Computational Physics; Modelling and Simulation of Electron Devices; Electron Optics; Physics of Intense Charged Particle Beams; Electron Beam Technologies; Computational Electro Magnetics; Microwave Radiation Sources; High Frequency Gyrotrons; Powerful Gyrotrons; Quasioptical Systems; Infrared, Millimeter and Terahertz Waves Phone: +359 02 979 5922 Address: Institute of Electronics of the Bulgarian Academy of Sciences 72 Tzarigradsko Shose Blvd. 1784 Sofia, BULGARIA
Nowadays, gyrotrons are used in numerous and diverse fields of research and technology. Their mos... more Nowadays, gyrotrons are used in numerous and diverse fields of research and technology. Their most prominent application is to electron cyclotron resonance plasma heating and current drive-in reactors for controlled thermonuclear fusion. Another matured field is the thermal microwave treatment of materials in industrial-grade gyrotron-based technological systems. The unique spectral properties of gyrotron radiation, frequency tunability, and the possibility for precise control and modulation of both the output power and frequency have made the gyrotrons attractive and appropriate radiation sources for various novel advanced spectroscopic techniques. Among them are ESR (electron spin resonance), NMR-DNP (nuclear magnetic resonance with a signal enhancement through dynamic nuclear polarization), XDMR (X-ray detected magnetic resonance), acoustic molecular spectroscopy, as well as high-precision spectroscopy for measuring the SFS (super-fine splitting of the energy levels of positroniu...
IOP Conference Series: Materials Science and Engineering, 2019
In this investigation, manganese has been produced from medium grade manganese ore from Karangnun... more In this investigation, manganese has been produced from medium grade manganese ore from Karangnunggal mine (West Java, Indonesia). The effects of keeping it at a temperature of 1200°C in methane gas on the structural properties have been studied. The material’s properties have been characterized on the basis of the experimental data obtained using X-ray fluorescence (XRF), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FTIR) spectroscopy. It has been found that MnO2 is reduced to hausmannite (Mn3O4), manganosite (MnO) and manganese carbide (Mn7C3). An increase of the keeping time up to 45 minutes during the sintering process leads to an increase of the MnO concentration, while at 90 minutes, the concentration decreases. The analysis based on the interpretation of both XRD patterns and FTIR spectrum allows one to explain the blockage in the particle surface of the ore by an increase of the carbon deposition.
抄録 The electron cyclotron autoresonance is of both theoretical and practical interest for acceler... more 抄録 The electron cyclotron autoresonance is of both theoretical and practical interest for acceleration of charged particles and for generation of microwave radiation in various gyro-devices. In this paper a unified approach is applied to the analysis of the interaction of electrons with electromagnetic waves with different characteristic impedance. In contrast to the previous works that consider only plane transverse waves and TE modes our analysis is applied also to TM modes. An approximate constant of motion (adiabatic invariant) is ...
Synopsis Positronium is an ideal system for the research of the QED. The hyperfine splitting of p... more Synopsis Positronium is an ideal system for the research of the QED. The hyperfine splitting of positronium (Ps-HFS) is sensitive to the new physics beyond the Standard Model via a vacuum oscillation. Previous experimental results of the Ps-HFS show 3.5 σ discrepancy from the QED calculation, and it might be caused by uncertainties of the indirect method with static magnetic field and a few GHz RF. We developed a new direct measurement system of the Ps-HFS without static magnetic field, using a sub-THz gyrotron and a quasi-optical ...
In this study, the calcium carbonate from onyx stone used as a pore-forming agent in the ceramic ... more In this study, the calcium carbonate from onyx stone used as a pore-forming agent in the ceramic membrane of kaolin, zeolite, and silica xerogel composites were investigated. Four different membrane samples were prepared with varying onyx stone content from 5 wt.% to 30 wt.% into composite and then the prepared samples were sintered at 1200C. The structural properties of the prepared sample was investigated in detail using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and N2 adsorption-desorption isotherms. The removal performance of the membrane was successfully tested during coconut sap treatment. It has been found that the prepared samples have a porous structure made up of interconnected pores and their volume fraction depends on onyx stone content. The sample with the onyx stone content of 30 wt.% provides the largest volume fraction of homogeneously interconnected pores and its presence demontrates the largest valu...
2021 22nd International Vacuum Electronics Conference (IVEC), 2021
An unexpected abrupt increase of the output power at magnetic field values corresponding to the e... more An unexpected abrupt increase of the output power at magnetic field values corresponding to the excitation of high-order axial modes (HOAM) was observed experimentally and is explained theoretically through an after-cavity interaction of the bunched electron beam with the next radial mode. The calculations showed that under certain conditions this effect can be either useful for a power increase at the HOAM operation of the frequency-tunable gyrotron or harmful for high cyclotron harmonic operation due to an expansion of the zone of fundamental cyclotron resonance mode excitation.
