The Diagnosis of Event Timing System in SuperKEKB Linac
1,2†
22334
D. Wang, M. Satoh , K. Furukawa , T. Kudou , S. Kusano ,Y. Iitsuka
1 SOKENDAI, Kanagawa 240-0193, Japan,
3 Mitsubishi Electric System & Service Co., Ltd, Ibaraki, Japan,

2 KEK, Ibaraki 305-0801, Japan,
4 East Japan Institute of Technology Co., Ltd, Ibaraki, Japan

Introduction
We introduced MRF event timing system in injector linac in SuperKEKB tosatisfy our demands. The event timing system is utilized to distribute high-level
precise timing signals and accompanying control instructions to synchronize
different subsystems and machines. EVG generates beam pulse pattern 50Hz
which contains several event codes while EVR receives them. The Event rate is114.24 MHz thus the minimal event time interval is about 9 ns. To certain thatevents are consistent between EVG and EVR, recording them one by one isessentially needed. Owing to some hardware and network restrictions it isdifficult to continuously send every event by EVR through EPICS Chanel
Access. An EVR based events diagnostic system is thus developed by modifying
the device support of some records as well as EVR driver mrfioc2 to send theevent codes thus comparing the received event codes with the beam-patterncontrol orders from beam operation and detecting the event timing interval
fault as well as providing a logging system of persistent event data. Then, we areable to locate the fault, analyze the data, fix bugs or replace hardware andresume accelerator operation quickly.

Event Log System•

32-bit wide FIFO memory (8-bit
event code and 24-bit timestamp).

•EPICS 3.15.5•

VxWorks 6.8•More than 300 records•

Self-defined waveform record,updated every 5 seconds•

Python 3.7 CA Client ( pyepics-3.3.3)• MVME5500 CPU frequency is 1
GHz, by contrast, the minimal
interval between linac event code is9 ns.
• VxWorks clock tick is 1000
• i.e. scan-5 task delay is 4.579 second.

CPU burden is too heavy !

Scan task delay is very high.

Event Based Timing Control System

Waveform data lost about 1000 times in one month owing to scan task delayupgrade

SuperKEKB Accelerator

Low-level system

No log system data lost error occurs !

•Lower MVME CPU burden.

•Only some EVR configuration
records and event code I/O interrupt
records are retained.

•Mrfioc2 module is modified.

•Using binary format to transit eventand timestamp•

About 429 MB data every day.

•Python analyzing program will checkthe log as well as sending email everyday (using crontab)

Results•••••

Simultaneous top-up injection for 5 independent rings.
Pulse-to-Pulse Modulation (PPM) every 20 ms (2 ms width of fluctuation).
(SKB e-/e+, e+ damping ring, PF, PF-AR) w/ different beam energies.
Beam pattern buffer length can be 2 to 500 (40 ms to 10 seconds).
More than 10 events are transferred every pulse.

Abnormal beam mode interval information.

• Event based system (EVG and EVR)•

256 Event codes, one event code/cycle (7 ns - 20 ns or 50 MHz to 142 MHz)• 114.24 MHz is used in SuperKEKB Linac.
• Event stream based on 8B10B encoding• Abnormal beam pulse interval was noticed during operation occasionally.
• Some devices like klystron will be triggered twice during 20 ms.

• Event log system is needed.

OutlookIn the near future, after the SuperKEKB injector linac operate on October, much more
event code data will be saved and analyzed. Subsequently, we hope to utilize some thefeature extraction algorithm to figure out the reason of abnormal beam mode intervals
with the help of these event code timestamp information.