Vol 59, No 4 (2016)

A method for analyzing the transverse beam feedback circuit in a ring accelerator and selecting its parameters using the concept of the active beam coupling impedance, which is externally imposed and controlled, is described. This approach is used for the physical substantiation of approaches to upgrading two operational transverse feedback systems that are available in the U-70 synchrotron of the Institute for High Energy Physics, National Research Centre Kurchatov Institute: narrow-band analog and broadband digital systems. Both systems were subjected to deep upgrading, which is based on this method, and were successfully commissioned in 2007 and 2011, respectively. A brief description of their updated engineering implementation is given. The presented experimental results confirm the adequacy of the impedance approach to designing and adjusting the transverse beam feedback circuits in the U-70 synchrotron.

The design of the position-sensitive neutron detector being developed by the Alikhanov Institute for Theoretical and Experimental Physics is described, and results of the simulation of its properties are presented. Based on the test results of the first prototype, the spatial resolution has been improved, and the detector shape has been optimized. The principal limitation on the positioning accuracy for neutrons is obtained from results of computer simulation in the GEANT4 environment. The expected spatial resolution of the designed detector is <1.5 cm.

A technique for calibrating cathode strip gains in multiwire drift chambers of the GlueX experiment is described. The accuracy of the technique is estimated based on Monte Carlo generated data with known gain coefficients in the strip signal channels. One of the four detector sections has been calibrated using cosmic rays. Results of drift chamber calibration on the accelerator beam upon inclusion in the GlueX experimental setup are presented.

A data acquisition system of the OKA experiment on studying rare kaon decays on the U-70 accelerator is described. The basis of the blocked data acquisition system was the high-speed multichannel information system MISS with autonomous controllers that read out the front-end electronics in the sequential data reading mode and buffering data during the accelerator burst. Data stored in the buffer memory are read out and processed at the end of the accelerator burst. The DATE package builds subevents from event fragments and events from subevents via the event building network. The event building network with the star topology is made with 1GbE-interfaces and 24 × 1 Gb E-switch. The GlusterFS cluster file system underlies the distributed storage system.

Based on fast gas electron multipliers, a beam monitor and recording electronics for reading information and transmitting it to the local network was manufactured. The speed of operation of the system is determined by the characteristics of driver amplifiers and equal to ~10⁸ (particle/s)/cm². The operation of the system was tested from a radioactive source.

A two-channel configured analog microcircuit, intended for applications in optoelectronic devices of space equipment, is created on complementary bipolar transistors. The different combination of microcircuit pins and connection of external RC-elements allow one to create several analog units with specified values of the conversion coefficient of the input signal, bandwidth, rate of rise, and consumed current. The maximal gain of the microcircuit with an open negative feedback loop exceeds 75 dB, and the bandwidth at the 20-fold gain is more than 19.4 MHz. The circuit designs of separate stages of the microcircuit and experimental characteristics are given.

The application of a PS-1/S1 picosecond streak camera (SC), which was developed at the General Physics Institute (Russian Academy of Sciences) for investigating fast processes in semiconductor physics, laser physics, and accelerator engineering, is described. It is shown that using the PS-1/S1 SC it is possible to record one-dimensional images (restricted by a narrow slit) of fast processes with a time resolution of no worse than 1 ps in a wide spectral range: from UV (115 nm) to near-IR (1.5 μm) radiation with a dynamic recording range of ≥10. The presented experimental results show the wide potential capabilities of applying the developed SC in various fields of experimental physics.

Visualization of the phase object with the use of a phase-contrast scheme incorporating a nonlinear Zernike filter was carried out. A liquid crystal or liquid crystalline polymer doped with azobenzene dye inducing orientational optical nonlinearity was used as the filter. Inversion of the image contrast depending on the angle of incidence of the light beam on a nematic liquid crystal cell was implemented.

A brief description is presented of the γ-ray spectrometer part of the Mercurian gamma-ray and neutron spectrometer (MGNS), the scientific instrument for planetary research on mapping of γ-ray and neutron emission from the Mercury surface onboard BepiColombo spacecraft of the European Space Agency (ESA) spacecraft. As the crystal for the γ-ray spectrometer, an innovative CeBr₃ scintillator was chosen on the basis of the ground tests and analysis of the results reported in this paper.

A digital colorimetric analytical instrument is described that allows one to determine the concentrations of substances in solutions using transparent polymeric optodes, which are able to change their color depending on a reagent and the determined-substance content. The structural and functional diagrams of the instrument that operates under the control of a LabVIEW-based program are presented. The instrumental error of the analyzer is within 1%. The instrument operation was demonstrated by the example of determining the cobalt content in drinking water, which was taken from an outdoor water pump. The metrological characteristics of the instrument are not worse than those implemented with the standard solid-phase spectrophotometry method. The instrument can be used in the industrial, environmental, clinical, and other kinds of monitoring, where the rapid determination of the concentrations of various substances is required.

The possibility of obtaining fracture cleavages of polyethylene naphthalate tracking membrane samples for electron microscope examinations has been investigated. These cleavages allow one to examine the pore channel structure along the whole pore length from one surface to the other. Due to a high radiation and thermal stability of polyethylene naphthalate films, thermal, ultraviolet, and radiation treatment methods applied for obtaining brittle films of such polymers as polyethylene terephthalate, polycarbonate, and polypropylene are unsuitable for them. The treatment of the samples with concentrated nitric acid vapors for 1.5 months makes them brittle. It is possible to obtain good cross-section.

A method for studying local and integral characteristics of heat transfer at pool boiling on a thinfilm heater using a high-speed thermal-imaging camera is described. Experiments have been carried out at pool boiling of saturated ethanol with a heat flux as high as 40 W/cm². A 1-μm-thick indium−tin oxide (ITO) film sputtered on a 0.4-mm-thick sapphire substrate by the vapor deposition method was used as a heater. Based on simultaneous measurements of the temperature field distribution at the back side of the ITO film using an IR thermal-imaging camera in combination with visual recording of vapor bubble growth and departure directly on the heater surface, it is possible to judge the temperature field evolution under individual vapor bubbles, the nucleation site density and the nucleation frequency, as well as the time of bubble growth and departure during boiling.