First observation of cyclotron radiation from MeV-scale ${\rm e}^{pm}$ following nuclear beta decay

Understand

We present an apparatus for detection of cyclotron radiation that allows a frequency-based beta energy determination in the 5 keV to 5 MeV range, characteristic of nuclear beta decays.

• The cyclotron frequency of the radiating beta particles in a magnetic field is used to determine the beta energy precisely.
• Our work establishes the foundation to apply the cyclotron radiation emission spectroscopy (CRES) technique, developed by the Project 8 collaboration, far beyond the 18-keV tritium endpoint region.
• We report initial measurements of beta^-s from 6He and beta^+s from 19Ne decays to demonstrate the broadband response of our detection system and assess potential systematic uncertainties for beta spectroscopy over the full (MeV) energy range.