Experimental Study on W-Band (75 - 110 GHz) Oversized Surface Wave Oscillator Driven by Weakly Relativistic Electron Beams

Abstract

A W-band (75-110 GHz) oversized surface wave oscillator driven by weakly relativistic electron beams with energy in the range of 10-80 keV is studied. Rectangular corrugations are used as slow-wave structures (SWS) having surface waves with an upper cutoff frequency of approximately 100 GHz (W-band). Uniformly distributed annular electron beams are generated by a disk-type cold cathode and then are injected into the W-band oscillator. A longer SWS length causes the oscillator to function in both backward wave oscillator (BWO) and travelling wave tube (TWT) operations, and no meaningful oscillation occurs at the π-point or the Bragg condition. When the SWS length is short enough, oscillation occurs in all regions: BWO, π-point and TWT. The operations of the oscillator are strongly affected by the structure length. The maximum radiation power is estimated to be approximately 20 kW with the figure of merit of about 2 × 10 2 MW.GHz 2 .

Non-Axisymmetric Radiation from Surface-Wave Oscillator Driven by Weakly Relativistic Electron Beam

“…F-band signals are observed from around 10 kV and correspond to the W-band oversized SWO oscillation presented in Ref. [2]. This oversized SWO has been shown to be a multimode system through radiation pattern measurements.…”

“…These devices are based on a periodic structure in which the kinetic energy of an electron beam is converted into electromagnetic (EM) wave energy. The surface-wave oscillator (SWO) is a slow-wave device utilizing a cylindrical corrugated waveguide [2][3][4][5]. This corrugated waveguide has two axisymmetric normal modes: transverse magnetic (TM) and transverse electric (TE).…”

Experimental Study on Backward Wave Oscillators Using Dielectric Discharge Cold Cathodes

“…π-point operation was not observed using a velvetwrapped cathode for the first phase, as it was not found in Ref. [9]. On the other hand, microwave oscillations were observed around 30 kV in the second phase when using the DDCC.…”

“…The annular shape electron beam moves through the SWS (80 periods) in an axial magnetic field of B z = 0.819 T. The beam voltage is approximately 30 kV for the π-point operation. Min Thu San et al [9] investigated the relationship between power and SWS length. Specifically, they detected microwave powers of about 1000 mW and about 150 mW at the π-point, for 40 and 80 periods, respectively, using a velvet-wrapped cathode.…”

Experimental study of surface-wave oscillator with different electron beam forms

“…[1][2][3][4][5][6] Among the various terahertz-wave sources, extensive studies on a surface-wave oscillator (SWO) and a backwardwave oscillator (BWO) have been carried out. [7][8][9][10][11][12][13][14][15][16][17][18][19] The SWO and BWO are wave sources based on an interaction between an electron beam and EM surface wave, which is formed on a surface of a periodic structure. In the process of the interaction, kinetic energy of the beam is converted into energy of the surface wave, leading to terahertz-wave generation.…”