Nowadays, gyrotrons are used in numerous and diverse fields of research and technology. Their mos... more Nowadays, gyrotrons are used in numerous and diverse fields of research and technology. Their most prominent application is to electron cyclotron resonance plasma heating and current drive-in reactors for controlled thermonuclear fusion. Another matured field is the thermal microwave treatment of materials in industrial-grade gyrotron-based technological systems. The unique spectral properties of gyrotron radiation, frequency tunability, and the possibility for precise control and modulation of both the output power and frequency have made the gyrotrons attractive and appropriate radiation sources for various novel advanced spectroscopic techniques. Among them are ESR (electron spin resonance), NMR-DNP (nuclear magnetic resonance with a signal enhancement through dynamic nuclear polarization), XDMR (X-ray detected magnetic resonance), acoustic molecular spectroscopy, as well as high-precision spectroscopy for measuring the SFS (super-fine splitting of the energy levels of positroniu...
IOP Conference Series: Materials Science and Engineering, 2019
In this investigation, manganese has been produced from medium grade manganese ore from Karangnun... more In this investigation, manganese has been produced from medium grade manganese ore from Karangnunggal mine (West Java, Indonesia). The effects of keeping it at a temperature of 1200°C in methane gas on the structural properties have been studied. The material’s properties have been characterized on the basis of the experimental data obtained using X-ray fluorescence (XRF), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared (FTIR) spectroscopy. It has been found that MnO2 is reduced to hausmannite (Mn3O4), manganosite (MnO) and manganese carbide (Mn7C3). An increase of the keeping time up to 45 minutes during the sintering process leads to an increase of the MnO concentration, while at 90 minutes, the concentration decreases. The analysis based on the interpretation of both XRD patterns and FTIR spectrum allows one to explain the blockage in the particle surface of the ore by an increase of the carbon deposition.
抄録 The electron cyclotron autoresonance is of both theoretical and practical interest for acceler... more 抄録 The electron cyclotron autoresonance is of both theoretical and practical interest for acceleration of charged particles and for generation of microwave radiation in various gyro-devices. In this paper a unified approach is applied to the analysis of the interaction of electrons with electromagnetic waves with different characteristic impedance. In contrast to the previous works that consider only plane transverse waves and TE modes our analysis is applied also to TM modes. An approximate constant of motion (adiabatic invariant) is ...
Synopsis Positronium is an ideal system for the research of the QED. The hyperfine splitting of p... more Synopsis Positronium is an ideal system for the research of the QED. The hyperfine splitting of positronium (Ps-HFS) is sensitive to the new physics beyond the Standard Model via a vacuum oscillation. Previous experimental results of the Ps-HFS show 3.5 σ discrepancy from the QED calculation, and it might be caused by uncertainties of the indirect method with static magnetic field and a few GHz RF. We developed a new direct measurement system of the Ps-HFS without static magnetic field, using a sub-THz gyrotron and a quasi-optical ...
In this study, the calcium carbonate from onyx stone used as a pore-forming agent in the ceramic ... more In this study, the calcium carbonate from onyx stone used as a pore-forming agent in the ceramic membrane of kaolin, zeolite, and silica xerogel composites were investigated. Four different membrane samples were prepared with varying onyx stone content from 5 wt.% to 30 wt.% into composite and then the prepared samples were sintered at 1200C. The structural properties of the prepared sample was investigated in detail using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and N2 adsorption-desorption isotherms. The removal performance of the membrane was successfully tested during coconut sap treatment. It has been found that the prepared samples have a porous structure made up of interconnected pores and their volume fraction depends on onyx stone content. The sample with the onyx stone content of 30 wt.% provides the largest volume fraction of homogeneously interconnected pores and its presence demontrates the largest valu...
2021 22nd International Vacuum Electronics Conference (IVEC), 2021
An unexpected abrupt increase of the output power at magnetic field values corresponding to the e... more An unexpected abrupt increase of the output power at magnetic field values corresponding to the excitation of high-order axial modes (HOAM) was observed experimentally and is explained theoretically through an after-cavity interaction of the bunched electron beam with the next radial mode. The calculations showed that under certain conditions this effect can be either useful for a power increase at the HOAM operation of the frequency-tunable gyrotron or harmful for high cyclotron harmonic operation due to an expansion of the zone of fundamental cyclotron resonance mode excitation.
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Papers by Dr. Svilen Sabchevski