Systematic cavity design approach for a multi-frequency gyrotron for DEMO and study of its RF behavior

Kalaria, P.; Avramidis, Konstantinos A.; Franck, J.; Gantenbein, G.; Illy, S.; Pagonakis, I.; Thumm, M.; Jelonnek, John

doi:10.1063/1.4962238

Cited by 29 publications

(9 citation statements)

References 25 publications

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“…The studies are in line with the European Fusion Roadmap towards a DEMO [13,111]. Following the development of 1 MW, CW 140 GHz and 170 GHz gyrotrons for the W7-X stellarator and the ITER tokamak, respectively, the conceptual designs of tubes with frequencies up to approximately GHz were perfomed at KIT-IHM [112][113][114][115][116][117]. Along with a 237.…”

Section: Eu Developments For Future Demo Gyrotronsmentioning

confidence: 76%

High-power gyrotrons for electron cyclotron heating and current drive

Thumm¹,

Денисов²,

Sakamoto³

et al. 2019

Nucl. Fusion

126

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In many tokamak and stellarator experiments around the globe that are investigating energy production via controlled thermonuclear fusion, electron cyclotron heating and current drive (ECH&CD) are used for plasma start-up, heating, non-inductive current drive and MHD stability control. ECH will be the first auxiliary heating method used on ITER. Megawatt-class, continuous wave (CW) gyrotrons are employed as high-power millimeter (mm)-wave sources. The present review reports on the worldwide state-of-the-art of high-power gyrotrons. Their successful development during the past years changed ECH from a minor to a major heating method. After a general introduction of the various functions of ECH&CD in fusion physics, especially for ITER, Section 2 will explain the fast-wave gyrotron interaction principle. Section 3 discusses innovations on the components of modern long-pulse fusion gyrotrons (magnetron injection electron gun (MIG), beam tunnel, cavity, quasi-optical output coupler, synthetic diamond output window, single-stage depressed collector) and auxiliary components (superconducting magnets, gyrotron diagnostics, high-power calorimetric dummy loads). Section 4 deals with present megawatt-class gyrotrons for ITER, W7-X, LHD, EAST, KSTAR and JT-60SA, and also includes tubes for moderate pulse length machines as, ASDEX-U, DIII-D, HL-2A, TCV, QUEST and GAMMA-10. In Section 5 the development of future advanced fusion gyrotrons is discussed. These are tubes with higher frequencies for DEMO, multi-frequency (multi-purpose) gyrotrons, stepwise frequency tunable tubes for plasma stabilization, injection-locked and coaxial-cavity multi-megawatt gyrotrons, as well as sub-THz gyrotrons for collective Thomson scattering (CTS). Efficiency enhancement via multi-stage depressed collectors, fast oscillation recovery methods and reliability, availability, maintainability and inspectability (RAMI) will be discussed at the end of this section.

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Section: Eu Developments For Future Demo Gyrotronsmentioning

confidence: 76%

High-power gyrotrons for electron cyclotron heating and current drive

Thumm¹,

Денисов²,

Sakamoto³

et al. 2019

Nucl. Fusion

126

View full text Add to dashboard Cite

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“…Furthermore, an advanced water cooling system for the beam tunnel, cavity and launcher has been designed for the extension of the pulse length towards the 1s keeping the modularity of the gyrotron. With regards to the conventional-cavity technology a generalized, systematic cavity design approach has been proposed and implemented for a TE 43,15 -mode cavity at 236GHz (see [18]). Based on this, optimum operating parameters of the gyrotron are shown.…”

Section: Gyrotron Randd and Advanced Developmentsmentioning

confidence: 99%

Conceptual design of the EU DEMO EC-system: main developments and R&D achievements

