Preliminary experimental results of a repetitive 0.14 THz overmoded relativistic surface wave oscillator (RSWO) are presented in this paper. The repetitive RSWO is developed by using a rectangularly corrugated slow-wave structure with overmoded ratio of 3 and a foilless diode emitting annular electron beam with thickness of 0.5 mm. The high quality electron beams at the repetition rate of 10 are obtained over a wide range of diode voltage (180 kV < U < 240 kV) and current (700 A < I < 1.2 kA). The generation experiments of RSWO are conducted at an axial pulsed magnetic field whose maximum strength and duration can reach about 2.7 T and 1 s, respectively. The experimental results show that the RSWO successfully produces reasonable uniform terahertz pulses at repetition rate of 10, and the pulse duration, frequency, and power of a single pulse are about 1.5 ns, 0.154 THz, and 2.6 MW, respectively, whereas the dominated radiation mode of the RSWO is TM 02 .

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Based on surface-wave oscillator (SWO), the high power 0.34 THz source using over-moded structure is studied. The attention is paid to the influence of the parameters of the slow-wave structure (SWS) on the dispersion curve, and then the SWS is optimized. According to the simulation results, the size of SWS and the requirements for the accuracy in the SWS machining are confirmed. Finally, the source is simulated by the particle-in-cell method. Numerical results show that the structure is capable of radiating a terahertz signal with a frequency of 0.34 THz and a maximum output power of about 7.8 MW. Moreover, the structure works in the state of an SWO stably. The research of the SWS is the foundation of the design of 0.34 THz source, and it is also very meaningful for the realization of the source in engineering.

A 0.14 THz high-power terahertz pulse detector based on hot electron effect in semiconductors is designed in this paper. First, the working principle of the detector is analyzed and its relative sensitivity is derived according to the structural characteristics of the detector. Then a three-dimensional finite-difference time-domain method is used to simulate the voltage standing wave ratio (VSWR) and relative sensitivity in a linear region. With optimized structural parameters, the VSWR of the designed detector is less than 1.3 while the relative sensitivity is about 0.6 kW-1, fluctuating no more than 10% in a frequency range of 0.13—0.16 THz. Subsequently discussed are the effect of Joule heat on the detector, and the relation between variation ratio of the output voltage and terahertz pulse duration. Finally the detecting simulations of the detector and its analysis results show that the detector with response time of picosecond-leval can handle a maximum power of about 2.2 kW, while the maximum power of its linear working region reaches tens of watts, so it can accomplish the direct measuring of 0.14 THz high-power terahertz pulses with nanosecond-level durations, increasing the accuracy of power measurement.

Results of theoretical analysis and numerical simulation studies of a MW-class, overmoded terahertz oscillator are presented. The device consists of a large diameter crosssection, slow wave structure with a unique profile of wall radius specifically designed to support surface wave and to provide a strong beam-wave coupling at a moderate voltage. Under the condition of 500 kV voltage and 2 kA beam current, the 2.5-D particle-in-cell simulation predicted the output power of 41 MW at the frequency of 0.143 THz. And an efficiency of 4.1% was also obtained with a perfect time plot and fine spectrum characteristic.