August 7, 2014

Rebuilding part of the Large Hadron Collider – with Legos

News and Information

The Atlas particle detector at the Large Hadron Collider has become pretty famous in the last few years, since it helped lead physicists to finally discover an important subatomic particle. So some University of Washington students got the idea of building their own version of Atlas, only much smaller – and using Legos.

UW physics graduate student Nikola Whallon shows off a Legos version of the Atlas detector.

Vince Stricherz / UW

UW physics graduate student Nikola Whallon points out a Legos version of the Atlas detector’s muon spectrometer, which the UW played a key role in developing. UW physicists continue their ongoing work with the Large Hadron Collider.

About 20 people – most of them UW physics graduate and undergraduate students, but with a few local high school students as well – took about 50 hours to assemble the diminutive replica, which is small enough to sit atop an office desk.

“We spent a lot of time learning how to build it,” said Nikola Whallon, who just completed his first year as a UW physics grad student. “We ran out of some of the original parts that we were supposed to use, so we had to improvise.”

It’s not the first time a university has built a model of the Atlas detector using Lego bricks. The “Build Your Own Particle Detector” effort was the brainchild of Sascha Mehlhase, a physicist at Ludwig-Maximilians-Universität in Munich, Germany.

More than that 100 model kits have been distributed worldwide. Recently, Mehlhase and numerous others at the European Organization for Nuclear Research, or CERN, volunteered to sort thousands of pieces into kits for more than 20 models that were then distributed to a variety of institutions around the world, including the one that came to the UW.

Building the model presents a great opportunity to broaden public interest in science and to explain, in lay terms, “the problems we are trying to attack,” said Shih-Chieh Hsu, a UW assistant professor of physics who has worked with the students.

“It’s about outreach education,” he said. “It is something that we think can inspire interest for all ages.”

The UW has strong ties to the Large Hadron Collider, operated by CERN near Geneva, Switzerland. The collider made history in 2012 by providing evidence for an elusive subatomic particle called the Higgs boson – sometimes referred to as “the God particle” – a discovery that provided a major step in understanding the origins of the universe.

UW scientists and engineers played a key role in building the Atlas detector, one of two detectors central to the Higgs discovery. The Atlas detector is half the size of Notre Dame Cathedral in Paris and weighs in at more than 7,700 tons. The UW group was instrumental in designing and building one of its subsystems, the muon spectrometer.

The forward muon detector on Atlas contains more than 430 chambers filled with aluminum tubes ranging in length from about 5 feet to 10 feet. About 30,000 of the tubes were made at UW between 2000 and 2007, fitted into 80 chambers and shipped to Geneva. Another 60,000 tubes were made with UW methods and specifications at two other U.S. sites and then shipped to Geneva. The chambers were mounted into 32 sections shaped like giant pie wedges, which fit together into two rings at either end of the main Atlas detector.

UW physicists continue to work on Atlas, helping to outfit the detector with a new component called the Insertable b-Layer to allow even more sensitive measurements of the Higgs boson and other related particles. The Insertable b-Layer is essentially a digital camera that can create pictures of what happens inside the detector immediately after particle collisions, but while a typical camera has one silicon detector the Atlas pixel detector has more than 1,700.

The dimensions of the UW’s Lego model, built in the Physics-Astronomy Building during May and June, are about one-fiftieth of the real thing. Getting the model just right was an engrossing prospect for the students, Whallon said.

“Surprisingly – or maybe not so surprisingly – the Legos proved to be attractive to the graduate students,” he said.

The Lego model is now displayed on campus in a clear-plastic case and is being featured during the annual U.S. Atlas workshop, which brings together physicists from across the country and this year is being held at the UW.

Eventually the model could be taken to other venues, such as the Pacific Science Center in Seattle, and even taken apart so that a whole new group of students can assemble it.

“It’s a good way to get kids interested in high-energy physics, which isn’t so easy to do,” Whallon said.


(This story was modified on Aug. 11, 2014, to clarify origins of the Atlas detector model outreach effort.)