Industrial Gyrotron Research Articles

Experimental Testing of the European TH1509U 170-GHz 1-MW CW Industrial Gyrotron—Long Pulse Operation

The upgraded European 1-MW, 170-GHz continuous wave (CW) industrial prototype gyrotron (TH1509U) for electron cyclotron resonance heating and current drive in ITER was tested at the Karlsruhe Institute of Technology (KIT). In this work, we report on the major achievements during the experimental campaigns that took place intermittently between October 2020 and July 2021. The upgraded gyrotron clearly surpassed the performance of the previous TH1509 tube. In particular, TH1509U delivered (i) 0.9 MW in 180 s pulses (maximum possible pulse length with the KIT test stand) and (ii) more than 1 MW at a pulse length limited to 40 s, due to an unforeseen problem with the test stand cooling circuit at that time. In addition, it was possible to also demonstrate gyrotron operation at (iii) 0.5 MW in 1600 s pulses. The experiments will be continued at the FALCON test stand at the École Polytechnique Fédérale de Lausanne (EPFL).

Design and Efficiency Enhancement of a Ka-Band Industrial Gyrotron

The key subsystems of a high efficiency material processing gyrotron are designed at an operating frequency of 27.885 GHz. A triode-type electron gun is designed to launch hollow spiraling electron beam. The outer diameter of the gun is kept at 50 mm to lower inside diameter of the magnet. Start oscillation current for TE02 operating as well as competing modes is plotted. The output power and efficiency are predicted to be 18.4 kW and 46%, respectively, based on single mode time-dependent analytical equation. Beam-wave interaction is studied by employing particle-in-cell (PIC) simulation. Electronic efficiency and output power are increased by operating the tube in hard excitation region. An axially slotted cavity is adopted to abridge mode competitions. The output power and electronic efficiency are obtained to be 20.08 kW and 50.2%, respectively, without considering any velocity spread of the electron beam. However, the efficiency is reduced to 45%, when a moderate transverse velocity spread of 5% is considered. The power efficiency is enhanced to 67.07% by introducing a 3-staged depressed collector.

Report of recent experiments with the European 1 MW, 170 GHz CW and SP prototype gyrotrons for ITER

The European 1 MW, 170 GHz industrial CW prototype gyrotron has been designed within EGYC (European GYrotron Consortium) in collaboration with the industrial partner Thales Electron Devices (TED) and under the coordination of Fusion for Energy (F4E). This is a conventional (hollow) cavity gyrotron that is based on the 1 MW, 170 GHz short-pulse (SP) modular gyrotron, which has been designed and manufactured by KIT in collaboration with TED. The SP prototype has been tested in multiple experimental campaigns since 2015 and the nominal cavity mode TE32,9is exited at 170.1 GHz, producing RF power above 1 MW with 35 % interaction efficiency. The first phase of the experiments with the CW industrial gyrotron was successfully completed at KIT in 2016, verifying most of the ITER specifications. Short pulses (<10ms) deliver RF power higher than 0.9 MW with a total efficiency of 26 % (in non-depressed collector operation). The Gaussian mode content of the RF beam is 97 %. Pulses with duration of 180 s (limited by the high-voltage power supply at KIT) produce power more than 0.8 MW with maximum efficiency 38 % (in depressed collector operation). In this work the achievements with the SP and the CW prototype gyrotrons are summarized.

Joining of ceramic tubes using a high-power 83-GHz Millimeter-wave beam

Summary form only given. The high power beams that can be generated by CW gyrotrons represent a promising energy source for high-temperature processing of materials. An experimental facility based on an 83-GHz, 15 kW CW industrial gyrotron has been set up at the Naval Research Laboratory to investigate novel mm-wave-beam-based approaches to processing ceramic materials including sintering, coating, and joining applications. Current experimental and theoretical studies are investigating the formation of strong bonds between ceramics and between ceramics and metals using controlled, selective heating of the joint area. In this paper, the results of current joining experiments were described. In particular, the results from the joining of ceramic tubes for a dielectric-loaded accelerator was presented. Additionally, novel methods for temperature sensing as well as monitoring of the ongoing process was given.

Sintering of advanced ceramics using a 30-GHz, 10-kW, CW industrial gyrotron

At the Forschungszentrum Karlsruhe, Germany, a compact gyrotron system was established in 1994 to investigate technological applications in the field of high-temperature materials processing by means of millimeter-wave (mm-wave) radiation. Besides the improvement of the system design, research activities are mainly engaged in studies on debindering and sintering of various types of advanced structural and functional ceramics. Due to volumetric heating and enhanced sintering kinetics, the application of microwaves allows one to shorten the processing time and therefore reduce energy consumption. Besides these effects, microwave technology gives the unique possibility of influencing the microstructure and physical properties of the ceramic materials. This paper will discuss the benefits of the mm-wave technology with respect to sintering of structural ceramics, such as TiO/sub 2/-ZrO/sub 2/-MgO multicomponent ceramics, nanocrystalline oxide ceramics, and Si/sub 3/N/sub 4/, as well as lead-zirconate-titanate piezoceramics as one of the most interesting classes of functional ceramics.

Gyrotrons for technological applications

Abstract A review is given of the possible uses of gyrotrons in industry. A comprehensive theoretical study of mode selection, mode competition, and resonator design for industrial gyrotrons is performed. It is shown that the TE02 mode at the second harmonic and the TE03 mode at the third harmonic are good candidates for the operating mode in an industrial gyrotron. Starting currents for these modes and modes oscillating at lower harmonics are calculated, and mode competition is examined on the basis of the nonlinear non-stationary theory. It is emphasized that in industrial gyrotrons, owing to a relatively large length of the cavity, it is possible to increase significantly the electron efficiency by introducing inhomogeneity into the profile of the guiding magnetic field in a cavity. The important issue of the negative influence of electron velocity spread on the efficiency is studied quantitatively both for tapered and untapered magnetic fields, This is of interest also for gyrotrons used for fusion plasma heating and diagnostics.