A high-speed gateable image pipeline

We present the performance of a high-speed gateable vacuum image pipeline, which permits individual images to be delayed and selected from continuous non-repetitive image stream. This device is composed of a vacuum tube equipped with a photocathode at one end, a phosphor screen at the other end, and a system of metal grids in between. Photoelectrons produced by the images focused on the photocathode, are guided by a uniform magnetic field, parallel to the tube axis. By changing the grid potentials, the drift time of the photoelectrons inside the tube can be varied from 0.35 to 1.5 μs. An image can then be selected by an external trigger with a time resolution in the range of 4–30 ns, depending on the delay time. The selected photoelectrons are finally accelerated onto the phosphor screen, set at 10 kV, where they reproduce the desired image. With a magnetic field of 0.1 T, a spatial resolution of 33 lp/mm was obtained. The high spatial and time resolution make this device an interesting tool for high-energy physics and astrophysics experiments, and for high-speed photography.     

Methods of improving information security by integrating multiplexing,ciphering and channel encoding operations

A regular rule for constructing infinite families of orthogonal Walsh W(n) and orthogonal C(n)systems is suggested, which possesses the property of two-loop cyclic shift and is based on complete classes of perfect binary arrays (PBA) H(N), where N = 2 ^k and N = 3 × 2 ^k is PBA order, n = N ² is orthogonal systems order, and k is an arbitrary integer. Methods that increase information security by integrating multiplexing, ciphering and channel encoding operation are developed on the basis of families of C(n)orthogonal systems, which also allow solving system tradeoffs in CDMA technologies.     

Effect of doping on properties of Zno:Cu and Zno:Ag thin films

ZnO:Cu and ZnS thin films were grown by metal-organic chemical vapour deposition (MOCVD) under atmospheric pressure onto glass substrates. The ZnO:Ag films were fabricated from ZnS films by non-vacuum method that consists of simultaneous oxidation and Ag-doping by the close spaced evaporation (CSE) of silver at the temperature of 500–600 °C. Photo-assisted rapid thermal annealing (PARTA) at ambient air during 10–30 s at the temperature of 700–800 °C was used for the ZnO:Cu films. The samples were studied by X-ray diffraction technique (XRD), atomic force microscopy (AFM), and photoluminescence (PL) measurements. The grain size of ZnO:Cu films increased with an increase of Cu concentration. PL spectra of as-deposited ZnO:Cu films depended on Cu concentration and contained the bands typical for the copper. After PARTA at high temperature the emission maximum shifted towards the short-wave region. During the fabrication of ZnO:Ag films the grain growth process was strongly affected by the Ag loading level. The grain size increased with an increase of Ag concentration and ZnO:Ag films with surface roughness of 8 nm were obtained. Observed 385 nm PL peak for these samples can be attributed to the exciton–exciton emission that proves the high quality of the obtained ZnO:Ag films.     

The nature of white luminescence in SiO2:C layers

Silicon oxide layers containing incorporated carbon (SiO₂:C) have been obtained by sequential thermal carbonization/oxidation of porous silicon. The as-synthesized SiO₂:C layers exhibit intense white photoluminescence (PL). The characteristics of excitation, emission, and relaxation of the white luminescence in the SiO₂:C layers have been studied. It is established that the observed broad PL band in fact consists of at least two subbands with the maxima of intensity in the green and blue spectral regions. Based on the experimental data, a model of the PL excitation and radiative recombination in SiO₂:C layers is proposed and justified.