Calculation of interaction in 0.22 THz high efficiency traveling wave tube

Using CST Microwave Studio，the dispersion characteristics of a staggered double rectangular grating slow wave structure(SDRG SWS) is calculated, and the structure parameters of SDRG SWS for a 0.22 THz（D band） traveling wave tube(TWT) are determined based on the dispersion data. Then phase velocity re-synchronization techniques are applied in D band TWT based on SDRG SWS, and four D band TWTs which have different period configurations are simulated by CST PIC solver. The results demonstrate that the phase velocity re-synchronization techniques have raised output power level from 10-13 W to 19-28 W, as well as electron efficiency from 1.4%-2.2% to 2.6%-3.9% within 218-232 GHz in those TWTs which has a concentrated attenuator, and have raised output power level from 8-16.8 W to 32-41 W, as well as electron efficiency from 1.5%-2.8% to 4.4%-5.7% within 218-232 GHz in those TWTs which has not a concentrated attenuator. Besides, whether a TWT has a concentrated attenuator or not, phase velocity re-synchronization techniques have obviously improved its gain flatness.