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98th BLM Thresholds Meeting (LESS, IR7 injection losses)
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Europe/Zurich
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Description
Scientific Secretary: Sara Morales Vigo
98th BLM Thresholds Meeting
Participants: C.Hernalsteens, M.Himmerlich, A.Lechner, D.Mirarchi, S.Morales, H.Neupert, A.Reascos, B.Salvachua, N.Triantafyllou, J.Wenninger, D.Wollmann, M.Zerlauth
- Installation of new monitors in IR6 - Sara Morales Vigo
- Installation of a short LESS treated vacuum chamber in IR6 to mitigate electron cloud formation (only Beam 1, Beam 2 cleaned Cu tube for reference)
- Will it generate for UFOs? This would increase the risk of premature beam dumps and magnet quenches
- Proposal to add two more beam loss monitors downstream the LESS treated beam pipe to help identify where the UFOs are originated
- Described on ECR LHC-VC-EC-003
- LESS treated beam pipe downstream Q5R6
- Only one BLM monitoring B1 losses (BLMQI.05R6.B1E30_MQY) was there before the YETS 23/24, two additional ionizaction chambers (IC) and one diamond BLM (dBLM) have been installed
- First additional IC (BLMEI.05R6.B1E20_LESS) installed on a movable support 1.3 m downstream the already existing one, second IC (BLMEI.05R6.B1E20_LESS) and dBLM (BLMED.05R6.B1E20_LESS) installed on another movable support 1.5 m downstream the first movable support. dBLM under the beam pipes.
- No other BLMs in the drift space, first one downstream the DFB
- The new detectors are already on the databases. The ICs will be assigned to the THRI_DRIFT family, will not be connected to the BIS (not interlocked) and will be maskable.
- Cedric asks if the dBLM data will be logged as well on the usual databases. Sara replies that it should indeed be logged following the same logic of the other dBLMs installed in IP7.
- Anton asks who will check the dBLM data. Cedric replies that this will be discussed offline with Christoph as well, but there will be a new student analyzing the data for UFOs. Belen says that we will need to discuss how to analyze this data in case these UFO events appear.
- Installation of a short LESS treated vacuum chamber in IR6 to mitigate electron cloud formation (only Beam 1, Beam 2 cleaned Cu tube for reference)
- BLM threshold changes and UFO monitoring for LESS chamber in IR6 - Anton Lechner
- How to monitor UFOs?
- Do we need changes to avoid quenches?
- Do we need changes to avoid premature dumps?
- Anton shows installation, concerned BLMs, already existing...
- UNderstand losses in terms of dust beam size
- They shouyld be smaller than 8 um in diameter
- Number of protons lost vs dust radius
- For 8um, lower than 1e6 protons, then a bit bigger it would be...
- How to monitor UFOs?
- UFO buster -> do not ned to change anything there
- Triggers if signals of at least two BLMs in ... -> can rely on three BLMs next to LESS chamber -> 1std+2 new
- Should be able to detect um dust particles, sub um would be difficult
- IMportant point: fine tune detection needed for the concerned BLMs
- (For the other chamber)-> also want to monitor UFOs here, also UFO Buster, three BLMs there, should manage to distinguish if UFO coming from B1 Or B2
- Risk of quenches by UFOs?
- First supercond magnet in MB.A8R6, 55m
- NO magnet with possibly non-conform diode up to cell 12
- FLUKA simulations performed -> would need grain diameter of at least 40-60 um, much larger than expected, risk expected to be low -> should still protect
- Markus-> comments that this 40-60 larger than any other? A says that it has been observed once, but overall... reaching that levels of losses maybe less than 3 events in all the events in all the LHC Runs
- Risk of prematyure BLM dumps?
- Three BLMs with this risk -> 1 next to LESS chamber, 1 nexy to DFB, 1 on top of interconnect...
