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The existing ECRH system at W7-X consists of 10 gyrotrons, with output power levels ranging from 0.6 MW up to 1.0 MW each at a frequency of 140 GHz, quasi-optical transmission lines and microwave launchers at the plasma vessel. Compared to other large fusion experiments, W7-X has a relatively low power-to-volume ratio. However high heating power is particularly necessary for achieving high plasma beta values, where the improved confinement of fast ions, one of the optimization criteria of W7-X, can be examined. It is therefore necessary to expand the ECRH systems in several consecutive steps. It is planned to increase the number of gyrotron positions from 10 to 12 and at the same time to evolve the gyrotron output power in several development steps from 1 MW to nominal 1.5 MW and, finally, up to 2 MW. At the same time, the transmission lines will also be upgraded for 2 MW operation. A special effort is also made to improve the reliability of the system by the fast control system. [ABSTRACT FROM AUTHOR]

In the frame of the TCV Tokamak upgrade, two 84/126 GHz/2 s dual frequency gyrotrons designed by SPC and KIT and manufactured by THALES will be added to the existing EC-System. The first unit has been delivered to EPFL-SPC and tested. In the commissioning configuration, a matching optics unit (MOU) is connected to the gyrotron window. The RF is then coupled to the HE11 mode of a 63.5mm corrugated waveguide and dissipated in a load procured by CNR after 4m of waveguide and 2 miter bends. Owing to the flexible triode gun design giving the possibility to adjust the pitch angle parameter, the specifications were met at both frequencies. At 84 GHz (TE17,5 mode), a power of 0.930 MW was measured in the calorimeter, with a pulse duration of 1.1 s. At the high frequency (126 GHz, TE26,7 mode), a power of 1.04 MW was reached for a pulse length of 1.2 s. Accounting for the load reflection and the ohmic losses in the various subcomponents of the transmission line and the tube, it is estimated that the output power at the gyrotron window is in excess of 1 MW at both frequencies, with an electronic efficiency of 32% and 34% at 84 GHz and 126 GHz respectively. The gyrotron behavior is remarkably robust and reproducible, and the pulse length is limited by external systems that will be improved shortly. [ABSTRACT FROM AUTHOR]

A research activity in the Institute for Plasma Science and Technology of National Research Council (ISTP-CNR, Italy, former IFP-CNR) and in L.T. Calcoli (LTC, Italy) is aimed at the design and construction of calorimetric loads for absorption and measurement of high power millimeter-waves in the electron cyclotron frequency range. Recently, two CW 170 GHz loads, one for the European ITER gyrotron test facility and the other for the FALCON test- bed, have been installed at the Swiss Plasma Center (SPC, Switzerland). One short pulse (2 s) load for 1 MW, designed and optimised to operate at two different frequencies (84 GHz and 126 GHz), was provided for testing and conditioning two new dual-frequency gyrotrons for the Tokamak à Configuration Variable (TCV, Switzerland). Two additional CW loads, designed for absorbing powers higher than 1 MW, have been delivered to the National Institutes for Quantum and Radiological Science and Technology (QST, Japan) and exploited for the acceptance tests and the conditioning of the prototype of the Japanese ITER gyrotron. The present status and the most recent experimental results achieved in the framework of this development activity are reported in the paper. [ABSTRACT FROM AUTHOR]

ECRH&CD is one of the favorite heating system for magnetically confined nuclear fusion plasmas. KIT is strongly involved in the development of high power gyrotrons for use in ECRH systems for nuclear fusion. KIT is upgrading the sub-components of the existing 2 MW, 170 GHz coaxial-cavity short-pulse gyrotron to support long-pulse operation up to 1 s, all components will be equipped with a specific active cooling system. Two important developments for future high power, highly efficient gyrotrons will be discussed: design of gyrotrons with high operating frequency (~ 240 GHz) and efficiency enhancement by using advanced collector designs with multi-staged voltage depression. [ABSTRACT FROM AUTHOR]

The European 1 MW, 170 GHz CW industrial prototype gyrotron for ECRH&CD on ITER was under test at the KIT test facility during 2016. In order to optimize the gyrotron operation, the tube was thoroughly tested in the short-pulse regime, with pulse lengths below 10 ms, for a wide range of operational parameters. The operation was extended to longer pulses with a duration of up to 180 s. In this work we present in detail the achievements and the challenges that were faced during the long-pulse experimental campaign. [ABSTRACT FROM AUTHOR]

