Detector R&D for HeRALD: The Helium Roton Apparatus for Light Dark Matter

The HeRALD experiment uses the unique properties of superfluid 4He to study dark matter-nucleon scattering.  The detector uses singlet and triplet electronic excitations, and quantum evaporation from vibrational quasiparticles to determine the energy and nature of the particle interaction.  In this talk I will present progress towards the observation of the quantum evaporation signal using a next generation athermal phonon detector.  I will also discuss the broader R&D program, with an emphasis on the helium and materials physics we will study to refine the detector and push the nuclear recoil detection threshold as low as possible.