Thermal cooling system development for LabPET II scanners by forced convection flow

This paper presents the development of a thermal model by forced convection flow for the LabPET II, a positron emission tomography scanner dedicated to small animal imaging. To address the mouse to rabbit requirements in size, scanners may contain up to 864 ASICs dissipating ~600 mW each and 36 FPGAs. A thermal model was developed based on two digital techniques: the computational fluid dynamics (CFD) and the heat transfer analysis (HTA). The CFD technique takes into account the strength of the specific heat flow mechanism around the ASICs to perform the HTA using its physical properties. The temperature control on the chip surface is achieved by fresh air blown into “Heat Pipes” to evacuate heat out from ASICs. The ASIC area model was reused to create a simplified 2D model of the scanner containing 864 ASICs. Two analyses were conducted in COMSOL tool: natural convection (without heat pipe) and forced convection (with heat pipe) in the system model. The forced convection effectively reduces the ASICs temperature and is a good candidate to stabilize the detector temperature in LabPET II scanner.