[en] When the particles having energy are irradiated on heavy hydride substances, D(d,p)T nuclear fusion reaction occurs in the substances, and protons are emitted. As the size of the irradiated particles becomes larger, or the number of composing atoms becomes more, it has been proposed that there is the nonlinearity in the increase of the number of proton emission. It was reported that cluster impact fusion was observed in the irradiation experiment on TiD with heavy water cluster. Its main course is shown by dividing into the experiments and theories. The authors carried out the experimental research on heavy ion impact nuclear fusion which becomes the object of comparison when the nonlinearity of the D(d,p)T reaction in cluster impact nuclear fusion experiment is discussed. The Van de Graaff accelerators in Tokyo Institute of Technology and Strasbourg Laboratory in France were used for the experiment, and the proton emission from D(d,p)T reaction was measured. The results are shown. In order to analyze the energy spectra of the protons from D(d,p)T, the calculation was carried out by using a simple two-step cascade model. The results of the analysis are shown, and were examined. It was found that this calculation reproduced the experimental results well. (K.I.)