MW Coaxial Gyrotron Research Articles

Research on the Conductivity, Starting Current, Mode Competition of a 250 GHz, MW Coaxial Gyrotron With Double-Electron-Beam

Research on the Conductivity, Starting Current, Mode Competition of a 250 GHz, MW Coaxial Gyrotron With Double-Electron-Beam

The study of a coaxial gyrotron with misaligned inner rod

The effects of a tiny misalignment of the inner rod in a coaxial-gyrotron on the eigenvalue, quality factor Q, resonant frequency, and electronic efficiency are investigated. As a practical application, with the electronic velocity spread and cavity wall resistivity being taken into account, the beam–wave interaction of a 170 GHz MW coaxial-gyrotron operating with TE31,12 mode has been studied. The results show that the eigenvalue of the operating mode decreases slightly when the ratio of misalignment to outer radius D/R increases for the case of smaller values of the ratio of outer to inner radius C = R/Rin, but is unchanged with the increasing value of D/R for the case of large ratio of C. The electronic efficiency decrease slightly when D/R increases within the range of 0–0.015. However it decreases at a faster rate when D/R is larger than 0.015. If D/R increases to 0.024, the efficiency decreases sharply to only about 2.2%. For both cold and hot cavity, the resonant frequency decreases slightly with D/R increasing.

Experimental results and recent developments on the EU 2 MW 170 GHz coaxial cavity gyrotron for ITER

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.

Investigations of Advanced Coaxial Gyrotrons at IAP RAS

Main results of experimental testing of the 140 GHz/1.5 MW coaxial gyrotron are summarized. High selective properties of the coaxial cavities and a possibility to increase considerably the efficiency of a coaxial gyrotron only by applying independently an appropriate voltage on its electrodes (without any design modification) have been confirmed. Successful uses of the two-potential connection scheme for the frequency step tuning and output power modulation in a coaxial gyrotron has been also demonstrated.

Tunable coaxial gyrotron for plasma heating and diagnostics

The possibility of tuning the frequency of a coaxial gyrotron by moving the inner conductor in the axial direction is investigated. A 1.5MW coaxial gyrotron at 140GHz with the TE28,16, operating mode is considered as an example.