First Operation of a Step-Frequency Tunable 1-MW Gyrotron With a Diamond Brewster Angle Output Window

Gantenbein, G.; Samartsev, A.; Aiello, G.; Dammertz, G.; Jelonnek, John; Losert, M.; Schlaich, A.; Scherer, T.; Strauß, D.; Thumm, M.; Wágner, D.

doi:10.1109/ted.2013.2294739

Cited by 58 publications

(24 citation statements)

References 19 publications

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“…At KIT the CVD-Diamond Brewster-angle window is the favorite. The successful operation of a step-frequency tunable 1 MW short-pulse (ms) gyrotron with a synthetically manufactured diamond Brewster angle output window was demonstrated earlier [15]. Nevertheless, for future DEMO gyrotrons the development of diamond discs of larger size for higher power capabilities, advanced cooling and brazing technologies are mandatorily required and pushed forward at KIT [16,17].…”

Section: Advances In Window Technologiesmentioning

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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Section: Advances In Window Technologiesmentioning

confidence: 99%

European research activities towards a future DEMO gyrotron

et al. 2017

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“…Additionally broadband window technologies, e.g. chemical vapour deposition diamond (CVD) Brewsterangle windows [17] and multi-stage depressed collectors will have to be developed ( Table 2). As part of the launcher studies different configurations on the remote steering (avoiding movable parts and mirrors due to high neutron and radiation fluxes) and their focussing capabilities of the EC millimetre wave were assessed for equatorial launchers and are being pursued for the upper port launcher.…”

Section: Ec Systemmentioning

confidence: 99%

Technological and physics assessments on heating and current drive systems for DEMO

Franke

Barbato

Bosia

et al. 2015

Fusion Engineering and Design

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The physics requirements of the heating and current (H&CD) systems in a Demonstration Fusion Power Plant (DEMO) are often beyond the actual level of design maturity and technology readiness required. The recent EU fusion roadmap advocates a pragmatic approach and favours, for the initial design integration studies, systems to be as much as possible, extrapolated from the ITER experience. To reach the goal of demonstrating the production of electricity in DEMO with a closed fuel cycle by 2050, one must ensure reliability, availability, maintainability, inspectability (RAMI) as well as performance, efficiency and optimized design for the H&CD systems.In the recent Power Plant Physics & Technology (PPP&T) Work Programme a number of H&CD studies were performed. The four H&CD systems Neutral Beam (NB) Injection, Electron Cyclotron (EC), Ion Cyclotron (IC) and Lower Hybrid (LH) were considered. First, a physics optimisation study was made assuming all technologies are available and identifying which parameters are needed to optimize performance for given plasma parameters. Separately, the (i) technological maturity was considered (e.g. 240 GHz gyrotrons for EC) and (ii) technologies were adapted (e.g. multi-stage depressed collector for EC) or (iii) novel solutions (e.g. photo-neutralization for NB or new antennae concepts for IC) were studied to overcome the limitations of the present H&CD systems with respect to DEMO requirements. Further constraints imposed by remote maintenance or breeding blanket interactions were considered.

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“…Application of ECCD for plasma control in DEMO will require remote steering or fast frequency tuning of gyrotrons, The latter requires a frequency step-tunable gyrotron using a broadband RF output window (preferably Brewster-angle window) and it requires the proper operation of the gyrotron at neighbouring modes (2-3GHz). The principle of frequency step-tunability has been demonstrated for the KIT 1MW D-band multi-frequency short-pulse prototype gyrotron for example [8]. Operating frequencies above 230GHz will be required for optimum ECCD efficiencies if assuming a high magnetic field at the tokamak as defined for DEMO baseline 2012 [9].…”

Section: Input To the Conceptual Design Of The Gyrotronmentioning

confidence: 99%