CANopen in high-energy physics
Source: CAN Newsletter June 2008
This year, European scientists working for CERN will start high-energy physics experiments hoping to discover among other things the Higgs particles. But nobody knows if they exist or not. For many years, engineers from all over Europe have designed and developed several detectors for the Large Hadron Collider (LHC) located close to Geneve under Switzerland and France in a depth between 50 m and 150 m. The 27-km ring tunnel connects several experiments. The largest is the Atlas detector (46-m length and 25‑m height). It is installed in a cavern that has place for four Notre Dame cathedrals. The Detector Control System (DCS) is based partly on CANopen network systems.
The Atlas experiment consists of three detectors, the inner tracker, the calorimeter, and the muon system, each of which is composed of several sub-detectors. The complexity of these detectors, containing a huge number of individual detector elements – the Pixel sub-detector alone already accounts for 60 million electronic channels – presented new challenges for the design and the implementation of the DCS. The DCS has the task to permit coherent and safe operation of Atlas and to serve as a homogenous interface to all sub-detectors and to the technical infrastructure of the experiment.
The DCS is able to bring the detector into any desired operational state, to continuously monitor and archive the operational parameters, to signal any abnormal behavior to the operator, and to allow manual or automatic actions to be taken. In order to synchronize the state of the detector with the operation of the physics data acquisition system, bi-directional communication between DCS and run control must be provided. Finally, the DCS has to handle the communication between the Atlas sub-detectors and other systems, which are controlled independently, such as the LHC accelerator, the CERN technical services, the Atlas magnets and the Detector Safety System (DSS).
