Reines participated in a number of nuclear tests , and writing reports on their results . These included Operation Crossroads at Bikini Atoll in 1946 , Operation Sandstone at Eniwetok Atoll in 1948 , and Operation Ranger and Operation Buster – Jangle at the Nevada Test Site . In 1951 he was the director of Operation Greenhouse series of nuclear tests in the Pacific . This saw the first American tests of boosted fission weapons , an important step towards thermonuclear weapons . He studied the effects of nuclear blasts , and coed @-@ authored a paper with John von Neumann on Mach stem formation , an important aspect of an air blast wave .