1. Concept idea for the modular 2PACL system for the Atlas ITK 3 June 2015 Bart Verlaat 1

2. CO 2 cooling: the current status The last year lots of progress in CO 2 cooling development is achieved. –2 new systems for detector operation have been developed: IBL cooling system (3kW @ -35°C) => In operation CMS pixel CO2 cooling system (15 kW@ -30°C) => under commissioning –Many laboratory test units have been build: 2x Traci V1, 3x Traci V2, 4x Traci V3 up to 400W Marco 1kW CMS-TIF prototype plant 15 kW –New development lessons learned: Operation at cold temperatures < -30°C Scaling from 1kW (LHCb-Velo) to 3kW (IBL) and 15 kW (CMS) –Scaling did not give surprises. Positive experience with vacuum shielded concentric lines. Standard approach for control. Redundancy policy From the current experience and the availability of standard components a scaling towards 40kW 2PACL units should be feasible 2

3. Atlas IBL CO 2 cooling system 2-Phase Accumulator Controlled Loop (2PACL) -35’C cooling 20’C cooling Accumulator pressure lowering for cool down Pressure increase for liquefying prior to start-up Sub cooled pumped liquid Saturation temperature Sub cooled liquid margin for pump operation (>10 ‘C) Liquid cooling 2-phase cooling

4. Atlas IBL cooling system CO 2 cooling plant layout

5. Cooling plants in USA-15 5

6. Transfer line CO 2 cooling hardware in UX Junction box Vacuum system Flex linesManifold box

7. CMS Pixel Cooling System 2x 15kW @ -30 ⁰ C 7

8. CMS Pixel Cooling System 8 2 Plants with accu’s Plant interior Transfer lines

9. Cooling systems for the ITK The ITK tracker has a total power of 180 kW (TBUpdated) The largest CO2 2PACL plant build for CMS is 15kW When looking to the “standard” components (Pumps, heat exchanger, valves etc.) a system scaling up to 40kW seems possible. The current approach to the ITK cooling is a modular approach of several stand alone operating systems. Redundancy is obtained by swapping a failing plant for a spare plant Segmentation to be decided based on best segmentation logic in the detector –10x 20kW or 5x 40 kW?? Roughly 2 possibilities for segmentation –Cool per sector (Take a pie of the combined detector (End-cap + barrel, but split strip and pixel) –Cool per sub detector Is preferred as it makes it possible to operate each sub detector at different temperatures, eg a colder pixel detector. 9

10. Cooling segmentation 10 19/55 31/55 12/21 5/11 7/20 2/3 Pixel, short strop barrel, long strip barrel, end cap, services, thermal enclosure x/y => x: power at begin without safety factor. y: Power after irradiation with safety factor Detector segmentation or pie segmentation PP2 segmentation 2x5 locations PP2 is the most likely space for the junction box and manifold

11. ITK cooling history In the past the large upgrade cooling plant is discussed several times. Below an overview of some relevant talks given in upgrade meetings with links. –Thermal management working group meeting - phase II system design 30 September 2009 @ CERN https://indico.cern.ch/conferenceDisplay.py?confId=68949 Topics: alternative concept solutions –Atlas Upgrade week April 2011 @ Oxford https://indico.cern.ch/contributionDisplay.py?contribId=207&sessionId=23&confId=116547 CO2 cooling activities at CERN –Atlas Upgrade week November 2011 @ CERN https://indico.cern.ch/materialDisplay.py?contribId=79&sessionId=35&materialId=slides&confId=108365 Cooling plant segmentation Cavern fit check –Atlas Upgrade week March 2012 @ SLAC https://indico.cern.ch/contributionDisplay.py?contribId=62&sessionId=53&confId=158038 Topics: Cooling pipe sizing Component availability –ECFA High Luminosity LHC Experiments Workshop, 2 October @ Aix Les Bains http://indico.cern.ch/materialDisplay.py?contribId=27&sessionId=9&materialId=slides&confId=252045 Topics: Future look on common cooling plant development –ITK kick-off 23 January 2014 @ CERN https://indico.cern.ch/event/288081/session/3/contribution/29/material/slides/ Topics: Wrap up of status –ITK Cooling kick-off 11 December 2014 @ Cracow https://indico.cern.ch/event/353053/ Topics: Kick-off of the cooling group Due to IBL – CO2 cooling development, the discussion of the Atlas upgrade system was stalled for a while, however most presented topics in the past are still relevant. 11

12. Modular 2PACL approach A modular approach of multiple 2PACL stations is a novelty. A 2PACL needs a dedicated filling to operate. –Linking systems together mixes up the fluid quantity –CMS has 2 systems connected together Complex recovery procedures to equalize the fluid quantity before separation –Atlas IBL has 2 plants, but 1 accumulator volume Easy approach in mixing and separation But accumulator cannot be taken out of service –Best approach would be to separate the accu volume from the actuators and sensors which need maintenance Possible concept for a modular 2PACL approach –Have the accu volume be always part of the transfer system –Separate accu cooling, heating and sensing by housing them in a separate siphon –The modular plant contains all hardware and its volume is small Not much fluid mixing during a swap, therefore no complex equalization procedure needed. –1 spare plant is always running over a manifold connecting all units. –When a unit fails the spare can take over 1 system –The out of service unit can be repaired or swapped with another plant –Redundancy of a common primary cooling system 12

13. Cooling plant concept for a modular 2PACL 13 Modular plant unit with the following features: 1.Local by pass for dP control 2.2 condensers connected to 2 primary cooling systems. 3.Remote head triple Lewa pump 4.Contain most sensors and actuators 5.Swappable for another unit Accu unit with the following features: 1.Heaters and sensors in a parallel siphons (1 for redundant hardware) 2.Thermosiphon condensers each connected to a dedicate primary cooling system 3.Able to access all active components in a separated volume PP2 manifold with heated by-pass Transfer line

14. Modular 2PACL concept 14 Plant 1 Plant 2 Plant 3 Spare plant (Without Accu) Runs cold over the spare manifold for direct kick-in Spare plant manifold USA-15 To UX15

15. Direct swapping in case of an event 15 Plant 1 Plant 2 Plant 3 Spare plant Replaces failed or serviced unit Spare plant manifold USA-15 To UX15 Accu as volume stays active (Belongs to the transfer line volume) Accu has its own redundancy for heating and cooling Failed plant can be taken out of service or repaired

16. Quantity of cooling units Given the fact that we have 2x5 PP2 manifold locations: –2x (5 systems +1 spare) = 12 active units (option 1) –2 spares ready for direct replacement –A total of 14 units are needed Quantity optimization –Less units possible if segmentation is not following the 5 PP2 locations –Less units possible if A and C side PP2 manifold are connected to the same system Option 2: 6 active + 2 passive plants With a 150 kW Tracker the subunits will need cooling power in the order of: –Option 1: 15 kW –Option 2: 30 kW –Both options are okay with respect to the availability of technology (CMS = 15kW) 2 primary cooling plants are needed to cool all units (1 redundant) –This could be the current surface unit with a liquid brine bridging the surface and the cavern –A local chiller is an option too, but might have space constraints 16

17. Conclusions A modular approach with x 2PACL stations is the baseline concept The concept seem feasible when a separation of the accu and plant is foreseen 1 running spare unit via a back-up manifold for immediate kick-in. Concept needs prototyping 17