A novel concept of hybrid dispersion slow wave structure (HD SWS) is reported. It is realized by alternatively connecting SWSs operating at the regions of relatively strong dispersion (SD) and relatively weak dispersion (WD). In this way, the HD SWS will be characterized by high interaction efficiency over a moderate bandwidth. The equivalent dispersion of the HD SWS is calculated, which is affected by the periods’ proportion of the WD and SD SWSs. Driven by an ideal beam of 16.0 kV, 20 mA, and an input power of 1 mW, the hot performance of the HD SWS is conducted by using particle-in-cell (PIC) method. Compared with the SD SWS, the 3dB bandwidth and maximum power have been expanded and improved by 51.6% and 32.6%, without significantly increasing the circuit length. Compared with the WD SWS, the saturated interaction length has decreased by 31.1% at 0.661 THz, releasing the electro-optical system constraints. The HD SWS shows great potential to improve the terahertz (THz) vacuum electron devices’ performance.

A 0.34-THz standing wave enhanced sheet electron beam traveling-wave tube (SWE-SEB-TWT) is proposed in this article. The high-frequency structure is composed of two sections of staggered double-vane slow wave structures (SDV-SWSs) and two multigap resonant cavities that fall in between. A sheet-beam optical system, which shows a 100% flow rate over 50 mm in simulation, is designed to provide the required electron beam. By means of particle-in-cell (PIC) simulations, the output power of the 0.34-THz SWE-SEB-TWT reaches 25 W with the voltage of 19.5 kV and the current of 60 mA, corresponding to a gain exceeding 40 dB. The test results of the high-frequency structure fabricated by computer numerical control (CNC) milling show that the high-frequency characteristics are consistent with the expectation.

In this letter, a novel power synthesis scheme is proposed for high-power terahertz (THz) traveling-wave tube (TWT), which features a quadruple folded groove-guide (Q-FGG) slow wave structure (SWS) and a power synthesis circuit. Numerical simulations validate the high-frequency characteristics of Q-FGG-SWS. Parti-cle-In-Cell (PIC) simulations predict that, driven by four 125 mA electron beams at 28.4 kV, the Q-FGG-TWT is ex-pected to achieve possibility of output power of approxi-mately 177.3 W at 316 GHz. The Q-FGG-SWSs were fabri-cated using high-precision computer numerical control (CNC) milling technology. The dispersion characteristics of Q-FGG-SWS and transmission characteristics of the Q-FGG-SWSs based on the compact multi-stage groove-T coupler were experimentally verified. Therefore, the Q-FGG-SWS with a compact power synthesis circuit offers a promising approach for enhancing the power output of THz-TWTs.

A novel planar meander slot-line slow-wave structure (MSL-SWS) configuration for a Q-band traveling wave tube (TWT) is proposed and investigated. Consisting of a thin metal sheet graved with a meander slot and a metal enclosure, the MSL-SWS can combine massive production and good heat dissipation. The high-frequency characteristics are obtained by numerical simulation and validated by experiment. The PIC simulation results suggest that for an 8.2 kV and 0.1 A sheet electron beam, the output power can reach 49 W at 40 GHz with a gain of 26.9 dB. A 3-dB bandwidth of roughly 15% centered at 40 GHz is also indicated. The proposed configuration is manufactured using laser cutting and computer numerical control (CNC) milling technology. Experimental confirmation that insertion losses can be reduced to 0.043 dB/mm by plating the MSL-SWS with copper. With a good potential for fabrication, this structure can be good candidate for millimeter TWT applications.

A 0.14 THz angular radial extended interaction oscillator (AREIO) is proposed in this article. The characteristic impedance ( ${R}/{Q}$ ), the normalized equivalent conductance ( ${g}_{e}$ ), and the starting condition of the cavity are calculated and analyzed. When the metal loss is considered, in order to achieve the starting condition, it is necessary to increase the period length ( ${p}$ ) to improve $\vert {g}_{e}\vert $ . The performance of the AREIO is simulated by particle-in-cell (PIC). The voltage tuning range and the output performance under different angular angles of the cavity are investigated. Under the condition of lossless and the electron beam of 11.5 kV and 1.5 A, the peak output power and interaction efficiency of the AREIO (8°) are 5.46 kW and 31.7%, which have increased by 24.1% and 6.2% in comparison with conventional sheet beam. When considering the metal loss, the optimal angular angle will decrease to 4°. In addition, the cavity is fabricated and tested, and the results of ${S}_{{11}}$ in operating mode are consistent with the simulation.

A novel low loss sawtooth (ST) slow wave structure (SWS) is proposed as a solution to the challenges presented by terahertz (THz) traveling wave tubes (TWTs), known for their machining difficulty and insertion loss. Compared with folded waveguide (FWG) SWS, the ST SWS is easier to machine and takes a 44.96% lower insertion loss. Driven by a pencil beam (PB) gun of 19.0 kV, 15.0 mA, and an input power of 1 mW, the comparative output performance of the ST circuit and FWG circuit is evaluated using the particle-in-cell (PIC) method. The ST circuit shows enhancement in both the maximum output power and 3-dB bandwidth, which improved by 13.21% and 42.86%, respectively.