CERN Accelerating science

European Organization for Nuclear Research

Integrated CO2 cooling system


The Integrated 2-Phase Accumulator Controlled Loop (2PACL) is a modification of the existing 2PACL system developed for the AMS-Tracker and LHCb-VELO CO2 cooling systems. The integrated 2PACL method is a different way of operating and control the original 2PACL concept. The modification makes the system simpler, more reliable, better to control and cheaper.

Figure 1 shows the integrated 2PACL principle. Here the accumulator cooling is integrated with the internal heat exchanger. The only remaining control of the system is a simple heater control in the accumulator. This makes the new principle easier to use and control. It will also be much cheaper to build.

Area of expertise

Cooling instrumentation, electronics.


Accurate thermal control of distant set-ups with small additional cooling hardware is a common goal in many hi-tech equipment. The easiness of using the Integrated 2PACL makes it ideal for experimental set-ups as its connection is as easy as the use of a normal thermostatic bath, which is often used now.


  • Clean and green technology
  • Small cooling tubes
  • Accurate (isothermal) and direct temperature control on distant experiments
  • CO2 is an inexpensive fluid


  • Large pressures, but only in small tubes

Intellectual Property status

Patent application filed.

Related Publications

Verlaat  B., Colijn A.P., “CO2 Cooling Developments for HEP Detectors”, 18th International Workshop on Vertex detectors, Putten, The Netherlands, 2009

Colijn A.P, Verlaat B, “CO2 Cooling for Particle Physics Experiments”, 9th IIF/IIR Gustav Lorentzen Conference on Natural Working Fluids, Sydney, Australia , 2010

Colijn A.P, Verlaat B, “Evaporative CO2 Heat Transfer Measurements for Cooling Systems of Particle Physics Detectors” , HEFAT-2010, 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Antalya, Turkey, 2010



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