Establishing and consolidating a research field: The biography of the Wilson cloud chamber in the history of particle physics

This paper retraces the biography of a milestone instrument in the history of physics-the cloud chamber-introduced by Charles Thomson Rees Wilson in 1911 and vastly adopted in successive studies on particle physics. It offers a comprehensive reading where the development of the instrument is kept in tight connection with the knowledge of microphysics from the late nineteenth century to the 1960s: it shows how the inception of the Wilson instrument of 1911, even in its smallest constructive details, can be seen as strongly influenced by the physics discoveries through the nineteenth and the beginning of the twentieth centuries. The confirmation of preliminary observations obtained with early versions of the cloud chamber drove, as in the case of the positron, further evolutions of the instrument into a “golden age” of the apparatus within particle physics research. The “sunset” will see the attempt to overcome the limitations of a fully developed apparatus by flexibly intervening in the geometry of the experiment, moving it up to the mountains or at different distances from the particle accelerator by stressing at maximum, and then exhausting, the generation of new knowledge from it. In doing so, the paper brings into light original aspects not yet explored in historical studies on the cloud chamber, such as Wilson's contribution to the field after 1911.