Building the Casaccia gamma feld. Nuclear energy, Cold War and the transnational circulation of scientifc knowledge in Italy (1955-1960) Francesco Cassata* The article will focus on the mutagenesis programme in agriculture implemented by the Italian Atomic Energy Commission, starting from 1955, through the establishment of a specifc technological and experimental system: the so-called “gamma feld”, a piece of agricultural land with a radioisotope of Cobalt-60 at the centre. The Cobalt-60 would emit constant radiation, which would bombard the specimens planted in concentric circles around the source, inducing genetic mutations. The Italian gamma feld went into operation in January 1960 at the Casaccia Laboratory, about twenty miles north of Rome, with a radia- tion device made available by the US Government for the Atoms for Peace programme This article will analyse, frst of all, how the American experimental model of mutation breeding was translated into the Italian context, becoming instrumental for the establishment of plant genetics within the local academic system; secondly, it will describe how the sociotechnical imaginary embodied by the gamma feld was part and parcel of this process of discipline- building and scientifc demarcation. Key words: Cold War, Atoms for Peace, Nuclear energy, Agriculture, Plant breeding, Genetics It was a round-shaped feld, covering a surface of some six thousand square metres: at the centre, in a hole made of concrete walls, the radiation unit that the United States had donated in 1958 as part of the Atoms for Peace programme. The unit was composed of a lead cylinder that weighed about a ton, which contained a radioactive source: two Cobalt-60 rings, approximately twenty centi- metres long. With the help of a steel tree and a special radio-controlled system, a control cabin placed at the outer edge of the feld — a building made of concrete and pot-metal glass — regulated the source’s extraction from its container and the subsequent radiation, 20 hours a day, of the surrounding plants. The feld was circumscribed by an earthwork of over fve metres high, and could be accessed via an opening in the earthwork, guarded by gates that were operated by a radio-controlled blockage and connected to the movements of the radioac- tive source. The opening itself was shielded by a high concrete wall. “Italia contemporanea”, Yearbook 2020 ISSNe 2036-4555, DOI 10.3280/icYearbook-oa12263 * Professore ordinario, Dipartimento di Antichità Filosofa Storia (DAFIST), Università di Genova; francesco.cassata@unige.it