Oliphant accused of subversive activities, but neither was it issued. This was the height of the Red Scare. The American McCarran Act restricted travel to the United States, and in Australia the Menzies government was attempting to ban the Communist Party, and was not inclined to support Oliphant against the American government. A subsequent request to travel to Canada via Hawaii in September 1954 was refused by the United States Department of State. Although Oliphant was granted a special waiver that allowed him to transit the US, he preferred to cancel the trip rather than accept this humiliation. The Menzies government subsequently excluded him from participating in or observing the British nuclear tests at Maralinga, nor was he allowed access to classified nuclear information for fear of antagonising the US. In 1955, Oliphant initiated the design and construction of a 500 megajoule homopolar generator (HPG), the world's largest. This massive machine contained three discs in diameter and weighing . He obtained £40,000 () initial funding from the Australian Atomic Energy Commission. Completed in 1963, the HPG was intended to be the power source for a synchrotron, but this was not built. Instead, it was used to power the LT-4 Tokamak and a large-scale railgun that was used as a scientific instrument for experiments with plasma physics. It was decommissioned in 1985. Oliphant founded the Australian Academy of Science in 1954, teaming up with David Martyn to overcome the obstacles that had frustrated previous attempts. Oliphant was its president until 1956. Deciding that the Academy of Science should have its own special building, Oliphant raised the required money from donations. As chairman of the Building Design Committee, he selected and oversaw the construction of one of Canberra's most striking architectural designs. He also delivered the Academy of Science's 1961 Matthew Flinders Lecture, on the subject of "Faraday in his time and today". Oliphant retired as Professor of Particle Physics in 1964, and was appointed Professor of Ionised Gases. In this chair he produced his first research papers since the 1930s. He was appointed Professor Emeritus in 1967. He was invited by the premier, Don Dunstan, to become the Governor of South Australia, a position he held from 1971 to 1976. During this period, he caused great concern to Dunstan when he strongly supported the decision of the Governor-General, Sir John Kerr, in the 1975 Australian constitutional crisis. He assisted in the