A 1.5-MW, 140-GHz, TE/sub 28,16/-coaxial cavity gyrotron

Piosczyk, B.; Braz, O.; Dammertz, G.; Iatrou, C.T.; Kern, Stefan; Kuntze, M.; Möbius, A.; Thumm, M.; Flyagin, V.A.; Khishnyak, V.I.; Малыгин, В. И.; Pavelyev, A.B.; Zapevalov, V. E.

doi:10.1109/27.597261

Cited by 59 publications

(8 citation statements)

References 8 publications

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“…In coaxial gyrotron cavities the existence of the longitudinally-corrugated inner rod reduces the problems of mode competition and limiting current, thus allowing one to use even higher order modes at 2 MW power level with the same Ohmic attenuation as in 1 MW-class cylindrical cavities [24]. Successful activities on the development of 1.5 -2 MW short-pulse gyrotrons with coaxial cavities and axial output window were conducted at IAP Nizhny Novgorod (TE28,16mode at 140 GHz [25]) and KIT (FZK) Karlsruhe (modes TE28,16 at 140 GHz and TE31,17 at 165 GHz) [24,26]. In preliminary 1 ms short pulse operation of the 165 GHz tube with R0 =27.38 mm cavity radius and Rb = 9.57 mm electron beam radius, at B = 6.61 T, Vb = 84.8 kV and Ib =52 A, a maximum RF output power in the co-rotating TE31,17-mode (OAM state l = 30) as high as 1.2 MW was achieved with an efficiency of 27 % [27].…”

Section: Kit 12 Mw 165 Ghz Te3117 Mode Coaxial-cavity Gyrotron With A...mentioning

confidence: 99%

Gyro-devices – natural sources of high-power high-order angular momentum millimeter-wave beams

Thumm

2020

TST

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The Orbital Angular Momentum (OAM) carried by light beams with helical phasefront (vortex beams) has been widely employed in many applications such as optical tweezers, optical drives of micro-machines, atom trapping, and optical communication. OAM provides an additional dimension (diversity) to multiplexing techniques, which can be utilized in addition to conventional multiplexing methods to achieve higher data rates in wireless communication. OAM beams have been thoroughly studied and used in the optical regime but in the mm-wave and THz-wave region, they are still under investigation. In these frequency bands, there are difficulties associated with beam-splitting and beam-combining processes as well as with the use of spiral phase plates and other methods for OAM generation, since the wavelength is much larger compared to those at optical frequencies, leading to higher diffraction losses. The present paper describes the natural generation of high-power OAM modes by gyro-type vacuum electron devices with cylindrical interaction circuit and axial output of the generated rotating higher-order transverse electric mode TEm,n, where m > 1 and n are the azimuthal and radial mode index, respectively. The ratio between the total angular momentum (TAM) JN and total energy WN of N photons is given by m/ω, where ω is the angular frequency of the operating mode, which in a gyrotron oscillator is close to the TEm,n-mode cutoff frequency in the cavity. Therefore, m/ω = Rc/c, where Rc is the caustic radius and c the velocity of light in vacuum. This means that the OAM is proportional to the caustic radius and at a given frequency the same for all modes with the same azimuthal index m. Right-hand rotation (co-rotation with the electrons) corresponds to a positive value of m and left-hand rotation to negative m. The corresponding OAM mode number (topological charge) is l = m – 1. Circularly polarized TE1n modes only possess a Spin Angular Momentum (SAM: s = ±1). TE0n modes have neither SAM nor OAM. This is the result of the photonic (quasi-optical) approach to derive the TAM of modes generated in gyrotrons. The same result follows from the electromagnetic (EM) wave approach for the TAM within a given waveguide volume per total energy of the EM wave in the same volume. Such high-power output beams with very pure higher-order OAM, generated by gyrotron oscillators or amplifiers (broadband) could be used for multiplexing in long-range wireless communications. The corresponding mode and helical wavefront sensitive detectors for selective OAM-mode sorting are available and described in the present paper.

