The method of spectral analysis of the determination of random digital signals

The methods of spectral analysis based on the use of any model to describe the signal are considered in the article, while using them some assumptions about the behavior of the signal outside the observation interval are made.  The task of spectral analysis or evaluation, in this case, is to find the parameters of the model used, which is selected based on the available a priori information about the studied process.A new spectral analysis method is proposed, which uses the partially classical Prony method, and this method has been improved by replacing the damping sine wave with the use of damped sine wave.Replacing damped sine wave with the use of non-damped sine wave, allows you to very accurately isolate the signal and determine its characteristics against the background of very rich in interference with air space, against the background of radio devices that work legally. For the first time, a fast conversion algorithm was applied to solve the normal equations for finding variables to sequentially determine the parameters of random short-term signals such as amplitude, frequency, and phase.  It is suggested to determine not only static parameters but also the rate of change of these parameters.  Speed of change of parameters allows determining more carefully the signal of the means of silent receiving of information.Modeling of processes of determination of random short-term pulses simulating digital signals of the means of silent receiving of information is carried out, on the basis of the proposed method of spectral analysis, the simulation results are presented in the form of three-dimensional graphs.The main difference is the use not only of the analysis of the amplitude, frequency, phase, and spectrum of the signal but the main analysis of the spectral density of the signal.Analyzes of the simulation result fully confirm the advantages of the proposed method for the determination of random short-term pulses

In situ measurement of the spectral reflectance of mirror-like metallic surfaces during plasma exposition

Visible spectroscopy in fusion plasmas crucially depends on the optical properties of first mirrors withstanding a considerable amount of radiation and particle fluxes. As a result of this interaction the optical properties of the mirrors could be changed so that a cleaning of the mirror is regularly required. Thus the reflectance of the first mirror must be monitored in situ. The newly developed Doppler-Shifted Reflectance Measurement (DSRM) diagnostic provides the spectral reflectance of mirrors in the absence of any calibration sources. It is based on the emission of fast H/D atoms in a low density Ar-H plasma by applying a negative potential on the order of −80⋯−200V to the mirror surface. Until now, the experimental data were restricted to measure only the fast atoms emission at the Hα line. In this work we prove that the new technique also provides the mirror reflectance at the Hβ line (Cu) (486 nm) relevant for the charge-exchange recombination spectroscopy (CXRS) measurements of the He II line (468 nm) in ITER. Moreover, the DSRM diagnostic remains sensitive to the polarization of the reflected light of a W mirror. We present the first experimental data on the time-dependent regime of operation: in situ monitoring of the degradation of an Al mirror is shown as a function of the mirror temperature. The passive heating of the mirror was performed by the plasma itself, which makes the separation between the impact of high temperature and plasma erosion on the mirror reflectance for the temperatures above 500 K impossible. A very good agreement of the experimental and the theoretical data calculated using the Drude theory for the temperature below 500 K is found. For the temperatures above 500 K the degradation of the reflectance of the mirror is determined by the erosion of Al, which is confirmed by monitoring the Al I spectral lines in unison. Keywords: optical emission spectroscopy, fast neutral atoms, spectral reflectance, light polarization, surface degradation, CXR

In situ measurements of the spectral reflectance of metallic mirrors at the Hα_α line in a low density Ar–H plasma

The efficient and reliable control and monitoring of the quality of the optical properties of mirrors is an open problem in laboratory plasmas. Until now, the measurement of the reflectance of the first mirrors was based on the methods that require additional light calibration sources. We propose a new technique based on the ratio of the red- and blue-shifted emission signals of the reflected hydrogen atoms which enables the in situ measurement of the spectral reflectance of metallic mirrors in low-density Ar–H or Ar–D plasmas. The spectral reflectance coefficients were measured for C, Al, Ag, Fe, Pd, Ti, Sn, Rh, Mo, and W mirrors installed in the linear magnetized plasma device PSI-2 operating in the pressure range of 0.01-0.1 Pa. The results are obtained for the Hα line using the emission of fast atoms induced by excitation of H atoms through Ar at a plasma-solid interface by applying a negative potential U = −80, …, −220 V to the mirror. The agreement between the measured and theoretical data of reflectance is found to be within 10% for the investigated materials (except for C). The spectra also allow us to efficiently determine the material of the mirror

Polarization by light reflection at metallic surfaces observed in the shape of the Balmer- α line of low density plasmas

The degree of linear polarization of light reflected at metallic surfaces is obtained from the shape of the Balmer-α line measured in a low density plasma. The measurements of the polarization properties of metallic surfaces utilize only the high-resolution emission spectra induced by fast reflected H atoms (≈100 eV) in ArH plasmas. The measurements are performed at two different lines-of-sight to the target surfaces of Mo and Cu. Only at the observation angle close to the Brewster one, a significant drop of the measured red-shifted signal is detected for the Mo target: the red-shifted emission reduces by ≈50% depending on whether the transverse (S) or the parallel (P) polarization component of the reflected light is selected. In contrast to this, a very weak change of emission is observed for the Cu surface for the same angle. The spectra measured in front of the Mo target were modeled utilizing the energy and angular distribution of reflected atoms and excitation of the cross section of Ar-H collision combined in a Doppler-shifted emission model. A good agreement with the theoretical calculations is found for polarization components (except for the weak P polarization at 70°). Finally, the undercosine distribution of the reflected atoms with b ≈ 0.2 (b is the power of the cosine distribution) shows the best agreement with the spectra measured at both lines-of-sigh

