1 CO 2 cooling of an endplate with Timepix readout Bart Verlaat, Nikhef LCTPC collaboration meeting DESY, 22 September

Contents Introduction to CO 2 Cooling Overview of the current CO 2 systems in HEP CO 2 cooling for LCTPC Conclusions 2

Why is evaporative CO 2 cooling good for HEP detectors? 3 CO 2 allows small tubing Why? Large latent heat & Low viscosity & High pressure Allow high pressure drop Allow low flow Low pressure drop Lower pressure drop Allow very small tubing Latent Heat of Evaporation (KJ/kg) Better CO 2 C3F8C3F8 Better CO 2 C3F8C3F Temperature (ºC ) Liquid Viscosity Temperature (ºC ) (Pa*s) Better CO 2 C3F8C3F8 1e-4 2e-4 3e-4 4e-4 5e

Temperature gradients in cooling tubes 4 Better CO 2 C3F8C3F8 C3F8C3F Temperature (ºC ) dT/dP ratio dT/dP (ºC/bar) Better Super heated vapor Sub cooled liquid 2-phase liquid / vapor Dry-out zone Target flow condition Temperature (°C) Fluid temperature Low ΔT Increasing ΔT Tube temperature Liquid 2-phase Gas Low dT/dP ratio due to high pressure  High pressure is good!

CO 2 safety issues Pressure Equipment Directive (PED): Stored energy determines the safety class. Stored Energy = Pressure x Volume CO 2 is environmental friendly, non- toxic and cheap 5 IDPressure at 30ºC Stored energy CO 2 1.4mm72.1 bar11.1 J/m C3F8C3F8 3.6mm9.9 bar10.1 J/m Atlas IBL cooling tube sizing 150 Watt, -25ºC

How to get the ideal 2-phase flow in the detector? DetectorCooling plant Warm transfer ChillerLiquid circulation Cold transfer 2PACL method: (LHCb) Traditional method: (Atlas) Vapor compression system Pumped liquid system Heater Compressor Pump Compressor BP. Regulator Liquid Vapor 2-phase Pressure Enthalpy Liquid Vapor 2-phase Pressure Enthalpy Cooling plantDetector 6

CO 2 systems in HEP 2 CO 2 cooling systems have been developed for HEP detectors so far. –AMS-TTCS (Tracker Thermal Control System) Q= 150 watt T=+15ºC to -20ºC –LHCb-VTCS (Velo Thermal Control System) Q=1500 Watt T= +8ºC to -30ºC Both systems are based on the 2PACL principle invented at Nikhef 7 AMS on the ISS Velo of LHCb

Deep space = Cold Pump 2PACL was developed for the AMS-TTCS 2PACL also implemented in LHCb-VELO 8 2PACL for AMS en LHCB \ LHCb-Velo AMS-Tracker 1 4 Liquid Vapor 2-phase Pressure Enthalpy In 2-phase area T=Constant P 3 2 Radiator 2-Phase Accumulator Controlled Loop (2PACL) Q= 150 watt T= +15ºC to -20ºC

Pump 9 2PACL for AMS en LHCB \ LHCb-Velo 2PACL was developed for the AMS-TTCS 2PACL also implemented in LHCb-VELO 1 4 Liquid Vapor 2-phase Pressure Enthalpy In 2-phase area T=Constant P Phase Accumulator Controlled Loop (2PACL) Chiller = Also cold Q= 1500 Watt T= +8ºC to -30ºC

The cooling tube temperature is: –Easy to control –Very stable –Independent of primary cooler temperature 10 Accumulator temperature = Cooling tube temperature Accumulator temperature = Cooling tube temperature Temperature of space radiator LHCb-VTCS Temperature of the chiller Temperature (ºC) 1 orbit (~1.5h) Time AMS-TTCS

11 Evaporator section Component box on satellites exterior Heat exchanger Pump Evaporator tube TTCS Space radiator The AMS-Tracker Thermal Control System (AMS-TTCS) AMS Accumulator

12 2 R507A Chillers: 1 water cooled 1 air cooled 2 CO 2 2PACL’s: 1 for each detector half 55 m Accessible and a friendly environment Inaccessible and a hostile environment 2 Evaporators 800 Watt max per detector half PLC 2 Concentric transfer lines 4m thick concrete shielding wall VELO Passive hardware only All the active hardware The LHCb-Velo Thermal Control System (LHCb-VTCS)

13 Evaporator The VTCS cooling plant CO 2 rack Velo module with cooling block The LHCb-Velo Thermal Control System (LHCb-VTCS)

Calculation of a LCTPC cooling tube Assumed TPC endplate layout 14 R1740 R400 Area ≈ 9m2 ≈ 5000chips/m2 Heat load ≈ 5kW/m2 Duty cycle ≈ 2% Total power ≈ 1kW Power per frame = 5 watt Cooling temperature = 20ºC ~200 frames (~223x223)

Temperature gradients (As function of cooling tube diameter and length) 15 Radial temperature gradient (ºC) (Heat transfer end of tube) Longitudinal temperature gradient (ºC) (Pressure drop) Tube length (m) Power per frame = 5 watt Frame length = 223mm Heat load = 22.5 Watt/m X=0.33 (3x overflow) ID~2.2mm ID~3mm ID~4.3mm ID~6.2mm 1x 2x 4x 6x

Similar to AMS-TTCS TPC end plate cooling tube routing 16 Qty Frames / loop Heat load per loop (W) Tube length (m) Inner diameter (mm) 1 loop m6.2 2 loops m4.3 4 loops m3 6 loops341718m2.2 ID=2.5mm L=10m AMS test data (2001) 0.4ºC temperature gradient Possible layout of the 6 loops option Liquid supply ring (~5mm ID) Vapor return ring (~8mm ID) Cooling tube (~2.5mm ID) Inlet capillary (~1mm ID) Restriction for flow distribution

LCTPC cooling tube performance (6 parallel loops) 17 Temperature22ºC Diameter2.5mm Length8m Heatload171Watt Massflow3.0g/s Vol. flow0.24l/min

Pump 18 2PACL for AMS en LHCB \ LCTPC Warm 2PACL very simple Accumulator is CO 2 room temperature Cold source is cold water Bottle temperature = Detector temperature 2PACL for LCTPC Q= 1000 Watt T= +20ºC H 2 O (~12ºC) CO 2 Bottle 1.5L/min AMS-TTCS was tested in the same way (Cold test done with bottle outside in winter)

Conclusions 19 CO 2 cooling seem feasible for LCTPC A 6 loop option looks reasonable –Inner diameter 2.5mm –Length ~8m –Gradient < 1ºC –Heat transfer ~8000W/m2K –Already tested for AMS-TTCS A room temperature CO 2 cooling system easy to realize. –Pump (LEWA LDC-1 with damper) –Heat exchanger (SWEP BDW16 DW-U) –Transfer tube (Concentric pipe in pipe) –Cold water (Available standard in lab) –Bottle (You get it for free if you order CO 2 )