F. Cismondi

From Series Production of Gyrotrons for W7-X Toward EU-1 MW Gyrotrons for ITER

Europe is devoting significant joint efforts to develop and to manufacture MW-level gyrotrons for electron cyclotron heating and current drive of future plasma experiments. The two most important ones are the stellarator Wendelstein W7-X at Greifswald and the Tokamak ITER at Cadarache. While the series production of the 140 GHz, 1 MW, CW gyrotrons for the 10-MW electron cyclotron resonance heating system of stellarator W7-X is proceeding, the European GYrotron Consortium is presently developing the EU-1 MW, 170 GHz, CW gyrotron for ITER. The initial design had already been initiated in 2007, as a risk mitigation measure during the development of the advanced ITER EU-2-MW coaxial-cavity gyrotron. The target of the ITER EU-1-MW conventional-cavity design is to benefit as much as possible from the experiences made during the development and series production of the W7-X gyrotron and of the experiences gained from the earlier EU-2-MW coaxial-cavity gyrotron design. Hence, the similarity of the construction will be made visible in this paper. During 2012, the scientific design of the ITER EU-1-MW gyrotron components has been finalized. In collaboration with the industrial partner Thales electron devices, Vélizy, France, the industrial design of the technological parts of the gyrotron is being completed. A short-pulse prototype is under development to support the design of the CW prototype tube. The technological path toward the EU ITER-1 MW gyrotron and the final design will be presented.

Design of the EU-1MW gyrotron for ITER

EU is developing a 1 MW cylindrical cavity gyrotron. In the last year the design of the components of the new gyrotron has been finalized while the technological design of the new tube has been defined. In the present paper, the main characteristics of the new EU gyrotron for ITER are presented.

Benchmark of the GETTHEM Vacuum Vessel Pressure Suppression System (VVPSS) model for a helium-cooled EU DEMO blanket

In the nuclear field, the correct evaluation of the effects of design-basis accidents is fundamental to correctly design the countermeasures needed to preserve the integrity of the containment barriers and to confine the ra-dioactive material. Therefore, both in fission and in fusion, notwithstanding the different amounts of radioac-tive materials, the availability of models that can predict the accidental transients is crucial. Here we describe the model recently developed to analyse an in-vessel Loss-Of-Coolant-Accident in the EU DEMO fusion reactor, and implemented in the GETTHEM code. In particular, we focus on the release of coolant inside the Vacuum Vessel (VV) following a break in the breeding blanket cooling loop, considering a helium-cooled blanket solution. The model of the VV pressure suppression system is calibrated and bench-marked exploiting results from the validated CONSEN code by ENEA.

Manufacturing and tests of the European 1 MW, 170 GHz CW gyrotron prototype for ITER

An industrial 1 MW, 170 GHz continuous-wave (CW) gyrotron prototype has been manufactured in 2015 at Thales. The physical design is provided by the European GYrotron Consortium (EGYC) and is supported by the construction and the measurement of a modular short-pulse (SP) prototype. In this presentation, the latest experimental results are discussed, with respect to the previous results acquired for the modular SP prototype gyrotron.

CFD analysis of mini-channel cooling for a gyrotron cavity

A pressurized sub-cooled water cooling option for a full-size gyrotron cavity, based on mini-channels, is developed and analyzed using the commercial computational fluid dynamics (CFD) tool STAR-CCM+. On the basis of this design, which guarantees a pressure drop below the maximum acceptable and the compliance with manufacturing constraints, we study the cooling of a representative mock-up to be experimentally tested in the near future. The solution of the conjugate heat transfer problem in the mock-up geometry is presented, aimed at assessing its thermal performance under increasing target heat load up to 24 MW/m2.

CFD Analysis of Different Cooling Options for a Gyrotron Cavity

Three different pressurized subcooled water cooling options [hypervapotron, mini-channels (MCs), and meander flow drivers] for a full-size gyrotron cavity are developed and analyzed using the commercial computational fluid dynamics code STAR-CCM+, to guarantee a pressure drop below the maximum acceptable, and the compliance with manufacturing constraints. The full-size designs are then transposed to corresponding mock-ups to identify the most suitable candidate for an experimental test. The conjugate multiphase heat transfer problem is solved in the three mock-up geometries, aimed at comparatively assessing their thermal performance at increasing heat load on the target up to 24 MW/m2. The most promising option for an effective cooling of the cavity results to be the mini-channels.

From W7-X towards ITER and beyond: Status and progress in EU fusion gyrotron developments

In Europe, significant progress in gyrotron research, development and manufacturing has been made in 2014, starting from the successful continuation of the 1 MW, 140 GHz gyrotron production for the stellarator Wendelstein 7-X (W7-X) at Greifswald, Germany and the accelerated development of the EU 1 MW, 170 GHz conventional cavity gyrotron for the ITER tokamak at Cadarache, France. Based on that, a physical design activity was started which shall lead to a dual frequency gyrotron for TCV, Lausanne, Switzerland. Within the European fusion development consortium (EUROfusion), advanced gyrotron research and development has started towards a future gyrotron design which shall fulfil the needs of DEMO, the nuclear fusion demonstration power plant that will follow ITER. Within that research and development, the development of advanced design tools, components, and proper test environment is progressing as well. A comprehensive view over the status and prospects of the different development lines shall be presented.

Numerical Studies on the Influence of Cavity Thermal Expansion on the Performance of a High-Power Gyrotron

An iterative procedure is described, which models the influence of the thermal expansion of the gyrotron cavity on the expected gyrotron performance. It is a multiphysics simulation method, which involves electrodynamic, thermal-hydraulic, and thermo-mechanical simulations. The method is applied to the first European 170-GHz, 1-MW continuous wave prototype gyrotron for the ITER. According to the simulations, a performance reduction of ~15% is expected at nominal operating parameters, because of the thermal expansion of the cavity. Alternative operating points to mitigate this effect are proposed and numerically validated. The numerical results are discussed in light of experimental findings.

Progress on the development of the EU-1 MW gyrotron for ITER

Summary form only given. EU is presently developing a 1 MW, 170 GHz cylindrical cavity gyrotron for ITER. This activity was initiated in 2008 as a risk mitigation measure in parallel with the development of a 2 MW coaxial-cavity gyrotron, and in 2012 became the main line. In the previous year, the scientific designs of the 1 MW gyrotron components, such as the electron gun, beam tunnel, cavity, quasi-optical output coupler and single-stage depressed collector have been finalized. In addition, in collaboration with the European industrial partner Thales Electron Devices (TED), after completion of the industrial design of the technological parts of the gyrotron, the procurement and manufacturing of subassemblies for a 1 MW CW prototype will start in 2014. Its specifications correspond to the ITER requirements.