Seoul Teracom Inc.

Seoul, South Korea

Seoul Teracom Inc.

Seoul, South Korea
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Min S.-H.,Korea Institute of Radiological and Medical Sciences | Min S.-H.,Seoul National University | Kwon O.,Korea Basic Science Institute | Sattorov M.,Seoul National University | And 8 more authors.
Review of Scientific Instruments | Year: 2017

Non-thermal irreversible electroporation (NTIRE) to avoid thermal damage to cells during intense DC ns pulsed electric fields (nsPEFs) is a recent modality for medical applications. This mechanism, related to bioelectrical dynamics of the cell, is linked to the effect of a DC electric field and a threshold effect with an electrically stimulated membrane for the charge distribution in the cell. To create the NTIRE condition, the pulse width of the nsPEF should be shorter than the charging time constant of the membrane related to the cell radius, membrane capacitance, cytoplasm resistivity, and medium resistivity. It is necessary to design and fabricate a very intense nanosecond DC electric field pulser that is capable of producing voltages up to the level of 100 kV/cm with an artificial pulse width (∼ns) with controllable repetition rates. Many devices to generate intense DC nsPEF using various pulse-forming line technologies have been introduced thus far. However, the previous Blumlein pulse-generating devices are clearly inefficient due to the energy loss between the input voltage and the output voltage. An improved two-stage stacked Blumlein pulse-forming line can overcome this limitation and decrease the energy loss from a DC power supply. A metal oxide silicon field-effect transistor switch with a fast rise and fall time would enable a high repetition rate (max. 100 kHz) and good endurance against very high voltages (DC ∼ 30 kV). The load is designed to match the sample for exposure to cell suspensions consisting of a 200 Ω resistor matched with a Blumlein circuit and two electrodes without the characteristic RC time effect of the circuit (capacitance =0.174 pF). © 2017 Author(s).


Rahaman S.E.,University of Burdwan | Barik R.K.,Academy of Scientific & Innovative Research AcSIR | Barik R.K.,Indian Central Electronics Engineering Research Institute | Singh A.K.,Academy of Scientific & Innovative Research AcSIR | And 7 more authors.
Journal of Electromagnetic Waves and Applications | Year: 2017

Ion thruster is the most efficient population system of satellite to control its orbits in deep space. Total efficiency, thrust, and specific impulse are the key characterization parameters of an ion thruster which define its performance. At present, total efficiency is limited within the range of 36–68%. In this paper, a new grid design is discussed to increase the total efficiency and thrust of ion thruster wherein screen grid has chamfered edges. The ion beam dynamics were simulated in OPERA14.0-3D. The simulated result is shown to have increased thrust and total efficiency from 0.196–0.364 mN and 41.29–74.66%, respectively. © 2017 CSIR-CEERI


Baek I.-K.,Seoul National University | Bhattacharya R.,Seoul National University | Lee J.S.,Seoul National University | Kim S.,Seoul National University | And 5 more authors.
Journal of Electromagnetic Waves and Applications | Year: 2017

The field emission properties of the controlled emission edge of a vertically aligned graphene-based thin film are presented. A current and current density of above 7 mA and 200 A/cm2, respectively, with uniform electron emission, are achieved. Uniform high current and current density emissions can be realized by the pre-mechanical shaping and post electrical conditioning of reduced graphene oxide (rGO) film emission, owing to the robustness, thinness (<1 μm), and well-defined uniform film thickness. Field emission luminance demonstrates uniform emission over the entire emission area with a high aspect ratio. Along with a high current emission, the rGO film exhibits excellent emission stability, long-term. This offers prospects for various applications in field emission displays, electron microscopy, and particularly for the realization of miniaturized terahertz vacuum electronic devices, which require electron sources with uniform high currents and current densities, such as long-lifetime cold cathodes. © 2017 Informa UK Limited, trading as Taylor & Francis Group


Baek I.,Seoul National University | Baek I.,and also with Seoul Teracom Inc. | Sattorov M.,Seoul Teracom Inc. | Sattorov M.,University of Suwon | And 6 more authors.
IEEE Transactions on Electron Devices | Year: 2017

The 3-D particle-in-cell (PIC) simulations are performed to determine the origin of sideband and spurious noises generated in a cooker magnetron. A novel simulation technique is used, which introduces cathode emission current nonuniformities. These nonuniformities are due to nonuniform distributions of electric field on a thermionic emission surface, which result from cathode geometry. It is shown that cathode end-caps shape and magnetic pole-piece geometries are the causes of sideband and spurious noises in conventional microwave ovens. The 3-D simulation results are in satisfactory agreement with the spectrum of a typical cooker magnetron. IEEE


Min S.-H.,Seoul National University | Min S.-H.,Korea Institute of Radiological and Medical Sciences | Kwon O.,Seoul National University | Kwon O.,Korea Basic Science Institute | And 9 more authors.
Physics of Plasmas | Year: 2016

An experimental result of a gigawatt-class L-band magnetically insulated transmission line oscillator (MILO) shows the generation of a transient axial mode pertaining to an anode plasma effect in the circuit of the MILO. The transient axial mode between the desired π mode and the 5 π / 6 mode causes the output power to become eccentric. When the electrons impact onto the metallic surface, plasma exists on the surface of the anode due to the electron-impact distortion process. As a result, the anode plasma causes the emitted current to increase the neutralization near the cathode. The increase of the current induces faster and stronger magnetic insulation, which lowers the drift velocity and suppresses the mode earlier during the beam pulse. After the 5 π / 6 mode, which initially interacts with the electron beam, remains as a transient axial mode for a very short time, it shows the capability to convert to the π mode, which is more stable and slowly grows. © 2016 Author(s).


