Search results for: Ioannis Pagonakis
article
Vakuum in Forschung und Praxis > 28 > 6 > 21 - 27
In Zukunft soll mit Fusionskraftwerken die Erzeugung von umweltfreundlicher, grundlastfähiger Energie gelingen. Dabei wird die Elektronen‐Zyklotron‐Heizung, deren Quelle das Gyrotron ist, verwendet, um das Fusionsplasma auf Fusionstemperaturen zu erhitzen. Zusammen mit Partnern aus Europa entwickelt das Karlsruher Institut für Technologie (KIT) bereits heute Gyrotrons für den Stellarator W7‐X und...
chapter
Fusion gyrotrons are high-power microwave sources which are capable to generate RF power in the MW range at millimeter wave and sub-THz frequencies. Today, typically around 35 % electronic efficiency is achieved in the energy transfer (interaction) from the electron beam to the electromagnetic field. Using a single-stage depressed collector (SDC), the overall efficiency of a gyrotron can be increased...
article
Journal of Infrared, Millimeter, and Terahertz Waves > 2015 > 36 > 9 > 797-818
During the first hundred milliseconds, the frequency and RF output power of long pulse operating gyrotrons undergo deterministic variation. This well-known behavior is caused by the thermal expansion of the cavity and internal electrostatic processes related to the ionization of residual gas. A macroscopic analytical investigation of the gas conditions in modern gyrotrons indicates that ionization...
chapter
During the first few seconds of longer pulses in high-power gyrotrons, the main mode frequency decreases over a few hundred MHz, until a stable operation is reached. This is due to the combination of two effects, namely the thermo-mechanical expansion of the cavity and a shift in the effective electron energy through ionization of residual gas in the tube. Most investigations focus on the quasi-stationary...
chapter
To control different types of magnetohydrodynamic (MHD) instabilities in ITER, various amplitude modulation scenarios for the gyrotrons of the Electron Cyclotron (EC) system are required. This work focuses on the impact of different modulation scenarios on the power loading on the collector wall of a 2 MW gyrotron, which has been originally proposed as the EU gyrotron for ITER. In addition, first...
article
IEEE Transactions on Plasma Science > 2013 > 41 > 10-1 > 2748 - 2753
A 1-MW, continuous wave, 170-GHz, -mode gyrotron for use in International Thermonuclear Experimental Reactor (ITER) is under development within the European Gyrotron Consortium. A quasi-optical mode converter is employed in the gyrotron to transform the high-order cavity mode into a fundamental Gaussian wave beam. The quasi-optical mode converter contains a launcher and a mirror system...
chapter
In ITER it is foreseen to control different types of MHD instabilities by means of modulated Electron Cyclotron Current Drive (ECCD) with modulation frequencies up to 5 kHz. This has direct consequences for the EC system of ITER, since both the gyrotons and power supplies have to be capable of modulated operation. Since the electron gun of the 2 MW EU gyrotron is a diode type gun and the gyrotron...
chapter
The European Gyrotron Consortium (EGYC) is responsible for developing one set of 170 GHz mm-wave sources, in support of Europe's contribution to ITER1. 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 2 MW gyrotron prototypes.
chapter
ECH & CD is widely used in fusion plasmas. Gyrotrons are applied as power sources as they offer continuous wave operation at MW power level. This contribution reports on the status and plans of major projects of KIT towards high power gyrotrons, i.e. results from series production of the W7-X gyrotron, the development of the EU pre-prototype coaxial-cavity gyrotron, the 2 MW, 170 GHz CW coaxial...
chapter
In this paper, the design of a 10kW/28GHz gyrotron tube with an emitter ring based on a controlled-porosity reservoir (CPR) cathode is presented. CPR emitters provide significantly higher current density (up to 50 A/cm2), as well as, longer life time (105 hours) than conventional emitters. The main goals of this experimental tube are to evaluate the use of CPR emitters for gyrotron applications, as...
chapter
An efficient intermodal decomposition technique is developed for an accurate reconstruction of the RF field obeying a paraxial approximation such as the output of a gyrotron. This method requires complete RF beam information i.e. its amplitude, measured using infrared thermography technique, and phase, which is calculated by an accurate phase retrieval method using complete scalar diffraction integral...
