The CANbus nodes were designed and developed by ATLAS in collaboration with the National Institute for Nuclear Physics and High Energy Physics in Amsterdam and the Petersburg Nuclear Physics Institute. Referred to by the researchers as Embedded Local Monitoring Boards (ELMBs), Kvaser worked with ATLAS staff to optimise the PCICanx boards to suit the ELMBs needs.
Asked why Kvaser’s boards were chosen, Dr Burckhart, in charge of the ATLAS Detector Control System (DCS) project at the time said:
Among the physical requirements determining CERN’s choice of a CAN interface board was that each port would need an independent buffer and be independently controlled (so resetting one port wouldn’t affect another). From a software perspective, it was necessary to support Windows and Linux, and that a simple and intuitive API was needed.
confirmed Dr. Stefan Schlenker, now responsible for the ATLAS detector controls at CERN. Dr. Schlenker took over from Dr. Helfried Burckhart, who led the specification of the system. As Dr Burckhart explained, CAN was an automatic choice:
In 2013 and 2014, during CERN’s first long shutdown, the control system was updated as it was becoming more difficult to find PCI-based servers, and it was necessary to increase CAN port density. ATLAS moved to rack-mounted CAN to USB interfaces, with two USB ports serving 16 CAN ports.
As speeds continue to increase within the LHC, so the detector control system (DCS) must evolve too. Whilst no major control system changes are planned during CERN’s second long shutdown (2020/2021), with many parts of the detector programmed for renewal during the next shutdown in 2025 – in particular, a move to an all silicon inner detector – more fundamental updates to the control system will be needed at that time. The original DCS monitored some 200,000 slowly changing parameters, such as voltage, current, temperature and pressure. Beyond 2024, the volume of data increases to millions of readouts per few seconds, so a move to CAN-to-Ethernet cards is scheduled for that time.