The European Gyrotron Consortium (EGYC) is responsible for developing one set of 170 GHz mm-wave sources, in support of Europe's contribution to ITER. The original plan of targeting a 2 MW coaxial gyrotron is currently under discussion, in view of essential delays and damages. This paper reports on the latest results and plans with regard to the two 2 MW gyrotron prototypes, the industrial prototype at CRPP's CW test stand and a modular pre-prototype at KIT. The industrial prototype was delivered to CRPP end of September 2011 and reached an output power of 2 MW at an efficiency of 45 % and with good RF beam pattern, in only four days of short pulse RF test. These results validated all design changes made in reaction to the results of the experiments in 2008. On the fifth experimental day, an internal absorber broke, terminating any further experiment with this tube. In parallel, design and experimental activities at KIT went on, in particular featuring reduced stray radiation down to 4% of the RF power. Next years' plans for the 2 MW modular pre-prototype foresee a stepwise increase of pulse length. [ABSTRACT FROM AUTHOR]

The long term strategy of the EU in the field of gyrotrons in fusion plasma applications is based on two approaches: R&D in laboratories to develop advanced concepts and industrial development of state-of-the-art tubes for use in present experiments like TCV, Tore Supra (118 GHz, 0.5 MW, CW) and W7-X (140 GHz, 1 MW, CW). The results from these two approaches are then applied to the development of a coaxial cavity gyrotron operating at 170 GHz and delivering 2 MW-CW for the electron cyclotron wave system of ITER. This paper will recall the main achievements of this program and will outline the present status of the 170 GHz coaxial cavity gyrotron development. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

At Forschungszentrum Karlsruhe (FZK) R&D investigations are performed both on a 2 MW, 170 GHz coaxial cavity gyrotron for ITER and on a stepwise frequency tunable 1 MW gyrotron for the ASDEX Upgrade tokamak (105–140 GHz). In case of the coaxial gyrotron the previously used experimental 165 GHz tube has been modified for operation at 170 GHz in order to verify the design of the main components (electron gun, cavity and RF output system) of a corresponding industrial prototype which is under development in cooperation between EURATOM Associations together with European tube industry. For the stepwise tunable gyrotron, work has been done on optimization of the quasi-optical RF output system and on a broadband CVD-diamond Brewster output window. [ABSTRACT FROM PUBLISHER]

Today's performance requirements for future DEMO gyrotrons are an operating frequency > 200 GHz and an output power of 2 MW. A total gyrotron efficiency of better than 60 % must be achieved. Multi-purpose/multi-frequency operation and frequency step-tunability are required also. It has been shown earlier, that the coaxial-cavity technology is a promising candidate [1] for future fusion power plants. In [1] a world record RF output power at 170 GHz of 2.2 MW has been presented in short-pulse operation (~ few milliseconds). However, it has to be proven that the coaxial-cavity technology can be used in steady-state operation. That shall be achieved by upgrading the existing 2 MW 170 GHz short-pulse prototype with a cooling system and the implementation of advanced Magnetron Injection Guns (MIGs) [3]. Both, the advanced MIGs as well as the longpulse gyrotron will show the way towards a possible solution for DEMO with a significantly higher output power at higher operating frequencies. [ABSTRACT FROM AUTHOR]

This paper gives an overview about three key measurement capabilities at KIT/IHM for fusion gyrotrons. The discussed topics are: RF window test facility, low power launcher test setup and the frequency measurement setup placed at the high power test facility. Further, approaches for upgrading the setups to frequencies above 200 GHz are discussed. [ABSTRACT FROM AUTHOR]

The article discusses the study of electromagnetic fields in arbitrary shaped electric conductors. It highlights the development of the three-dimensional simulation system known as KarLESSS in addressing the issues in electromagnetic scattering and study the behavior of electromagnetic fields in electric conductors. Moreover the potential use of KarLESSS to various fields is also mentioned.

The article discusses the development of coaxial-cavity longer-pulse gyrotron at Karlsruhe Institute of Technology in Germany. Topics discussed include the significance of gyrotron in power generation, an overview on the construction of the modular coaxial-cavity tube and notes the development of Inverse Magnetron Injection Gun in increasing output power of gyrotrons.

The article focuses on the development of fusion technologies in Europe. It notes the consortium among European research institutes in developing fusion power plants in generating sustainable supply of electricity in the region, through the use of Electron Cyclotron Resonance Heating (ECRH) and Current Drive systems, and stresses benefit of the fusion technology in power efficiency is also mentioned.