The works of IAP in the field of high-power microwave electronics are widely known in the world. A globally recognized achievement is the invention of gyroresonance devices and a high engineering level of this development. Such devices are a variety of cyclotron resonance masers (CRMs), which employ resonance interaction of electrons moving along helical trajectories in a magnetostatic field with fast waves propagating almost across the direction of the magnetic field. The main mechanism, which ensures predomination of stimulated microwave radiation over absorption in gyrodevices, is azimuthal electron bunching on Larmor circles. This bunching is due to the relativistic dependence of the cyclotron frequency on the particle energy.
In contrast to the microwave sources with straight electron beams, in gyrodevices (as well as in other electron masers) the electron beam interacts with the microwave field of electrodynamic systems, whose characteristic size exceeds the wavelength significantly. In this case, gyrodevices ensure an extremely high level of electronic and electrodynamic mode selection, which allows one to achieve single-mode generation and high efficiency even at very high working currents.
The radiation mechanism employed in CRM was discovered in the late 1950s by several authors in different countries independently and almost simultaneously. However, only one of the pioneers, namely, A. V. Gaponov-Grekhov, led on the team of his collaborators implementing this idea within high-power electronics. Specifically, important contributions were made by M .I. Petelin (development of basic concepts of various high-power gyrodevices), V. K. Yulpatov (development of the nonlinear theory of such devices), V. L. Bratman, N. S. Nusinovich,
and N. S. Ginzburg (development of the theory for gyrodevices with relativistic electron beams), A. L. Gol'denberg, I. I. Antakov and Sh. E. Tsimring (experimental studies), V. A. Flyagin (practical development of high-power devices), and A. G. Litvak, G. G. Denisov and V. E. Zapevalov (development of high-efficiency quasi-CW megawatt generators).
Recent years have shown a qualitative leap in the development of high-power millimeter-wave generators, i.e., gyrotrons. In particular, devices generating at a megawatt power level in nearly continuous-wave regimes (with durations of "pulses" of about an hour) have been developed and tested. This allowed advancing electron-cyclotron plasma heating in fusion facilities with magnetic confinement to the position of one of the main methods of additional heating, alongside with neutral injection and the ion cyclotron method. Currently, IAP is one of the world leaders in making of such devices.
The devices with an average power level (up to 15—20 kW), which are developed at IAP for various technological applications, have almost infinite life, are easy to control, reliable in operation, and relatively inexpensive, since they do not contain complex cryomagnetic systems. Such devices have been delivered on a contractual basis to 15 leading laboratories of the world, which are engaged in development of advanced technologies. The IAP team uses such systems successfully in CVD reactors for growing of poly- and monocrystalline diamond films and plates, gas-phase deposition of isotope-pure silicon with record-breaking purity parameters, in ECR systems that form beams of multi-charge ions with record-breaking parameters, for generation of high-power radiation in the extreme UV range, etc.
High-power electronics keeps being developed on the basis of high-current beams of relativistic electrons with the purpose of increasing both the peak and average radiation power. In combination with the systems of active and passive compression, which have been implemented at IAP successfully, these relativistic generators ensure record-breaking levels of the peak output power, which is rather important for such applications as linear accelerators with ultra-fast rates of particle acceleration, precision radars, material processing, etc.
In recent years, the methods of vacuum electronics are actively used at IAP to invade the terahertz frequency range, which is promising for many applications. Along with traditional gyrodevices that operate with extremely strong magnetic fields at the fundamental cyclotron resonance and the second cyclotron harmonics, gyrodevices at higher cyclotron harmonics (large-orbit gyrotrons and gyromultipliers) are also developed. In recent experiments, a pulse solenoid with a magnetic field of up to 50 T generated a power of several kilowatts at the fundamental cyclotron resonance in the single-pulse operation regime with a pulse duration of 50 μs at record-breaking frequencies of 1—1.3 THz. In large-orbit gyrotrons, generation at frequencies up to 1 THz with pulsed (10 μs) power about 0.5 kW has been obtained at the second and third harmonics.