Khutoryan E.,Ukrainian Academy of Sciences | Sattorov M.,Seoul Teracom Inc. | Sattorov M.,Seoul National University | Lukin K.A.,Ukrainian Academy of Sciences | And 8 more authors.
IEEE Transactions on Electron Devices | Year: 2015

A multimode theory of the resonant backward-wave oscillator (BWO) with an electron beam inclined with respect to the surface of a periodic structure - a clinotron - is presented. It is shown that mode interaction provides phase velocity variation in the interaction space. The beam-wave interaction power increases at a favorable phase velocity profile along the interaction space, which manifests as power peaks in the clinotron zone. In contrast, when it is nonfavorable, there is power drop in the bandwidth. Developed multimode theory results are in satisfactory agreement with the theory of a BWO with reflections and with particle-in-cell simulations. © 1963-2012 IEEE.


Sattorov M.,Seoul Teracom Inc. | Sattorov M.,Seoul National University | Khutoryan E.,Ukrainian Academy of Sciences | Lukin K.,Ukrainian Academy of Sciences | And 9 more authors.
IEEE Transactions on Electron Devices | Year: 2015

The automodulation processes in backward-wave oscillator with an inclined electron beam (the clinotron) operating at low-focusing magnetic fields have been studied. The automodulation behavior has been analyzed in the clinotron for different angles of the beam inclination. It has been shown that at low magnetic fields, the RF transverse electric field may cause significant changes in electron trajectories, and hence in the beam-wave interaction power that leads to the automodulation. © 2015 IEEE.


Bera A.,Seoul National University | Barik R.K.,Seoul National University | Sattorov M.,Seoul National University | Sattorov M.,Seoul Teracom Inc. | And 10 more authors.
Optics Express | Year: 2014

Metallic metamaterials with positive dielectric responses are promising as an alternative to dielectrics for the generation of Cerenkov radiation [J.-K. So et al., Appl. Phys. Lett. 97(15), 151107 (2010)]. We propose here by theoretical analysis a mechanism to couple out Cerenkov radiation from the slab surfaces in the transverse direction. The proposed method based on Brillouin-zone folding is to periodically modify the thickness of the metamaterial slab in the axial direction. Moreover, the intensity of the surface-coupled radiation by this mechanism shows an order-of-magnitude enhancement compared to that of ordinary Smith- Purcell radiation. © 2014 Optical Society of America.


Sattorov M.A.,Seoul National University | Bera A.,Seoul National University | Bera A.,Indian Central Electronics Engineering Research Institute | Sharma A.,Seoul National University | And 12 more authors.
IEEE Transactions on Electron Devices | Year: 2011

Thermal analysis of an L-band 60-kW (continuous-wave) double-ring strapped magnetron for optimizing the design of a cathode support structure and cooling system is presented. This magnetron consists of an oxygen-free copper anode with ten built-in cooling channels and a directly heated tungsten cathode. The operating temperature of the cathode is greater than 2000 °C; therefore, proper thermal design of the cathode support structure is essential for reliable operation. The heat convection coefficient for the forced air is estimated by simulations comparing the simulated temperatures for different heat convection coefficients with the measured one. It is observed that the comparison between simulations with measurement is in good agreement for various temperatures from 1000 °C to 2000 °C when the estimated heat convection coefficient of the forced air is used. © 2010 IEEE.


Sattorov M.,Seoul National University | Sattorov M.,Seoul Teracom Inc. | Khutoryan E.,Ukrainian Academy of Sciences | Lukin K.,Ukrainian Academy of Sciences | And 3 more authors.
IEEE Transactions on Electron Devices | Year: 2013

The possibility of the efficient operation of a backward-wave oscillator (BWO) with an electron beam inclined with respect to the surface of a periodic structure-a clinotron-is analyzed here. The beam inclination provides the possibility of effective interaction by all particles of a thick electron beam with the slow evanescent harmonic of the cavity modes. The problem of electron-beam-wave interaction is treated in a self-consistent formulation. A theoretical analysis shows that the inclination of the electron beam to the grating surface decreases the demand of the clinotron for magnetic field magnitude and beam velocity spread compared to a conventional BWO. It is demonstrated that, for an optimal inclination angle and an optimal beam thickness, the clinotron efficiency exceeds the efficiency of a conventional BWO considerably given the same electron beam parameters. The developed multimode theory results are in satisfactory agreement with the theory of a BWO in terms of reflections and particle-in-cell simulations. © 1963-2012 IEEE.

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