Louis Slotin

Louis Slotin (December 1, 1910 – May 30, 1946) was a Canadian physicist/chemist who took part in the Manhattan Project. He died of massive radiation poisoning after a criticality accident at Los Alamos.

Early life and training
Louis Slotin was born December 1, 1910 in Winnipeg, Manitoba, to the family of Israel and Sonia Slotin, Yiddish-speaking refugees from Russia. He was the eldest of three children. Slotin received his Bachelor of Science degree from the University of Manitoba in 1932 and Master of Science degree in 1933. He went to King's College, London University where he received a doctorate in physical chemistry in 1936. To his friends back home, he managed to give an impression that he had fought for the Spanish Republic and flown with the Royal Air Force.

In 1937 Slotin tried to obtain a job with Canada's National Research Council but was not accepted. The University of Chicago accepted him as a research associate later in the year. The job paid poorly and Slotin's father had to support him for two years. On December 2, 1942, he was around during the start-up of "Chicago Pile-1", the first man-made nuclear reactor, created by Enrico Fermi, but there are conflicting accounts of him being actually present at the event.

In 1942, through professor William D. Harkins of the University of Chicago, Slotin got involved with the Manhattan Project, the Allied program to develop the first nuclear weapon. In December 1944 he moved to the Los Alamos laboratory in New Mexico to work in the bomb physics group of R.F. Bacher. Technically, he received a leave-of-absence from the University of Chicago.

Los Alamos
At Los Alamos, Slotin's duties consisted of criticality testing, first with Otto Frisch's uranium experiments, and then with plutonium cores. Criticality testing involved dangerous experiments to bring masses of fissile materials to near-critical levels to establish experimentally their critical mass values. Scientists called this dangerous testing "tickling the dragon's tail", after a remark by Richard Feynman that it was "tickling the tail of a sleeping dragon" or due to its flirtations with nuclear chain reaction. Some sources have erroneously claimed that he was involved with triggering devices.

After the war, Slotin's work was still required at Los Alamos because, as he said, "I am one of the few people left here who are experienced bomb putter-togetherers." He looked forward to resuming his research into biophysics and radiobiology at the University of Chicago and was training a replacement, Alvin C. Graves. He received US citizenship in 1946.

The prompt criticality accident
On August 21, 1945, a 6.2 kg plutonium core (later nicknamed the "Demon core" because of these accidents) had produced a burst of ionizing radiation that caused lethal radiation poisoning to Harry Daghlian, an experimenter who had made a mistake while working alone doing neutron reflection experiments on it. This core, subject to experiments so shortly after the end of the war, had probably been the intended core for the 3rd nuclear weapon never used on Japan.

In 21 May 1946, Slotin, among others, was in a laboratory performing an experiment that involved creation of the beginning of the fission reaction by placing two half-spheres of beryllium (a neutron reflector) around the same plutonium core. Slotin grasped the upper beryllium hemisphere with his left hand through a thumb hole at the top while he maintained the separation of the half-spheres by a blade of a screwdriver with his right hand, having removed the shims normally used. Using a screwdriver was not a normal part of the experimental protocol. The screwdriver slipped allowing the upper beryllium hemisphere to fall causing a "prompt critical" reaction, resulting in a burst of hard radiation. The "blue glow" of air ionization was observed and a "heat wave" was felt by the scientists in the room. Slotin instinctively jerked his left hand upward, lifting the upper beryllium hemisphere and dropping it to the floor. He exposed himself to a lethal dose (around 2100 rems, or 21 Sv) of neutron and gamma radiation, in history's second criticality accident. In addition to the blue glow and heat, Slotin experienced a sour taste in his mouth and an intense burning sensation in his left hand.

As soon as Slotin left the building, he vomited, a common reaction from exposure to extremely intense ionizing radiation. The official line was that Slotin, by quickly removing the upper hemisphere, was a hero for ending the critical reaction and protecting seven other observers in the room. The official release from the authorities while Slotin was dying in the hospital after the accident was: "Dr. Slotin's quick reaction at the immediate risk of his own life prevented a more serious development of the experiment which would certainly have resulted in the death of the seven men working with him, as well as serious injury to others in the general vicinity." The designation as a hero is moderated by criticisms (from, for example, Robert B. Brode) that the accident was avoidable and that Slotin was not using proper procedures, endangering the others in the lab along with himself.

Slotin's colleagues rushed him to hospital but Slotin was aware of his condition and, realizing he would die, is said to have remarked: "You'll be OK, but I think I'm done for." His parents were informed and a number of volunteers wanted to donate blood but the efforts proved futile. The accident ended all hands-on assembly work at Los Alamos. The incident was at first classified and not made known even within the laboratory; Robert Oppenheimer and other colleagues later reported severe emotional distress at having to carry on with normal work and social activities while they secretly knew that their friend lay dying.

Louis Slotin died nine days later on May 30, in the presence of his parents. Three of the seven survivors of the accident died years later from causes possibly related to the radiation exposure. The accident and its aftermath were dramatized in the 1989 motion picture Fat Man and Little Boy, although the date of the event was changed for dramatic purposes, and some technical details were wrong.

Louis Slotin was buried in Winnipeg on June 2, 1946 (though not in a lead coffin, as was later rumored). In 1948, Slotin's colleagues at Los Alamos and the University of Chicago initiated the Louis A. Slotin Memorial Fund for lectures on physics. It lasted until 1962.

Asteroid 12423 Slotin is named in his honour.

Quotes
"Slotin's personal sacrifice undoubtedly saved those who were in the room with him. For himself, there was no hope of recovery, something he must have known at once," —Robin Connor, professor of physics, University of Manitoba.