125 research outputs found
Self-consistent modeling of the electron-cyclotron maser interaction in lossy structures based on a full-wave Green's function approach
No full textWe develop a new self-consistent model for simulation of the electron-cyclotron maser interaction in cylindrical structures, where expansion of the fields in transverse eigenmodes cannot be directly applied. Instead of solving the nonhomogeneous equation for the fields as a differential equation, a different approach is followed. First, the Green's function for elementary azimuthal and radial RF current sources is analytically derived by expanding the fields in longitudinal modes. Then, the total generated field is calculated by representing the perturbed electron beam as a sum of elementary RF current sources along the axis with amplitude coefficients that are found from the kinematic quantities of the electrons. The self-consistent stationary solution is found by solving the equations of motion along with the field equation in an iterative procedure. The model is useful for the full-wave simulation of lossy structures, which are frequently found in gyro-devices, such as ceramic-loaded interaction circuits of gyro-traveling-wave tubes and beam tunnels of gyrotron oscillators. © 2022 Author(s)
Towards a 1.5 MW, 140 GHz gyrotron for the upgraded ECRH system at W7-X
No full textFor the required upgrades of the Electron Cyclotron Resonance Heating system at the stellarator Wendelstein 7-X, the development of a 1.5 MW 140 GHz Continuous Wave (CW) prototype gyrotron has started. KIT has been responsible to deliver the scientific design of the tube (i.e. the electron optics design and the RF design), with contributions from NKUA and IPP. The prototype gyrotron has been ordered at the industrial partner, Thales, France, and is expected to be delivered in 2021. In parallel, a short-pulse pre-prototype gyrotron has been developed at KIT, to provide the means for a first experimental validation of the scientific design in ms pulses, prior to the construction of the CW prototype. This paper reports on the status of the 1.5 MW CW gyrotron development, focusing on the scientific design and its numerical and experimental validation. © 2021 Konstantinos A. Avramidis, Zisis C. Ioannidis, Gaetano Aiello, Patrick Bénin, Ioannis Chelis, Andreas Dinklage, Gerd Gantenbein, Stefan Illy, John Jelonnek, Jianbo Jin, Heinrich P. Laqua, Alberto Leggieri, François Legrand, Alexander Marek, Stefan Marsen, Ioannis Gr. Pagonakis, Tobias Ruess, Tomasz Rzesnicki, Theo Scherer, Dirk Strauss, Manfred Thumm, Ioannis Tigelis, Dietmar Wagner, Jörg Weggen, Robert C. Wolf, the Wendelstein 7-X Tea
CONTRIBUTI ALLA CONOSCENZA DELLA LEPIDOTTEROFAUNA DELL'ITALIA MERIDIONALE IV. Heterocera (Bombyces et Sphinges) di Puglia e Lucania
No full textCONTRIBUTIONS TO THE KNOWLEDGE OF LEPIDOPTERA IN SOURTHERN ITALY IV. Heterocera (Bombyces ET Sphinges) OF APULIA AND LUCANIA By this first work on the Heterocera the author gives some results of researches on the Lepidopterofauna, carried out in Apulia and Lucania during 1967-77. In the first part are described the main localities explored, except the ones already dealt with in a former paper on the Rhopalocera. In the second part the collected species are listed with some data upon geonemy, frequency and, in the case of agricultural and foresta! interesting species, with regard to the damages they have clone. There are also listed the species mentioned by other authors for Apulia and Lucania, and not collected during the present researches. The species l i s t follows FoRSTER & WoHLFARTH's terminology , w i t h some necessary revisions and the addition of species since now uncollected in Centrai Europe. 182 species are listed (45,8% of the species known as living in Continental ltaly). Eilema rungsi Toulg. is reported for the first time in Europe; Orgyia ericae Germ., Notodonta tiefi Bartel and Hypopta thrips Hb. as new in Italy; Penestoglossa dardoinella Mill. are mentioned for the first time in Continental Italy; Eilema depressa Esp. and Celama subchlamydula Stgr. are mentioned for the first time in Centrai and Southern Italy . Also in Southern Italy are mentioned for the first time: Nola cucullatella L., Ocneria prolai Htg., Nudaria mundana L., Apaidia rufeola Rbr., Eilema unita Schifi., Eilema lurideola Zinck., Chelis maculosa Germ., Rhyparia purpurata L., Hyphoraia testu- dinaria Fourc., Pelosia muscerda Hfn., Pelosia obtusa H.-S., Sphinx ligustri L., Hemaris t i t y u s L., Malacosoma castrensis L., Malacosoma franconica Esp., T richiura crataegi L., Macrothylacia rubi L., Acanthopsyche atra L., Amictoides sera Wisk., Phalacropteryx api- formis Rossi, Fumea crassiorelia Brd., Pryropteron chrysidiformis Esp., Hypopta caestrum Hb., Phragmatecia castaneae Hb. Most of the other species here reported are not yet mentioned in Apulia or Lucania
Experimental Classification and Enhanced Suppression of Parasitic Oscillations in Gyrotron Beam Tunnels
