  Traveling wave SRF accelerating structures offer several advantages over the
traditional standing wave structures: substantially lower $H_pk/E_acc$ and
lower $E_pk/E_acc$, ratios of peak magnetic field and peak electric field to
the accelerating gradient, respectively, together with substantially higher
$R/Q$. In this paper we discuss how a linear collider Higgs Factory HELEN can
be built using TW-based SRF linacs. We cover a plan to address technological
challenges and describe ways to upgrade the collider luminosity and energy.
