The paper presents gyrotron-based system (developed by IAP RAS jointly with GYCOM Ltd.) for ECR plasma heating in the new T-15MD tokamak which is under construction in National Research Center "Kurchatov Institute". The first of a series (8 units) of microwave setups of a megawatt power level was developed and successfully tested. The setup includes a gyrotron, set of power supplies, a microwave radiation transmission line, and a fast protection system. 1 MW/82.6 GHz generation regime during 30 second pulse with an efficiency of 57% was experimentally demonstrated.
The report proposes the project of a CW coaxial cavity gyrotron with an output frequency of 0.78 THz and an output power of about 100–200 W, intended for spectroscopy applications and diagnostics of various media. As a magnetic system, it is possible to use a cryomagnet, available at the FIR UF, with a maximum magnetic field intensity of 15 T and a diameter of a warm bore of 52 mm made by Jastec, Inc. To achieve the required value of an output frequency such a value of the magnetic field implies the development of a gyrotron operating at the 2rd cyclotron harmonic. The project assumes that the tube can operate on TE14,9 mode.
Due to a growing interest for microwave radiation sources with a radiation frequency of several tens of GHz and output power of several tens of kW, we developed a new generation of technological gyrotron setups. The key feature of these systems is a novel magnetic system based on magnetically shielded solenoids (MSS). This magnetic system is several times more energy efficient than the common warm solenoids and it also allows to control the properties of the helical electron beam to make it interact with various cavity modes. The developed MSS provides a high field induction in the interaction space and a small stray field, so the gyrotron can operate in wide range of magnetic fields (from 1 T to 1.8 T in relatively low-consumption regime). It allows a gyrotron complex to operate within a wide frequency range (from 24 to 50 GHz on main cyclotron resonance). A total system efficiency expected to be about 35%, which is significantly higher than the existing analogs.
This report aims to bring together information about the most striking experimental results, new trends in gyrotron development, modern remarkable applications, new demands in parameter enhancement and future goals. The paper separated into two parts: first, related to progress in MW class gyrotron development for nuclear fusion and second, focused on the development of terahertz band gyrotrons. The data about pulsed and CW tubes, working in both specified frequencies ranges, are given. In particular, the series of 1MW/170 GHz/CW tubes with efficiency more than 50% has been developed successfully for ITER project. Same time, despite the requirement for strong magnetic fields, the problem of high ohmic losses and electron beam formation, the gyrotrons go through magic 1 THz mark with kW power level and demonstrate (in some specific combinations) operation at extremely low voltage and beam current, narrow frequency spectrum, wide frequency tuning. Novel schemes of high-frequency gyrotrons are analyzed. The novel quasioptical mode converters opened the possibility of phase-locking a number of tubes, which makes maximum power almost "unlimited"
A technique for imaging of high-power millimeter-wave (MMW) beams using visible light emission from a surfaceinitiated microwave gas breakdown is discussed. A wave beam from pulsed 250 GHz gyrotron was imaged using a microwave gas breakdown initiated by a surface of a metal-dielectric screen. The screen was placed in a shallow metal chamber filled with helium with an admixture of argon. In the region, where MMW intensity was higher than the threshold intensity of the surface-initiated microwave gas breakdown, the intensity profile of a high-power MMW beam, which was obtained using this technique, was in good agreement with the data obtained using the thermographic technique.
The paper presents the results of recent experimental studies. The subject of research was the discharge of atmospheric pressure in a gas stream in focused beams of microwave radiation. The radiation sources were: a gyrotron with a radiation frequency of 263 GHz and a power of up to 1 kW, a free-electron laser with a radiation frequency of 2.3 GHz and with an average power of up to 400 W. The paper presents the results of measurements and calculations of breakdown fields, the results of measuring plasma parameters in these cases. Possible applications are discussed.
This paper presents the results of the studies of the subthreshold discharge propagation under the action of the focused beam of sub-terahertz CW gyrotron (1 kW@0.26 THz). The discharge propagation velocity towards electromagnetic radiation was measured in various noble gases in the wide pressure range (0.1 – 2 atm) for various field intensities into the focal spot (5-15 kW/cm2). It was demonstrated that discharge velocity increase along with pressure decrease and drops with electric field decrease as it moves away from the focal spot. Typical velocity values and discharge spatial structure suggest the so-called equilibrium mechanism of discharge propagation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.