MHE - All Russian Electro-Technical Institute
Plasma Beam Wide Band Amplifiers (WBA)
Fundamental scientific research in Russia has led to the development of high-power, wide-band, beam-plasma, microwave amplifiers (WBA). The basic element of these powerful amplifiers is a plasma-beam TWT, which provides microwave power of over 10kW with a frequency bandwidth of 25 - 30%.
This technology is based on electron beam interaction with plasma-cavity slow waves, which has been investigated both theoretically and experimentally. These wide-band microwave amplifiers have wide potential applications such as:
- Controlled nuclear fusion (such as a radiation source for stochastic plasma heating);
- Non-equilibrium plasma chemistry (stochastic microwave discharge techniques);
- Charged particle stochastic acceleration;
- Ecological applications, for example -- ionosphere ozone restoration.
A prototype WBA has been designed, manufactured and tested. Experimental data show that the WBA can achieve a combination of large values for W, h , and D f /f which are not possible with vacuum TWTs. Some experimental results are shown below.
Microwave Generation |
Beam Parameters |
Wm < 20kW |
Ub = 20kV |
h = < 40% |
Ib = 3A |
D f /f= 25 - 30% |
r = 10-3 - 10-4 Torr |
This data is based on a wavelength in the cm range operated in a continuous regime.
A Wide Band Microwave Generator consists of:
Technical Characteristics of a Plasma-Filled TWT
| Output power | 10 kW |
| Electronic efficiency | 30% |
| Working bandwidth | 20% |
| Wavelength range | cm and dm |
| Operation modes | frequency pulsed and continuous |
| Accelerating voltage | 20 kV |
| Electron beam current | 2.5 - 3.5 A |
The high voltage power supply consists of:
EBV 50/100 - Characteristic Properties and Applications
Electron Beam Valves (EBV) are switching electron tubes which have been designed especially for use in high voltage devices of high average power. They differ from ordinary electron tubes due to a potential at the grid (control electrode) which increases anode potential by 3-4 times. Deceleration of the electron beam at the anode increases the electron efficiency of EBVs in comparison with a typical electron tube. A fine flow of electrons in the beam provides small losses at the grid which also increases the efficiency. The internal resistance of an EBV is sometimes lower in comparison with electron tubes of standard design. EBV is a tetrode with the second grid (protective electrode) having a cathode potential. The voltage-current characteristic of the EBV is flat current flowing through the valve independent of the anode voltage. In connection with the EBV's ability to dissipate high power at the anode, such a characteristic also allows it to stabilize the load current and to prevent development of breakdown. The main advantages of Electron-Beam Valves in comparison with other switch devices (semiconductor switches, gas discharge tubes) are the following:
- the ability to control load current and to switch it off at full applied voltage,
- the opportunity to get short operation time for protection switching-off and to have short pulse fronts (down to mks),
- an option to use one device (without series connection) in high voltage circuits (up to 200 kV),
- optional frequency-pulse mode of operation with high frequency and high power (mean switched power up to 5 MW),
- ability to recover electrical strength after breakdown,
- an option to use several EBVs in parallel without special dividing devices.
The EBV 50/100 is intended for use in power supply units of power radioelectronic devices, in particular, in gyrotrons, injectors of ions and neutral atoms, in technological facilities with a rated voltage of 80-100 kV and power of 1-5 MW in the long pulse mode of operation, and also for protection functions in the continuous operation mode. It is also possible to use the EBV 50/100 in the frequency-pulse operation mode with peak current of 300-400 A with mean power in the load of 1-2 MW. In the event that the peak current is being increased in comparison with the rated value in the continuous operation mode, the voltage level at the accelerating grid and at the anode is increased by a ratio I3/2 .
The EBV 50/100 is currently in use at facilities around the world including at the Kurchatov Nuclear Energy Institute in Moscow, in the power supply of a particle injector, and at the CIEMAT facility in Madrid, in the modulator of long pulse forming unit for a gyrotron. Currently the use of the EBV 50/100 in the frequency-pulse operation mode is being investigated for an application in the power supply system of electrostatic precipitators to provide combined cleaning of dust and oxide effluents in power plants.