Gyrotrons, ACTION NO. F4E-2009-GRT-049-01
EUROPEN JOINT UNDERTAKING FOR ITER AND THE DEVELOPMENT OF FUSION ENERGY (Fusion for Energy) "DESIGN AND DEVELOPMENT OF THE EUROPEAN GYROTRON"
Dates: 01.07.2010.-31.10.2011.
Responsible person: Dr O.Dumbrajs
E-mail: Olgerts.Dumbrajs@lu.lv
Tel. 67187480
Abstract
Gyrotrons are microwave sources whose operation is based on the stimulated cyclotron radiation of electrons oscillating in a static magnetic field. Gyrotron devices are now able to generate several orders of magnitude as much power at millimeter wavelength as classical microwave tubes, and can operate at frequencies higher than are conveniently available from other types of tubes. Gyrotron oscillators can have a wide application, including technological processes, atmospheric sensing, ozone conservation, artificial ionospheric mirror, extra-high resolution electron spin resonance spectroscopy, nuclear magnetic resonance spectroscopy, new medical technology spectroscopy, etc. However, the main application of powerful gyrotrons is electron cyclotron resonance plasma heating in tokamaks and stellarators and the noninductive current drive in tokamaks. Europe is developing the 170 GHz 2 MW coaxial cavity gyrotron for ITER. However, due to numerous delays and existing uncertainties related to coaxial gyrotrons, it has been decided to work in parallel on the 170 GHz 1 MW gyrotron with a cylindrical cavity as a fallback solution. In these gyrotrons the launcher supports the negative rotation. This means that the positively rotating modes in the cavity diverge from the quasi-optical mode converter and do not reach the window at all. The negatively rotating modes in the cavity reach the window and are partially reflected. After reflections and a backward passage through the system of mirrors, these modes enter the launcher where they are transformed into the positively rotating modes, which are “injected” into the cavity with the amplitude proportional to the reflection coefficient. Our project is aimed at developing a theory describing these complex phenomena. This will be followed by systematic numerical calculations.