Flexible terahertz wire grid polarizer with high extinction ratio and low loss

An aluminum-based THz wire grid polarizer is theoretically investigated and experimentally demonstrated on a sub-wavelength thin flexible and conformal foil of the cyclo-olefin Zeonor© polymer. THz time-domain spectroscopy characterization, performed on both flat and curved configurations, reveals a high extinction ratio between 40 and 45 dB in the 0.3-1 THz range and in excess of 30 dB up to 2.5 THz. The insertion losses are lower than 1 dB and are almost exclusively due to moderate Fabry-Perót reflections, which vanish at targeted frequencies. The polarizer can be easily fabricated with low-cost techniques such as roll-to-roll and/or large area electronics processes and promises to pen the way for a new class of flexible and conformal THz devices

Gyrotron cavity analysis for single mode third-harmonic,continuous-wave operation at a sub-terahertz and terahertz frequencies

A cavity design of a 395 GHz gyrotron for DNP experiments operating at the third cyclotron harmonic is presented. The gyrotron is designed to operate at the TE6,4-mode,which allows one to produce several hundreds watts output power with the density of ohmic losses acceptable for continuous operation. It is shown that the desired mode is well separated from competing modes. Special attention is paid to the effect of imperfections in resonator fabrication on the gyrotron performance. It is found that to keep the gyrotron performance close to the designed data obtained for an ideal resonator shape the resonator should be fabricated with the tolerances of about one micron,which seems doable in view of the recent experimental data. The same analysis presented for third harmonic 1 THz gyrotron with TE9,7 operating mode. The results demonstrate the moderate optimism for high frequency gyrotrons using ordinary magnet systems.research repor

INFLUENCE OF VOLTAGE FLUCTIONS ON GYROTRON EFFICIENCY AND STABILITY

Influence of power supply voltage instability on gyrotron operation regime is investigated. Dependence of efficiency versus variations of external parameters is given and conditions of oscillations cutoff are determined. It is shown that positive voltage fluctuations result in sharp falling efficiency and failure of self-oscillations and the steadiest gyrotrons are those with short cavities and the large raito of transverse electron speed to longitudinal one around 1.5-2. Comparison of theoretical and experimental results is given.research repor

The numerical analysis of the submillimeter wavelength continuously tunable gyrotron

The results of the output characteristics calculations for the coaxial cavity gyrotron with smooth mechanical frequency tuning are presented. The tuning is based on displacement of an internal coneshaped rod of coaxial cavity along device axis what allows of smooth variations in eigen frequencies of the cavity. The application of an inner conductor with impedance surface allows reducing its thermal load. The results of the calculations demonstrate the possibility of frequency tuning of the oscillator by 3-4% on frequencies up to 330 GHz with output power about 10 kW in CW regime.research repor

Modeling and simulation of gyrotrons

Modeling and simulation of gyrotrons have two interconnected aspects, namely beam formation in the election-optical system (EOS) and beam-field interaction in the resonant cavity. In this paper we address both problems and outline the physical models and numerical techniques implemented in our problem-oriented package of experiments carried out at FIR FU Center and directed towards analysis and optimization of the existing devices of the Gyrotron FU Series an well as applied to the development of simulation-based design (SBD) of a novel high harmonic gyrotron with axis encircling electron beam and permanent magnet system.research repor

Simulation of a high harmonic gyrotron with axis-encircling beam and permanent magnet

A compute code for simulation of beam-field interaction in a resonant cavity of a gyrotron has been developed. It is based on a self-consistent, time-independent, single-mode physical model. The code has been applied to the analysis of the electrodynamical system of a novel high-harmonic gyrotron physical model and the use of the numerical experiment are presented and discussed.research repor

COMPUTER SIMULATION OF AXIS-ENCIRCLING BEAMS GENERATED BY AN ELECTRON GUN WITH A PERMANENT MAGNET SYSTEM

Results from computer aided design of electron gun generating axis-encircling beams are presented and discussed. Numerical experiment were performed by the new version of the software package GUN-MIG named GUN-MIG/CUSP. It is based on a self-consistent relativistic model and is developed as a problem oriented tool for analysis of conventional magnetron injection guns (MIG) and electron guns with field reversal, forming axis-encircling beams. As a result of the simulations an electron-optical design of an electron gun with permanent magnet system was accomplished. The gun is expected to from a high quality beam with small velocity spread and beam ripple. Parameters of the generated beam are appropriate for a prospective high harmonic gyro-device with axis-encircling beam. Design of such device is in progress now.research repor

NUMERICAL ANALYSIS OF WEAKLY RELATIVISTIC LARGE ORBIT GYROTRON WITH PERMANENT MAGNET SYSTEM

High-harmonic gyro-devices with axis-encircling electron beam known as large orbit gyrotrons (LOG) represent an appealing alternative to the conventional gyrotrons. In this paper we investigate the feasibility of such device operating with low current and low energy electron beams formed by a novel electron gun with permanent magnet system. The results from the numerical experiments indicate the possibility to excite TE41 mode at fourth harmonic of the cyclotron frequency. Simulations predict generation of microwave radiation with frequency 104 GHz and output power near 1KW.research repor