Cosmic Ray Center, Millard County, Utah

Out in the isolated West Desert of Utah a strange sight may cause drivers along US Highway 6 & 50 to take a second look. Is that a tanning bed out in the sagebrush?  And another? And another, each spaced out in lines that cross the highway?

These strange apparatuses are part of a study being conducted west of Delta, Utah, to measure cosmic rays. Educational institutions from Japan, Korea, Russia, China, Taiwan, and the United States are involved. The headquarters is in Delta, and that's where the data is also processed.

The study is "to observe cosmic-ray-induced air showers at extremely high energies using a combination of ground array and air-fluorescence techniques." Okay, what does that mean? It probably makes perfect sense to my brother, the physicist, but for those of us who are not immersed in physics, it may be a little nebulous.

First off, what are cosmic rays? Here's the simplistic answer: tiny stuff you can't see with the naked eye that comes from outer space. Now here's the official answer: The term "Cosmic Rays" refers to elementary particles, nuclei, and electro-magnetic radiation of extra-terrestrial origin. These may include exotic, short-lived particles such as muons, pi-mesons or lambda baryons. (okay--did any of you have fun saying "muons"? I started imagining cows flying through space. Sorry for this tangent, but I couldn't help myself. Moo.)

Cosmic rays weren't discovered until the 1930s, when Austrian physicist Victor F. Hess went up in a hot air balloon over 17,000 feet high, measuring radiation along the way. He was surprised to find that the radiation increased with altitude, and surmised that radiation was entering the earth's atmosphere from outer space. He called this phenomenon "cosmic radiation," and later it was coined "cosmic rays." For his trouble, he earned a Nobel prize in 1936.

Next, what is a ground array technique? The ground array uses 576 scintillation detectors. Here's what one looks like:

And from its better side:
These scintillation detectors are laid out in a grid, each 1.2 km away from the next. The research area covers 760 square kilometers. Helicopters were used to install them, with each one weighing about 250 kg. 

The map below shows the ground array of scintillation detectors.

On the sides of the grid are fluorescence detectors. Sorry, I haven't made it to any of them to photograph yet, but researching this study has piqued my interest and I may have to wrangle an invitation. The fluorescence detectors are able to detect cosmic rays with much less energy (between 3x10^16 eV and 10^19 eV to be exact) than those detected by the scintillation detectors (which only detect cosmic rays greater than 10^19 eV).

Let's get back to the tanning beds--oh, I mean scintillator detectors. They are double layer scintillators which sample the charge particle density of the air shower footprint when it reaches the earth's surface. Okay, I took that last sentence directly from the project website. I think that means when the cosmic rays get close to earth, these detectors see how close together they are. (Please correct me if I'm wrong!)

The solar panel on the scintillator detector collects enough energy to power it for an entire week in complete darkness. Unless Yellowstone explodes and we're shrouded in really thick ash blocking out the sun, we probably don't have to worry about that. 

The magazine Science took note of this huge project, called the Telescope Array. It came about when two rival groups merged, using their two different techniques in this one project. Despite its name, no telescopes are part of the project; they had been included in an earlier proposal. Japan put up $13 million of the $16 needed to install and operate the project, but it was never planned to be installed in Japan because of the increased humidity there. 

One of the reasons to study cosmic rays is that physicists had been noting more higher energy cosmic rays than expected. Some can hit the ground with the force equivalent of a golf ball hitting the fairway. It makes me want to duck under one of those thick scintillation detectors so I can avoid getting hit.

This post just scratches the surface of this interesting project, which includes lots more acronyms (like TALE) and terms (such as "energy spectrum"). To learn more about this project, visit the Telescope Array website. And if you happen to be driving near the project area, you might  think about particles falling from outer space all around you. Someday we might understand what's out there.