Influence of Emitter Surface Roughness and Emission Inhomogeneity on Efficiency and Stability of High Power Fusion Gyrotrons
Influence of Emitter Surface Roughness and Emission Inhomogeneity on Efficiency and Stability of High Power Fusion Gyrotrons

Author: Zhang, Jianghua

Publisher: KIT Scientific Publishing

Published: 2016-11-30

Total Pages: 226

ISBN-13: 3731505789

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The increasing demand for powerful, reliable, and efficient gyrotron oscillators for Electron Cyclotron Resonance Heating (ECRH) in fusion plasma experiments requires a close look at the various factors in gyrotrons that determine gyrotron performance. In this frame, the influence of emitter surface roughness, emission inhomogeneity, and secondary electron generation on gyrotron operation is presented, with focus on Low Frequency Oscillations (LFOs) and Electron Beam Halo (EBH) generation.

Systematic Study of Key Components for a Coaxial-Cavity Gyrotron for DEMO
Systematic Study of Key Components for a Coaxial-Cavity Gyrotron for DEMO

Author: Franck, Joachim

Publisher: KIT Scientific Publishing

Published: 2017-05-11

Total Pages: 274

ISBN-13: 3731506521

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The physical design of cavity and magnetron injection gun (MIG) for a realistic, DEMO-compatible, coaxial-cavity 238 GHz 2 MW CW fusion gyrotron is developed in this work, having auxiliary frequencies at 170 GHz and 204 GHz. Novel systematic approaches towards multi-frequency mode selection, magnet requirements, and MIG design are presented. Mode deterioration and voltage depression variation due to insert misalignment versus cavity wall and/or versus electron beam are studied.

Influence of Emitter Surface Roughness and Emission Inhomogeneity on Efficiency and Stability of High Power Fusion Gyrotrons
Influence of Emitter Surface Roughness and Emission Inhomogeneity on Efficiency and Stability of High Power Fusion Gyrotrons

Author: Jianghua Zhang

Publisher:

Published: 2020-10-09

Total Pages: 220

ISBN-13: 9781013281587

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The increasing demand for powerful, reliable, and efficient gyrotron oscillators for Electron Cyclotron Resonance Heating (ECRH) in fusion plasma experiments requires a close look at the various factors in gyrotrons that determine gyrotron performance. In this frame, the influence of emitter surface roughness, emission inhomogeneity, and secondary electron generation on gyrotron operation is presented, with focus on Low Frequency Oscillations (LFOs) and Electron Beam Halo (EBH) generation. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

Automated Mode Recovery and Electronic Stability Control for Wendelstein 7-X Gyrotrons
Automated Mode Recovery and Electronic Stability Control for Wendelstein 7-X Gyrotrons

Author: Wilde, Fabian

Publisher: KIT Scientific Publishing

Published: 2024-08-07

Total Pages: 272

ISBN-13: 3731511606

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Magnetic confinement fusion relies on plasma heating and plasma control using gyrotron oscillators providing at megawatt power levels. The operational reliability decreases when operating at the performance limits due to increasing parasitic mode activity. This work demonstrates for the first time the automated, fast recovery of nominal gyrotron operation during a pulse by exploiting the hysteretic gyrotron behaviour after a mode switch being in use at the Wendelstein 7-X ECRH facility.

Energy-efficient, scalable and modular industrial microwave applicator for high temperature alkaline hydrolysis of PET
Energy-efficient, scalable and modular industrial microwave applicator for high temperature alkaline hydrolysis of PET

Author: Ramopoulos, Vasileios

Publisher: KIT Scientific Publishing

Published: 2023-01-27

Total Pages: 162

ISBN-13: 3731510995

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Microwave-assisted alkaline hydrolysis of PET can be 20 times faster and at lower temperatures. This work presents a novel industrial microwave applicator at 2.45 GHz with homogeneous distribution to support this reaction, which allows an efficient and continuous operation. In addition, an innovative dielectric and calorimetric measurements setup is presented. Furthermore, the modelling of the reaction kinetics based on the measured dielectric parameters is presented.

