Concept of muon catalysis of nuclear fusion

Of the two types of muons, only the μ− is involved in muon catalyzed fusion (hereafter designated μCF) processes. As depicted in Figure 5.1, nuclear fusion reactions take place when two nuclei such as d and t approach one another to within the range of the nuclear interaction rn(≅ a few times 10–13 cm). However, because of the Coulomb repulsion between positively charged nuclei which increases with decreasing distance, the realization of nuclear fusion is not at all easy.

In the concept of thermal nuclear fusion, the additional energy is given by thermal energy (kT) through the satisfaction of the condition kT ≥ e2/rn. By assuming rn ≅ 10–12 cm, the right-hand side of the inequality becomes 7 × 104 eV (note that the radius and binding energy for the ground state of a hydrogen-like atom are 0.53 × 10−8 cm and 13.6 eV), the required temperature is 7 × 108 K (while room temperature, 300 K, corresponds to 0.03 eV). In the μCF concept, the fusion reaction is mediated by the neutral small atom formed between μ− and a hydrogen isotope and the subsequent formation of a small muonic molecule, and the relevant energy is the appropriate overall formation energy.

Here, it might be relevant to mention significant features of fusion energy as a possible energy source in future centuries.