et al. 2017

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For the development of a DEMOnstration Fusion Power Plant the design of auxiliary heating systems is a key activity in order to achieve controlled burning plasma. The present heating mix considers Electron Cyclotron Resonance Heating (ECRH), Neutral Beam Injection (NBI) and Ion Cyclotron Resonance Heating (ICRH) with a target power to the plasma of about 50MW for each system. The main tasks assigned to the EC system are plasma breakdown and assisted start-up, heating to L-H transition and plasma current ramp up to burn, MHD stability control and assistance in plasma current ramp down. The consequent requirements are used for the conceptual design of the EC system, from the RF source to the launcher, with an extensive R&D program focused on relevant technologies to be developed. Gyrotron: the R&D and Advanced Developments on EC RF sources are targeting for gyrotrons operating at 240GHz, considered as optimum EC Current Drive frequency in case of higher magnetic field than for the 2015 EU DEMO1 baseline. Multipurpose (multi-frequency) and frequency step-tunable gyrotrons are under investigation to increase the flexibility of the system. As main targets an output power of significantly above 1MW (target: 2MW) and a total efficiency higher than 60% are set. The principle feasibility at limits of a 236GHz, conventional-cavity and, alternatively, of a 238GHz coaxial-cavity gyrotron are under investigation together with the development of a synthetic diamond Brewster-angle window technology. Advanced developments are ongoing in the field of multi-stage depressed collector technologies. Transmission Line (TL): Different TL options are under investigation and a preliminary study of an evacuated quasi-optical multiple-beam TL, considered for a hybrid solution, is presented and discussed in terms of layout, dimensions and theoretical losses. Launcher: Remote Steering Antennas have been considered as a possible launcher solution especially under the constraints to avoid movable mirrors close to the plasma. With dedicated beam tracing calculations, the deposition locations coverage and the wave absorption efficiency have been investigated, considering a selection of frequencies, injection angles and launching points. An option for the EC system structure is proposed in clusters, in order to allow the necessary redundancy and flexibility to guarantee the required EC power in the different phases of the plasma pulse. Number and composition of the clusters are analysed to have high availability and therefore maximum reliability with a minimum number of components.

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“…Operating scenarios close to 2 MW for the coaxial-cavity technology and around 1.5 MW for the conventional cavity technology have been found in the theoretical analyses (ref. [11][12][13][14]). …”

Section: Studies Towards a 240 Ghz Gyrotronmentioning

confidence: 99%

European research activities towards a future DEMO gyrotron

et al. 2017

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Coordinated by the EUROfusion Consortium, several European research institutes are working on fusion technologies towards options for a European DEMOnstration Fusion Power Plant (FPP), as a single step between ITER and a commercial FPP, to deliver net electricity by mid of this century. One of the focus areas is the research on a proper Electron Cyclotron Resonance Heating (ECRH) and Current Drive (ECCD) system for which the fusion gyrotron is one of its major key components [1].A future FPP will probably require an ECCD operating frequency ranging from 170 GHz up to 240 GHz depending on the DEMO baseline. An RF output power of significantly higher than 1 MW (target: 2 MW) and a total gyrotron efficiency better than 60% are required. Multi-purpose operation at multiples of the λ/2-resonance frequency of the vacuum window of the gyrotron, hence in leaps of about 30 GHz (e. g. 170 / 204 / 238 GHz) needs to be considered for plasma start-up, heating and current drive. Optionally for possible steering of the absorption layer the gyrotron shall allow a fast frequency tuning in steps of around 2-3 GHz. The R&D work within the EUROfusion work package "WP HCD EC Gyrotron R&D and Advanced Developments (AD)" is focusing on all of the named targets. Verification of the coaxial-cavity technologyThe coaxial-cavity gyrotron is a promising technology for future multi-MW fusion gyrotrons [2]. In [3] a world record RF output power of 2.2 MW at short pulses (ms-range) was demonstrated. Nevertheless, the 2 MW coaxial-cavity technology, already considered for the first installation in ITER earlier [4], is still lacking its proofof-concept regarding long-pulse operation. Major concerns are the proper alignment and thermal loading of the cavity wall and its inner conductor as well as the thermal loading of the collector. Its feasibility shall be finally demonstrated by upgrading the existing KIT 2 MW 170 GHz short-pulse pre-prototype to pulse lengths up to 1 s [5]. In parallel, work is ongoing in the field of advanced cooling concepts [6,7]. Additionally, two new coaxial-cavity Magnetron Injection Guns (MIGs) are under manufacturing. The first is employing an advanced emitter technology whose major element is a new nonemissive coating. That will significantly reduce the velocity spread of the electrons at the emitter [8]. Secondly, a newly designed Inverse Magnetron Injection Gun (IMIG) will allow for a significant larger emitter radius and therefore increased output power at operating frequencies significantly above 200 GHz by keeping the same or even smaller size of the bore hole of the gyrotron SC magnet [9]. Studies towards a 240 GHz gyrotronA frequency up to 240 GHz was selected for the theoretical research work towards a future FPP, considering the requirements for "multi-purpose" and "fast frequency step-tunable" operation at high-field tokamaks and for a wide range of RF beam steering. The coaxialcavity gyrotron technology, and, as a possible fallback solution, the conventional hollow-cavity gyrotron are under investigation. ...

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Systematic cavity design approach for a multi-frequency gyrotron for DEMO and study of its RF behavior

Cited by 29 publications

References 25 publications

High-power gyrotrons for electron cyclotron heating and current drive

High-power gyrotrons for electron cyclotron heating and current drive

Conceptual design of the EU DEMO EC-system: main developments and R&D achievements

European research activities towards a future DEMO gyrotron

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