Лидарная система комбинационного рассеяния света для зондирования молекул водорода в атмосфере

Computer simulation of the Raman lidar equation for measurement of the hydrogen molecules at the concentration level of 1013 cm-3 and higher in atmosphere at the ranging distances up to 100 m in the synchronous photon counting mode and selection of such a lidar optimal parameters have been fulfilled. It is shown that for hydrogen molecules concentration of N(z)=1013 cm-3 measurement at the distances from 5 to 100 m the measurement time t is in the range from 3.83 s to 26.5 min, for measurement of concentration N(z) = 1015 cm-3 - from 38 ms to 15.9 s and for the concentration measurement of N(z) = 1017 cm-3 - already from 0.4 ms to 160 ms, respectively.

Ab initio phasing macromolecular structures using electron-counted MicroED data

Structures of two globular proteins were determined ab initio using microcrystal electron diffraction (MicroED) data that was collected on a direct electron detector in counting mode. Microcrystals were identified using a scanning electron microscope (SEM) and thinned with a focused ion-beam (FIB) to produce crystalline lamellae of ideal thickness. Continuous rotation data were collected using an ultra-low exposure rate on a Falcon 4 direct electron detector in electron-counting mode. For the first sample, triclinic lysozyme extending to 0.87 A resolution, an ideal helical fragment of only three alanine residues provided initial phases. These phases were improved using density modification, allowing the entire atomic structure to be built automatically. A similar approach was successful on a second macromolecular sample, proteinase K, which is much larger and diffracted to a modest 1.5 A resolution. These results demonstrate that macromolecules can be determined to sub-Angstrom resolution by MicroED and that ab initio phasing can be successfully applied to counting data collected on a direct electron detector.

Investigation of the characteristics of matrix multi-element avalanche photodetectors operating in the photon counting mode

At present, matrix multi-element avalanche photodetectors operating in the photon counting mode are widely used for detecting optical radiation. However, the char-acteristics of matrix multi-element avalanche photodetectors operating in this mode are currently insufficiently studied. Prototypes of Si-photomultiplier tubes (Si-PMTs) with a p+–p–n+ structure produced by JSC Integral (Republic of Belarus), as well as serially produced silicon photomultipliers Ketek PM 3325 and ON Semi FC 30035 have been used as objects of research. This article presents the research results of characteristics in the photon counting mode of the specified photodetec-tors. The dependences of the specific amplitude sensitivity ratio on the wavelength of optical radiation, the temperature, the supply voltage of the matrix multi-element avalanche photodetector are determined.

Probabilistic characteristics of a two-channel detector with two inertial single-photon photoemission devices and a logical adder

Analytical expressions are obtained for calculating the probabilities of correct detection of a two-channel inertial detector of pulsed optical radiation in the photon counting mode, containing a receiving optical complex of two lens antennas, two single-photon photoemission devices and a logic adder.