Calculations of muon capture in D/sub 2//T/sub 2//He mixtures

The first step in the muon-catalyzed fusion cycle is slowing down and capture of the negative muon in isotopic hydrogen mixtures. The authors used two methods for calculating this process: the classical-trajectory Monte Carlo (CTMC) approach and the diabatic-state model. Previous CTMC calculations probably give the most accurate published cross sections for μ/sup -/capture by hydrogen isotopes. However, those results are somewhat uncertain since, while the momentum distribution in the H-atom is given exactly, the position distribution is not described well by the microcanonical ensemble employed. A description has now been developed that simultaneously treats the position and the momentum distributions with sufficient accuracy. As the moment of helium in the mixture builds up (/sup 3/He from tritium decay or /sup 4/He from fusion), the catalytic action is poisoned. Cross sections for μ/sup -/ capture by He have also been calculated. Determination of the fraction captured by He requires, in addition, proper description of the muon-energy transport. Results for hydrogen/helium mixtures are presented and the tolerable contamination by He deduced. All existing calculations for capture of μ/sup -/ by hydrogen have actually been done for H atoms. The molecular case is considerably more complicated; e.g., in μ/sup -/ + H/sub 2/ collisions, adiabatic ionization is impossible, but rovibrational excitation or dissociation can occur. A theory to treat the dynamics of μ/sup -/ + H/sub 2/ has been developed. Preliminary results are discussed