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High-speed CARIBU and Other Behemoths

April 8, 2011 - 12:11pm


Argonne physicist Richard Pardo stands next to CARIBU | Photo Courtesy of ANL's Flickr page.

Argonne physicist Richard Pardo stands next to CARIBU | Photo Courtesy of ANL's Flickr page.

Question: Why did the caribou cross the road, at 76 million miles per hour? Answer: To catch up with the chicken.

Visitors to the Department of Energy’s Argonne National Laboratory won’t actually encounter any hyper-speed fowl, but they will see a high-speed CARIBU, which recently started to chase other exotic beasts in the particle zoo.

Argonne’s CARIBU – which stands for Californium Rare Isotope Breeder Upgrade – is designed to study the inner part of an atom known as its nucleus. A nucleus consists of a collection of two types of particles, the proton, with a positive charge, and the neutron, with no charge, just mass. Those particles themselves are made of even smaller particles called quarks. CARIBU creates extra-heavy (neutron-rich) nuclei, and then spits them out of a nozzle for acceleration.

Indeed, beams of those particles are then sent into another machine called ATLAS (Argonne Tandem-Linac Accelerator System), and subsequently shot at speeds of roughly 76 million miles per hour into targets so that scientists can study them.

Unlike their counterparts, extra-heavy nuclei are actually quite unstable. Naturally created only in stars – especially in giant explosions known as supernovae – they usually exist for just seconds at a time, before flying apart (decaying) into a more stable form.

So why create these hyper-speed, quickly-decaying atomic behemoths? Unlike the beasts themselves, atomic decay is quite commonplace – in fact, it’s responsible for nuclear power. So by studying them and the ways they decay, scientists may gain new knowledge into nuclear fuel as it ages, and perhaps find ways to make reactors even safer. CARIBU’s monsters might shed more light on supernovas. And they will reveal more about the fundamental forces that keep atomic nuclei together in the first place.

Argonne has its CARIBU, but researchers all across the Department of Energy are trying to gain more insight into the exotic beasts of the particle zoo. For instance, in collaboration with others, scientists at the Department’s SLAC National Accelerator Laboratory used their BaBar detector (which has since been deactivated and disassembled), to collect data that points to a new member of the “bottomonium” family of subatomic particles.

Bottomonium particles – which are composed of quarks – are held together by the strong force, which holds atomic nuclei together. Scientists around the world are working to observe them, to better understand how nuclei – and ultimately all matter – are put together. (Yes, this is a case of a race to the bottom . . . oninum.)

There are many more particles out there, and Department of Energy scientists are chasing them with elephantine detectors and their new high-speed CARIBU.

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Charles Rousseaux is a Senior Writer in the Office of Science.