Ion Barrier Film Research Articles

Effect of defects in ion barrier film on field of view of image intensifier

防离子反馈膜是三代微光像增强器的重要组成部分，其质量对像增强器的寿命和视场起着至关重要的作用。研究了防离子反馈膜质量对像增强器视场的影响。选取具有典型缺陷的防离子反馈微通道板（micro-channel plate，MCP），对防离子反馈微通道板在工作时的视场和防离子反馈膜质量进行分析，获得了防离子反馈膜的缺陷对微光像增强器工作时视场的影响。分析得到防离子反馈膜制备过程中缺陷产生的原因，并初步提出缺陷的解决方案，对后续制备出高质量防离子反馈膜有着非常积极的作用。

Experimental Study of Carbon Pollution Removal from Microchannel Plate with Ion Barrier Film

Experimental Study of Carbon Pollution Removal from Microchannel Plate with Ion Barrier Film

Effective Evaluation of the Noise Factor of Microchannel Plate

To improve the noise performance of microchannel plate (MCP), we have presented a method using the sine random signals with Poisson distribution as the noise-excitation for electron source. By using this method, the effective evaluation of noise characteristics of MCP has been implemented through measuring and analyzing its noise factor. The results have demonstrated that the noise factor of filmed MCP is lower than 1.8. Additionally, as the open area ratio and the input electron energy are 72% and 400 eV, respectively, the noise characteristics of unfilmed MCP are improved evidently. Moreover, larger open area ratio, higher input electron energy, and higher voltage across the MCP all can reduce effectively the noise factor within a certain range. Meanwhile, the ion barrier film extends the life of image tube but at the cost of an increased noise factor. Therefore, it is necessary that a compromise between the optimum thickness of ion barrier film, open area ratio, input electron energy, and voltage across the MCP must be reached.

The Research on Preparation Process Optimization of Ion Barrier Film on the Input Side of MCP

Micro-channel Plate (MCP) with Ion Barrier Film(IBF) is one of the main technical indicators that restrict the performance of the third generations of Low Light Level Image Intensifier(LLLII). IBF with inferior quality can be a direct impact on the performance of the third generations of LLLII or even makes it not work, and it’s very unfavorable in the tube mass production and promotion. In response to this urgent requirement, in order to improve the quality and preparation of the finished product of the Al2O3 on the input side of MCP prepared by magnetron sputtering, the paper carries out the process optimization of magnetron sputtering used for image intensifier. By simulation of Ar ion bombarding Al2O3 target, while under the guidance of the working principles of the magnetron sputtering and thin film growth theory, we change the working pressure、 sputtering power、 argon flow and other process parameters by using magnetron sputtering machine developed in China, to change the coating deposition rate of Al2O3, and to increase the lateral migration of the film-forming process of Al2O3. Finally we prepare a uniform、 continuous and compact Al2O3 Ion Barrier Film. At last the optimal technique is obtained: Sputtering pressure is 2.6×10-1Pa, Ar2 flux is 90sccm, sputtering power is 170W, and the thickness of film is 80Å. We test the performance of MCP with optimized films by using the MCP performance testing devices, contrasting with pre-fabricated thin-film quality, and the results show that the average gain decline is dropped, the dead volt is lower, and the quality of the films prepared by this process is significantly better, yield and view pass rate is as high as 90%, meeting the dual demands of high electronic transmittance and high ion blocking rate of IBF.

Monte Carlo Simulation of Electron Scattering in Ion Barrier Film in Generation III Image Intensifier

In Generation III image intensifier tubes, the input of the microchannel plate is typically coated with a thin Al2O3 film to prevent ions penetrating and damaging the delicate Cs-O activation layer of GaAs cathode. While the application of an ion barrier film to the MCP greatly improves the mean time to failure of the image intensifier tube, it unfortunately produces electron scattering to cause a significant degradation in the Modulation Transfer Function and resolution of the image tubes. To obtain an overview of the role of the ion barrier in Generation III image intensifiers, in this paper, we present the results of a Monte Carlo simulation on scattering electron transport through Al2O3 film with various photocathode voltage, density, thickness, and stoichiometry. Using Monte Carlo simulation on scattering electron ways, we get the MTF curve of film at the accelerating voltage of 400v, a thickness of 10nm, and a density of 0.3 g/cm3. The simulation results play an important role on optimizing the quality and facture technique of ion barrier film.

