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A 340GHz backward wave oscillator (BWO) based on the sine waveguide and pencil electron beam is presented as a novel terahertz radiation source. The particle-in-cell (PIC) simulation results predicts that this device can produce the output power of over 2.7W in the frequency range of 335.8–348.5GHz by utilizing a 20mA pencil beam and adjusting the voltage from 12kV to 14 kV.
The use of the “negative mass” regime provides stabilization of longitudinal size of dense photo-injector electron bunches at long distances. This allows one to increase significantly the power capabilities of a terahertz source based on coherent spontaneous undulator emission from a short bunch. However, such type of emission is produced, if the bunch length is comparable with the radiation wavelength...
Two types of thermionic cathodes were constructed to investigate the effect of thermal insulation gaps on the performance of a gyrotron. They were installed and tested in a 0.2-THz gyrotron, FU-CW-GIA. The simulation results have shown substantial deterioration in the electron beam quality and decreases in the output power in case of a cathode which has the thermal insulation gaps at the edge of the...
We proposed and fabricated a novel resonant-tunneling-diode (RTD) terahertz (THz) oscillators for circularly polarized wave radiation, which is convenient for THz wireless communication without the alignment of polarization direction. The oscillator is composed of an RTD, crossed slots for resonator and in-plane radiation, radial line slot pairs for output radiation in the upward direction from the...
We found the full analytical solution of the semiclassical model, described the stationary profile of the electric field in the miniband semiconductors, subjected to the DC voltage. The analysis of obtained solution shown the three different types of the field distribution, taken place in the semiconductor depending on the emitter current-field characteristics. Among the observed profiles we found...
We demonstrate a 40 W peak power terahertz (THz) wave from an off-axis parametric oscillator by pumping a y-cut monolithic lithium niobate slab crystal with a pulsed laser at 1064 nm. This is a demonstration that, for the first time, a THz parametric oscillator resonates a THz wave, having the advantages of compact size, easy alignment, and high efficiency. The experimental results show that the efficiency...
A high power 300 GHz band pulse gyrotron has been developed based on the design concept for stable and single mode oscillation verified with a prototype gyrotron. The oscillation frequency is 303.3 GHz and the power target is 300 kW. Oscillation test has been carried out and a maximum single mode oscillation power higher than 320 kW was attained. No competing mode was observed during the turn on and...
We considered the nonstationar charge transport through the nanoscaled heterostructrure, consisting of the muniband semiconductor superlattices (SL), divided by the layers of heavy doped semiconductor. We demonstrate that compared with the regular SL, such design provides simultaneously the significant increase of both the output power and the frequency of the produced current oscillation.
Quad-frequency oscillation from 100 GHz to 200 GHz was demonstrated using ITER gyrotron at QST. Those RF beam passed through the center of the gyrotron window and good couples to transmission line were obtained for each oscillation. The mega-watt-class power was obtained for all frequencies. Validation of gyrotron for a demo reactor is numerically started on the basis of our multi-frequency gyrotron.
Compact and coherent source is a key component for various applications of the THz waves. We report on our recent results of THz oscillators using resonant tunneling diodes (RTDs). To achieve high-frequency oscillation, the electron delay time in RTD and conduction loss around the antenna integrated with RTD were reduced. By these methods, a fundamental oscillation up to 1.92 THz was obtained at room...
In this paper, a three-section periodical grating structure (PGS) is investigated for Smith-Purcell (SP) backward wave oscillator (BWO). The first and second sections are used to pre-modulate the electron beam and the open grating (section-III) is for terahertz SP radiation. By theoretical analysis and particle-in-cell simulations, the SP radiation is studied in detail. The results show that the three-section...
A frequency tunable and Gaussian beam output gyrotron, Gyrotron FU CW GIV, has been developed on the basis of Gyrotron FU CW X. Wide frequency tunability in 200 GHz band at fundamental harmonic resonance was observed as well as frequency tunable oscillation in 400 GHz band at second harmonic resonance.
We proposed and fabricated a novel resonant-tunneling-diode terahertz oscillator integrated with dipole array antennas coupled with a slot resonator to obtain output power with multiple peaks, which is convenient for imaging without interference fringes caused by coherence. We measured the radiation pattern for single and arrayed oscillators, and calculated the output power using the integration of...
Resonant tunneling diode based transmitters for wireless communication systems in the terahertz frequency range around 300 GHz are investigated. Two possible modulation schemes are investigated to increase the data rate of the transmitter. An error-free data rate of 4 Gbps is achieved using the best modulation scheme and a RTD based receiver.
We studied adsorption state of water molecules in a porous coordination polymer (PCP) using infrared spectroscopy. We observed two absorbance peaks below 4% relative humidity (RH) that originate from OH stretch modes of adsorbed water molecules. Their peak frequencies and areas indicate that one of the OH is free, and the other is hydrogen bonded. We also found that Free-OH plays a role of water attraction...
We show photonics-based field visualization technique which enables us to map the spatial distribution of the amplitude and phase of the millimeter and terahertz waves generated by the self-oscillating free-running sources. The frequency of the electromagnetic wave to be measured is down-converted to an IF signal by a non-polarimetric electrooptic (EO) detection technique. The frequency fluctuation...
We report the observation of multiple polariton branches in an ultra-strongly coupled system of Landau level transitions in strained Ge quantum wells (sGe QWs) and a THz metamaterial. The sGe QW system shows narrow spin-split heavy-hole cyclotron resonances and thus leads to multiple cyclotrons. The coupled system can be described by an expanded ultra-strong coupling Hamiltonian including all oscillators...
We present results of theoretical study of influence of the electron velocity spread and the radial width on the efficiency and mode competition in a 300-GHz gyrotron operating in the TE22,2,1 mode, with which 300-kW level high power single mode oscillation has been demonstrated. Effects of a finite voltage rise time corresponding to the real power supply of this gyrotron is also considered. Simulations...
Project of narrow-band 300 GHz / 500 kW radiation source operating in a quasi-continuous regime and aimed on modern plasma fusion applications is under development at ENEA (Frascati). As a solution of such source based on a moderately relativistic 500–700 keV/10–20 A electron beam cyclotron masers of different type are considered. The use of such a beam makes it possible to achieve high powers at...
The paper describes recent results of theoretical and experimental studies of the FEM-oscillator driven by linac LIU-3000 0.8 MeV / 200 A / 200 ns. At the present stage efficient operation of the JINR-IAP FEM has been demonstrated at 30 GHz / 15 MW and 60 GHz / 5 MW powers. Project of multimegawatt power 90 GHz FEM is in progress currently. The key components of the FEM are short period tapered wiggler,...
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