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Accelerator control at iThemba LABS. Some background. No formal reliability procedures Cost considerations SSC operational 24/7 Shutdown total of 2 months/year Equipment often unavailable during shutdown Want it working NOW Inadequate testing time Reliable delivery of beam. Some history. - PowerPoint PPT Presentation
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Accelerator control at iThemba LABS
Some background
• No formal reliability procedures • Cost considerations• SSC operational 24/7• Shutdown total of 2 months/year• Equipment often unavailable during shutdown• Want it working NOW• Inadequate testing time• Reliable delivery of beam
Some history
• Cyclotron control systems originally designed (late 70s) around a few mini-computers (HP 1000s running RTE)
• Control electronics and instrumentation interfaced via CAMAC
• Lab-built interactive devices (joysticks, set-point units, etc)
Some more history
• Control system migrated to distributed PC-based system in the early 90s
• Distributed memory-resident tables of control variables
• Originator node computers controlling interface electronics maintain their own control variables
• The console and other nodes requiring access to these variables link to this originator node
• Adequate diagnostic messages for debugging and more efficient fault-finding
• Communication over Ethernet LAN• Development of in-house interfaces
(SABUS)
Contributions to control system reliability
• Control system migrated to distributed PC-based system running OS/2
• If a particular node computer fails, other nodes are not affected
• Minimal preventative maintenance• All fans and filters checked, cleaned and/or
replaced during annual major shutdown• Daily archiving of control system database• Communication over Ethernet LAN• The original CSMA/CD Ethernet is a
“passive” broadcast bus which is resilient to most node failures
Contributions to control system reliability
• Development of in-house “simple” interfaces (SABUS) to control electronics
• Simple, robust, noise-immune 8-bit parallel differential bus connecting up to 15 SABUS crates per PC controller card
• Each crate contains up to 13 cards, each card controlling between 2 (e.g., power supplies) and 64 (e.g., relays) pieces of equipment
• An assortment of I/O cards developed using readily-available components
• Simple bus design allows for easier maintenance and development, easier migration to new/upgraded operating system and longevity of hardware
Contributions to control system reliability
• Design for graceful degradation• Highest level of control at the console nodes• Control can devolve down to the
instrumentation interface nodes with each having a graphical control screen for the variables originated on that node
• Enables convenient testing of variables and their associated interface electronics
• Many hardware interfaces can be switched into local mode and controlled from front panel
Improvements to control system infrastructure
• Network with 1Gb/s fibre-optic backbone to distributed managed switches
• VLAN with private IP addresses (restricted routing to campus VLAN)
• Nodes assembled from good quality components (motherboards, CPUs, RAM, disk drives, power supplies, etc)
• Adequate cooling (particularly of disk drives)• On-site stock of spares (PC components,
interface modules, etc)• Back-up clones of critical disk drives for fast
replacement following failures• Most nodes and I/O module crates powered
via individual UPSs
Current control system developments
• Migrate control system onto EPICS platform• Mature stable code• Active development in, and support from, a
number of similar international labs• Many useful utilities available in EPICS
(logging, archiving, alarming, etc.)• Run old and EPICS-based subsystems in
parallel• Retain hardware (SABUS) interfaces
EPICS migration roadmap
• Cyclotrons – all new developments on EPICS platform (for example, beam splitter control)
• Develop gateway between old table-based control variables and EPICS process variables
• Port old subsystems onto EPICS over time• Electrostatic accelerators’ controls at both lab
sites (Cape and Gauteng) have successfully migrated almost 100% to EPICS
EPICS-based VDG vacuum control
Improve resilience of cooling, power and network infrastructure
Eskom Transformer 1
Transformer 2
Diesel Generator
UPS
High-intensity beam project
• Increase 66MeV proton beam intensity up to 500µA
• New vertical beam target station to accommodate high intensities
• Tighter control required to reduce possibilities of equipment damage and other safety issues
• Flattop systems for SPC1 injector and SSC cyclotrons
• Non-destructive beam position monitors• Continuous beam position monitoring and
automatic alignment• Beam splitter to deliver beams simultaneously
to two radioisotope production targets
Control diagnostics for high-intensity beam
Target ruptures and other damage
Initial analysis of damage
Autoradiography of targets
Simulation of target charge distribution
Search for instabilities
Control diagnostics for high-intensity beam
• Urgent development of control diagnostics to increase protection
• Beam halo monitors to detect stray beam in high-energy beam line
• Real-time analysis of beam distribution on production target
• Monitoring of RF systems for instabilities