A First 2 MW-Class (136)/170/204 GHz Multi-Frequency Gyrotron Pre-Prototype for DEMO: Design, Construction and Key Components Verification
A First 2 MW-Class (136)/170/204 GHz Multi-Frequency Gyrotron Pre-Prototype for DEMO: Design, Construction and Key Components Verification

Author: Ruess, Tobias

Publisher: KIT Scientific Publishing

Published: 2023-10-26

Total Pages: 258

ISBN-13: 3731513099

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Ein Gyrotron wird in magnetisch eingeschlossenen Plasmaexperimenten für Heizung, Stromtrieb, Plasmastabilisierung und Plasmadiagnostik verwendet. In dieser Arbeit wird der erste Entwurf und Bau eines Mehrfrequenz-/Mehrzweck Pre-Prototyp Gyrotrons in koaxialer Technologie vorgestellt, das bei (136)/170/204 GHz mit einer Ausgangsleistung von 2 MW arbeitet. Dies ist der erste Schritt zum Betrieb bei Frequenzen bis zu 240 GHz unter Verwendung der Koaxialhohlraum-Gyrotrontechnologie. - A gyrotron is used in magnetically confined plasma experiments for heating, current drive, plasma stabilization and plasma diagnostics. This work presents the first design and construction of a multi-frequency / multi-purpose coaxial-cavity pre-prototype gyrotron operating at (136)/170/204 GHz with an output power of 2 MW. It is the first step towards operating frequencies up to 240 GHz using the coaxial-cavity gyrotron technology.

Pushing the KIT 2 MW Coaxial-Cavity Short-Pulse Gyrotron Towards a DEMO Relevant Design
Pushing the KIT 2 MW Coaxial-Cavity Short-Pulse Gyrotron Towards a DEMO Relevant Design

Author: Ruess, Sebastian

Publisher: KIT Scientific Publishing

Published: 2021-01-22

Total Pages: 190

ISBN-13: 3731510243

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Magnetic fusion is one approach to generate thermonuclear fusion power in an environmental friendly way. The Electron Cyclotron Resonance Heating is considered as the major concept for startup, heating and control of the fusion plasma. Megawatt-class gyrotrons generate the required microwave power. This work focuses on advanced key components and technologies for a DEMO relevant 2 MW gyrotron. One major focus is on the development of advanced Magnetron Injection Guns. Another focus is on the red

MultPhysics Modelling towards the Stabilization of PAN Fibers with Microwaves Based on Experimental Data
MultPhysics Modelling towards the Stabilization of PAN Fibers with Microwaves Based on Experimental Data

Author: Hofele, Julia

Publisher: KIT Scientific Publishing

Published: 2024-07-10

Total Pages: 174

ISBN-13: 3731513501

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High energy demand is one reason for high costs of carbon fibers. One option to decrease them is to use microwave heating instead of conventional heating. In this work, steps towards a microwave assisted process during the stabilization phase are presented. In-situ dielectric measurements are performed and a reaction kinetics model is setup in connection to the dielectric loss. This allows to calculate a stabilization degree and fiber temperatures leading to a basic process understanding.

New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs
New Type of sub-THz Oscillator and Amplifier Systems Based on Helical-Type Gyro-TWTs

Author: Marek, Alexander

Publisher: KIT Scientific Publishing

Published: 2023-01-26

Total Pages: 322

ISBN-13: 3731512505

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This work presents the development of a new sub-THz source for the generation of trains of coherent high-power ultra-short pulses at 263 GHz via passive mode-locking of two coupled helical gyro-TWTs. For the first time, it is shown that the operation of such passive mode-locked helical gyro-TWTs in the hard excitation regime is of particular importance to reach the optimal coherency of the generated pulses. This could be of particular interest for some new time-domain DNP-NMR methods.