By Malka Gorbunov
The cyclotron, invented by nuclear physicist Ernest O. Lawrence (1901-1958), was an invention with a troubled history and a happy ending. Lawrence, whose life’s work focused primarily on radioisotopes, eventually merited the distinction of having element 103 on the periodic table, lawrencium, named for him.
A morally objectionable individual, Lawrence was a contributor to the Manhattan Project and (unlike many of his colleagues) took great pride in the resulting nuclear bomb which was dropped on Hiroshima. But there is no denying the good that his invention eventually did for humanity.
What is a cyclotron? It is, essentially, a compact and highly practical particle accelerator– the predecessor of colossal particle accelerators such as the Large Hadron Collider at CERN (an acronym derived from the French for European Organization for Nuclear Research, located in Geneva, Switzerland).
Lawrence created the cyclotron on the principle of accelerating charged particles along a circular path, held in place by a magnetic field. The particles were accelerated by varying the radio frequency. The cyclotron was useful for creating high-energy beams which provided valuable information in nuclear experiments, such as the products of high-energy atomic collisions. Lawrence won the Nobel Prize for the cyclotron in 1939 and his invention soon became all too relevant as the Second World War broke out.
Cyclotrons were being built in select locations throughout Europe, including in the lab of Otto Hahn (co-discoverer of nuclear fission with Lise Meitner). The Allies (and much of the world) were terrified at the prospect of a nuclear Third Reich, something which seemed very real based on information collected by Allied intelligence. In addition to spurring the Manhattan Project along, this fear prompted many efforts by the Allies to derail Nazi nuclear progress, including Project Alsos: a specialized team sent to Europe for just this purpose.
At this time, a cyclotron was being built in the lab of the French physicist Frédéric Joliot-Curie (son-in-law of Marie Curie). When France fell to the Nazis and the government of Vichy France was established, Wolfgang Gentner of the Nazi Uranium Club was appointed head of this lab and its newly built cyclotron. However, Gentner had been a friend of Joliot-Curie, who was now an active member of the Resistance, and discreetly aided him. While the sabotage was petty and cautious, it did aid the cause for a while. This, and other obstacles put in the way of the Nazis made a cumulative difference.
In the end, nothing came of the Nazi nuclear project and the reasons for this are disputed to this day. Some speculate that head scientist Werner Heisenberg subtly held it back; others name different causes. The much feared and coveted cyclotron (along with other resources) did not put a nuclear bomb in Hitler’s hands, whatever sinister potential it might’ve had to do so.
And the continuation of the cyclotron’s story is happier, concerning its applications to medicine after the war and through this day.
Beginning in the 1950s, the cyclotron (and later its more potent successor, the synchrotron) has found its use in nuclear medicine. Proton therapy uses a beam of protons (originating in the cyclotron) directed at cancerous tissue to destroy it. It has the advantage of minimally affecting nearby healthy tissue, due to its highly focused beam. The use of proton therapy has become a major milestone in cancer medicine. Another medical application of the cyclotron is that its beam can be used to create isotopes used for positron emission tomography (PET) scans. These scans are helpful in diagnosing cancer as well as heart disease and other illnesses. The cyclotron has become an integral part of medicine, to the extent that several hospitals are equipped with their own cyclotrons, a reality that would’ve seemed absurd during the Second World War. Memorial Sloan Kettering operates two cyclotrons on site.
This is a demonstration of the potential that scientific innovation has, to shape our world for the better or the worse. The cyclotron passed through many hands and was built with varying intentions, but ultimately found a benevolent niche in medicine.
Sam Kean, “The Bastard Brigade: The True Story of the Renegade Scientists and Spies Who Sabotaged the Nazi Atomic Bomb”. 2019.