No full textHigh-power gyrotrons may suffer from parasitic oscillations that are excited in the electron-beam compression zone. Different damping structures are proposed in the literature that reduce the possibility of parasitic excitation by increasing the starting currents of the modes. In this work, we focus on a dielectric-loaded (stacked) beam tunnel. Based on our previous theoretical studies, we make targeted modifications to the beam tunnel in order to classify the parasitic signals and localize the areas where they are excited. After two successive modifications, the beam tunnel exhibits improved behavior with higher starting currents of the parasitic modes. The experiments are performed by using a modular 170-GHz, 1-MW short-pulse gyrotron, which due to its flanged construction gives the possibility to modify the beam tunnel without affecting the rest of the tube. © 1963-2012 IEEE
Industrial Qualification of the THALES TH1509U European 170 GHz 1 MW CW Gyrotron
No full textThe progress of the European THALES TH1509U 170 GHz 1 MW CW industrial gyrotron program is presented in this report. The test results on the upgraded TH1509U and the compliance with main technical requirements are discussed
Modeling of parasitic oscillations in smooth-wall circular symmetric dielectric-loaded gyrotron beam ducts
No full textThe self-consistent simulation of the electron beam interaction was performed in the presence of a lossy dielectric layer in the smooth-wall beam duct of a gyrotron oscillator. For this purpose, the linear and spectral code TWANGlinspec was extended. In this code, the local transverse structure of the TE mode is adapted to the solution of the complex cold dispersion relation of an infinite, homogeneous, dielectric coated cylindrical waveguide. Before considering the realistic situation, the validity of the TE pure mode (E-z = 0) assumed in TWANGlinspec had to be assessed for SiC or BeOSiC materials. The effect of the dielectric layer on the parasitic starting current is large for parasitic oscillations localized at the end of the beam duct and in the so-called spacer region. For the realistic case, the geometry of the dual frequency gyrotron for the Tokamak a Configuration Variable was considered, and the effect of a dielectric layer was numerically investigated. The electron beam velocity spread was also included in the simulations. The result is that in such conditions, the parasitic oscillation starting currents are increased above the operating beam current. The observation of these spurious modes would therefore not be expected.SP
Simulation of Parasitic Backward-Wave Excitation in High-Power Gyrotron Cavities
No full textThe possibility of parasitic excitation of backward waves directly in the gyrotron cavity is demonstrated, by simulation, for two existing high-power gyrotrons. These are the 140-GHz 1-MW TE28,8-mode gyrotron for the stellarator W7-X and the 140-GHz 1.5-MW TE28,10 -mode gyrotron, also for W7-X. The parasitic backward waves, namely, the TE23,7 mode in the 1-MW gyrotron and the TE-24,10 mode in the 1.5-MW gyrotron, are excited at high frequencies (RF), which are of the order of ∼ 10% lower than the nominal operating frequency and which can lead to significant performance degradation, with respect to the output power, efficiency, and stability of the tube. This finding offers an additional possibility, besides parasitic mode excitation in the gyrotron beam tunnel or after the gyrotron cavity, for the origin of experimentally observed RF parasitic oscillations in high-power, high-frequency gyrotrons, operating in high-order modes. To strengthen the confidence in the simulation, the results of two codes, each using different modeling of the interaction between the electron beam and the RF wave, are compared and the appropriateness of the modeling with respect to the accurate simulation of backward waves is discussed in detail. © 1963-2012 IEEE
Modeling of parasitic oscillations in smooth-wall circular symmetric dielectric-loaded gyrotron beam ducts
No full textModeling of parasitic oscillations in smooth-wall circular symmetric dielectric-loaded gyrotron beam ducts
No full textThe self-consistent simulation of the electron beam interaction was performed in the presence of a lossy dielectric layer in the smooth-wall beam duct of a gyrotron oscillator. For this purpose, the linear and spectral code TWANGlinspec was extended. In this code, the local transverse structure of the TE mode is adapted to the solution of the complex cold dispersion relation of an infinite, homogeneous, dielectric coated cylindrical waveguide. Before considering the realistic situation, the validity of the TE pure mode (Ez = 0) assumed in TWANGlinspec had to be assessed for SiC or BeOSiC materials. The effect of the dielectric layer on the parasitic starting current is large for parasitic oscillations localized at the end of the beam duct and in the so-called spacer region. For the realistic case, the geometry of the dual frequency gyrotron for the Tokamak à Configuration Variable was considered, and the effect of a dielectric layer was numerically investigated. The electron beam velocity spread was also included in the simulations. The result is that in such conditions, the parasitic oscillation starting currents are increased above the operating beam current. The observation of these spurious modes would therefore not be expected. © 2019 Author(s)
Development of a self-consistent simulation code for the electron cyclotron interaction in dielectric-loaded gyrotron beam tunnels
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