The PPPL Express

A toy train was circling the tracks at the Princeton Plasma Physics Lab for three days in early December, but it wasn’t a holiday display that technician “Sly” Vinson was watching. Inside the lab’s primary fusion-energy experiment, the National Spherical Torus Experiment, researchers used the train to carry a Californium-252 neutron source that simulated fusion neutrons emitted by plasmas. The goal was to calibrate the neutron rate during fusion experiments. “A model train may sound low-tech, but it provides us with exactly the right arrangement we need for this calibration,” said PPPL physicist Doug Darrow.