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

2B. Di Girolamo – LSC Meeting - 16 August 2013

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


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


UPDATE: Tests done with very good results


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


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


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


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


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.


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

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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