SLS Timing Master
Timo Korhonen, PSI
Outline
-What is a “Master Pattern Generator”
-SLS operation
-Possibilities of the SLS/Diamond-type system
Master Pattern Generator
•generates and distributes data to modify beam
operation pulse-by-pulse
–typically a bit pattern to tell what kind of beam is
coming next, where it should go and what devices
should trigger in the next cycle
•in (ring) light sources with a single-purpose
injector this is usually not (very much) an
issue
–concept is unknown to many
SLS Operation
• Single type of operation: inject from linac to
booster to storage ring
– Sequence of events is always the same; preprogrammed with EPICS records
• Slow changes of mode
– Top-up, parasitic linac measurements, booster
tuning
– Implemented with EPICS tools, operation
synchronized with timing system
SLS Operation
• Example implementation: top-up
– When injector is idle, e-gun, kickers and magnet ramps are turned
off
– Ramping starts a few cycles before injection (to warm up the
magnets), kickers also a couple of cycles before injection
– Bucket numbers to fill are sent (well in) advance to the related
ioc’s (as waveforms)
– The cycle is started by master timing ioc sending an “topup-on”
event (start e-gun triggers), and stopped with another event.
• No other data is sent with the events
– With our cycle time (3 Hz), sending the required data in advance
(to not to rely on network response time) and a bit of organization
the system works fine
– No big safety issues
SLS Operation
• Other sequencing has no big real-time
requirements
– Measurements with linac between injection cycles:
drive in a screen monitor, turn on the data acquisition
(camera triggers). Reverse procedure when injector
needed
• Real-time data transmission was not a (big) issue
for us
– we had to learn the limitations in CA response, though
(like sending a list of bucket numbers in advance)
Pattern generator using the event
system
• For other facilities, the real-time
requirements are more strict
– CA-based approach would not be enough
• Can the (Diamond) event system be used in
a master pattern generator
– What modifications would need to be done?
– What kind of software tools would be needed?
Possibilities of real-time data
transfer with the event system
• The APS event system has 8-bit frames for events. For
SLS, we (mainly for technical reasons) decided to make
the frames 16-bit.
– However, retained the 8-bit wide event codes for SW compatibility
• The remaining 8 bits are “free” (although we found use for
them – distributing clock signals
– By modifying the firmware they can be used for data transfer
• Also the frame size could be changed (64, 128, 256,…bits)
– This implies a change in the frame rate (events per second)
• The Diamond event system cards have (for Diamond
specs) a frame rate of 125 MHz (with 16-bit events)
Conclusions
• The hardware should have enough capacity (128
MB/s using the idle channel)
– Would be good to agree on the data transfer method to
avoid too many firmware versions and too many EPICS
support versions
• What kind of software tools are necessary to
generate the patterns?
• For a slow-cycling light source with a dedicated
injector, the need is not immediate (but might be,
depending on the outcome.)