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This paper aims to present some selected fundamentals of the theory of a broad class of gyro-devices in a systematic and consistent manner and with sufficient detail necessary for understanding the underlying physical principles of their operation. The focus of this work is on the derivation and analysis of important invariants (constants of motion), as well as on comments concerning their analytical power and the physical insights they provide. [ABSTRACT FROM AUTHOR]

This paper aims to present some selected fundamentals of the theory of a broad class of gyro-devices in a systematic and consistent manner and with sufficient detail necessary for understanding the underlying physical principles of their operation. The focus of this work is on the derivation and analysis of important invariants (constants of motion), as well as on comments concerning their analytical power and the physical insights they provide.

Gyrotrons are used as high-power sources of coherent radiation operating in pulsed and CW regimes in many scientific and technological fields. In this paper, we discuss two of their numerous applications. The first one is in gyrotron-powered electromagnetic wigglers and undulators. The second one is for driving high-gradient accelerating structures in compact particle accelerators. The comparison, between the requirements imposed by these two concepts on the radiation sources on one hand and the output parameters of the currently available high-performance gyrotrons on the other hand, show that they match each other to a high degree. We consider this as a manifestation of the feasibility and potential of these concepts. It is believed that after the first successful proof-of-principle experiments they will find more wide usage in the advanced FEL and particle accelerators. [ABSTRACT FROM AUTHOR]

Gyrotrons are used as high-power sources of coherent radiation operating in pulsed and CW regimes in many scientific and technological fields. In this paper, we discuss two of their numerous applications. The first one is in gyrotron-powered electromagnetic wigglers and undulators. The second one is for driving high-gradient accelerating structures in compact particle accelerators. The comparison, between the requirements imposed by these two concepts on the radiation sources on one hand and the output parameters of the currently available high-performance gyrotrons on the other hand, show that they match each other to a high degree. We consider this as a manifestation of the feasibility and potential of these concepts. It is believed that after the first successful proof-of-principle experiments they will find more wide usage in the advanced FEL and particle accelerators.

The gyrotron travelling wave tube amplifiers (gyro-TWAs) presented in this paper can operate with high efficiency (30%), huge powers and wide bandwidths at high frequencies that no other amplifier can provide. In principle, this is a technology that can be scaled to >1 THz and operate with 20% bandwidths. Resonant coupling of two dispersive waveguide modes in a helically corrugated interaction region (HCIR) can give rise to a non-dispersive eigenwave over a wide frequency band. The synchronism between the ideal wave and an electron cyclotron mode, either fundamental or harmonic, of a large orbit electron beam contributes to the broadband amplification. An electron beam of 55 keV, 1.5 A with a velocity pitch angle of ~1 generated by a thermionic cusp gun is used in our 100 GHz gyro-TWA experiment, which achieves an unsaturated output power of 3.4 kW and gain of 36-38 dB. The design and experimental results of the many components making the gyro-TWA will be presented individually and then the whole system will be introduced. The amplification of a swept signal by the W-band gyro-TWA is demonstrated showing its capabilities in the field of telecommunications. Furthermore, the design studies of a cusp electron gun in the triode configuration and the realization of a 3-fold HCIR operating at 372 GHz will also be displayed. [ABSTRACT FROM AUTHOR]

In this paper, techniques to improve the collector’s dissipated power density threshold are discussed first. Then, theories of electron collection are presented, aiming at improving the effective electron-collecting area and collecting uniformity. Specifically, the layered electron beam collection in linear-taper collector, respectively, with constant and gradually varying magnetic field is modeled and discussed. Results indicate that a quasi-rectangular shape collection can be realized as the tangential collection dominates. Finally, the using of a compensation coil is analyzed and the corresponding collector is designed. [ABSTRACT FROM AUTHOR]

The frequency agility of a ${W}$ -band gyrotron travelling wave amplifier (gyro-TWA) was demonstrated by the amplification of a frequency-swept input signal (chirp signal). The gyro-TWA was developed to provide high output power and wide bandwidth by using a helically corrugated interaction region. In the experiment a ~0.5-W signal of linearly swept frequency bandwidth of 1 GHz was amplified and a gain of over 30 dB was measured when driven by a 40 keV, 1.5 A, and axis-encircling electron beam. [ABSTRACT FROM AUTHOR]

The global bandgaps of photonic crystal are theoretically analyzed in this paper. The electromagnetic-wave propagation characteristics of photonic bandgap (PBG) structures, which is used in the the millimeter-wave, submillimeter-wave, and terahertz regime vacuum electronic devices and accelerators, were numerically simulated using the finite-element method software high-frequency structural simulator. The dispersion curves of the lattices in different rod radius to-rod spacing ratios and the global bandgaps for the general 2-D PBG structures formed by triangular and square arrays of metal rods were simulated. A mode map that shows the relationship between the structures and the contained modes was plotted and a 220-GHz metallic PBG resonator operating in TE \mathrm {\mathbf {04}} mode was designed for a gyrotron device to verify the theoretical and numerical simulations, and a comparison of mode density and quality factor between the PBG resonator and the equivalent cylindrical resonator has been carried out. [ABSTRACT FROM PUBLISHER]