LHC operators in the CERN Control Centre on March 30, 2010, the day of the first collisions of protons at 7 TeV. Image copyright CERN.
The Large Hadron Collider is finally up and running, colliding billions of protons at seven tera electronvolts in the center of the LHC's four major particle detectors. If you happened to peek into the control room for CERN's accelerators--called the CERN Control Centre, or CCC--you would see activity twenty-four hours a day, seven days a week, as scientists and engineers study computer monitors and discuss the status of the collider. But what exactly do the LHC's operators do to get the collider up and running, and keep it that way?
LHC operators are responsible for running the world's largest particle accelerator, ensuring that all of the equipment on the seventeen-mile ring works in synchrony. The operators include machine coordinators, engineers in charge, and teams of experts who specialize in different accelerator subsystems.
Twice a day, the machine coordinator leads an informational meeting to update operators on the status of the LHC and outline the tasks at hand for operators on shift. Depending on the mode of operation, whether preparing for particle beams or colliding particles, the tasks will vary.
Once the meeting has concluded, the engineer in charge takes over directs activity accordingly. The engineer in charge sees to it that the LHC is prepared for whatever measurement or test needs to be run, then hands the machine to the specialists to conduct their studies.
The engineer in charge is also responsible for the safety of any personnel who need to work on machinery underground while the LHC is running. This procedure, referred to as an access, involves several safety procedures that temporarily halt the ongoing run. For a technical fix requiring ten minutes in the LHC tunnel, the entire access process can easily require four hours.
Experts specialize in monitoring each LHC subystem. Specialists study more than 9000 magnets, the systems in place to protect them, and the cryogenics that keep the magnets cool, as well as a range of other systems that control how particles move through the accelerator. Their tests can take hours or minutes depending on the condition of the accelerator. Testing that the beam can be injected into the accelerator, for example, may require only minutes. By contrast, studying the radio frequency, which regulates the spacing of bunches of particles in the beam, could take eight to ten hours.
All of the LHC operators rely on software that monitors, measures, and activates every aspect of the accelerator. Specialized applications are used for everything from injecting the first bunch of particles through ejection of beams out of the LHC, and for all of the fine-tuning in between.
“The most difficult part is knowing all of the software applications,” says engineer in charge Mirko Pojer.
Right now, operators are focused on providing stable beams for experimental collisions. This operation mode is referred to as a physics run because during this period, the goal is to provide fruitful collisions for the 8000 physicists working on the LHC experiments.
Crucial to a physics run is maximizing the amount of time that the accelerator has stable beam. Beam is declared stable when all of the conditions are configured so that beams can run through the accelerator and collider at the target energy level without additional interference on the part of the operators.
“The optimal configuration and lifetime for stable beam during collisions is something that we don’t yet know, and won't until we have the entire machine running in synchrony for a bit,” explains engineer in charge Stephano Redaeli.
Operators want to optimize this hands-off period so that experiments can receive the greatest number of collisions during the time that beam is circulating. In the weeks and months ahead, operators will be learning how to provide the best settings possible to provide LHC experiments with the data they need to investigate the universe’s mysteries.
by Daisy Yuhas
