Roberto Losito - CERN
Alessandro Masi - CERN
The European Organization for Nuclear Research, more commonly known as CERN, is the world’s largest particle physics laboratory. Located on the border between France and Switzerland, CERN was founded in 1954 and serves as a research organization where scientists gather to study the building blocks of matter and the forces that hold them together.
LHC Expected to Answer Fundamental Questions about the Universe
CERN relies on machines called particle accelerators to crash beams of ions or protons either together or into other targets. These collisions release enormous amounts of energy – enough to recreate the high-energy conditions that existed during the formation of the universe. The data collected from the particle collisions in the LHC will likely provide unprecedented information about how our universe came to be and help answer such questions as why particles have mass and what is the origin of dark matter.
The LHC, which is 27 km in circumference and is buried up to 150 m underground, is capable of producing head-on collisions between particle beams traveling at close to the speed of light. To produce these collisions, the LHC sends two beams of protons or other positively charged heavy ions around the circular tunnel in opposite directions. Superconducting magnets that operate in a superfluid helium bath at just 1.9 K (-271 ºC or -456 ºF) control the trajectory of LHC beams. The total energy in each beam at full power is 350 MJ, approximately the energy in a 400-ton train traveling at 150 km/h and enough energy to melt 500 kg of copper.
Control System Reliability Critical to Safety
Because of the extremely high energy levels in the beams, reliability is critical. A beam that travels off-course can cause catastrophic damage to the collider. To prevent particles from straying from their intended paths, we are installing more than 100 devices called collimators. A collimator uses blocks of graphite or other heavy materials to absorb energetic particles out of the nominal beam core. Each collimator is controlled with NI reconfigurable I/O modules mounted in separate NI PXI chassis for redundancy for a total of 120 PXI systems. In the standard configuration, one chassis controls up to 15 stepper motors mounted on three different collimators through a 20-minute motion profile to accurately and synchronously align the graphite blocks, and a second chassis checks the real-time positioning of the same collimators. In phase II of the project, we plan to add about 60 more collimators and approximately 60 PXI systems for a total of about 200 PXI systems.
In a given collimator, both PXI chassis run LabVIEW Real-Time on the controller for reliability and LabVIEW FPGA on the reconfigurable I/O devices in the peripheral slots to perform the collimator control. We use the NI SoftMotion Development Module (no longer offered) and NI reconfigurable modules to quickly create a custom motion controller for approximately 600 stepper motors with millisecond synchronization over the 27 km of the LHC. The field-programmable gate arrays (FPGAs) on these devices give us the level of control we need. We selected the LabVIEW and PXI solution for the deployment platform due to the small size, ruggedness, and cost savings over the traditional VME and programmable logic controller-based model.
A Solution for Precise Timing, Accuracy, and Reliability
To meet strict timing, accuracy, and reliability requirements, we chose a motion control and feedback system based on reconfigurable I/O and LabVIEW FPGA. We selected a design platform that incorporated only the features we needed without adding unnecessary cost and helped us avoid creating our own software drivers to reduce the manpower required to complete the system.
The LHC began operation on September 10, 2008, whereupon a beam of accelerated protons entered the LHC's 17-mile underground tunnel and successfully completed a full lap less than an hour later, passing through each of the particle detectors spaced along the tunnel. Scientists and researchers worldwide are excited to begin uncovering the mysteries regarding the building blocks of the universe.