- Person
- Leo Szilard
- Lived
- 1898–1964
- Field
- Nuclear physics
- From
- Hungarian-American
The story
After fleeing Germany in 1933, Leo Szilard settled in London, where he had just conceived the idea of the nuclear chain reaction. In early 1934 he began working at St Bartholomew's Hospital, where he and a young physicist on the hospital staff, Thomas A. Chalmers, began studying radioactive isotopes for medical purposes.
The physics of the moment made this possible. Enrico Fermi had recently shown that bombarding elements with neutrons could produce heavier, radioactive isotopes of the same element. The difficulty was that only a tiny fraction of the atoms in a sample became radioactive, and because they were chemically identical to the rest, they could not easily be separated. A useful medical source needed the radioactive atoms in concentrated form.
Szilard and Chalmers found a solution. They bombarded ethyl iodide, a simple compound containing iodine, with neutrons from a radon–beryllium source. The newly radioactive iodine atoms broke away from the compound and could be separated from the far larger mass of unchanged material, leaving a concentrated radioactive sample. They had discovered a new means of isotope separation.
This method became known as the Szilard–Chalmers effect, and it was widely used in the preparation of radioactive isotopes for medicine. It was one of the earliest practical techniques of what became nuclear chemistry. Szilard kept experimenting in London, trying unsuccessfully to produce a chain reaction by bombarding beryllium with X-rays, before moving to the United States in 1938.
The work was an early example of Szilard turning physics toward medicine, a theme that recurred throughout his life. After the war he became a biologist, and when he was diagnosed with bladder cancer in 1960, he helped design his own cobalt-60 radiation treatment at Memorial Sloan-Kettering Hospital in New York. A second round with a higher dose followed in 1962, and the cancer never returned.
Radioactive isotopes became essential in modern medicine for imaging, diagnosis and cancer treatment. The Szilard–Chalmers technique was one of the first practical ways to concentrate them, and it showed how the new nuclear physics of the 1930s could be put to work in hospitals.
Why it matters
Concentrated radioisotopes became essential tools for diagnosis, cancer treatment and research, and Szilard's method helped make them available.
About Leo Szilard
Physicist who conceived the nuclear chain reaction in 1933, drafted Einstein’s letter to Roosevelt, co-built the first reactor, then campaigned for the rest of his life against nuclear war.
More about Leo Szilard
- Szilard's advice helped clone the first human cellLeo Szilard gave essential advice that, according to Theodore Puck and Philip Marcus, made their 1955 cloning of a human cell a reality.
- Leo Szilard saw the chain reaction, and rescued scholarsWaiting at a London traffic light in September 1933, Leo Szilard conceived the nuclear chain reaction; that same year he helped found a group that found posts for 2,500 refugee scholars.
- Szilard co-invented the chemostat for growing microbesAfter the war Leo Szilard and Aaron Novick invented the chemostat for growing microbes and discovered feedback inhibition, a key way cells control their chemistry.
- Szilard first proposed the cyclotron and electron microscopeLeo Szilard filed the earliest known patent applications for the electron microscope (1928) and the cyclotron (1929), and one for the linear accelerator (1928).
- Szilard and Einstein invented a silent refrigeratorBetween 1926 and 1930 Leo Szilard worked with Albert Einstein on a refrigerator with no moving parts, patented in the United States in 1930.
- Leo Szilard linked information and thermodynamicsIn his Berlin research of the 1920s, Leo Szilard showed a deep connection between information and entropy, making him a founding figure of information theory.
- Szilard petitioned Truman not to bomb without warningIn July 1945 Leo Szilard drafted a petition, signed by about 70 Manhattan Project scientists, urging President Truman not to use the atomic bomb on Japan without warning.
- Szilard fought for civilian control of the atomAfter the war Leo Szilard lobbied for changes to the Atomic Energy Act of 1946 that placed American nuclear energy under civilian rather than military control.
- Leo Szilard helped rescue 2,500 refugee scholarsIn 1933 Leo Szilard helped found the Academic Assistance Council in Britain, which by 1939 had found places for more than 2,500 refugee scholars.
Sources
- Leo Szilard Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.