Based on 2+2 Roman Pot Stations on each side of ATLAS at ~ 240 m from the Interaction Point Aim in...
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Transcript of Based on 2+2 Roman Pot Stations on each side of ATLAS at ~ 240 m from the Interaction Point Aim in...
ATLAS – ALFAECRs
Beniamino Di GirolamoWith slides from Sune
Jakobsen
LSC Meeting16 August 2013
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Based on 2+2 Roman Pot Stations on each side of ATLAS at ~ 240 m from the Interaction Point
Aim in Run 2 at measuring the total cross section and absolute luminosity at full LHC energy
The measurement is based on elastically scattered particles at very small angles and for the ultimate performance it requires a very high b* optics (~2.6 km) But this needs the installation of water cooled cables scheduled
to be installed in 2015 winter stop or earlier if possible In the meanwhile the measurement, with lower precision, can be
done OR knowing the optics to extreme details (difficult) AND/OR by using the local angle measurement (one of the ECRs)
ALFA Detector
The ATLAS ALFA Detector prepared two ECRs LHC-XRP-EC-0008: Upgrade of the ATLAS/ALFA
Roman Pots Concerning impedance improvements to contrast the
heating from wake field and limitations imposed to LHC Circulated and approved after the requested
modifications LHC-XRP-something: Moving ATLAS/ALFA RP Stations
Being put om EDMS for circulation
Two ECRs
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Starting in 2011 the ALFA detectors have suffered increasing temperature with increasing luminosity
We need to correct this to allow smooth LHC operations at higher luminosity after LS1 and the survival of the detector
This ECR illustrates the measures to upgrade the Roman Pots to minimize impedance (always good) and therefore the heating of the Pots that would induce damages to the (not cooled) scintillating fibre detectors
LHC-XRP-EC-0008
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UPDATE: Tests done with very good results
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Additional measures are being implemented with heat spreaders inside the Pots and provisions for possible extrenal cooling if all measures won’t be enough (and if LHC outperforms)
Additional measures
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The document is in approved state in EDMS A second version with all comments responses is
being uploaded Main risks
Schedule: pointed out by Katy and addressed Not readiness and catastrophic scenario pointed out by
Beniamino: replacement chambers with supports are in hand Other mitigations: a spare vacuum chamber has been
ordered in case of issues; An external cooling system is being investigated if the simulations and the lab measurement would have been too optimistic
All the stations are in lab, being reworked and they have a precise rendez-vous with TE/VSC to be requalified prior to re-installation
Status
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Second ECR on station move As said earlier, without the special water cooled
cables the measurement is complicated Improvement to precision can come from a better
measurement of the scattering angle locally That entails that if stations can be moved apart
the angle is better measured with the increased lever arm
Status: being put in the system now Opinion: the first idea was too complicated, then
thanks to all EN and TE help it became a feasible one
LHC-XRP-something
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The solution has been deeply analysed and reviewed by LTEX
The best would be to have the water cooled cable installed, this is a mitigation to the lack of these cables It doesn’t cost much and it has a verified low impact
(but let’s see the results of the ECR circulation) In very simple words, the distance between the
stations is doubled and the benefit on the precision is a factor ~2.
Impact: Connection between DQRs need to be shortened:
extension were installed exactly to accommodate ALFA, now they only need to be removed. Simple (Knud D-P)
Status and impacts
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Impacts: The DJRQD box needs to go on top of DQR3, as done in
RR17: we have been told it is simple (Knud D-P) Rearrengement of beam pipes: no new pipes needed,
got ensured it is simple (Mark G) New positions needed for floor mounted cable box,
owner TE-CRG. 20 kCHF for both sides (Knud D-P) No clearance problems vs QRLs Extension (4 meters) of the ALFA cables done by
ATLAS/ALFA resources Schedule: same contraints as first ECR Catastrophic scenario: replacement chambers in hands
if stations not ready, but that is indipendent of this ECR
Impacts cont.
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The ALFA upgrade ECR is in approved state and I pushed to get the second version addressing all the comments: it will be in EDMS next week
The ALFA stations move ECR is mature on paper and it needs to go through the circulation
Concluding