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While Princeton University’s National Spherical Torus Experiment was shut down for improvements over the winter break, scientists and engineers availed themselves of the opportunity to recalibrate the reactor’s neutron sensors. To do so, they assembled a circular toy train track around the torus and ran a toy locomotive carrying a chunk of neutron-emitting californium-252 along it for three days. The New York Times explains:

A stationary neutron source was previously used for the calibration, but that did not fully capture how the neutrons bounced around. Putting the californium on the moving train improved the accuracy by about a factor of 10, Dr. Ono said.

[Thanks, Pete!]

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.



  1. RocketGuy says:

    Just as soon as I build it. Any day now.

    Setting a record for most expensive single track RR layout?

    here’s what I wonder though, did they regulate the speed with a standard controller or make something more accurate?

    I was also wondering if the neutron source could be used as a rtg for the train, but I’m guessing not since calibration probably needs a pretty low power source.

  2. Woody says:

    The look on the researcher’s face in that pic is priceless!

  3. LC says:

    Any excuse for the big kids to play with a train set wil do.