1. SLS Timing Master
Timo Korhonen, PSI

2. Outline -What is a “Master Pattern Generator” -SLS operation
-Possibilities of the SLS/Diamond-type system

3. 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

4. SLS Operation
Single type of operation: inject from linac to booster to storage ring
Sequence of events is always the same; pre-programmed with EPICS records
Slow changes of mode
Top-up, parasitic linac measurements, booster tuning
Implemented with EPICS tools, operation synchronized with timing system

5. 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

6. 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)

7. 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?

8. 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)

9. 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.)