Development and Applications of High—Frequency Gyrotrons in FIR FU Covering the sub-THz to THz Range

Abstract

Powerful sources of coherent radiation in the sub-terahertz and in the terahertz frequency range of the electromagnetic spectrum are necessary for a great and continuously expanding number of applications in the physical research and in various advanced technological processes as well as in radars, communication systems, for remote sensing and inspection etc.. In recent years, a spectacular progress in the development of various gyrodevices and in particular of the powerful high frequency (sub-terahertz and terahertz) gyrotron oscillators has demonstrated a remarkable potential for bridging the so-called terahertz power gap and stimulated many novel and prospective applications. In this review paper we outline two series of such devices, namely the Gyrotron FU Series which includes pulsed gyrotrons and Gyrotron FU CW Series which consist of tubes operated in a CW (continuous wave) or long pulse mode, both developed at the FIR FU Center. We present the most remarkable achievements of these devices and illustrate their applications by some characteristic examples. An outlook for the further extension of the Gyrotron FU CW Series is also provided.

Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25K

“…A popular approach is to use continuous-wave gyrotron microwave sources, capable of producing many watts at frequencies above 200 GHz [15–18], and to operate at sample temperatures in the 80–100 K range [19, 20]. In these studies, samples are typically doped with nitroxide-based biradical dopants in frozen solutions [21, 22], although other dopants have also been described [23–25].…”

Development of the Multifrequency Gyrotron FU CW GV with Gaussian Beam Output

“…7 Signal intensity and frequency measurements on Gyrotron FU CW GV with single-disk window, the upper and lower letters indicate the identified modes and the measured frequencies (in GHz), respectively thus be significantly improved by setting appropriate disk distances for the doubledisk window. For the TE 7,4 and TE 6,4 modes which oscillate at B of less than 6.8 T, the operating conditions were optimized, and the output signals were observed with small body currents. We thus confirmed the oscillations of all the expected modes in Table 1.…”

“…At the Research Center for Development of Far-Infrared Region, University of Fukui, Japan (FIR UF), a number of high-frequency gyrotrons operating at frequencies in ranges from subTHz to THz, including those of the Gyrotron FU-series, the Gyrotron FU CW-series, and the Gyrotron FU CW G-series, have been developed [1][2][3][4][5][6][7][8][9]. The gyrotrons of the FU CW G-series are equipped with an internal mode converter that converts the electromagnetic (EM) wave that is oscillating in the cavity into a Gaussian beam.…”

High power terahertz sources for spectroscopy and material diagnostics

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