To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, ...manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 musec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given.
A 250 GHz continuous-wave (CW) gyrotron has been developed at the IAP RAS jointly with GYCOM Ltd., as a prototype of the microwave source for the envisaged prospective nuclear fusion power plants ...(DEMO). The main applications of such a tube are electron cyclotron resonance heating and electron cyclotron resonance current drive of magnetically confined plasma as well as its diagnostics based on collective Thomson scattering in various reactors for controlled thermonuclear fusion (e.g., tokamaks and stellarators). The results of the preliminary experimental tests in a pulsed mode of operation are presented. The microwave power of up to 330 kW with an efficiency of 30% without collector depression was obtained. At an accelerating voltage of 55 kV and an electron beam current of 12.5 A (which corresponds to the design parameters for CW operation), the measured output power was about 200 kW. The TEM
mode content evaluated at the tube output is not less than 98.6%.
We review the development of radiation sources and present the most notable examples of the use of gyrotrons in spectroscopy and material diagnostics. We describe the main features of terahertz ...gyrotrons, present the most prominent examples of modern continuous-wave and pulsed gyrotrons for a specified frequency range, examine a number of topical applications, and discuss near-term development prospects for high-frequency gyrotrons.
The study of the gas discharge in quasioptical beams of electromagnetic radiation of the terahertz (THz) frequency band is attractive for fundamental and applied research. The study of this discharge ...was made possible by the emergence of unique and reliable sources of radiation of the THz frequency band. Electrovacuum radiation sources of THz band (gyrotrons) have been created at the Institute of Applied Physics (IAP RAS) (Nizhny Novgorod) with a power order of 100 kW in pulsed mode of operation (pulse duration ~ several dozens of µs) and a kilowatt in continuous mode, and investigations of gas discharge phenomena in various gases have been started. Even the first experimental studies of the discharge in noble gases (argon) showed a significant difference in the THz discharge from the discharge at lower frequencies, even in the dynamics of discharge glow. The maximum of the discharge glow was observed after the end of the THz pulse and the afterglow duration was hundreds of microseconds. This paper is devoted to the theoretical and experimental study of the breakdown thresholds of various gases by radiation at 263 and 670 GHz and the study of discharge dynamics in noble and molecular gases under the action of 670 GHz radiation.
The feasibility of a high-power sub-THz gyrotron with smooth wideband frequency tuning suitable for direct measurement of the positronium hyperfine structure is demonstrated numerically using both ...averaged equations and PIC-code simulations. Analytical estimates show that the frequency-tunable powerful sub-THz radiation can be generated through the excitation of high-order axial modes in a gyrotron with short cavity driven by an electron beam with high current. Simulations show that an output power of 0.5–1 kW can be obtained at a frequency of about 0.2 THz within a 10-GHz band which are the parameters needed for testing of quantum electrodynamics predictions through the spectroscopy of positronium.
We describe a series of gyrotron facilities developed at the Institute of Applied Physics of the Russian Academy of Sciences for studying physical processes during interaction of millimeter-wave ...electromagnetic radiation and matter. This paper presents the universal principle of designing such systems on the basis of a facility having an output radiation power of 5 kW at a frequency of 24 GHz. The main components of the facility and their technical parameters are described. Design of high-efficiency radiation sources and radiation transmission lines for various research applications is a sophisticated radiophysical problem, and the need for long-term stable operation with automatic adjustment of the parameters of the generation regime requires unique engineering solutions. Application of multimode electrodynamic devices in the radiation transmission line allows one to treat materials with significantly different dielectric properties, in particular, heat them up to temperatures of about (and exceeding) 2000°C. The vacuum-tight working chamber of the facility is a high-Q untuned cavity resonator having a volume of about 0.1 m
3
, in which microwave heating of items with characteristic dimensions of more than 10 cm can be performed. The automatic control system of the facility ensures its reliable and long-term failure-free operation.
Nowadays, the development of multifrequency high-power subterahertz gyrotrons for electron cyclotron (EC) heating and plasma diagnostics is in great demand. The article examines the prospects of ...using a special two-channel quasi-optical converter for the output of radiation at several frequencies through two separate windows. The converter was developed by hybrid synthesis and the MoM/electric field integral equation (EFIE) method. The approach is being investigated for the gyrotron with a frequency of 250 GHz and a power of up to 330 kW. The designed system makes it possible to output radiation at up to five frequencies in the range of 176-250 GHz with efficiency at the level of optimized single-frequency gyrotrons.
This work presents the results of investigation of THz gas discharge in inhomogeneous flow of nitrogen. As a source of sub-millimetre radiation we used 40 kW@670 GHz gyrotron created in IAP RAS. It ...is shown that, despite the tendency of the discharge in electromagnetic wave beams to propagate towards the heating radiation from the breakdown region, in the case of a strongly inhomogeneous gas flow (nitrogen in our case), conditions can be created under which the discharge practically does not propagate and becomes point-like. The features of the glow of a THz discharge in a nitrogen flow in a wide range of background gas pressures are studied. The presence of a powerful afterglow in some bands of the second positive system of nitrogen at high pressures was demonstrated. The prospects of using such a discharge as a source of UV radiation are discussed.
We give a brief review of the results of using gyrotrons to study molecular spectra by means of a radioacoustic absorption detection (RAD) spectrometer. Examples of recording molecular spectral lines ...of sulfur dioxide (SO
2
), carbon sulfide (OCS), and methane (CH
4
) are presented. The achievement of a record-breaking sensitivity for the sub-terahertz frequency range in terms of the absorption coefficient is demonstrated when observing weak methane lines. The possibility of spectroscopy at harmonics of the gyrotron radiation with a frequency of up to 1 THz is shown. Spectroscopic estimates of the radiation power at the second and third harmonics with respect to the power at the fundamental frequency are given. The possibilities of using the methods of nonlinear spectroscopy, namely, two-photon spectroscopy, which extend the range of potential spectroscopic studies using intense gyrotron radiation, are demonstrated. The results of observations with a RAD spectrometer and a direct absorption spectrometer for the lines of two-photon rotational transitions of OCS and SO
2
molecules, which have well-studied spectra and a large dipole moment, are presented. Promising opportunities for using gyrotrons to solve fundamental and practical problems are discussed.
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