1. Fill-pattern Control System for KEKB
Eiji KIKUTANI
KEK
(Factories03, Oct SLAC)
11/21/2018
Factories03

2. Plan of talk What is the Fill Pattern Control System?
KEKB fast timing system (brief)
Architecture of the system
Software system
Summary
11/21/2018
Factories03

3. 1. Introduction What is the Fill Pattern Control System?
11/21/2018
Factories03

4. Fill Pattern is important !
Fill pattern which rf-buckets are filled with beam, while which are not ---
Fill pattern is one of the important para-meters in operating the rings, because
strength of the coupled-bunch instability is strongly depends on the fill pattern, however, …
it is practically hard to find an ideal pattern from calculations.
11/21/2018
Factories03

5. What is a “Fill Pattern control system”?
We must find the ideal filling-pattern with the trial-and-error method, it means …..
we need a fill pattern control system, which should be
operator-friendly
flexible for modification
11/21/2018
Factories03

6. Fill pattern with mod. 4-bucket
11/21/2018
Factories03

7. Structure of the fill pattern control system
fill-pattern generating mechanism +
bucket selection system
11/21/2018
Factories03

8. What is “the fill pattern generating mechanism”?
An environment for generating a suitable fill pattern easily
creates a table of rf-buckets which should be filled with beam (the fill-pattern table) from given fill pattern
11/21/2018
Factories03

9. What is “the bucket selection system”?
distributes the linac beam-pulses into the ring rf-buckets, and consequently realizes a desired fill pattern in the rings
a sub-system of the KEKB fast timing system
Real time
11/21/2018
Factories03

10. 2. KEB fast timing system
11/21/2018
Factories03

11. KEKB fast timing system
We have no damp-ing rings.
Phase relation between the linac-rf and the ring-rf should be finely controlled to main-tain the injection rate high.
11/21/2018
Factories03

12. RF freq. of the linac and the rings
Each rf-signal is obtained by frequency-multiplying the common signal of 10.38MHz
10.38MHz x 275 =2856MHz (for linac)
10.38MHz x 49 =508.9MHz (for rings)
11/21/2018
Factories03

13. 11/21/2018
Factories03

14. Conceptual Block Diagram of the KEKB fast timing system
11/21/2018
Factories03

15. Timings for the injection (to maintain good injection)
11/21/2018
Factories03

16. Method for the bucket selecting
Control the timing triggering the linac gun
the timing is controlled by delay modules named “TD4”.
11/21/2018
Factories03

17. The subrack of the Linac IOC
11/21/2018
Factories03

18. 3. Architecture
11/21/2018
Factories03

19. Architecture of the Fill Pattern Control System
Basically, system is constructed under the EPICS environment
The system consists of 3 parts.
The delay control (TD4) part, (in linac)
(Linac IOC)
the Operator-communication-part
(Op-IOC)
the Bunch-Current monitor part
(BC-IOC)
11/21/2018
Factories03

20. delay modules bunch-current monitor Central control room linac
11/21/2018
Factories03

21. Architecture of the fill pattern control system (cont.)
These are connected with a dedicated communication system with optical fiber cables
which is realized with a commercial product Shared Memory System (Advanet Company in Japan)
11/21/2018
Factories03

22. Shared Memory System http://www.advanet.co.jp
Communication Port/module
Communication System Fiber channel
Bit rate Mbit/s
# of connectable of boards in a loop (max.)
Wiring Distance between Board km (max.)
Connector SC
Size of Shared Memory Kbyte (Expandable to M/2M/4M/8Mbytes)
11/21/2018
Factories03

23. Shared Memory System (VME memory board)
11/21/2018
Factories03

24. Connection of the three IOCs
11/21/2018
Factories03

25. 4. Software
11/21/2018
Factories03

26. Software structure of the fill pattern control system
11/21/2018
Factories03

27. Software in the Op-IOC Communicates with operators
accepts the fill patterns from the built-in panel, as well as the fill pattern files
generates the fill pattern table (in Shared Memory System), in accordance with the fill pattern specified by the operator
11/21/2018
Factories03

28. Pattern generation
11/21/2018
Factories03

29. The panel for the built-in pattern generator.
11/21/2018
Factories03

30. A panel for fill pattern generation (custom)
11/21/2018
Factories03

31. Software in the Linac IOC
a Vx-Works real time task
essentially no I/O, except for the Shared Memory System
“fetch” the bucket address to be filled from the shared memory, and set the delay
Two operation modes (BCE and non-BCE)
11/21/2018
Factories03

32. Operation modes of the bucket selection system
Bunch current equalizing (BCE) mode
Compares bunch current of each bucket, and fill the beam into the bucket with smallest current (except for those near the last-filled buckets)
The comparison is done pulse to pulse (every injection trigger)
switch on/off easily
Non-BCE mode
Ad (this pulse) = Ad (last pulse) + some prime number
11/21/2018
Factories03

33. Timing shake-hands of the IOC tasks
A task in the BC-IOC is triggered by the injection triggering signal. After writing the bunch-current information into the shared memory, it generate the interrupt signal to the Linac-IOC
A task in the Linac-IOC is triggered by this interrupt signal
11/21/2018
Factories03

34. 11/21/2018
Factories03

35. Uses of the bunch-current information
Simple bunch current monitoring (relative bunch-current)
For bucket selection. Bunch Current Equalizer (BCE) is working
High bunch-current alarming
11/21/2018
Factories03

36. The bunch-current board
Bunch-current information is stored in the “memory board” a by-product of the KEKB bunch-feedback systems.
The stored information is read out by the trigger signal of the injection kicker
No averaging process
11/21/2018
Factories03

37. 11/21/2018
Factories03

38. Bunch-current detector
11/21/2018
Factories03

39. Recent improvements
For positron beam, we started use the 2-bunch acceleration in the Linac
In the positron linac, two bunches, separated by 98ns, are accelerated and injected to the ring.
It increases the injection rate of positrons by a factor ~2.
11/21/2018
Factories03

40. Two bunch acceleration in the Linac
11/21/2018
Factories03

41. Two bunch acceleration
Real-time two/single switch
Two-bunch acceleration ==> BCE off
Every 50-th pulse : single bunch acceleration ==> BCE on (equalization)
variable
11/21/2018
Factories03

42. Summary
KEKB Fill Pattern Control System is working for realizing a desired fill patterns in the rings.
The BCE technique works very well
2-bunch acceleration scheme works with a satisfactory performance
11/21/2018
Factories03