Epithermal effects in muon-catalyzed dt fusion: Comparison of experimental data with theoretical calculations

Epithermal effects in muonic molecular formation were observed during experiments in a low-density deuterium-tritium gas target carried out at the Paul Scherrer Institute. The high molecular formation rate of ''epithermal'' (not yet thermalized) muonic tritium atoms was reflected by a strong fast component in the fusion neutron time spectra followed by a smaller ''steady-state'' component where molecular formation occurs mostly from thermalized (''cold'') tμ atoms. Further experimental evidence for high epithermal dtμ molecular formation rates has been derived from measurements in triple H-D-T mixtures. First, theoretical calculations predicted strong resonances at high tμ kinetic energies and showed qualitative agreement with the observed experimental data, but yielded molecular formation rates that differed substantially from the observed values. At present, refined calculations are being carried out which may improve the agreement with experiment. Further experiments are being planned to clarify open questions.