Application of surface coating for radon mitigation in rare-event searches

Rare-event searches offer a powerful avenue for investigating some of the most fundamental questions in modern physics, most prominently the particle nature of dark matter and the possible Majorana nature of the neutrino. Often, their dominant source of background comes from the radioactive noble gas radon emanating from materials. We report on a novel strategy to mitigate this background by the application of coating layers. A method for electroplating of copper was developed that showed a thousandfold reduction of the ${}^{222}$Rn emanation rate from a ${}^{226}$Ra-implanted stainless steel sample.