Selex ES has a well consolidated heritage in design and production of conventional traveling wave tubes and helix mini-TWT for military naval, airborne and missile applications. Strong on his own experience Selex ES is developing a wideband, 100 Watts CW, helix mini-TWT to satisfy the increasing demand of systems capable of high power level over wide operating bandwidth; the main application being as power final RF amplifier inside a Microwave Power Module. Design approach, simulation results and performances obtained with the first two mini-TWT are presented in this paper.