The Large Hadron Collider (LHC) is often called the atom smasher but in reality, it doesn’t smash atoms together. It is used to smash protons and lead nuclei together, but not atoms per se. But last week, things changed. The LHC was used to accelerate a lead atom with all but one of its electrons removed.
The task is far from simple but it is important to test the limits of what can be achieved with the LHC. The team hopes that by accelerating ions they can create gamma rays energetic enough to create other particles. This ambitious goal is still far into the future but the test on July 25 was a very important one.
“We’re investigating new ideas of how we could broaden the present CERN research programme and infrastructure,” Michaela Schaumann, an LHC Engineer, said in a statement. “Finding out what’s possible is the first step.”
The first test run involved 24 bunches of “atoms” being injected into a low-energy stable beam for about an hour. The team raised the beam to its maximum possible energy in the LHC and kept it stable for about two minutes before it was ejected into the system's beam dump. The second run, with just six bunches, was kept stable for two hours.
“It’s really easy to accidentally strip off the electron,” explained Schaumann. “When that happens, the nucleus crashes into the wall of the beam pipe because its charge is no longer synchronised with the LHC’s magnetic field. If too many particles go off course, the LHC automatically dumps the beam. Our main priority is to protect the LHC and its magnets.”
This gamma-ray factory would work in the following way. The atoms would be shot by a laser exciting an electron, and this electron would eventually decay back to its original orbital, re-emitting a photon. However, since the atoms are moving close to the speed of light, the emitted photons get an energy boost, causing them to become gamma rays.
The LHC smashes protons for about half the year and roughly four weeks are dedicated to atomic nuclei collisions. There have been tests with other beams, such as xenon nuclei. The Super Proton Synchrotron, which is one of the other accelerators at CERN, was previously tested using lead ion collisions like these.