Instruments and Experimental Techniques最新文献

The factors determining the gain stability in thick gas electron multipliers are considered. A new design of this detector type with wire focus electrodes is presented. Laboratory tests have shown good prospects of its use in intense accelerator beams.

A liquid sample holder for small-angle X-ray scattering measurements has been developed and tested that allows for a significant increase in the signal-to-noise ratio with a small amount of sample material. The proposed device consists of a vertically positioned capillary made of a chemically resistant material with a diameter of 0.005–5.0 mm, the lower edge of which is rigidly fixed above the center of the incident X‑ray beam at a distance equal to the radius of the drop. A drop of liquid sample is squeezed out through the lower end of the capillary. Surface tension forces ensure the spherical shape of the droplet and hold it at the end of the capillary. The scattering of a beam passing through a drop is axisymmetric since the spherical shape of the sample drop best meets this requirement. The presence of a sample in such a device eliminates the presence of additional elements in the radiation beam that could introduce distortions into the signal, which allows for high-precision measurements using the small-angle X-ray scattering method. Test measurements were carried out that showed a significantly more isotropic scattering pattern, and the optimal relative positions of the radiation beam and the sample drop were determined. The simplicity of the proposed holder design and its versatility for measuring various samples are undeniable advantages.

Devices based on the effect of plasma compression by a magnetic field (plasma pinching), i.e., plasma focus chambers with non-cylindrical z pinch formed in them, are considered. A range of plasma focus chambers covering the neutron yield range from 10⁵ to 10¹² neutrons/pulse at neutron energies of 2.5 and 14 MeV has been developed by Dukhov All-Russia Research Institute of Automatics. The experimental results for the influence of pulsed thermal, electrical, and mechanical actions on the service life of these chambers are summarized. The experimentally achieved operating lives of plasma focus chambers with deuterium or deuterium−tritium fillings are thousands of shots at discharge currents I = 100−300 kA, hundreds of shots at I = 600 kA, and approximately 100−200 shots at I > 1 MA.

This paper presents the results of the first technological run of the Booster synchrotron of the NICA accelerator complex located at the Veksler and Baldin Laboratory of High Energy Physics of the Joint Institute for Nuclear Research. The megascience NICA project is a complex comprising a chain of accelerators and a collider ring with two interaction points, MPD (Multi-Purpose Detector) and SPD (Spin Physics Detector), designed to study interactions of two colliding beams. Within the accelerator chain, the first circular superconducting accelerator is the Booster synchrotron. The accelerator consists of 41 dipole magnets, 48 quadrupole lenses, and 32 corrector magnets (24 dipole and 8 multipole). The total cold mass of the accelerator is 61.44 t.

The technique for calibration of receiving equipment for an experiment on recording spectra of collective Thomson scattering at a frequency of 54.5 GHz in an open magnetic trap is described. This scattering is the basis for ion-distribution function diagnostics, widely used in toroidal traps, tokamaks, and stellarators, and the challenge is to adapt this method to an open trap. The transition to a new type of trap required the use of an original approach to calibration, which solved two problems. Firstly, using the existing equipment, the spectrum of the signal from a thermal source with a temperature of approximately 200 K was recorded with an accuracy of 3%. Secondly, the receiver was matched with the noise generator.

The detection and location of partial discharge are crucial for assessing the insulation condition of equipment efficiently, which is of great significance to the safety and stability operation of electrical equipment. However, accurate time delay estimation is the prerequisite for high precision localization of partial discharge. To address the challenge of degraded delay estimation accuracy under low signal-to-noise ratio conditions, this paper proposes a novel generalized cross-correlation algorithm incorporating PHAT-SCOT joint weighting. A double exponential oscillation attenuation model is employed to simulate characteristic partial discharge pulse signals. The original signal and the delay signal are firstly cross-correlated and the power spectral density function is obtained by PHAT-SCOT joint weighting. Then, the inverse Fourier transform is carried out and the delay estimate value is obtained by peak detection. The proposed algorithm is comparatively evaluated against conventional cross-correlation and quadratic cross-correlation methods through statistical analysis of delay estimation accuracy rates and mean square error metrics. An experimental system of partial discharge signal detection is implemented to validate the proposed methodology through practical time delay estimation experiments. The simulation and experimental results show that the algorithm can sharpen the peak value of cross-correlation function under the condition of low SNR and that it has the advantages of high accuracy of delay estimation and small root mean square error, so it can be applied to partial discharge detection and location.

A modification of the method of multiple mutual synchronization of parallel computing threads, which was used in spectral-domain optical coherence tomography systems controlled by computing systems with a central processor using HyperThreading technology, is proposed. This modification ensures uniform computational load of all involved logical processors and reduces peak load rates. Due to this, the stable performance of the computational method was demonstrated in solving tomographic problems of varying complexity using multiscalar processors of different generations, different performance, and different manufacturers.

The scrape-off layer (SOL) of tokamak plasmas is characterized by complex transport phenomena, significantly influenced by transient plasma structures known as blobs. To investigate these dynamics in the IR-T1 tokamak, a novel electrostatic diagnostic, the Mix-probe, integrating both Langmuir probe (LP) and Ball-Pen probe (BPP) functionalities, was deployed. This advanced probe enabled simultaneous local measurements of electron density fluctuations ((widetilde {{{n}_{e}}})), plasma potential fluctuations ((widetilde {{{{{varphi }}}_{p}}})), and electron temperature fluctuations ((widetilde {{{T}_{e}}})). Conditional averaging of the ion saturation current (I_sat) revealed the presence of blob-like structures at the plasma edge. Utilizing these measurements and simplified theoretical models, we estimated the turbulent particle flux (({{{{Gamma }}}_{r}})) and the turbulence spreading term (S), providing initial insights into the role of blobs in particle transport and turbulence propagation in the IR-T1 SOL. The successful implementation of the Mix-probe demonstrates its potential for detailed investigations of plasma edge turbulence, contributing to a better understanding of transport mechanisms crucial for fusion energy development.

The problem of increasing the accuracy of determining the position of a patient’s head during the vHIT medical test using video recordings obtained from a smartphone camera is considered. The focus is on comparing the output of three machine-learning models (Dense Head Pose Estimation, Head Pose Estimation, and Lightweight Head Pose Estimation) designed for head pose detection with reference data obtained using IMU sensors. To improve the accuracy of signals obtained from a video stream, four digital filtering methods were compared, namely, empirical mode decomposition (EMD), variational mode decomposition (VMD), discrete wavelet transform, and Butterworth filtering. The mean square error (MSE), weighted by the signal amplitude, was used as a quality metric. The results showed that the best fit to the benchmark data was achieved by using the LHPE model in combination with the wavelet transform and Butterworth filtering. The presented approach confirms the feasibility of using a smartphone camera for high-precision head detection, which opens up the prospect of using ordinary smartphones as hardware for the vHIT test.

The results of the development and tests of a high-voltage charging power supply (CPS) for a module of a multimegajoule-level capacitive energy storage are presented. The features of operation and design of the main functional components included in the CPS are described. A digital–analog control-system implementation is considered, providing the frequency–pulse modulation of the CPS output power during the charging cycle to ensure optimal thermal conditions for the power transistors. The test results of an experimental prototype of the charging device are presented. Currently, approximately 100 CPSs featuring the circuit design, technical characteristics, and a similar design described in this paper have been manufactured and are in operation.