A marble nucleus factory

This is a demonstration that has become an integral part of how I explain what we do here, and we used to great effect with last Saturday's visiting sixth graders. I call it the "Fragmentation Box", and most of the credit for it goes to Jon Delauter.

We created it to demonstrate, using marble nuclei, how NSCL smashes fast beams of ions from the cyclotron into a target, fragmenting nuclei and creating a wide variety of isotopes. The simulation with these models is quite effective because it's loud and violent.

The "accelerator" for our marble nucleus is composed of PVC pipe and gravity, standing in for the cyclotrons. After exiting the 90-degree bend, the "beam nucleus" collides with the "target nucleus" suspended in the fragmentation box. A simple screw hanging from the top of the box is enough to hold the magnetic target nucleus. Predictably, smashing two bunches of marbles together causes them to break apart, sending the model protons, neutrons, and resulting isotopes flying. Hence, the box serves to protect the experimenter. As you can see above, Ania Kwiatkowski has no qualms about sitting next to the business end of the accelerator.

Students are able to use this simulation to explore the fragmentation process with different beam nuclei, target nuclei, beam energies, impact parameters, etc. One telling result is the variety of isotopes that can be produced on multiple trials with the same conditions. This leads into the need for a fragment separator, which students can simulate with another hands-on experiment created by Lindsay Hebeler.

I've had requests from teachers who want to build their own, and we may have this summer's PAN teachers do just that. The materials aren't that expensive, and the construction is pretty simple. My next project is to carefully document the fragmentation box and write up a paper on "how to build your own." So, dear reader, if you feel that you've been missing the ability to smash marble nuclei in the privacy of your own home, stay tuned...