The vaned helix TWT for MPM application is designed, fabricated and tested to develop a wideband microwave source. The phase velocity and interaction impedance of a vaned helix circuit shown is predicted by use of the high frequency structure simulation (HFSS) code. To predict nonlinear performance of the vaned helix TWT, we utilize LMsuit code, which is a 1-D non-linear simulation code. From the HFSS and LMsuite simulation results, we obtained optimized design parameters. Fabricated vaned helix TWT which consists of electron gun, input coupler, output coupler, interaction circuit and collector is shown