John Riley Holt, FRS[1] (15 February 1918 – 6 January 2009) was an English experimental physicist who played a part in the development of the atom bomb and later became one of the pioneers of elementary particle physics research.
Holt was born in Runcorn, Cheshire, England, in 1918, his father being a worker in a boat-building yard, and his mother the owner of a bakery and confectionery shop.
[2] During the Second World War, Chadwick formed a team, which included Holt, to perform measurements, some of which involved the cyclotron, to confirm the findings in the Frisch–Peierls memorandum relating to the critical mass required for an atomic bomb.
[4] Using the more powerful synchrocyclotron, Holt's team carried out experiments on the weak interaction responsible for the decay of the muon, which played a large part in the current understanding of the Standard Model.
[2][4] In the early 1960s, Holt was involved with the design of the electromagnets for the electron synchrotron at Daresbury Laboratory and in 1964 he was elected a Fellow of the Royal Society.