Microfluidic devices for thermal management Timothée Frei Neuchâtel, 6 June 2017

outline Intro to CERN, HEP, silicon detectors and their thermal management. NA62 microfluidic cooling Closed loop cooling with Micro-engineered enhanced interconnection.. My thesis To get started silicon microchannels with RTDs for CO2 tests We still need connectors This is how we did Could we do it better? CSEM – soldered option 3D printing Neuchâtel, 6 June 2017

NA62 Silicon Microchannel Cooling 1. LASER welding 1/16” SS capillaries to KOVAR connectors 3. NICROBRAZ brazing 1/16” SS capillaries to SS manifolds 4. Au-plating KOVAR connectors 5. Vacuum brazing KOVAR connectors do Si 2. Bending of the capillaries 1/16” SS capillaries with 0.1 mm wall thickness 3 detector modules Liquid C6F14 Top below -10ºC Power dissipation 25W-48W over 6x4cm2 Kovar, Cu-plated -> Au-100nm, Ni-350nm, Ti-200nm + SnPb wire (dia 0.5mm) A. Mapelli et al. 2012 JINST 7 C01111 P. Petagna et al., Microelec. Journal 44 (2013) 612–618 G. Romagnoli et al., Microelec. Eng. 145 (2015) 133-137 Neuchâtel, 6 June 2017

Cooling System Schematic ON-DETECTOR COOLING SYSTEM Microchannels Single or two-phases flows Heat transferred to external cooler Fluidic lines come near the detector Neuchâtel, 6 June 2017

Thermal Management in HEP and Space Applications Dissipate heat generated by electronics Extend service-life of components Vacuum + Radiation Silicon embedded microchannel cooling (e.g. NA62 GTK) Cooling Plant Connection to main cooling circuit is challenging

Envisioned Cooling System Schematic ON-DETECTOR COOLING SYSTEM Two cooling circuits Primary circuits transfer heat from detector to the secondary cooling circuit Secondary circuit transfer the heat to external cooler Micro-engineered enhanced interconnection Transfer heat from primary circuit’s condenser to secondary circuit evaporator Re-workability Activation Control system Additional heat if required What we want to implement in the future Neuchâtel, 6 June 2017

Primary circuits Monolithic oscillating heat pipe (OHP), also known as pulsating heat pipe (PHP) for high energy physic and space applications Non-linear stochastic phenomena Few CFD analyses and models Transfer several kW to distances of the order of 1 m Sensible to orientation with respect to gravity (depending on the diameter) Made of Si, wickless Heater in Activation Control System is used to start oscillations of vapor 𝑔 Si detector Bump bond iramis.cea.fr Read-out chips Thermal interface PHP Neuchâtel, 6 June 2017

Micro-engineered enhanced interconnection Transfer heat from primary circuit’s condenser to secondary circuit evaporator Re-workability Secondary cooling system stays closed / No intervention on the refrigerant Neuchâtel, 6 June 2017

Open issues Neuchâtel, 6 June 2017

Vacuum flask with refrigerant Filling procedure Back-filling process OHP/PHP Valve 2 Valve 1 H. Ma, Oscillating Heat Pipes, 2015 Vacuum Sensor Mass balance Valve 3 Vacuum Pump Valve 4 Cold Trap Vacuum flask with refrigerant Quick-filling process Vacuum Sensor Valve 1 Valve 2 Vacuum Pump Valve 3 Ruler OHP/PHP Refrigerant Neuchâtel, 6 June 2017

Test Test performance in different positions 𝜃 𝜙 Test performance in different positions Test performance with different filing ratio Test performance with different power inputs, refrigerants, and refrigerant temperatures Thermal performances using RTDs or IR imagery Flow visualization using high speed camera Filing ratio of ~30% (left) and ~60% (right) Neuchâtel, 6 June 2017

ALICE ITS Microfluidic Interconnect 3D printed interconnector (3D Systems printer/Accura 25) Connects two silicon frames Liquid C4F10 Replace out-of-plane connection for in-plane connection T. Morais, 2016 Neuchâtel, 6 June 2017

ALICE ITS Microfluidics Connectors 3D printed connector glued to silicon frame (3D Systems printer/ Accura 25) Connects Ø1.2mm tubing to Ø0.6mm inlet Liquid C4F10 A. Toros, 2015 Neuchâtel, 6 June 2017