Fu Rongguo

The design of low-light night seeing helmet

The article studies the reflection and radiation light spectrum of the object under the night sky light or with the aid of laser calculates and analyzes the spectrum matching factor of typical optoelectronic cathode to the common objects and the effect on the light contrast and give the detailed mechanical design of the low light night observing instrument on helmet.

Electron emitting features and design of thermionic electron area emission sources

In vacuum system, area source electron gun emits electrons to bombard the standard screen. With the first anode and the second anode in different potentials, the images show the features of divergent, uniform, convergence and submerge. Photos, images acquired by brightness meter, and the image gray values are listed in Table 1. By image gray value analysis, it can be seen that in item no. 1, the electrons emitted by area source electron gun are divergent ( not remarkable) ; in no. 2, it is uniform; in no. 3 it is convergence and in no. 4 it is submerged. It is deduced that when the voltage of first anode of electron gun is -4000 V and the second anode voltage is -2000 V, the fluorescence screen receives the uniformly distributed electrons. The difference is less than 5%. Based on this theory, the area source electron gun is developed. The electron gun is placed in a vacuum better than 1 x 10-4Pa to be tested and it is further verified that its electron emission is uniform. The successful development of hot-electron area source provide an effective guarantee for testing the fluorescence screen parameters such as uniformity, brightness, luminous efficiency and afterglow .

The spectral responding characteristic research of the ultraviolet image intensifier

The ultraviolet image intensifier is a kind of vacuum image device with photocathode of Cs2Te (Cesium Tellurium). Its spectral response characteristic curve is measured with a specially designed spectral response measuring system, the quantum efficiency is calculated, the diffusing length of the minor carriers is analyzed. At last some opinions are brought to improve the technique.

Influences of light illumination on (Cs,O) activated GaAs photocathode

Some experiments were made on the effects of light illumination on the (Cs,O) activated GaAs(110) photocathode in previous work. It was observed that if the GaAs photocathode activated without illumination were illuminated by light of proper intensities, its photosensitivity would increase to a new maximum in several minutes and that too intensive illumination could decrease the photosensitivity on the contrary. We also made a stability and recovery study of GaAs photocathodes under varies intensities illumination, which was sealed in image intensifier and placed in UHV chamber respectively, with the help of the self-developed spectral response testing instruments. We found that when the photocathode sealed in the image intensifier illuminated by light of weak intensities, the photosensitivity first increased to a new maximum and then decreased. After removing the light for several hours, the photosensitivity can be recovered itself. Contrast to the weak illumination case, the photosensitivity of photocathode under intensive illumination would decrease monotonously and could not be recovered. By another experiment on photocathode that had been activated successfully in the UHV chamber, we found some new phenomena. Monotonous degradation is produced not only by intensive illumination, but also by weak illumination. Furthermore, photosensitivity after illuminating was unrecoverable. One of the most important phenomena observed by us was that the intensity of pressure in UHV system varied with the intense of illumination. The more intense the illumination was, the more intense would be the pressure in vacuum chamber in the several minutes of beginning. In this paper, the phenomena above-mentioned are analyzed and discussed. It is suggested that excess minority carrier induced by incident photons would damage the surface composition and structure of (Cs,O) activated GaAs photocathode. According to our research, an effective solution to increase photoemission stability is put forward. In our discussion the dipole model is strongly supported.