Entwicklung und Test von Prototypkomponenten für ITER

Das Bundesministerium für Bildung und und Forschung (BMBF) stellte in 2007/2008 Mittel imRahmen der Projektförderung zur Verfügung, mit der Zielsetzung eine stärker sichtbareBeteiligung der deutschen Fusionsinstitute am Aufbau von ITER zu erreichen, sowie dieChancen deutscher Unternehmen auf die Übernahme von Aufträgen für den Aufbau vonITER zu stärken.Eine wichtige Zielsetzung des hier beschriebenen Forschungsvorhabens (Projektnummer03FUS0007) war es demnach, kritische Prototyp-Komponenten für ITER zu entwickeln undzu testen, sowie entsprechende Mess- und Prüfeinrichtungen aufzubauen. Gleichzeitigwurde in der Projektbearbeitung sehr eng mit einer ganzen Reihe von Unternehmenzusammengearbeitet, um so einen intensiven Know-How Transfer in beiden Richtungen imHinblick auf die Entwicklung von Komponenten für Fusionsanlagen zu erreiche

Main design features of the Rh-based first mirror developed for the ITER CXRS core diagnostics

Main design features of the Rh-based first mirror developed for the ITER CXRS core diagnosticsYu. Krasikov1, I. Ivashov1, W. Behr1, J. Assmann1, M. Fischer1, V. Kotov1, A. Krimmer1,T. Koppitz1, A. Litnovsky1, D. Leichtle3, O. Marchuk1, Ph. Mertens1, K. Mlynczak1, M. Rasinski1, M. Schrader1, F. Le Guern2, J. Park3, J. Piqueras21 Institut fuer Energie- und Klimaforschung –Plasmaphysik, Forschungszentrum Juelich GmbH, 52425 Julich, Germany2 F4E - Fusion for Energy, 08019 Barcelona, Spain 3 Karlsruher Institut fuer Technologie (KIT), Institut fuer Neutronenphysik and Reaktortechnik (INR), 76344 Eggenstein-Leopoldshafen, GermanyThe ITER core charge exchange recombination spectroscopy (cCXRS), containing five in-port optical mirrors, is intended to transfer the visible light emitted by interaction of the plasma with the diagnostic neutral beam to the corresponding spectrometers. The first mirror (M1) is a key and the most vulnerable component of the diagnostics. In order to provide the required mirror lifetime, maintainability and structural integrity, M1 is composed of special materials, i.e. it is made of a thin 1 mm single-crystal rhodium (ScRh) plate diffusion bonded to a special WCu substrate. A rhodium nanocrystalline coating (NcRh) can be an option. The main mirror features are: -optical surface dimensions: 86 mm×170 mm; ScRh/NcRh material, 0.8÷1 mm thickness (≥10 μm for the coating if selected); -adjustability with 3 (2 rotations and 1 translation) DOF (degrees of freedom); -substrate electrically insulated from the ground during cleaning; -cooling via mechanical contacts;-maximum mirror operation temperature of 300C; -remote handling compatibility; -acceptable thermal distortion (within 100 fringes); -a compatibility with repetitive cleaning. The mirror can be cleaned with about 100-500 procedures of 60 MHz plasma discharges (depending on the Rh material used). The paper presents an evolution of M1 design presented in [1], [2] and [3]. The design is supported by multifield thermal, electromagnetic and structural analyses and uses experimental data of the R&D made by Forschungszentrum Juelich, Germany. The study conducted confirms the workability of the proposeddesign solutions.Parts of this work (the actual bolted solution) were supported by Fusion for Energy under the Framework Partnership Agreement F4E-FPA-408 (DG). The views and opinions expressed herein reflect only the authors’ views. Fusion for Energy is not liable for any use that may be made of the information contained in the present contribution.Keywords: ITER, CXRS diagnostics, port plug, first mirror, Rh single crystal, mirror cleaning[1] Yu. Krasikov et.al., Major aspects of the design of a first mirror for the ITER core CXRSDiagnostics, http://dx.doi.org/10.1016/j.fusengdes.2015.05.031[2] Yu. Krasikov et.al., Specific design and structural issues of single crystalline first mirrors for diagnostics, http://dx.doi.org/10.1016/j.fusengdes.2017.04.038[3] Ph. Mertens et.al,. On the use of rhodium mirrors for optical diagnostics in ITER, http://dx.doi.org/10.1016/j.fusengdes.2019.04.03