Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 1 ATLAS FCal Upgrade for sLHC: Modifications to the Calorimeter Cryogenic System a Preliminary Study (cf. Eng.Note: ATL-AE-EN-0017) ATLAS FCal Upgrade for sLHC: Modifications to the Calorimeter Cryogenic System a Preliminary Study (cf. Eng.Note: ATL-AE-EN-0017)

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 2 Cool-down time of one end-cap from room temperature down to 90 K is about 9 weeks Cryo system designed to cool-down one cryostat at a time  Optimize scheduling  modify cryo system to be able to cool- down both end-caps in parallel How to cool-down both end-caps in parallel? (1)

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre bar End-cap LAr Tanks LN 2 tank LN 2 pump Expansion vessel 1.25 bar 5.3 bar Barrel End-Caps LN 2 phase separator Cooling principles, a reminder How to cool-down both end-caps in parallel? (2)  Procedures : 1.Rinsing cycles 2.Gas cooling: forced convection of GN 2 in heat exchangers inlet T decreased on a ramp 3.Liquid cooling: circulation of vaporizing LN 2 4.Filling: Condensing of argon Cool-down rate limited by an interlock triggered by the cooling criteria  Cooling criteria:∆T must be kept within strict limits to avoid excessive stresses or displacements (< 6…45 K)

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 4 How to cool-down both end-caps in parallel? (3) Limitations of the existing cryogenic system and proposed modifications  Nitrogen flow necessary in gas & liquid cooling phases exceeds design flow of: –The water heater used to warm-up the gas to be vented above ground –The water evaporator used to vaporize liquid for the gas cooling phase –The electrical heater used to control the nitrogen gas temperature  The distribution valve and some foam insulated piping has to be replaced to accommodate these changes.  The stand-alone computer station and associated PVSS software used to trigger the interlock is obsolete and need to be re-built and integrated in DCS To be replaced

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 5 How to warm-up both end-caps in parallel? As for the cool-down sequence, the warm-up time of one end-cap to room temperature being about 8 weeks, in order to optimize the scheduling of the FCal sLHC upgrade tasks it may be required to warm-up both end-caps in parallel.  The same PVSS software as for the cool-down sequence is used leading to the same requirement to rebuilt this system.  No other cryogenics hardware modification is in principle required.

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 6 How to bring extra cooling power to the FCal? (1) At sLHC 400 W to 800 W additional beam induced heat load expected in the FCal detector  argon bubbling ? Absence of detailed information about cooling requirements for the new FCal  only preliminary feasibility description of the modifications which would be required to the existing cryogenic system How to bring an extra cooling loop to the Fcal? 1. Option 1: 2 FCal extra cooling loops coupled to the existing heat exchangers  insert one FCal cooling loop in series to each of the existing heat exchangers, sticking to the same pipe diameter (20/22 mm) so as to preserve the symmetry of these heat exchangers, to be able to control the flow through them and to limit the pressure drop.  going to a smaller pipe diameter in the FCal volume would require careful study to ensure that enough flow can be passed through the heat exchangers.

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 7 Pipes routed from bayonets to FCal small cover through vacuum space on cryostat cold cover surface How to bring extra cooling power to the FCal? (2) Clearance between cold and warm cover is 42 mm, superinsulation thickness is approximatively 12 mm which leaves about 30 mm to route the pipes along the cold cover and final 8 mm clearance between superinsulation and warm cover. Possible place to insert new cooling loop in series with existing piping LN2 bayonet transition through vacuum space heat exchanger return

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 8 How to bring extra cooling power to the FCal? (3) Clearance is too small to route the piping. Can the design of the new FCal cold cover be adjusted to allow routing of the pipes? 4 SS pipes have to go through the FCal aluminum cold cover via bi-metallic transitions to be included in new FCal cold cover design  detailed study required Bi-metallic transition used for the existing LN2 heat exchangers through the cryostat cold shell FCal cold cover

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 9 How to bring extra cooling power to the FCal? (4) Theoretical clearance of 22mm, 12 mm superinsulation  routing not possible unless a local groove can be machined in the warm cover Large omega weld details

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 10 How to bring extra cooling power to the FCal? (5) 2. Option 2: 1 FCal dedicated cooling loop Adding a dedicated cooling loop to the FCal, which could be controlled independently from the existing heat exchangers would require much heavier interventions:  Manufacturing and installation of a new “heat-echangers regulation valve box” (1/4VBN8)  Manufacturing and installation in the ATLAS chains of 2 new flexible transfer- lines  Modification of feed-though 8 (non equipped) or of warm shell in the vicinity of the existing LN2 bayonet connections to accommodate 2 new bayonnet transitions through warm shell  Installation of 2 pipes along the cold cover in the vacuum space to be welded to bimetallic transitions prepared in the new FCal cold cover

Fcal upgrade for sLHC: Cryogenics modifications – TE-CRG/ C.Fabre 11 Modifications to the cryogenic systemPreliminary cost estimate 1. Parallel cool-down option Cool-down/warm-up interlock software: 1 project associate for 6 months CHF Modification of cryogenic hardware installation55000 CHF Manufacturing of new vent water heater15500 CHF Manufacturing of new evaporator water heater15500 CHF Manufacturing of a second GN2 electrical heater12000 CHF Installation + upgrade of existing piping and valve12000 CHF 2. Parallel warm-up option (included in the parallel cool-down option) Cool-down/warm-up interlock software: 1 project associate for 6 months CHF 3. Option 1 for FCal extra cooling loop (for both end-caps)60000 CHF For 1 end-cap: manufacturing, installation and welding of 4 compensated pipes including bimetallic transitions (manufacturing, qualification and welding to FCal cover), 100% radiographic control, tests and qualifications CHF 4. Option 2 for FCal dedicated cooling loop (for both end- caps) In progress... Summary of the modifications to the cryogenic system and associated preliminary cost estimate Nota: Cost estimate based on a very preliminary study, does not include any costing for access nor for eventual radioprotection equipment.