Accelerator control at iThemba LABS
Some background
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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
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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, setpoint units, etc)
Some more history
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Control system migrated to distributed PCbased 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
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Control system migrated to distributed PCbased 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
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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
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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
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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
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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
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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
UPS
Diesel
Generator
High-intensity beam project
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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
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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