Instruments and Experimental Techniques最新文献

A system for improving the uniformity of ion-beam treatment of substrate surfaces and minimizing coating thickness inhomogeneity during magnetron sputtering has been proposed. A system for varying the ion incidence angle and substrate positioning has been tested, demonstrating a ninefold increase in the ion-beam treatment area and an increase in thickness uniformity during magnetron sputtering of up to 90%.

The main requirements for a new mobile radio telescope for very-long-baseline radio interferometry (VLBI) have been formulated. Several options for implementing the antenna system of a radio telescope are presented. The basic operating principles and design features of dual-band and wideband receiving systems for a mobile VLBI station are considered. The calculated characteristics of the receiving system and the new radio telescope of the mobile VLBI station are presented.

A digital filter for trapezoidal pulse shaping of exponential doublets has been implemented in a field programmable gate array (FPGA). These signals are typical of particle detectors, and the shaping is necessary to avoid pileup of smoothly decaying pulses in order to precisely measure their relative amplitudes. It was found out that, in single-board ADC-SoC computer combining an analog-to-digital converter (ADC) and an FPGA, the input ADC circuit adds the third time constant to exponential doublets, thereby distorting them. So, the digital filter has been analytically calculated and implemented in the FPGA for the trapezoidal shaping of pulses that we call the exponential triplets. The conditions for the stability of this filter have been determined. The amplitude spectrum of artificial exponential doublets has been measured.

The design of the MEPhIST-0 tokamak microwave interferometer and its system of data acquisition and processing are described. Examples of the time evolution of the linear electron density in MEPhIST-0 discharges are presented. The use of a phasemeter based on AD8302 detectors and digital post-processing of interferometer signals is compared. The beam refraction in the MEPhIST-0 chamber has been calculated. The possibility of plasma probing with a microwave interferometer for single- and two-pass configurations has been evaluated. It is shown that the transition to single-pass plasma probing allows the upper limit of the measured density to be significantly expanded (up to n₀ = 3 × 10¹⁹ m⁻³).

The design of a miniature flow helium cryostat intended for Mössbauer, X-ray diffraction, and optical studies of samples in the temperature range of 4.2–300 K is described. The cryostat’s miniature size allows for maximum compatibility with other devices, such as Mössbauer spectrometers, magnets, and optical systems. On the other hand, the low mass of the “cold finger” on which the sample is placed reduces the consumption of helium required to maintain the cryostat’s operating temperature. This also makes it less inert, i.e., it speeds up the transition from one temperature to another.

The paper proposes a new approach to the design of measuring circuits for monitoring the progress of the radio-wave surgery operations, in which the testing-effect loop is excluded from the measurement process, and monitoring is carried out by analyzing the characteristics of the oscillator signal that sets the active influence. The paper describes a method for assessing and tracking the state of the biological tissue using a directional coupler. A design and a scheme for integrating such a transducer in a surgical device have been developed. The functionality of the proposed device has been mathematically simulated and experimentally verified. It has been proven and demonstrated that monitoring the dynamic active impedance allows tracking the effects of electromagnetic radiation on the structural changes in biological tissues. This proposed method of real-time monitoring enhances the efficiency and safety of high-frequency electrosurgery.

A new method for constructing a measurement system for interrogating fiber-optic interferometric sensors has been experimentally demonstrated. This method is based on a software-defined radio receiver (SDR, Analog Devices PlutoSDR plus). The object of investigation is a Mach−Zehnder interferometer subjected to acoustical action from a low-power dynamic head and a step motor. A key feature of the proposed approach is to use a single SDR device in two functions: as a generator of an RF modulating signal for a laser source and as a receiver/demodulator for the photodetector signal of the interferometer. The fundamental applicability of the method for recording acoustic vibrations by receiving and processing the RF signal has been experimentally shown.

A compact time-of-flight neutron spectrometer was developed to study the production of neutrons at large angles in the energy range of 1–200 MeV. This spectrometer is a part of the BM@N facility at the extracted heavy ion beam of the Nuclotron accelerator at JINR. Stilbene-based detectors with silicon photomultipliers are used for the neutron registration. The main features of the spectrometer are high time resolution, short flight path, complete suppression of gamma-ray background using pulse shape discrimination, operation in a strong magnetic field, and event-by-event recording of digital data. The spectrometer’s characteristics were studied in an experiment with a beam of xenon nuclei at the energy of 3.8 A GeV.

In magnetic confinement nuclear fusion research, precise measurement of plasma radiative power is fundamental to understanding energy balance, physics of transportation, and ensuring safe device operation. This paper presentsmulti-channel integrated electronics, featuring an FPGA as the main controller and GbE communication, designed for metal foil detector with both positive and negative response channels for bolometer diagnostic. In this electronics design, compared to the single-channel electronics prototype developed recently, the phase shift circuit is optimized, DDS is adopted to generate carrier reference signal, and dynamic range compensation circuitry is incorporated. Within the constrained chassis, it integrates eight channels, significantly enhancing channel integration compared to the original BOLOMETER electronics on EAST. Performance testing in the electronics laboratory verified that all channels of this multi-channel integrated electronics exhibit consistent carrier excitation frequencies, with thethe maximum relative amplitude error of 0.48%. The linear correlation coefficient R-square between the electronics output and the detector output is 0.99997. At channel gain of 1000, the single-channel electronics noise is ±1.25 mV. Radiation response experiments on EAST demonstrate that the output signal trend of this electronics matched the time-varying trend of the plasma current and is similar to the output signal trend of the original BOLOMETER electronics, confirming the correctness of this electronics.

An approach to modifying the configuration of an optical frequency reflectometer by replacing two special service channels, including an auxiliary interferometer and a gas cell, with a single channel is described. In this configuration, the sensory characteristics of the system were studied. Digital filtering methods were used to extract useful information. It is shown that the presented method allows to avoid the use of an extra channel of the analog-to-digital converter and photodetector, while the reflectogram and correlation functions are restored by the equal-frequency resampling algorithm without loss of information.