Inner Pixel Cooling Manifold: Meeting the Cooling Requirements for ATLAS ITk Detector

1. Inner Pixel Cooling Manifold Marco Oriunno, SLAC Eugene, OR 9/4/2019 Pedro Lopez Macia, CERN

2. Cooling requirements • Cooling Manifold • Local Supports evaporators

3. ATLAS ITk cooling requirements ITk CO2 Cooling system Specifications Review Paris, November 2018 https://indico.cern.ch/event/759197/ EDMS N. 2044760 : “Technical Specification ATLAS ITk detector specification for cooling system design”

4. Cooling system requirements: Operation conditions • Cold operation: This is the cooling operation during data-taking. The cooling temperature set-point can be selected • Cold temperature during shutdowns: During shutdowns the ITk might need to be kept cold, without a heat load, to prevent detrimental annealing effects. The cooling temperature set point can be selected • Beam pipe bake-out: During beam-pipe bake-outs the heat on the inner pixel detectors from the bake-out (with the front-end electronics turned off) must be removed under all circumstances. Adequate redundancy needs to be implemented to maintain cooling even incase of a fault.

5. Sections of the ITk CO2 cooling

6. On-detector manifolding The detector is fed with flexible cooling lines towards the detector connections in PP1 Each flex line has a capacity of 5 kW and the cooling lines from the detector must be grouped such that the total power for the lines in the group is around 5 kW The flow restriction (capillary or orifice) must be placed after the last inlet manifold level. No splitting after the flow restriction is allowed. It is assumed that there are no restrictions with orifices smaller than 200 μm. If so, the filtering scheme must be reconsidered.

7. PXI splitter box and Warm Nose hex

8. Evaporation temperature requirements 4 3 4 3 The minimum stable temperature demonstrate to date with the Baby-DEMO is -47°C

9. On-Detector Cooilng Requirements • Maximum grouping of power per internal manifold is 5 kW (flex line design capacity) • Minimum evaporation temperature at PP1 outlet (specific location depends on sub-system geometry): • Pixel detector: -40°C • Design mass flow rate per evaporator: 1 g/s per 100 W • Maximum vapour quality at evaporator outlet: 0.35 • Design pressure drop over on-detector cooling lines: 10 bar • In capillary: 8 bar < ∆pcap • In evaporator and return lines: • Pixel: ∆pevap+RL < 2.0 bar ∆T < 5°C

10. Internal Segmentation Inner Pixel Heat loads [@ 2’000 fb-1] Inner Pixel manifold segmentation < 5 kW/flex line

11. CoBra introduction • MATLAB code predicting thermal behavior of long cooling branches • Pressure drop and HTC calculation for single and branched cooling loops in both single phase and 2-phase flow • CO2 two-phase correlations for ∆p and HTC are based on CO2 flow patterns model • Develop at NIKHEF and used by the CERN-DT group for the ITk sub-detectors (Pedro Macia Lopez is actually running the simulations for the Inner Pixel).

12. Single Loop Simulations

13. Mass Flux Mass Flux = mass flow/cross section

15. Single Loop Simulations (L1, R1, R0/1) • The simulations show that the large evaporator diameters ID2.1 or ID1.995 are OK for the L1 stave, the R1 ring and the Coupled Ring • The results are summarized in the spare slides

16. Multi-branched Simulations

17. Multi-branched Two phase Flow – Golden Rules Golden Rule#1 (requirement) :The flow restriction (capillary or orifice) must be placed after the last inlet manifold level. No manifolding after the flow restriction is allowed. Mass flow in paralleled loops need to be balanced Golden Rule#2 : The capillary is supposed to work adiabatically, i.e. should not pick up heat from environment, like adjacent cables Golden Rule#3 : Orifices clog and are strongly discouraged in not accessible area Golden Rule#4 : Capillaries below 0.5 m are thermally unstable, strong discouraged For the Inner Pixel, Single, Long, adiabatic capillaries on each evaporators have large impact on the routing of the service, already very complex

18. Evaporators regrouping - Barrel Option 1 Common Return Line Capillaries High Pressure PP1 Common Return Line High Pressure PP1 Capillaries Common Return Line Capillaries Option 2

22. Summary • The ATLAS ITk cooling system put clear and tight requirements on the Inner Pixel • We need to work our way out thorough simulations and prototypes, proving that we can meet them before we commit to the final construction. • The preliminary simulations with CoBra for the single branch loop show not optimized performances of large ID evaporators for the L0 staves and very likely also for the R0 rings. Need a trade off of the local performance optimization vs the manifold performance and complexity • The regrouping of multiple evaporators with single capillaries may help the integration of the services but we need more simulations to design a well balanced system • The return lines with ID5 mm and ID6 mm for the Half Barrel and the Quarter Shell respectively, meet the requirements but without margin. They an impact on the routing of the services

23. Going Forward • The integration of the cooling manifolds is strongly interlinked to PP0 interconnections and Type-1 service routing, both design are in flow with still many unresolved issues • The design of capillaries, evaporators, flow splitters, E-breaks and G&S considerations cannot be parallel developments need to be be blended in at the earliest stage. • An optimized cooling manifold is useful only if it can be built : orbital welding, assembly procedures and testing procedures

24. EXTRA SLIDES

31. Warm nose concept With warm nose HX Without warm nose HX Warm nose circuit concept