MVTRAD is a 2.5D frequency-domain PIC code specialized on helix TWT. It computes the beam-wave interaction by modeling the electron beam as macro-particles in a twodimensional plane, assuming rotational symmetry of the electromagnetic fields and the beam, while still taking the azimuthal movement of the particles into account. It is a parametric code, as the slow-wave circuit is represented by phase velocity and coupling impedance, which are generated, e.g. by full-wave simulation or analytical models. Large-signal continuous-wave computation can be carried out in less than a minute per frequency and power setting.