- Estimates considering typical UFO
- First BLM -> MF = 0.333, Even with 30 um, should be ok, we could change MF if needed, a priori no dumps there
- Upstream end of dipole, assigned to DFB, thresholds to MB quench level, needs to be updated, but never limiting
- Asking if we are close to the quench level (markus), but Anton says no, thresholds implemented before start, now more info, Anton says with this values they would dump much below the quench level
- Margin to increase, very low MF too
- Holger asks about MF -> applied thresholds
- Third BLM -> likely avoid quench, but also avoiding premature beam dumps, but comes from assumptions.. cannot exclude this will prevent quench always, risk of quench should be reduced
- Proposals:
- First: no change of thresholds, in case of premature dumps increase MF
- DFB BLM (thresholds actually for dipole): risk of premature dumps, could increase MF now? reassign to another family in case of premature dumps. Jorg says why not reassigning directly? and conservative MF... Markus why it was there? Anton says this dates back to start of LHC, belen says we could have a look offline, to see reason why it was there, if no reason, best approach is to move it to correct family already, anton says something should be done.. daniel says DFB family has nothing to protect the DFB... Belen says there are BLMs but not interlocked (DFB), markus says maybe there is a reason.. old model of quench test of dipole, rest of blms of dipoles have been updated
- Last blm: no change of thresholds, but decrease MF in case of quench or if many large events. Jorg says no sure about ufo buster, could be that it ignores new BLMs, need to look at it.. anton says they should be taken into account, in the past movable have been, but wil be checked. Belen says they should be as they are part of the standard system, not yet as concentrators not restarted yet, but after that yes... cedric asks if it makes sense to set thresholds on ufo buster a bit low... jorg says we are already triggering with noise.. zerlauth asks how easy it is to change... jorg says that it is in the code.. anton would not go too low... 2xe-4, will detect um induced... zerlauth says check blms during intensity ramp up.. anton says of course...Himmer -> calculations from nominal operation conditions? any risk during scrubbing? anton says we saw but scrubbing is at injection, showers less energetic, calculations at top energy... injection ufos were never a problem, only one in RUn 2 that caused a dump, belen says it would be interesting to advance detection of ufos at injection... anton sys but not with ufo buster...
- Fast losses in IR7: new layout configuration - Belen Salvachua Ferrando
- Summarize changes during YETS to study possibilities to miitgate effect of sat of BLMs in short RS
- Recap of previous infos
- Dumps from B1 with 236bpi trains-> fast losses in RS01 reaching sat in BLMs at primary hor and skew collimators
- Problem of sensitivity of chambers, no problem of thresholds, no changes of software or hardware possible
- Observed already during the quench test, blm triggering before the 1MW
- Estimation of protons, less than a pilot, equivalent of 50J in 40us
- Saturation affects all energies
- LImits from specifications of collimators
- ONly option: reduce blm response for each monitor, to have access to top..
- Example of signals during injection
- THree that were really saturating, but many others that could saturate at some point
- Two ptions:
- Installation of transversally displaced IC in order to reduce response, check and eventually move interlock
- Replacement of SEM detectors by Little Ionization chambers for B1, B2 was already the case
- Never limited until now, with quench test and inejction losses
- Can we reduce the BLM response?
- Fluka simulations by Anton with transversal displacement
- Could only displace to position 3 because otherwise transport area (integration team)
- Installation done, ECR circulated to relevant people beforehand
- 2 IC BLM in positin 3 for TCP.C and TCP.B
- For TCLA egular BLM already i the porposed position, new installation with BLM directly on the passage wall
- Therefore, 3 additional BLMs in the wall -> very good possibility, also for maintenance of BLMs, but integration not easy
- Replacement of 10 SEMS by LICS
- Thresholds strategy
- Thresholds families for the affected ones...
- Proposal to create new families, cannot reuse because also B2 also there, suffix to be decided
- SCale correction or new response
- STart up cable connected but not BIS connected, then check during early commissioning and move interlock functionality, decide maybe with an ad-hoc meeting which we move and what response we put
- Jorg says shcedule one shift on tuesday 12 for interlock BLM tests and data for this, do they exist in databases? belen says yes, only missing reboot of concentrators
- Cedric asks 35 or 30 cm transveral displacement? Not very exact displacement, signal a bit different from Anton simulations, for the skew more or less aligned
- Daniel happy with teh BLMs on the wall, have this measurement early, maybe not needed ad-hoc, great to have MPP when officially changing interlock,
- Anton says to see if changes wrt injection at top energy, to see if scale correction or something different
- Anton says normal detectors or not? yes usual, not yellow in more radioactive areas
- Next meeting losses in IR3 second half of March...
- Daniel procedure in case of sparking RF fingers... send around email to people related
- careful not to quench the triplet...
- Put a proper strategy-> first locate, then simulations, etc
- Also experiments limiting on losses...
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