AbstractSeveral effects related to the influence of radiation, emitted by hot thermonuclear target, and residual gas in the reactor chamber on cluster ion beams moving toward the target are considered. It is shown that if the temperature of radiation emitted by the target is of the order of 100 eV, attenuation of radiation by the bombarding beams cannot prevent destruction of the clusters. It is also shown that destruction of the clusters or molecules containing hydrogen can be useful, because expulsion of protons will ‘discharge’ the beams and, thereby, improve focusing of the main ions bombarding the targets