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The analytical estimation of optimal parameters is fulfilled for the terahertz M-type generator operating at frequency about 0.330 THz with anode voltage of 13 ??V and magnetic field of 0.7 T. Revealing from this model, the magnetron interaction space geometry providing the effective electron interaction with a high-frequency field on (+1) spatial harmonic of p-mode oscillations is proposed for the...
We demonstrated a novel point-typed carbon nanotube field emitters using a triangular-shaped carbon nanotube films. We also investigated the field emission properties of the field emitters according to the tip angles. The wider field emitters exhibited higher emission current, and the field emitters with a tip angle of 120° showed extremely high emission current density over 104 A/cm2 (> 10 mA)...
Authors introduce a novel on-line partial discharge monitoring sensor, which frequency band is in 100 kHz – 20 MHz. The novel sensor called CSC (Capacitive Slot Coupler) is very compact in size and could be inserted between wedge and stator bar. In this paper, an equivalent partial discharge detection circuit is introduced considering the various PD sources. And its capability in PD source identification...
We demonstrated field emission properties of a CNT point emitter fabricated by using CNTs on a graphite rod. The emitter has the highest current of 6.3 mA; the corresponding current density is 1.6 A/cm2. The emitter is stable at a current of 0.1 mA for 20 hours. It also showed a small and uniform emission pattern at the phosphor coated ITO glass. Our point emitter could be a good candidate for X-ray...
A 0.1 THz 10 W clinotron is numerically and experimentally investigated for compact high-power terahertz radiation source. The output characteristics of the clinotron with the inclined sheet electron beam are examined by using the 3D particle-in-cell simulation code MAGIC and are compared with the measurements.
For application to electron field emission devices, a metal grid based on a silicon frame is introduced. Silicon frame is used to improve the thermal resistivity and electrical stability by electron beam. Silicon based micro-scale metal grid fabricated using MEMS technology.
Research activities for development of a compact and high power terahertz radiation source using a CNT cold cathode are presented. Basic principles of the proposed device and experimental challenges to realize the device are discussed.
Generation of electron bunch from a dc-biased, single surface multipactor was studied theoretically and by PIC simulations. The condition for a spatially narrow bunch was obtained and verified by PIC simulations. This kind of multipactor is proposed to be used as a compact electron gun for various applications, such as linear accelerators.
A terahertz Smith-Purcell backward-wave oscillator (BWO) with an inverse wet-etched grating based on silicon has been studied to enhance radiation intensity. Particle-in-cell simulation shows that the radiated power is increased up to 2.3 times higher at the radiated frequency of 0.66 THz for an electron-beam energy of 30 keV.
We suggest that THz wave is an alternative tool for the void detection in multilayer semiconductor. We measured the THz pulse using a reflective THz imaging system and obtained THz imaging by signal processing. And, to verify possibility of THz inspection, we compared with ultrasound.
We report frequency propagation characteristics for two-dimensional photonic crystal using terahertz time-domain spectroscopy. The transmission frequency spectrum obtained by the 3D FDTD simulation and the experiment, and the frequency range of stop bands is in good agreement with the results.
Two-dimensional photonic crystals (PCs) are fabricated by using the wet chemical etching of high-resistivity silicon. The formation of the photonic band gap at a frequency of about 100 GHz is demonstrated by the measured and the 3D FDTD simulated transmittance of the transverse magnetic (TM) mode.
A 35 GHz 3 kW spatial-harmonic magnetron employing 20-vane resonator is numerically and experimentally investigated. Simulated output power is 3.2 kW at beam voltage of 6.5 kV and anode current of 4 A using 3D PIC simulation. The measured resonant frequency for operation mode of p = 16 is 34.96 GHz.
We suggest a simple method overcoming the limitation of spatial resolution for wavelength by using a horn antenna. And, we verify detection limitation by THz imaging for a foreign object in flour.
Physical characteristics of a dc-biased single-surface multipactor are investigated theoretically, and a novel scheme of the multipactor using a photonic crystal cavity resonator to maximize insulation gap distance is introduced. A fixed rf phase minimizing rf electric field is analytically obtained, which is universal for any surface material. With an assumption of zero initial velocity, analytical...
A 35 GHz 3 kW spatial harmonic magnetron (SHM) employing the 20-vane unstrapped resonator is designed and is investigated by using a three-dimensional (3D) particle-in-cell (PIC) simulation. The saturated output power is 3.2 kW when the beam voltage is 6.5 kV and the anode current is 4 A.
Two-dimensional millimeter wave photonic crystals (PCs) are fabricated by wet etching of the high-resistivity (HR) silicon. The measured and the simulated transmittance demonstrate the formation of the photonic-band-gap (PBG) at the frequencies of about 100 GHz.
An experimental prototype of a pulse magnetron has been developed, having the output power of 2.5 kW at a frequency of 35 GHz with the operation voltage of 6.5 kV. The interaction space of the magnetron has been extended due to the properly selected operation mode - it works at the first negative spatial harmonics. The magnetron's structural scheme includes the main secondary-emission cold cathode...
An analytical estimation has been performed to determine the optimal parameters of pulsed magnetrons, operating at a spatial harmonic at a frequency of 35 GHz and an anode voltage of 6.5 kV in the drift-resonance mode, with the main cathode being the cold secondary-emission one. A 3D simulation experiment on a magnetron with the analytically determined characteristics has been conducted to check its...
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