Development of High Power 140 GHz Gyrotrons at KfK for Applications in Fusion

Piosczyk, B.; Kuntze, M.; Borie, E.; Dammertz, G.; Dumbrājs, O.; Gantenbein, G.; Möbius, A.; Nickel, H.-U.; Thumm, M.

doi:10.1016/b978-0-444-89995-8.50117-x

Cited by 5 publications

(11 citation statements)

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“…The main factors producing the velocity spread are [10]: spread of the initial velocities, roughness of the emitting surface, disturbance of axial symmetry of the electron gun, space charge effects within the beam, inhomogeneaus fields on the cathode and nonadiabatic fields in the intermediate region ( compression zone) between the cathode and the interaction cavity. Relatively high compression ratios of up to 30-40 are used [24]. Diode-typeguns [10] as weil as triode-type guns with a modulation anode [2], which give the option of powerless modulation of the electron beam and thus of the output power for heat pulse propagation experiments [24] are employed.…”

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“…Relatively high compression ratios of up to 30-40 are used [24]. Diode-typeguns [10] as weil as triode-type guns with a modulation anode [2], which give the option of powerless modulation of the electron beam and thus of the output power for heat pulse propagation experiments [24] are employed.…”

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confidence: 99%

“…The choice of the working mode of a high-power CW mm-wave gyrotron is based on an intricate set of design trade-offs. The frrst 140 GHz gyrotrons [2,24] employed rotationally symmetric TEo3 mode cavities. The TEon circular symmetric family of modes is part of a general class of modes called volume modes.…”

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“…To alleviate the many conflicting requirements posed on cavity wall losses, potential depression, mode competition and efficiency considerations, a different interaction approach has to be utilized. Only rotating whispering gallery modes (WGM: TEmn with m > > 1 and n = 1 ,2) or asymmetric volume modes (A VM: TErno with m > > 1 and n > 2) are now considered to have the potential to meet high power requirements (0.5-1.0 MW) in CW operation at frequencies around 140 GHz [1,2,[7][8][9][10][20][21][22][23][24][25][26][27][28][29].…”

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“…A general scaling law for the maximum power density Po in the cavity walls is approximately given by [2,24]: Po = K P 00 t Q fS/2 I (X:Un2-m2) (7) when Pout is the power output and K is a scaling constant which depends upon a number of factors including material selection, surface finish, manufacturing process, operating ternperature and thermal cycling history of the cavity.…”

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State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers

Thumm

2020

J Infrared Milli Terahz Waves

296

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STATE-OF-THE-ART OF HIGH POWER GYRO-DEVICES AND FREE ELECTRON MASERSAt present, gyrotron oscillators are mainly used as high power millimeter wave sources for electron cyclotron resonance heating (ECRH) and diagnostics of magnetically confmed plasmas for generation of energy by controlled thermonuclear fusion. 140 GHz gyrotrons with output power Pout = 0.58 MW, pulse length 't = 2.0 s and efficiency 11 = 34 % are commercially available. Diagnostic gyrotrons deliver P out = 40 kW with 't = 40 J-lS at frequencies up to 650 GHz (11 2_ 4 %). Recently, gyrotron oscillators have also been successfully used in matedal processing and plasma chemistry. Such technological applications require gyrotrons with the following parameters: f 2. 28 GHz , Pout = 10-30 kW, CW, 11 2. 30 %. This paper reports on achievements and problems related to the development of very high power mm-wave gyrotrons for long pulse or CW operation and describes the microwave technological pecularities of the different development steps. In addition, this work gives a short overview of the present development of gyrotrons for technological applications, quasi-optical gyrotrons, cyclotron autoresonance masers (CARMs), gyro-ldystrons, gyro-TWT amplifiers, gyro-BWO's and free electron masers (FEMs). The most impressive FEM output parameters are: Pout = 2GW, 't = 20 ns, 11 = 13 % at 140 GHz (LLNL) and Pout = 15 kW, 't = 20 J-tS, 11 = 5 % in the range from 120 to 900 GHz (UCSB). ENTWICKLUNGSSTAND VON HOCHLEISTUNGS-GYRO-RÖHREN UND FREI-ELEKTRONEN-MASERN Übersiebt Gyrotronoszillatoren werden derzeit vorwiegend als Hochleistungsmillimeterwellenquellen für die Elektron-Zyklotron-Resonanzheizung (ECRH) und Diagnostik von magnetisch eingeschlossenen Plasmen zur Erforschung der Energiegewinnung durch kontrollierte Kernfusion eingesetzt. 140 GHz Gyrotrons mit einer Ausgangsleistung von Pout = 0.58 MW bei Pulslängen von 't = 2.0 s und Wirkungsgraden von • 11 = 34% sind kommerziell erhältlich. Gyrotrons zur Plasmadiagnostik erreichen Frequenzen bis zu 650 GHz bei P out = 40 kW und 't = 40 ~-ts (11 2. 4 %). In jüngster Zeit jedoch finden Gyrotronoszillatoren auch für technologische Prozesse und in der Plasmachemie erfolgreich Verwendung. Dabei werden Röhren mit folgenden Parametern eingesetzt: f 2_ 28 GHz, Pout = 10-30 kW, CW, 11 2. 30 %. In diesem Beitrag wird auf den aktuellen Stand und die Probleme bei der Entwicklung von Hochleistungs-mm-Wellen-Gyrotrons für Langpuls-und Dauerstrichbetrieb sowie auf die mikrowellentechnischen Besonderheiten der einzelnen Entwicklungsphasen eingegangen: Außerdem wird auch kurz über den neuesten Stand der Entwicklung von Gyrotrons für technologische Anwendungen, quasi-optischen Gyrotrons, Zyklotron-Autoresonanz-Masern (CARMs), Gyroklystrons, Gyro-TWT-Verstärkern, Gyro-Rückwärtswellenoszillatoren (BWOs) und Frei-Elektronen-Maser (FEM) berichtet. FEM-Rekordausgangsparameter sind hier: Pout = 2 GW, 't = 20 ns, 11 = 13 % bei 140 GHz (LLNL) und Pout = 15 kW, 't = 20 J-lS, 11 = 5 % im Bereich von 120 bis 900 GHz (UCSB). Contents

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State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers

Thumm

2020

J Infrared Milli Terahz Waves

296

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The gyrotron – a natural source of high-power orbital angular momentum millimeter-wave beams

et al. 2017

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Orbital angular momentum (OAM) of electromagnetic-wave beams provides further diversity to multiplexing in wireless communication. The present report shows that higher-order mode gyrotrons are natural sources of highpower OAM millimeter (mm) wave beams. The welldefined OAM of their rotating cavity modes operating at near cutoff frequency has been derived by photonic and electromagnetic wave approaches.

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State-of-the-art of high power gyro-devices and free electron masers. Update 2004

Thumm¹

2005

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Development of High Power 140 GHz Gyrotrons at KfK for Applications in Fusion

Cited by 5 publications

References 3 publications

State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers

State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers

The gyrotron – a natural source of high-power orbital angular momentum millimeter-wave beams

State-of-the-art of high power gyro-devices and free electron masers. Update 2004

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