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Section: Kit 12 Mw 165 Ghz Te3117 Mode Coaxial-cavity Gyrotron With A...mentioning

confidence: 99%

Gyro-devices – natural sources of high-power high-order angular momentum millimeter-wave beams

Thumm

2020

TST

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“…For a future DEMO an RF output power level of minimum 2 MW CW at even higher operating frequencies up to 240 GHz is under consideration [3,4,5]. It is expected that the coaxialcavity gyrotron [6,7] technology will allow an operation at those output power levels. Compared to the conventional hollow-cavity gyrotron technology as used for e.g.…”

Section: Introductionmentioning

confidence: 99%

Recent Status and Future Prospects of Coaxial-Cavity Gyrotron Development at KIT

et al. 2019

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Coaxial-cavity gyrotrons are microwave sources that can extend the possible power levels of hollow cavity gyrotrons significantly and make them attractive for future fusion experiments and power plants. KIT already demonstrated operation of a modular short-pulse 170 GHz coaxial-cavity gyrotron with an output power of 2.2 MW, operating in the TE34,19 mode. Today’s focus of KIT is the verification of this technology at longer pulses, which will prove the long-pulse capabilities also. At the moment, the current KIT prototype has been extended with cooling capabilities for all critical, highly loaded components of the tube and two new, different electron guns are available for operation. This paper will give an overview about the recent status and the future prospects connected to the coaxial-cavity gyrotron development at KIT, including both experimental and theoretical activities.

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“…Generally, the rf structure of a CARM is a cylindrical waveguide for an amplifier or a cylindrical cavity for an oscillator. Recently, a new concept, the coaxial-structure CARM [8], has been proposed by combining the advantages of both the coaxial-cavity gyrotron [9] and the cylindrical-structure CARM, where the rf structure is a coaxial waveguide (or cavity) and the mechanism of the beam-wave interaction is based on the CARM. This proposal has the following comprehensive features: large structure dimension, good mode selectivity and low operating magnetic field and might be developed to be a new kind of radiation source, which has significant benefits for the power-capacity increase of the device and the extension of the operation frequency to the ranges of sub-millimetre and far-infrared waves.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear theory of a cyclotron autoresonance maser (CARM) amplifier with outer-slotted-coaxial waveguide

Qiu¹,

Ouyang²,

Zhang³

et al. 2005

J. Phys. D: Appl. Phys.

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A self-consistent nonlinear theory for the outer-slotted-coaxial-waveguide cyclotron autoresonance maser (CARM) amplifier is presented, which includes the characteristic equation of the wave, coupling equation of the wave with the relativistic electron beam and the simulation model. The influences of the magnetic field, the slot depth and width are investigated. The interesting characteristic of the device is that the mode competition can be efficiently suppressed by slotting the outer wall of the coaxial waveguide. A typical example is given by the theoretical design of a 137 GHz outer-slotted-coaxial-waveguide CARM amplifier by utilizing an electron beam with a voltage of 90 kV, current of 50 A, velocity pitch angle of 0.85 and a magnetic field of 43.0 kG. The nonlinear simulation predicts a power of 467.9 kW, an electronic efficiency of 10.4% and a saturated gain of 46.7 dB, if the electron beam has no velocity spread. However, the axial velocity spread deteriorates the device; for example, if the axial velocity spread is 2%, the peak power decreases to 332.4 kW with an efficiency of 7.4% and a saturated gain of 45.22 dB. Simulation shows that the efficiency of the outer-slotted-coaxial-waveguide CARM amplifier may be increased from 10.4% to 29.6% by tapering the magnetic field.

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A 1.5-MW, 140-GHz, TE/sub 28,16/-coaxial cavity gyrotron

Cited by 59 publications

References 8 publications

Gyro-devices – natural sources of high-power high-order angular momentum millimeter-wave beams

Gyro-devices – natural sources of high-power high-order angular momentum millimeter-wave beams

Recent Status and Future Prospects of Coaxial-Cavity Gyrotron Development at KIT

Nonlinear theory of a cyclotron autoresonance maser (CARM) amplifier with outer-slotted-coaxial waveguide

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