Experience with Cod-Magnet
BLM Thresholds in Arcs/DS/LSS
6.10.2015, B. Auchmann, BLMTWG Meeting 22
Full List of UFO Dumps
9 arc BLM dumps without quenches
2 arc BLM dumps with quenches
1 arc quench without BLM dump
6 LSS BLM dumps without quenches
• How many dumps were unnecessary?
• How many quenches were prevented?
3
LSS UFO BLM Dumps
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•
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2x Collimation – see Alessio’s talk.
1x ALFA – see Matti’s talk.
1x IPQ (MQM), 1x IPD (MBX)
see http://indico.cern.ch/e/blmtwg5
•
IPQ: dynamic orbit-bump scenario since UFO thresholds
would be “excessively high”.
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•
•
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MQYs got 3x AdHoc correction to take into account operational experience with
MKI UFOs.
IPD: UFO at 0-m-location since otherwise thresholds
would be “excessively high”.
Pending collimation analysis – all other LSS dumps were
unnecessary.
MF from 0.1 to 0.333 could be a short-term mitigation.
(_INJ, _RC, _MF families require special attention).
Permanently, a low-RS AdHoc-correction should be implemented.
4
Arc and DS BLM Dumps
•
•
1x dump on empty cryostat – to be avoided!
All other 9 dumps on monitors that were set
for the arc UFO scenario.
5
Is the model consistent with data?
•
In all but one case, the FLUKA model confirms that
based on the PM data we should not have quenched.
6
BLMBI.19R2.B0T10_MBB-MBA
Did the dumps avoid quenches?
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Were some beam-dumps efficient in interrupting the loss event and
avoiding a quench?
Example: 16.9.15, 14:29:42, BLMBI.19R2.B0T10_MBB-MBA.
B2 event with VERY low sensitivity of neighboring BLMs.
Signal/Thres 124%. Sensitivity ~150% of min. used for threshold.
Dump occurred AFTER the UFO event!
7
Preliminary study of all dumps
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•
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Out of 9 Arc/DS dumps, only 1 appears to have the UFO losses
significantly cut short by BLM-triggered beam dump (extra slides).
BLM thresholds had nothing to do with the fact we
did not quench.
The fact that we so far only quenched in low-sensitivity spots
may be low-statistics artefact or explainable by FLUKA energy
deposition simulation.
Quench UFO locations.
8
Next steps?
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Avoidance of dumps in LSS via threshold
changes.
•
•
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Implementation unlikely for remaining 3 weeks
of proton physics.
MF increase? Many families (injection)
concerned!
Gather more statistics on Arc/DS thresholds.
•
•
Increase MF from 0.333 to 0.5 (50% threshold
increase) to see if quenches are more likely?
Needs to pass through LMC. Could be done
next week and tried out in last 1 ½ weeks.
9
Extra Slides
10
FLUKA Energy Deposition
FLUKA model by A. Lechner et al.
11
15.8.15, 00:56:49, 2nd UFO BIQ
Reached 190% of threshold
12
1.10.15, 16:00:47,
rd
3
UFO BIQ
Reached 140% of threshold
13
13.7.15, 21:27:43
14
20.7.15, 1:23:25
15
20.7.15, 4:26:39
16
16.9.15, 14:29:42
17
23.8.15, 19:16:04, 420% of thres.
18
17.9.15, 15:06:34
19
20.9.15, 21:21:28
20
26.9.15, 1:2:16 – extra short event
21
4.10.15, 22:10:17
22
Recovery Times 26.9.-2.10.15
23
Recovery Times 15.8.15
24
Recovery Times 14.7.15
25