Instruments and Experimental Techniques最新文献

The article presents a dual-band S + X receiving system for a mobile VLBI station. The input frequency range is 2.2–2.6 GHz in the S-band and 8.2–9.1 GHz in the X-band. The receiving system output frequency range is 0.1–1 GHz. The paper presents the receiving system’s functional diagram and the cryogenic receiving focal unit (CRFU) layout. CRFU structure and operating principle are considered. The calculated and measured characteristics of the receiving system and CRFU are presented. The control, power-supply, and telemetry system structure, composition, and operating principle are discussed.

The design of an installation that allows conducting experiments to test the theory of interaction of two charged bodies is presented. A description of individual design elements and their main technical characteristics is provided. The results of testing this installation and their comparison with calculations are given. This design is used as a training laboratory setup and can also be used as a prototype for electrical separation of solid mixtures or electrical cleaning of gases. This laboratory work can be completed remotely.

A method is presented for measuring and analyzing the parameters of charged microparticles (micrometeorites) in the velocity range of 0.5–10 km/s and the range of electric charges from 1 fC to 1 pC. The method is based on a five-electrode grid time-of-flight detector with a 10-mm pitch and a 1-mm cell. A nonstandard approach to signal digitization has been developed. An SDRplay RSP1 software-defined radio (SDR) receiver operating in direct conversion mode at a minimum frequency with the capture bandwidth of 8 MHz is used as a wideband analog-to-digital converter. Processing of digitized data, including bandpass filtering, envelope detection, threshold event selection, and pulse parameter analysis, is implemented in the GNU Radio environment. The particle velocity and electric charge are determined from the time interval between pulses and their amplitude, respectively. It has been experimentally confirmed that the proposed SDR-based hardware and software provide flexibility and reduce the cost of the measuring system, keeping its metrological characteristics sufficient for the stated measurement ranges.

The results of calibration of a multicathode proportional counter designed for recording single-electron events in experiments to search for hidden photons of dark matter are presented. Two operating modes of the counter were investigated: the classical single-avalanche mode described by the Polya distribution, and the multiavalanche mode with the Poisson distribution. It has been shown that the application of fresh polyurethane varnish to the internal surfaces followed by immediate pumping leads to an increase in the pulse amplitude by two orders of magnitude and a transition to a multiavalanche regime. The effect disappears only after prolonged contact of the varnish with air and subsequent pumping out. Both modes are used in experimental practice to improve detection reliability.

A Solntse–Terahertz space experiment is scheduled for implementing aboard the Russian segment of the International Space Station starting in 2026. The objectives of the experiment are to obtain data on the terahertz radiation of the Sun and to study solar active regions and solar flares in the 0.4–12.0-THz range. This work presents preliminary experimental results on measuring solar radiation in the 8–14-μm atmospheric transparency window (~20–40 THz) using a ground-based setup equipped with a detector analogous to those employed in the “Solntse-Terahertz” scientific instrumentation.

A nanosecond microwave pulse source based on a nonlinear transmission line (NLTL) with saturated ferrite, operating in the S-band, has been developed and experimentally tested. Its key feature is the absence of electromagnets in its design. The source consists of a sharpening NLTL with an unsaturated ferrite, a corrugated NLTL, a coaxial high-pass filter, and a combined antenna. Both the sharpening and corrugated lines utilize NiZn ferrite rings. NdFeB permanent magnets are used to saturate the ferrite in the corrugated NLTL. The line provides efficient generation of high-frequency pulses in the frequency range of 2.7–3.6 GHz. The operating voltage range of the source is 50–190 kV. The coaxial high-pass filter has a passband of 1.2–4 GHz, which allows for effective radiation of oscillations excited in the line as well as the high-frequency energy concentrated on the front of the voltage pulse. The combined antenna has an operating range of 1–4 GHz. A pulsed periodic operating mode was implemented with a pulse repetition rate of 50 Hz up to 2000 pulses per burst. At an operating voltage of 170 kV, the central frequency of the radiated pulse is 3.4 GHz. The effective potential of the source is 65 kV.

A microprocessor-based temperature-compensated bias voltage source is presented. It stabilizes the gain of a silicon photomultiplier (SiPM) within the temperature range of 10–60°C. The temperature dependence is compensated via dynamic correction of the bias voltage according to the measured temperature and individual parameters of a particular photomultiplier. Experimental studies were performed on two PM3325-WB-D0 SiPM specimens and confirmed the efficiency of the proposed approach: the gain spread does not exceed ±1.5% for an overvoltage of 1 V or more, and the gain spread is within ±2.5% for lower overvoltage values. The presented microprocessor-based temperature-compensated bias-voltage source can be scaled for multichannel systems and adapted to various types of micropixel silicon photomultipliers.

The description of an experimental setup is presented, which allows the generation of high-frequency and microwave discharges for creating plasma streams in a wide range of operating parameters. Experiments on the generation of these discharges are described. Numerical modeling of the spatial distribution of electromagnetic fields that ensure the discharge sustainment under conditions corresponding to the actual parameters of the existing design and setup has been performed. Calculations of the absorption coefficients for waves at working frequency made it possible to determine the localization of absorption regions of the discharge and estimate the efficiency of the power introduced into the discharge for given discharge initiation techniques. The plasma parameters (the electron temperature and concentration) were obtained experimentally, and their dependences on the initial values of the pressure and power of electromagnetic field deposited into the discharge are presented. In the region of the placement of biopolymer samples, the parameters of the ion component of the plasma flow were determined. The results of the pilot studies on the influence of plasma on the physical and chemical properties of biopolymer samples are presented.

A prototype plasma rocket thruster based on a quasi-stationary high-current plasma accelerator (QSPA) is being developed at JSC SRC RF TRINITI. According to the technical specifications, the accelerator must operate in a pulse-periodic mode with a frequency of 10 Hz. It is necessary to register the plasma flow velocity at each launch, because it is an important characteristic of accelerator operation. An algorithm for automated processing of time-of-flight diagnostics of plasma flow velocity, a traditional approach at QSPA, has been developed. The proposed algorithm allows for determining the time dependence of the delay time between signals during a discharge pulse. The estimated error in the calculation results is less than 30%. The algorithm is implemented using concurrency computing on GPU, which made it possible to achieve a single launch processing time of less than 20 ms. Thus, the proposed algorithm for processing time-of-flight diagnostics data allows for calculating the plasma flow velocity after each launch when the accelerator operates in a pulse-periodic mode with a frequency of 10 Hz.

Attention is drawn to the effect of the self-field H_HT of bias current I_HT through a Hall transducer (HT) on the objects of study and the measurement accuracy of the Hall magnetometer. The field H_HT of the n-InSb-i-GaAs heteroepitaxial HT is considered. It is found that the force lines of the induction of H_HT undergo a stepwise change in their direction at the edges of a thin epitaxial n-InSb film. In the case of nonuniform distribution of I_HT over the cross section of the film, these jumps create a voltage across the Hall contacts due to the anisotropy, growth-induced defects, and nonequipotentiality of the Hall contacts, thus, leading to the measurement error. Exact compensation of H_HT by the field of a current in antiphase to I_HT makes it possible not only to eliminate the effect of the self-field on the objects of study but also to lower the detection threshold of the magnetometer from approximately 2.5 × 10^–7 to approximately 5.75 × 10^–9 T in the range of fields from 2.5 × 10^–9 to 5 × 10^–7 T and temperatures from 77.4 to 150 K.