[en] Tellurium powder in improved targets is bombarded with a cyclotron beam to produce ¹²³Xe. Flowing gas streams carry the ¹²³Xe through one cold trap which removes contaminants to another cold trap which removes ¹²³Xe that subsequently decays to ¹²³I. During this bombardment energy is deposited in the target material causing its temperature to rise. Some of the tellurium vaporizes and subsequently condenses on surfaces that are cooler than the vaporization temperature. Provision is made for the repeated bombardment of this condensed tellurium