Cyclotron Radiation Emission Spectroscopy

Major advances in experimental nuclear and particle physics are often motivated by the need to answer challenging questions. In 2009, Monreal and Formaggio were motivated by the problem of measuring the absolute mass of the neutrino to propose the technique that would come to be called cyclotron radiation emission spectroscopy (CRES). They needed to measure the energies of the electrons from tritium beta decay with extremely high precision, which could be achieved by measuring the frequency of the cyclotron radiation from many individual magnetically trapped electrons. The technique was put into practice first by the Project 8 Collaboration and then by the He6-CRES Collaboration for the study of nonstandard weak interactions. In this review, we present the CRES experiments that have been performed to date, describe the phenomenology of CRES that has so far been explored, and cover potential applications of CRES that have been proposed.