1. Failure analysis experience at TLS Yi Chih Liu 15 April ARW 2013

2. Outline Introduction Motivation Some examples Explanation and conclusion

3. Introduction Taiwan Light Source (TLS) is 3rd generation synchrotron light source 361 ± 0.5mA top-up mode operation, injection period is one minute

4. Background information The schedule is regular. A routine system check and study time is arranged per week. We have two weekly meeting on Tuesday morning and on Friday morning. The on-duty operator should prepare a half weekly report of machine operation.

5. Motivation

6. What happened in 2000

7. Failure analysis for the unknown beam trips Phenomena : operator heard click voice from the racks in the control room when beam trip occurred Possible reason : related to voltage drop event Could not find out the subsystem related to the voltage drop event A faulty relay of RF master clock saw a small voltage drop, a faulty UPS could not block the small voltage drop, auto-shutdown and auto-start instantaneously. The click voice was resulted from power off/on of RF master clock We suffered this kind of failure in 2000

8. Some examples Make failure analysis easier Failure and preventive maintenance Find out the aged component early

9. Example 1

10. Determine whether SRF fault was SRF interlock sum signal RF transmitted power RF reversed power activated SRF interlock Beam trip occurred due to RF voltage off Tuner angle Tuner phase Machine parameters

11. SRF trip was caused by fast change in tuning angle 50 ms RF interlock sum RF forward power RF transmitted power RF reversed power Beam current Cavity harmonic current Tuner angle Tuner phase

12. Example 2

13. R61QPS2 cable connector was broken The broken connectorAfter fixing the connector another abnormal connector The normal connector Failure and preventive maintenance

14. Before crimpingAfter crimping normalworsenormal 〜 45 ℃ 35 ℃〜 40 ℃〜 70 ℃〜 35 ℃ 〜 25 ℃〜 35 ℃〜 25 ℃ The temperature distribution of dipole cable after crimping the terminals Preventive maintenance

15. Example 3

16. Observed abnormal beam instability

17. Find out the correlation (current ripple of Q4 power supply)

18. Aged voltage regulator

19. Explanation and conclusion

20. Machine shutdown Machine shutdown JanFebMarAprMayJunJulAugSepOctNovDec User Time User time Beam instability related problem during injection period Two frontend emergence stop events Booster problems : bumper3, potential transformer of #6 dipole, ungrounded white circuit, Septum’s water leaking problem of inside Swagelok SRF tuner phase oscillation (20 Hz) related to GHe pressure variation of SW6 Wrong BPMs synchronization rate (2 Hz ) Kick 3 misfired R2IASW & R4IASW related problems after a voltage sag Unknown orbit change and beam instability problem Q4 power supply Current ripple problem of Q4 power supply Radiation secure interlock problem 2012 TPS civil construction

21. Add second bunch-by-bunch transverse feedback loop to treat beam instability during injection

22. Explanation Observed the major problem (28) in 2011 It got worse and worse (39) in 2012

23. The major problem in 2012 Machine shutdown Machine shutdown JanFebMarAprMayJunJulAugSepOctNovDec User Time User time An insufficient margin of transverse bunch-by-bunch feedback system arose from stronger beam instability excited by mismatched injection scheme, the situation was enhanced after the replacing k1 pulser (January), became worse when a signal cable was broken. The same situation happened again after replacing k3 (September) pulser and became worse when a power amplifier failed (insufficient output power) BeforeNow

24. Conclusion The motivation shows how important to use diagnostics tool more effectively and efficiently We try to train the operators to have capability to find out the failures via preparation and presentation the weekly report The more answers we try to find, the more questions we tend to find We need many eyes to take care our machine

25. Thank you for your attention