278 research outputs found
Forward modeling of collective Thomson scattering for Wendelstein 7-X plasmas: Electrostatic approximation
No full textIn this paper, we present a method for numerical computation of collective Thomson scattering (CTS). We developed a forward model, eCTS, in the electrostatic approximation and benchmarked it against a full electromagnetic model. Differences between the electrostatic and the electromagnetic models are discussed. The sensitivity of the results to the ion temperature and the plasma composition is demonstrated. We integrated the model into the Bayesian data analysis framework Minerva and used it for the analysis of noisy synthetic data sets produced by a full electromagnetic model. It is shown that eCTS can be used for the inference of the bulk ion temperature. The model has been used to infer the bulk ion temperature from the first CTS measurements on Wendelstein 7-X.</p
Collective Thomson Scattering Diagnostic for Wendelstein 7-X at 175 GHz
No full textThe Collective Thomson Scattering (CTS) diagnostic measures the scattering spectrum of incident radiation off collective fluctuations in plasmas. In Wendelstein 7-X (W7-X) the diagnostic uses a 140 GHz heating gyrotron as a source of the probing radiation. At this frequency, the CTS spectra are heavily affected by the electron cyclotron emission, and the microwave beam propagation is restricted at typical W7-X plasma parameters. The diagnostic was successfully commissioned in the last experimental campaign and demonstrated ion temperature measurements. However, the signal-to-noise ratio was too low for measuring other quantities such as the fast-ion velocity distribution function or the fuel ion ratio. Currently, the W7-X CTS diagnostic is undergoing an upgrade to a frequency of 175 GHz. This will increase the sensitivity of the diagnostic, since the noise due to electron cyclotron emission will be reduced, and it will relax the constraints on microwave beam propagation in W7-X. Here we present the salient features of the upgraded CTS system and discuss its prospects for both thermal-ion and fast-ion measurements.</p
3D particle tracking velocimetry using dynamic discrete tomography for plasma physics applications
No full text3D particle tracking velocimetry (PTV) is a diagnostic technique which is widely used for studying flows, combustion, and plasmas. Current tomographic particle tracking methods are based on the multiplicative algebraic reconstruction technique and used for reconstructing the distribution of multi-pixel sized particles as greylevel images. Reconstructions obtained by these methods do not necessarily match the experimental data. We propose a new algorithm which can be used for tracking dust particles in tokamaks and stellarators, as well as in low-temperature and complex plasmas. The dynamic discrete tomography algorithm is efficient for data from two projection directions and exact. The non-uniqueness can be detected and tracked individually. The algorithm performance is proportional to N3 on average where N is the number of particles in the reconstruction. There is a room for further improvement of the computational cost scaling. Information from previously reconstructed frames is incorporated in the reconstruction procedure that is formulated as a discrete optimization problem, which has not been applied in PTV previously
Metal-free C–H functionalization of 2H-imidazole 1-oxides with pyrrolyl fragments in the design of novel azaheterocyclic ensembles
No full textNovel pyrrolyl-2H-imidazoles have been synthesizedviametal-free C–H/C–H coupling reactions under mild conditions and in good to excellent yields.</p
3D particle tracking velocimetry using dynamic discrete tomography
No full textParticle tracking velocimetry in 3D is becoming an increasingly important imaging tool in the study of fluid dynamics and combustion as well as plasmas. We introduce a dynamic discrete tomography algorithm for reconstructing particle trajectories from projections. The algorithm is efficient for data from two projection directions and exact in the sense that it finds a solution consistent with the experimental data. Non-uniqueness of solutions can be detected and solutions can be tracked individually
3D particle tracking velocimetry using dynamic discrete tomography
No full textParticle tracking velocimetry in 3D is becoming an increasingly important imaging tool in the study of fluid dynamics and combustion as well as plasmas. We introduce a dynamic discrete tomography algorithm for reconstructing particle trajectories from projections. The algorithm is efficient for data from two projection directions and exact in the sense that it finds a solution consistent with the experimental data. Non-uniqueness of solutions can be detected and solutions can be tracked individually
Generation of electrostatic oscillations in the ion cyclotron frequency range by modulated ECRH
No full text
Optimization of fast-ion diagnostic sets in tokamaks and stellarators using diagnostic weight functions
No full textThe fast-ion phase-space distribution function in the magnetic fusion devices is always underdiagnosed, and every new fast-ion diagnostic should be carefully assessed before installation to minimize redundancies in measurements and maximize the information from the yet undiagnosed part of the fast-ion phase space distribution function. Here, we present a novel method of assessing the added value of a considered fast-ion diagnostic, taking actual geometry and an existing set of fast-ion diagnostics into account. The new method is based on a reformulation of the diagnostic weight functions in constants of motion (COM). We compare the proposed method with the previous approach using Monte Carlo simulations.</p
Variability of preoperative rehabilitation in preparation for primary arthroplasty in patients with osteoarthritis of the knee joint
No full textRelevance. In the last decade, preoperative rehabilitation has attracted considerable attention from both domestic and foreign specialists, however, its effectiveness and impact on the early recovery of patients with osteoarthritis of the knee joint after primary arthroplasty causes many contradictions and remains controversial.Objective. To analyze the scientific literature and evaluate the results, potential advantages and disadvantages of using available and modern methods of preoperative rehabilitation in preparation for primary arthroplasty in patients with osteoarthritis of the knee joint.Materials and methods. In the course of this study, data was searched using Scopus, Web of Sciеnce, Pubmed, and RSCI databases for the period from 2009 to 2024.Results. As a result of the analysis, the key methods of preoperative rehabilitation used during the preparation for total knee arthroplasty were identified, and the effect of these methods on the restoration of functional parameters in patients, changes in pain and the duration of hospital stay after surgery was studied in comparison with the standard program of preparation for total knee arthroplasty.Conclusion. During the study, it was revealed that preoperative rehabilitation before total knee replacement can significantly reduce the duration of hospital stay, however, convincing evidence of improvement in postoperative functional parameters has not been established. To determine the real effectiveness of preoperative rehabilitation, clinical studies are needed to study the effect of comprehensive preoperative rehabilitation programs on the pathogenetic aspects of osteoarthritis, clinical symptoms and functional parameters in the postoperative period
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