V. K. Lygin

Advanced Numerical and Experimental Investigation for Gyrotrons Helical Electron Beams

The paper presents a modern approach to studies of characteristics of intense helical electron beams (HEBs) for gyrotrons. The essence of the method consists in finding functions of electron distribution with respect to oscillatory velocities in the beam both by numerical simulation and experimentally. Experimental and calculated data for beams with different topologies were compared in different frequency ranges. Evolution of the electron oscillatory velocities distribution function as the beam current grows has been traced. Influence of the reflected electrons on beam parameters has been simulated numerically.

Development of 1 mw output power level gyrotron for ITER

Abstract The report presents the results of calculation, design and experimental study of the 170 GHz/1 MW and other ITER related gyrotrons in Russia. The main problems of powerful gyrotrons at present are discussed. The dependence of gyrotron parameters on the beam current, accelerating voltage and magnetic field is analysed. ITER – related 110 GHz and 140 GHz gyrotrons are also investigated including a single-stage depressed collector version (CPD). The possibility to make high – efficient 170 GHz/1 MW gyrotron for the ITER is proved by calculations and experiments.

Highly efficient relativistic SHF gyrotron with a microsecond pulse width

Based on extensive theoretical and experimental investigations, a new relativistic gyrotron is created with an efficiency of 45% and an output power of up to 7 MW at an SHF pulse width of up to 6 μs. Under optimum conditions, the gyrotron operates in a single-mode regime featuring excitation of the electrically strong TE01 mode at a frequency of 9.2 GHz.

Experimental investigation of technological gyrotrons

Powerful gyrotrons for technological applications, including material processing, are presented. 30 GHz gyrotrons at the second cyclotron harmonic TE/sub 02/ mode with oil-cooled solenoid were tested. On CW regime with output power 10 kW obtained efficiency 42% and output power 30 kW with efficiency 35%. The highest for the second harmonic gyrotrons efficiency 50% with 13 kW output power level was observed after modification of the tube. Experimental dependencies of output power and gyrotron efficiency before and after modification magnetic field profile are given. Conditions of high efficiency operation taking into account space-charge effects, velocity spread, RF field and static magnetic field profiles are discussed. Results of quality testing of cathodes and dependencies of the gyrotron efficiency on cathode emission inhomogeneity are presented.

Development of the 300 GHz/4 kW/CW gyrotron

The report presents results for design elaboration of 300 GHz/4 kW/CW gyrotron. The gyrotron is used with 12 T LiHe-free superconducting magnet. The possibilities to optimize an electron gun, mode converter and processes of mode interaction in the electron beam-cavity system are discussed for different versions of the 300 GHz gyrotron. The influence of ohmic load on the cavity, mode competition and other effects are also investigated.

Optimization of the frequency step tunable 105-170 GHz 1 MW gyrotron prototype

The report presents results of investigation of the possibility to optimize numerically and experimentally the helical electron beam formation system, mode converter system and processes of mode interaction in the electron beam-cavity system for the prototype 105-170 GHz 1 MW step tunable gyrotron with different operating modes. The influence of ohmic load on the cavity, mode competition, electron beam potential depression and possibility of beam energy recovery is also investigated.

Development of the step tunable 140/110 GHz 1 MW gyrotron for fusion

Electron-cyclotron heating and current control in plasma set-ups require gyrotrons with a level of CW power up to 1 MW at frequencies 80-170 GHz and efficiency not less than 50%. The output window was the key factor that limited the achievable pulse duration in gyrotrons. The CVD diamond single disk window is capable of full 1 MW CW operation. Recent results generated interest in the use of frequency tunable gyrotrons for ECRH plasma experiments. In this paper we discuss the main problems of the step tunable gyrotron and present the design of a step tunable 110/140 GHz 1 MW gyrotron. The 80 kV, 40 A beam is produced by a magnetron injection gun (MIG) with an average perpendicular-to-parallel velocity ratio of 1.2 and a transversal velocity spread below 25%. The microwave circuit has a TE/sub 22.81/-TE/sub 19.61/ cavity, which operates at 140 GHz and 111.5 GHz respectively. Electron beam parameters were optimized for efficient generation of the modes. These modes were chosen from the condition of the gyrotron CVD window transparency at the operation frequencies. The highly efficient quasi-optical mode converter was elaborated for operation with two different cavity modes.

Ka band /spl sim/10 MW gyro-devices: an experiment and a project

Summary form only given. The international program for development of electron-positron colliders needs high-power microwave sources at frequencies up to the millimeter-wave band. At the shortest microwaves, the highest powers are produced with fast-wave devices. Among them, the gyroklystron seems especially robust and reliable. As an introduction, a 30 GHz free running gyrotron operating at the H/sub 53/ mode and driven with 300 kV/80 A electron beam was manufactured and tested: 12 MW/200 ns pulses were produces with 50% efficiency. The gyrotron is planned to be converted into a gyroklystron amplifier; for better coupling to the electron beam and better suppression of parasitic modes, the modulating and intermediate cavities will operate at the H/sub 51/ mode. For further experiments, a test stand with a 500 kV/ 300 A/1 /spl mu/s modulator is being designed and a relevant electron gun is being manufactured.

Technological gyrotrons with permanent magnet system

The fulfillment of the new project of creation of the industrial prototype of a technological gyrotron on permanent magnets are discussed. The permanent magnet system was designed, constructed and successfully tested for a gyrotron. A 30 GHz gyrotron (n=2) with rf-output power of 10 kW is under development with the TE/sub 12/ operating mode. An output power of 12 kW was obtained (efficiency 24%).

New results in development of MW output power gyrotrons for fusion systems

Gyrotrons are widely used in electron-cyclotron-wave systems of fusion installations. Modern and future installations require microwave sources with power at least 1 MW. CVD diamond windows are implemented into the gyrotrons with frequencies 140 GHz and 170 GHz. The goal of these near-time tests is to demonstrate 0.8-1 MW power in microwave pulse of 10 seconds at least at two frequencies 105 GHz and 140 GHz, corresponding to pass bands of the single diamond disc.