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Accelerator control at iThemba LABS

This project aims to develop a reliable control system for a high-intensity beam project, improving safety and reducing equipment damage. It includes control diagnostics, beam position monitoring, beam splitters, and target analysis.

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Accelerator control at iThemba LABS

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  1. Accelerator control at iThemba LABS

  2. 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

  3. 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)

  4. 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)

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. EPICS-based VDG vacuum control

  12. Improve resilience of cooling, power and network infrastructure Transformer 1 Eskom Transformer 2 UPS Diesel Generator

  13. 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

  14. Control diagnostics for high-intensity beam Target ruptures and other damage

  15. Initial analysis of damageAutoradiography of targets

  16. Simulation of target charge distribution

  17. Search for instabilities

  18. 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

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