The development of a high-frequency, step-tunable gyrotron operating at submillimeter wavelengths is described. The gyrotron design was optimized for operation at the second harmonic of the electron cyclotron frequency in the TE261 cavity mode, whose resonant frequency is 384 GHz. Experimental results show that second harmonic operation can occur without mode competition as long as the beam current is low (Ib ≲0.8 A), but as the current is increased, the fundamental TE231 cavity mode increases and eventually (Ib ≳1 A) suppresses the second harmonic. The competition between the two modes is studied in detail. The starting current for second harmonic operation is also studied experimentally and compared with calculated results. Other resonances have also been examined. With the present superconducting magnet, the maximum frequency achieved is 402 GHz (second harmonic operation in the TE551 cavity mode) at several kilowatts.

Articles you may be interested inHighfrequency broadband (150-600 kHz) acoustic backscattering from oceanic microstructure and zooplankton in the presence of internal solitary waves

A conducting strip grating can convert a linearly polarized plane wave into one that is circularly polarized. The conversion of a normally incident wave is most efficient when the grating period is 0.874 times the wavelength, the width of the strips is half the grating period and the angle between the direction of polarization and the strips is 45°. This result is confirmed by a microwave experiment at 35 GHz.

Beams of electromagnetic radiation with phase singularities can transport angular momentum and exert torques on objects. In this paper we discuss the generation of such beams and present a simple analysis of the phenomenon. These beams and their effects have been studied at optical and at millimeter wavelengths. We describe a particularly efficient way of generating these beams at millimeter wavelengths employing a specially configured blazed grating.

No abstract