V.G. Ivanenko

Super-power generator of mm-waves driven by microsecond sheet beam

Results of experimental investigations of a powerful mm-band FEM-oscillator driven by a sheet electron beam are presented. For mode selection, a planar geometry Bragg resonator was used. Microsecond pulses at a wavelength of 4 mm and power of 200 MW corresponding to record energy per pulse of 200 J were generated. The possibility to increase the energy content of the millimetre wave pulse up to tens kilojoules is discussed.

Experimets on pulse elongation of high-power microsecond e-beam for plasma heating in multi mirror trap GOL-3

Essential progress was achieved in experiments on heating the dense plasma in the multimirror trap GOL-3 by high-power relativistic electron beam in last few years. The beam parameters at the experiments were the following: electron energy ~1 MeV, beam current ~25 kA, beam current density in plasma ~2 kA/cm2, pulse duration 9 mus, total energy of the beam pulse ~150 kJ. Due to the high level of the current density and effect of a novel mechanism of ion heating the temperature of ions reached 2-3 keV at the electron temperature about 3 keV for the plasma density ~1015 cm-3. Energy confinement time of the plasma in these experiments has reached the level of 1 ms. The mechanism of fast ion heating is based on the collective ion acceleration along the magnetic field lines produced by high-gradients of the electron pressure in the plasma due to enhanced heating in the mirrors. The basic condition for such mechanism realization is anomalously low electron thermal conductivity along the trap axis which is provided by small scale Langmuir turbulence developing as result of two-stream instability. In order to analyze fusion prospects of such way of plasma heating in the long solenoid trap it is necessary to investigate experimentally the possibility of further increase of plasma parameters by the elongation of the beam pulse. As the first step on solving this task we have performed the experiments at the accelerator U-2 on 1.5 fold increase of the e-beam duration. Results of these experiments are presented in this paper. Conditions for durable generation in magnetically insulated diode, stable transportation and compression in the magnetic field of intense REB found in the experiments, permit us to increase the beam pulse duration from 9 mus to 14 mus with somewhat less energy of the electrons but with the same level of the energy content in the pulse. In the paper we describe the experiments on the diode voltage shaping for better matching of pulse generator with the accelerator diode as well as the results of measurements of the beam cross section by means of X-ray obscure and sectional calorimeter. Also we discuss the directions of future investigations aimed to the increase of the beam parameters in order to obtain (5-10) keV temperature of the plasma confined in multimirror trap.

Recent results in generation of powerful pulses of 75GHz radiation at ELMI-device

The novel scheme of separation of the mm-wave radiation from the intense electron beam using planar Bragg wave transformer, is suggested and realized. In the experiments at the planar FEM with the new scheme of separation, the generation of powerful 4-mm radiation pulses was observed. The duration of these pulses is increased in two times in comparison with the old scheme of the beam dump and has reached 300ns. By means of the panel with neon lamps the angular distribution of the generated radiation at the exit of the maser is registered. The distribution of the luminescence intensity qualitatively agrees with the results of “cold” measurements and computer simulations.

Multichannel planar FEM as a base for archiving large energy content in pulses of coherent mm-radiation

Novel approach to generate GW power microwave radiation on the basis of multichannel planar FEM-generator is investigated both theoretically and numerically. The problem of cophase operation of many generation channels is solved. The project of 4 channel FEM-generator is considered.

Progress in investigations on microwave FEL driven by microsecond sheet beam

For production of mm-radiation with 10 GW power one needs a few tens of kAs current of 1 MeV electrons passing through a generator. Ribbon or sheet E-beams allow one to reach this value of the current. In the result of our investigations at U-2 accelerator in 1994 this type of the beams with 30 kA current at 10 /spl mu/s duration was generated and transported through the slit vacuum channel. In 1996 at this accelerator in modelling experiments with the beam current 3-5 kA in a passive magnetic undulator of 4 cm period we also obtained 200 J energy of 4 mm radiation in a few /spl mu/s pulse. The next step of investigations was aimed to reach the maximal efficiency of the microwave generation at a single mode operation of the generator. On this goal in 1997-98 we made reconstruction of the experimental setup intended to investigate FEM-oscillator. In order to increase productivity of the investigations this setup was replaced from the U-2 accelerator to the U-3 one that was specially reconstructed for generation of sheet beams.