 In September 1951 , Oliphant applied for a visa to travel to the United States for a nuclear physics conference in Chicago . The visa was not refused , nor was 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 . 
