Technician operates the control board of a cyclotron, St. Louis, Missouri, 1945
![](https://49fe30bb3aa7406c16dc-5c968119d095dc32d807923c59347cc2.ssl.cf1.rackcdn.com/2012.019.589_1.jpg)
Photograph. Man at control board of a cyclotron, an apparatus in which charged atomic and subatomic particles are accelerated by an alternating electric field while following an outward spiral or circular path in a magnetic field. Official Caption: "This is the control board of the cyclotron, protected from its destructive rays by impervious walls. The technician regulates the electric energy to be applied for transforming a stable element into an unstable one with radioactive properties. 6533-D." St. Louis, Missouri, United States. 1945