HELEN: Traveling Wave SRF Linear Collider Higgs Factory

Traveling wave SRF accelerating structures offer several advantages over the traditional standing wave structures: substantially lower $H_{p}k\mathrm{/}{E}_{a}cc$ and lower $E_{p}k\mathrm{/}{E}_{a}cc$, ratios of peak magnetic field and peak electric field to the accelerating gradient, respectively, together with substantially higher $R\mathrm{/}Q$. 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.