The Formation of Super-Thin Dielectric Film on Porous Substrate and its Stopping – Transmittance Characteristics for Particles

The formation of super-thin continuous dielectric film (e.g. the ion barrier film-IBF) on microchannel plate (a kind of porous substrate) is most important for prolonging the operating life of the third generation micro-light image tube. In this paper, firstly, the formation of Al2O3 ion barrier film on microchannel plate (MCP) using a new contamination-free technology was introduced. According to the analysis and the comparison with the traditional direct formation technology, it was found that the productivity of the new technology is better (90%) and the carbon contamination can be minimized. Next, the stopping and transmittance characteristic of the film for electrons were studied and the measurement principle was shown. In this measurement, the concepts of “dead-voltage” and “electron transmittance” were proposed to evaluate the stopping and transmittance of the film for electrons. The dead-voltage was 220V for the MCP covered the ion barrier film with a thickness of 5nm and the electron transmittance was over 90%.

微通道板离子壁垒膜粒子阻透特性的蒙特卡罗模拟

In the third-generation low-level-light image tube,a super thinner ion barrier film(IBF) was covered on the input surface of microchannel plate(MCP) to protect the photocathode and prolong the operation life of the image tube.In order to further investigate the properties of IBF,a Monte-Carlo simulation on the stopping and transmission characteristics of particles in Al2O3 and SiO2 IBFs were conducted.It was found that the dead-voltage was 230～240 V and 220～230 V for Al2O3 and SiO2 IBF with the thickness of 5 nm,respectively.The number of the back-scattered electron was as high as 19% for the incident electrons with energy of 0.24 keV.For the incident energy of 0.8 keV,the electron transmittance was 87.16% and 88.12%,and the limited thickness of the IBF was 15 nm and 16nm for Al2O3 and SiO2 film,respectively.For C+,N+ and O+ ions with energy of 0.26 keV,the ion stopping power was 95%～99% for Al2O3 IBF.The Al2O3 IBF showed satisfied electron transmittance and ion stopping power when the thickness of IBF was 5 nm.

High temporal resolution coordinate-sensitive detector with gallium-arsenide photocathode

We present a coordinate-sensitive detector with a gallium-arsenide photocathode—a vacuum photoelectronic device featuring microchannel gain and a multi-element collector—which had several prototypes manufactured. Quantum efficiency of the photocathode amounts to 48% at maximum, its sensitivity range spans from 350 to 900 nm. The microchannel gain unit consists of two plates with an ion barrier film at the entrance. The coordinates of electron avalanches are determined using a 16-element collector. The spatial resolution, diameter of the working field, and temporal resolution of the detector are equal to 25 µm, 18 mm, and about 1 µs, respectively.

Optical Ranicon detectors for photon counting imaging. I

We discuss the design and development of Ranicon detectors for optical photon counting imaging on ground-based telescopes. The significant factors which determine the performance of these detectors are found to be the proximity focusing stage, the microchannel-plate stack (MCP), and the signal processing electronics. For applications in optical astronomy, the low photon counting efficiency typically found with optical MCP-based detectors, due to ion barrier films, presents an additional consideration. We review the performance of each stage of the Ranicon detector and the techniques for achieving optimal performance. A new approach to the signal processing electronics reduces nonlinearity, while achieving increased processing speeds and a position error corresponding to <21 μm FWHM. A significant improvement in detector performance is achieved with an advanced Ranicon incorporating a reduced proximity focusing gap and an unfilmed input plate in the MCP stack. The theoretical spatial resolution of both standard and advanced Ranicon designs is derived and compared to the experimentally determined values. For the advanced Ranicon, this spatial resolution is shown to be typically 40 μm FWHM at ∼650 nm. The point spread function of the Ranicon system is shown to be stationary over the active imaging area, principally due to the removal of nonlinearities and noise sources from the signal processing electronics.