Question: What was the inventor of the atomic bomb trigger a participant in?

Knowledge 1: Dayton Project
At Los Alamos, physicist Robert Serber proposed that instead of relying on spontaneous fission, the chain reaction inside the atomic bomb should be triggered by a neutron initiator. The best - known neutron sources were radium - beryllium and polonium - beryllium. The latter was chosen, as polonium has a 138 - day half - life, which made it intense enough to be useful but not long - lived enough to be stockpiled. Thomas took charge of the development of techniques to industrially refine polonium for use with beryllium in the ``urchin ''internal neutron initiators. This effort became the Dayton Project. [SEP] Knowledge 2: Robert Serber
Robert Serber (March 14, 1909 – June 1, 1997) was an American physicist who participated in the Manhattan Project. Serber's lectures explaining the basic principles and goals of the project were printed and supplied to all incoming scientific staff, and became known as "The Los Alamos Primer". The "New York Times" called him “the intellectual midwife at the birth of the atomic bomb.”
Knowledge 1: Dayton Project
At Los Alamos, physicist Robert Serber proposed that instead of relying on spontaneous fission, the chain reaction inside the atomic bomb should be triggered by a neutron initiator. The best - known neutron sources were radium - beryllium and polonium - beryllium. The latter was chosen, as polonium has a 138 - day half - life, which made it intense enough to be useful but not long - lived enough to be stockpiled. Thomas took charge of the development of techniques to industrially refine polonium for use with beryllium in the ``urchin ''internal neutron initiators. This effort became the Dayton Project. [SEP] Knowledge 2: Richard Feynman
Due to the top secret nature of the work, Los Alamos was isolated. In Feynman's own words, "There wasn't anything to do there." Bored, he indulged his curiosity by learning to pick the combination locks on cabinets and desks used to secure papers. Feynman played many jokes on colleagues. In one case he found the combination to a locked filing cabinet by trying the numbers he thought a physicist would use (it proved to be 27–18–28 after the base of natural logarithms, e = 2.71828...), and found that the three filing cabinets where a colleague kept a set of atomic bomb research notes all had the same combination. He left a series of notes in the cabinets as a prank, which initially spooked his colleague, Frederic de Hoffmann, into thinking a spy or saboteur had gained access to atomic bomb secrets. On several occasions, Feynman drove to Albuquerque to see his ailing wife in a car borrowed from Klaus Fuchs, who was later discovered to be a real spy for the Soviets, transporting nuclear secrets in his car to Santa Fe.
Knowledge 1: Dayton Project
At Los Alamos, physicist Robert Serber proposed that instead of relying on spontaneous fission, the chain reaction inside the atomic bomb should be triggered by a neutron initiator. The best - known neutron sources were radium - beryllium and polonium - beryllium. The latter was chosen, as polonium has a 138 - day half - life, which made it intense enough to be useful but not long - lived enough to be stockpiled. Thomas took charge of the development of techniques to industrially refine polonium for use with beryllium in the ``urchin ''internal neutron initiators. This effort became the Dayton Project. [SEP] Knowledge 2: Uranium
Two major types of atomic bombs were developed by the United States during World War II: a uranium-based device (codenamed "Little Boy") whose fissile material was highly enriched uranium, and a plutonium-based device (see Trinity test and "Fat Man") whose plutonium was derived from uranium-238. The uranium-based Little Boy device became the first nuclear weapon used in war when it was detonated over the Japanese city of Hiroshima on 6 August 1945. Exploding with a yield equivalent to 12,500 tonnes of TNT, the blast and thermal wave of the bomb destroyed nearly 50,000 buildings and killed approximately 75,000 people (see Atomic bombings of Hiroshima and Nagasaki). Initially it was believed that uranium was relatively rare, and that nuclear proliferation could be avoided by simply buying up all known uranium stocks, but within a decade large deposits of it were discovered in many places around the world.

Answer: Manhattan Project