Instruments and Experimental Techniques最新文献

This article describes a method for optimizing the distribution of capacitances of a voltage multiplier. This action is necessary to reduce the weight of the device without reducing the output power at the load. The simulation was carried out for the case of an input voltage of 950 V, an output voltage of 10 kV, a frequency of 750 kHz, and a capacitance range from 1 to 25 nF. A comparison was made for constant and variable capacity. It is shown that using the dependence of capacitance on capacitor number allows for reducing mass of the device by 7% compared with a constant distribution. The main elements of a voltage multiplier are diodes and capacitors. A diode and a capacitor connected in parallel form a stage that increases the voltage amplitude. A pair of series connected steps form a cascade. In addition to increasing the output voltage, the first stage cuts off the negative components of a signal, and the second one cuts off the positive one.

This article presents the description of a prototype readout electronics for capacitive detectors based on an application-specific integrated circuit (ASIC) designed specifically for the readout and pre-processing of signals from the flat resistive chambers of the SPD (spectrometer with pixel detectors) experiment at the NICA collider under construction at JINR (Joint Institute for Nuclear Research) in Dubna. The eight-channel ASIC is optimized to work with detectors featuring a characteristic impedance of the readout electrodes in the range of 35–110 Ω, with an equivalent input noise charge of no more than 2500 electrons. The ASIC includes adjustments for the threshold by the input charge in the range of 10–450 fC, hysteresis of the threshold characteristic in the range of 0–12%, and signal extension time in the range of 0.5–100 ns. The circuit was optimized to reduce jitter on the front edge (less than 10 ps) and power consumption (less than 25 mW per channel).

A single-crystal converter oriented along the axis is placed in front of an electromagnetic spectrometer to change the response of the spectrometer that measures electrons with energies of several tens of GeV. The relative energy resolution of the spectrometer is improved by 15−80% depending on the orientation, thickness, and type of the crystal converter and the spectrometer thickness at electron energies of 26 and 28 GeV.

The Nanogate‑38 gated camera was used to measure the transverse beam dimensions in the BEP booster of the VEPP‑2000 electron−positron collider. The camera is used to measure the vertical beam size by a double-slit interferometer and to visualize a transverse beam profile in single-turn mode with the projection optics. The purpose of the experiments is to assess the applicability of the camera to measurements of the transverse beam dimensions and beam emittance in accelerator experiments at the SKIF synchrotron-radiation source.

Josephson traveling wave parametric amplifiers can have high gain and wide frequency range, high sensitivity, and low noise, which makes them promising for quantum computing, array receiver readout systems, spectroscopy, single-photon detectors, etc. In this paper, the authors investigate samples of traveling wave parametric amplifiers based on a three-layer Nb/AlO_x/Nb superconductor–insulator–superconductor (SIS) structure with a SNAIL (Superconducting Nonlinear Asymmetric Inductive Elements) series array. Each SNAIL cell consists of the kinetic inductance of four SIS junctions and the nonlinear inductance of a smaller SIS junction. The cells are alternately connected in antiphase with respect to the magnetic flux, which ensures a change in the sign of the Kerr nonlinearity and a reduction in the phase mismatch for the pump frequency, signal frequency, and idler frequency. The transmission spectra of the samples were measured at temperatures of 4.2 and 2.8 K in the frequency range of 0.1–6 GHz.

Atomic force microscopy (AFM) is a valuable method for measuring the surface properties of a sample, where the accurate estimation of the relative distance between the probe and the sample (depth) is a prerequisite for fast, accurate measurement. This paper uses geometric optical modeling to establish a function model between the blur amount in the AFM probe image and depth. This model estimates the depth by the lens via the blur information of strong edge images according to the characteristics of a small depth of field and multiple blurs in microscopic images. To estimate the probe position, the study embedded the convolutional block attention module attention mechanism model into the Resnet18 network, allowing the network to learn blur target classification under different depths. After being trained with a custom dataset, the neural network achieved 99.26% accuracy and the error of 1.25 μm in the measurement range to ±100 μm. In actual operational application, the neural network achieved an accuracy of 90.10% with an error of 1.35 μm over a measurement range of ±100 μm. Experimental results illustrate the effectiveness of the proposed method, and have guidance in implementing efficient, accurate, and fully automatic probe depth estimation.

The purpose of this review is to provide researchers involved in the development of time-to-digital converters (TDC) on FPGAs with the most complete understanding of the existing approaches and methods for implementing such converters. The paper summarizes the most significant characteristics of TDCs and describes the basic time interval measurement methods used in the implementation of TDCs on FPGAs. The main problems arising in the development of such circuits are outlined. The FPGA elements on which the TDC is implemented and the procedure of TDC calibration are briefly considered. The approaches used to increase the resolution and to reduce the nonlinearity of TDC on FPGA are analyzed. Different structures of encoders used in the TDCs are considered. Based on the results of the analysis, recommendations for the development of an FPGA-based TDC are given.

The article presents a concept of an uncooled subterahertz radiometer designed for estimating the atmospheric absorption in the 1.3-mm atmospheric transparency window, which can possibly operate under mountain expedition conditions. Estimation of the atmospheric absorption is based on radiometric measurements of the sky brightness temperature. A comparative analysis of two typical schemes of radiometer receivers (heterodyne and tuned radio frequency receiver schemes) was carried out based on the modern stage of development of the subterahertz electronic components. The noise temperature and fluctuation sensitivity of both schemes were estimated. The results of designing a horn–lens antenna with a radiation pattern of 3° at a level of –3 dB at a frequency of 230 GHz are presented. The general structure of the high-frequency part of the radiometer is described, including some design features that are necessary to provide continuous measurements in a wide range of climatic conditions.

The article relates to the field of contact power nano- and microlithography used for marking samples and surface areas examined with high-resolution microscopes. The device of a marking machine built on the basis of a commercially available Generic-CNC2418 engraving machine with program control in G-codes and using a tungsten probe as a working tool is described. A process for operating the motors of the marking machine based on the monitoring of the probe-surface contact by means of an optical microscope is described. The marking obtained with the help of such a probe is a pattern of individual probe imprints. The marker drives ensure positioning accuracy of 10 μm. The transverse size of the resulting marking prints is 10–15 μm. The marker is recommended for use on surfaces with a roughness of Ra no more than 0.1 μm and a Mohs hardness of no more than 7.5.

This paper presents an effective approach to the fabrication of glass microfluidic chips for studying physical and chemical processes on the pore scale during multiphase flows in porous media, including the description of material selection, methods of microchannel formation and substrate bonding, and the fabrication of tooling for chip fixation and connection to fluid sources. The main advantage of the proposed method is related to the availability of the materials used and relative ease of fabrication. At the same time, the chips produced in this way have good mechanical properties, high optical transparency, and chemical inertness. The influence of different material-processing parameters during chip fabrication on their characteristics and properties is studied. The described experience of the authors can be used by a wide range of researchers in developing their own microfluidic platforms based on glass chips not only for studying multiphase filtration in porous media but also for chemical reactions and various studies in the field of biomedicine.