Abstract
Many state-of-the-art fundamental and industrial projects need the use of terahertz radiation with high power and small linewidth. Gyrotrons as radiation sources provide the desired level of power in the sub-THz and THz frequency range, but have substantial free-running frequency fluctuations of the order of 10−4. Here, we demonstrate that the precise frequency stability of a high-power sub-THz gyrotron can be achieved by a phase-lock loop in the anode voltage control. The relative width of the frequency spectrum and the frequency stability obtained for a 0.263 THz/100 W gyrotron are 4 × 10−12 and 10−10, respectively, and these parameters are better than those demonstrated so far with high-power sources by almost three orders of magnitude. This approach confirms its potential for ultra-high precision spectroscopy, the development of sources with large-scale radiating apertures, and other new projects.
Highlights
In recent years, considerable progress has been achieved in the development of high-power radiation sources – gyrotrons operating in the sub-terahertz and terahertz frequency range
The field amplitude and frequency in the stationary regime are defined by the balance equations for imaginary and real parts of the complex susceptibility of an electron beam, I0χ′′ = 1
Where I0 is the normalized current parameter, and the susceptibility of an electron beam is determined by the motion of electrons in the presence of a high-frequency field as
Summary
Considerable progress has been achieved in the development of high-power radiation sources – gyrotrons operating in the sub-terahertz and terahertz frequency range. Gyro-devices are promising for application in radar studies, in particle temperature measurements using the collective Thomson scattering of gyrotron radiation, for synchronization of a large number of high-power THz sources, and as sources for spectroscopy and diagnostics of various media, for example, dynamic nuclear polarization-enhanced nuclear magnetic resonance (DNP-NMR) spectrometry. DNP improves the sensitivity of NMR spectra by about a factor of 100, reducing the acquisition time in multidimensional NMR2,3 This enhancement permits the study of larger molecules, response dynamics, or high-throughput screening. The devices based on multiplication of a signal from solid-state sources[6] with relative linewidths of about 10−12 produce subterahertz and terahertz radiation at a power level from hundreds of microwatts to a milliwatt. Cyclotron Resonance Masers (CRMs) represent a wide class of high-frequency electron devices based on stimulated (induced) radiation of electromagnetic waves[14]. Gyrotrons[15], being the most efficient version of CRMs, are based on interaction of electrons tracing out helical trajectories in a homogeneous magnetostatic field with fast electromagnetic waves under the cyclotron resonance condition; they are much more compact and cheaper than FELs and can be employed in many laboratories
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