Helium Physics Using HeRALD: The Helium Roton Apparatus for Light Dark Matter

The HeRALD experiment uses sub-100 mK superfluid 4He to study particle interactions, in particular, 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.