V. M. Grachev

Technology for developing databases of information systems

The problem of the creation of the needed technology allowing the effective development of corporate databases is considered. As a solution, we propose a new technology based on the “object-event” semantic model and the use of the universal data model, data model language, and special database software development tools. The principal features of the proposed technology and its advantages are considered.

Data security mechanisms implemented in the database with universal model

The problem of database security is examined. By the example of the database with universal model, the tools and methods providing security of stored corporate data are considered. The security mechanisms implemented due to the capabilities of the database management systems (DBMSs), used as database, platforms and special data protection tools implemented in the schema of the database with universal data model are discussed.

New modification of xenon gamma-ray detector with high energy resolution

Abstract. Performance of a new modification of xenon gamma-ray detector (XGD) is presented. This detector differs from the previous ones by virtue of improved energy resolution (1.7±0.1)% at 662 keV and the ability to function in the presence of external acoustic noise (up to 100 dB) with virtually no degradation of spectrometric characteristics. These results have been achieved by developing a digital method of processing every electric signal coming from the XGD. For this method, digital electronics based on field-programmable gate array has also been developed.

Prospects of the Study of Geological Structures by Muon Radiography Based on Emulsion Track Detectors

For the first time in Russia, researchers of the Lebedev Physical Institute and Skobeltsyn Institute of Nuclear Physics perform test experiments for studying the internal structure of large natural and industrial objects by the muon radiography method using the emulsion technique. The used technique is based on the high penetrability of cosmic muons and implies the detection of the attenuation of their flux passed through the object under study using nuclear photoemulsions with a uniquely high spatial resolution. The results of the first test experiment are presented, which confirm the promising application of the method when using emulsion track detectors and their subsequent hi-tech automated processing.

High-pressure xenon cylindrical ionization chamber with a shielding mesh

Construction of cylindrical ionization chamber with shielding mesh is considered. The chamber has sensitive volume 2 liters filled by xenon with pressure about 50 atm. Main characteristics of this detector such as energy resolution and efficiency of gamma-rays with energy 0.1 - 2.0 MeV are presented. It is shown that the detector energy resolution for Eequals0,662 MeV line at optimal electric field strength in the chamber is about 4%. Comparison of experimentally measured characteristics of this detector and standard scintillator NaI(T1) is fulfilled. Applications of the high pressure xenon cylindrical ionization chamber with a shielding mesh in geology, geophysics and diagnostic of oil and gas wells are considered.

Xenon detector with high energy resolution for gamma-ray line emission registration

A description of the xenon detector (XD) for gamma-ray line emission registration is presented. The detector provides high energy resolution and is able to operate under extreme environmental conditions (wide temperature range and unfavorable acoustic action). Resistance to acoustic noise as well as improvement in energy resolution has been achieved by means of real-time digital pulse processing. Another important XD feature is the ionization chamber’s thin wall with composite housing, which significantly decreases the mass of the device and expands its energy range, especially at low energies.

High-pressure xenon gamma-ray large-volume spectrometer

Design of the cylindrical ionization chamber with shielding mesh is considered. The chamber has sensitive volume 5 liters and is filled with xenon at the pressure about 35 atm. Main characteristics of this detector are submitted: the energy resolution, efficiency of detection and position of the peak of full absorption for various energies of gamma-rays. It is shown that the energy resolution at 662 keV is 2.9% at the optimum electrical field in the chamber. Prospects of use of cylindrical compressed xenon ionization chamber with a shielding mesh in various fields of science and engineering are considered.

Xenon gamma-ray spectrometer in the experiment Signal on board the spacecraft Interhelioprobe

In the experiment SIGNAL, which is planned to take place on board spacecraft INTERHELIOPROBE, a xenon gammaray spectrometer is to be used. The gamma-ray spectrometer in question has been chosen because of its characteristics permitting detailed study of solar gamma-radiation under rough experimental conditions. The equipment is able to provide: high energy resolution (5-6-fold better than that of scintillation detectors), performance at high temperatures, steady operation under significant vibroacoustic load, and high radiation resistance of the working medium. The aforesaid properties of the xenon gamma-ray spectrometer meet goals and objectives of the experiment SIGNAL. The description of ballistics scenario and operation orbit of the INTERHELIOPROBE spacecraft (SC) are presented.

Electromagnetic shields based on multilayer film structures

Electrodeposited multilayer-film electromagnetic shields are very promising for protecting various devices due to high shielding efficiency and the possibility of depositing on complex-shaped objects. In this communication, we present the results of measurements of the shielding efficiency of such shields. The shields represent alternating layers of materials with high magnetic permeability (Ni-Fe) and high conductivity (Cu). The maximum number of double layers is 45. It is shown that the shielding efficiency in the weak magnetic fields (0.1–0.2 mT) is 8–10; at higher magnetic field strengths (1.5–2.5 mT), it reaches 80–100. It is shown that the shielding factor increases with the number of layers in the shield at the same thickness of a soft magnetic material. A permalloy shield at the same amount of a soft magnetic material has an efficiency lower by a factor of 3–15 depending on the magnetic field strength.

Measurement of Electron Drift Velocities in the Mixture of Xe and He for a New High-Pressure Xe Gamma-Ray Detector

Drift velocities of electrons in a mixture of Xe (20 atm)–He (3 atm) were measured using a cylindrical high-pressure xenon chamber. The drift velocities were found to be greater than 3 ×105 cm/s above the reduced electric field of 2.0 ×10-18 Vcm2 at room temperature, which are close to those in Xe–H2 (0.3%). The mixture of He gas into high-pressure xenon improved the resolving time of detectors because it increased the electron drift velocities. This implies that a high-pressure xenon chamber mixed with 3He instead of He gas operates as a gamma-ray detector sensitive to thermal neutrons.