produce more transition electrons, with higher transition levels, more possibilities of escape from the surface, and greater sensitivity of cathode obtained. Therefore, after the Na2KSbcathode film has experienced the Cs-Sb surface activation, the spectral response increases not only because the work function on the surface decreases, but also because the internal energy band structure of the Na2KSb film is changed. After the Na2KSb cathode film has gone through the Cs-Sb activation, there will be a layer of Cs-Sb film on the surface. Stress existing between the two films result in lattice distortion of the Na2KSb film. As a result, the energy band structure is changed. To further improve the sensitivity of the multi-alkali cathode, we need further reduce the work function of the multi-alkali cathode, and further perfect the performance of the Na 2KSb basic layer, so that the incident light with the same power and frequency can generate more transition electrons with higher transition levels, which requires constant process improvement of the process and the Na 2KSb material performance. © 2013 Copyright SPIE.


Wang Y.-J.,Northwestern Polytechnical University | Wang Y.-J.,Xianyang Normal University | Wang L.-D.,Northwestern Polytechnical University | Yang M.,Northwestern Polytechnical University | And 2 more authors.
Wuli Xuebao/Acta Physica Sinica | Year: 2010

The structural stability and electronic field emission properties of carbon nanotubes doped with a boron atom in different layers and adsorbed with several H2O molecules, as well as located in the applied electric field, are analyzed by means of the density functional theory based on the first-principles. The results show that the structure of B3CNT + 5H2O doped by a boron atom in the third layer and adsorbed with five H2O molecules is most stable, the distribution of Mulliken charge on the tube cap is most dense. In particular, compared with the B3CNT doped by a boron atom and CNT + 5H2O adsorbed with five H2O molecules solely, the density of states at the Fermi energy level for B3CNT + 5H2O increases by 20% and 33% respectively. Therefore, the latter has the best field emission property. © 2010 Chin.Phys.Soc.

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