2. AOB: Adjustments to BLM Thresholds in Light of Run-2 Experience with UFOs B. Auchmann, J. Ghini, L. Grob, A. Lechner, D. Wollmann. 118 th MPP, 9.10.2015.

3. List of UFO-Related Dumps Full list on http://cern.ch/blmtwg > Run-2 UFO Events.http://cern.ch/blmtwg Non-negligible number of dumps from LSS! *… according to thresholds model. *

4. LSS Mitigation Cumulative effect of several element types needs to be addressed. ALFA – changes implemented. TCTs IPQs an IPDs Empty Cryostats 4

5. IPQs, IPDs IPQs and D2-4: Assumed scenarios are conservative wrt. UFO losses. (For details see http://indico.cern.ch/e/blmtwg5)http://indico.cern.ch/e/blmtwg5) Monitor factor of 0.1 is more conservative than 0.333 in Arc/DS. Proposal for short-term action: Increase the monitor factor from 0.1 to 0.333. Leave special monitor-families for injection losses unchanged. Would have prevented the observed beam dumps. D1 thresholds must remain conservative to avoid symmetric beam-induced quench. 5

6. Empty Cryostat Mitigation No risk of damage or quenches. Proposal for ion-runs (under preparation) foresees to set the monitors in question to maximum thresholds. Short-term proposal: Set empty-cryostat BLM thresholds to maximum. 6

7. Arc/DS Observations Three quenches were not prevented. However, avoiding three quenches means >20 additional unnecessary dumps. Can we, on the contrary, increase thresholds to improve availability? 7

8. Arc/DS Observations Out of 10 dumps without quench: 8 were too late to significantly shorten the UFO. 1 may have shortened the UFO but there was no risk of quenching. 1 potentially avoided a quench. 8 BLM Signal @ UFO location 15 L2 BLM Signal @ dump absorber 4L6 Synchronization accurate to 40-80 µs (C. Zamantzas priv. comm.) 160 µs 20.7.15, 04:26:39, Beam 1

9. Arc/DS Observations Counter-example: 3 rd UFO-induced quench. Loss-event clearly cut short – but too late to prevent the quench. 9 BLM Signal @ UFO location 20L3 BLM Signal @ dump absorber 4R6 Synchronization accurate to 40-80 µs (C. Zamantzas priv. comm.) 1.10.15, 16:00:47, Beam 2

10. Arc/DS Mitigation Down time due to a quench is 3-4 times longer than for a protection dump without quench. Proposal for short-term action: Increase of monitor factor from 0.333 to 0.5 would have prevented 7-8 out of 10 beam dumps. would have increased the probability to quench in 1 case. 10

11. Summary of Proposals IPQ, IPD (except B1): Monitor factor from 0.1 to 0.333 for all but injection families. Empty cryostat: Set thresholds to maximum. TCTs: adjust fast RSs. Arc/DS: Monitor factor from 0.333 to 0.5. MP3 has give green light for cold-magnet threshold increase. If unsuccessful, changes will be rolled back after proton run. 11

12. 12 Extra Slides

13. BLM Response and Quench Locations 13 Quench UFO locations. FLUKA model by A. Lechner et al.

14. Energy Deposition 14 FLUKA model by A. Lechner et al.

15. 15.8.15, 00:56:49, 2 nd UFO BIQ 15 Reached 190% of threshold 86 bunches

16. 1.10.15, 16:00:47, 3 rd UFO BIQ 16 Reached 140% of threshold

17. 13.7.15, 21:27:43 17

18. 20.7.15, 1:23:25 18

19. 20.7.15, 4:26:39 19

20. 16.9.15, 14:29:42 20

21. 23.8.15, 19:16:04, 420% of thres. 21 Shortened the event and potentially avoided a quench.

22. 17.9.15, 15:06:34 22

23. 20.9.15, 21:21:28 23

24. 26.9.15, 1:2:16 – extra short event 24 Potentially shortened the event. No risk of quenching (high BLM sensitivity in the UFO location). (not recorded by UFO buster!)

25. 4.10.15, 22:10:17 25

26. 11.10.15, 01:32:39 – very short event 26 Probably did not significantly shorten event. (B2 dumped R6, UFO is R7, i.e., at least first 40 µs of dump are inconsequential for UFO location)

27. Recovery Times 26.9.-2.10.15 27

28. Recovery Times 15.8.15 28

29. Recovery Times 14.7.15 29