College of Liberal Arts

University of Mississippi

Physics Professors Witness Lowering of Last Piece of Giant CMS Magnet

Seven University of Mississippi physicists have kept a keen eye on a huge construction project in Switzerland this week.

Researchers at the European Organization for Nuclear Research, known as CERN, lowered the final piece of the Compact Muon Solenoid particle detector into its experimental cavern 328 feet underground on Tuesday (Jan. 22).

UM physics professors are among some 1,500 scientists from 155 institutes in 36 countries working with Fermilab to build the CMS, one of the experiments preparing to take data at CERN’s Large Hadron Collider, scheduled to begin operating this summer. UM has received funding for this project since 1991 from the U.S. Department of Energy.

This final piece is a large disk, nearly 45 feet in diameter, with an asymmetrical cap on one face that fits into the central barrel of the experiment. The whole assembly weighs about 1,430 tons. It includes fragile detectors to help identify and measure the energy of particles created in LHC collisions.

“The University of Mississippi is a founding member of the CMS experiment, having built fiber optical splicers and electronic cooling boxes for the CMS Hadron Calorimeter, which sits within the large solenoidal magnet,” said Lucien Cremaldi, a UM physics professor who has been closely involved with the installation progress at CERN. Other UM professors in the Hadron Calorimeter group are Jim Reidy, Rob Kroeger, Don Summers, Breese Quinn, Romulus Godang and David Sanders.

“We have been building the CMS detector for nearly a decade, and now we’re 99.8 percent done,” said Fermilab physicist Dan Green, construction project manager for U.S. CMS and chair-elect of the collaboration board. “The first collisions are just around the corner.”

CMS is the first experiment of its kind to be constructed above ground and then lowered, piece by piece, into a cavern below. After eight years of work in the surface hall, the lowering of this final piece moves CMS into its final commissioning stage.

For this last large piece, scientists at the University of Wisconsin-Madison designed the large iron disks that help guide the magnetic field created by the detector’s powerful solenoid magnet.

“From the design to the construction, we were involved all the way,” said physicist Dick Loveless of the University of Wisconsin-Madison, who watched as the huge gantry crane lowered the disk. “It was phenomenal to see this last piece go down. Everything went down without excitement, which is exactly what we want.”

American universities designed and built the cathode strip chambers that are bolted onto the disks. These chambers accurately track muons, the heavier versions of electrons that indicate interesting collisions. U.S. funding also contributed to the plastic scintillating layers and all the electronics in the hadron calorimeter, part of which is the “nose” of the disk that absorbs and measures energies of all particles flying through the detector.

From shedding light on dark matter to searching for extra dimensions of space, experiments at the LHC promise to unlock some of the deepest mysteries of the universe.

“This is a very exciting time for physics,” said CMS spokesman Tejinder Virdee. “The LHC is poised to take us to a new level of understanding our universe.”

Photos and a video of the descent are available at

For photos and graphics of the Compact Muon Solenoid Hadron Calorimeter or Pixel Detector, visit