Fig. (21) The neutrino mass sensitivity expected in the Project 8 measurement using cyclotron radiation of single electrons emitted in tritium β-decay [161]. The dependence on the effective volume of gaseous sources of molecular or atomic tritium is shown for indicated number densities per cm³. A source temperature will be 30 K for molecular T₂ and 1 K for atomic tritium. Further assumptions were a magnetic field uniformity of 0.1 ppm rms, a background of 10^-6 s^-1 eV^-1 and a live time of 3·10⁷ s. The m_ve sensitivity for T₂ is limited to about 100 meV because of the width of the rotational-vibrational states of the (³HeT)⁺ daughter ion and a minimum operating temperature near 30 K.